json_view: check_utf8 skips well-formed runs with the parser's string scan

Strings of 32 bytes or more that are written into an editable document are validated with scan_string_run(), which skips well-formed UTF-8 16 bytes at a time; the byte-wise check runs only from where the scan found ill-formed UTF-8, to report the same type_error.316. Shorter strings keep the byte-wise check (inlined with a constant start, so that this path is the code it was), where the vector scan costs more than it saves. set()/push_back() of strings of 32 bytes or more take 0.29-0.76 of the time (x86-64 GCC, averaged over code layouts) and 0.25-0.80 (AArch64 clang); shorter strings take 1.5-4 % fewer instructions; the json_view rows of bench_edit execute at most 0.04 % more instructions. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
docs: writing generic code for json_view
2026-10-25 23:38:58 +00:00 · 2026-10-25 20:42:02 +01:00 · 2026-10-25 20:41:59 +01:00 · 2026-10-25 20:41:56 +01:00 · 2026-10-25 20:41:54 +01:00 · 2026-10-25 20:41:51 +01:00
529 changed files with 5342 additions and 9389 deletions
@@ -1,33 +1,3 @@
-# Style or vendor rule sets that do not fit a header-only library:
-#   altera-*, fuchsia-*, llvmlibc-*, android-cloexec-fopen, boost-use-ranges, llvm-header-guard,
-#   llvm-include-order, llvm-prefer-static-over-anonymous-namespace, llvm-use-ranges,
-#   misc-use-anonymous-namespace, google-runtime-float, google-runtime-int, hicpp-signed-bitwise,
-#   bugprone-signed-bitwise, hicpp-explicit-conversions, google-explicit-constructor,
-#   cppcoreguidelines-explicit-constructor, misc-explicit-constructor (implicit conversions are the
-#   API), readability-trailing-comma,
-#   hicpp-avoid-goto / cppcoreguidelines-avoid-goto, hicpp-no-array-decay,
-#   hicpp-uppercase-literal-suffix, readability-uppercase-literal-suffix, modernize-use-trailing-return-type.
-# Constructs the library needs on purpose (the library supports C++11 and legacy compilers):
-#   cppcoreguidelines-macro-usage, cppcoreguidelines-avoid-do-while (macros),
-#   cppcoreguidelines-pro-bounds-*, cppcoreguidelines-pro-type-reinterpret-cast,
-#   cppcoreguidelines-pro-type-union-access (parsers, serializers, basic_json's value union),
-#   cppcoreguidelines-avoid-const-or-ref-data-members, cppcoreguidelines-rvalue-reference-param-not-moved,
-#   cppcoreguidelines-avoid-non-const-global-variables, misc-non-private-member-variables-in-classes,
-#   misc-no-recursion (value walks are recursive, bounded by detail::recursion_depth_limit()),
-#   modernize-type-traits, modernize-use-constraints, modernize-use-ranges, modernize-use-std-numbers,
-#   modernize-use-designated-initializers, modernize-use-nodiscard, modernize-concat-nested-namespaces,
-#   readability-redundant-typename, readability-redundant-parentheses,
-#   readability-redundant-access-specifiers, readability-simplify-boolean-expr,
-#   readability-use-concise-preprocessor-directives, modernize-use-string-view,
-#   modernize-use-integer-sign-comparison (needs std::cmp_less; the flagged
-#   static_cast<std::size_t>(end - pos) < n comparisons are deliberate)
-#   (all need a newer standard or compiler than C++11, or would change macro-generated or
-#   deliberately explicit code).
-# Too noisy to be useful (numeric parsing/formatting code, doctest, tests):
-#   bugprone-easily-swappable-parameters, cppcoreguidelines-avoid-magic-numbers, readability-magic-numbers,
-#   readability-identifier-length, readability-function-cognitive-complexity, performance-enum-size,
-#   concurrency-mt-unsafe, misc-confusable-identifiers, misc-include-cleaner (run on its own for
-#   the consumer headers in cmake/ci.cmake).
 # portability-avoid-pragma-once: kept disabled on purpose. #pragma once is accepted
 # by every supported compiler, and tools/amalgamate/amalgamate.py strips it from
 # single_include, so there is nothing left to fix here.
@@ -40,14 +10,14 @@ Checks: '*,
         -android-cloexec-fopen,
         -boost-use-ranges,
         -bugprone-easily-swappable-parameters,
-         -bugprone-signed-bitwise,
+         -cert-err58-cpp,
+         -clang-analyzer-webkit.NoUncountedMemberChecker,
         -concurrency-mt-unsafe,
         -cppcoreguidelines-avoid-const-or-ref-data-members,
         -cppcoreguidelines-avoid-do-while,
         -cppcoreguidelines-avoid-goto,
         -cppcoreguidelines-avoid-magic-numbers,
         -cppcoreguidelines-avoid-non-const-global-variables,
-         -cppcoreguidelines-explicit-constructor,
         -cppcoreguidelines-macro-usage,
         -cppcoreguidelines-pro-bounds-avoid-unchecked-container-access,
         -cppcoreguidelines-pro-bounds-array-to-pointer-decay,
@@ -56,15 +26,19 @@ Checks: '*,
         -cppcoreguidelines-pro-type-reinterpret-cast,
         -cppcoreguidelines-pro-type-union-access,
         -cppcoreguidelines-rvalue-reference-param-not-moved,
+         -cppcoreguidelines-virtual-class-destructor,
         -fuchsia-default-arguments-calls,
         -fuchsia-default-arguments-declarations,
         -fuchsia-overloaded-operator,
         -google-explicit-constructor,
+         -google-readability-function-size,
         -google-runtime-float,
         -google-runtime-int,
         -hicpp-avoid-goto,
         -hicpp-explicit-conversions,
+         -hicpp-function-size,
         -hicpp-no-array-decay,
+         -hicpp-no-assembler,
         -hicpp-signed-bitwise,
         -hicpp-uppercase-literal-suffix,
         -llvm-header-guard,
@@ -74,7 +48,6 @@ Checks: '*,
         -llvmlibc-*,
         -misc-use-anonymous-namespace,
         -misc-confusable-identifiers,
-         -misc-explicit-constructor,
         -misc-include-cleaner,
         -misc-no-recursion,
         -misc-non-private-member-variables-in-classes,
@@ -82,22 +55,20 @@ Checks: '*,
         -modernize-type-traits,
         -modernize-use-constraints,
         -modernize-use-designated-initializers,
-         -modernize-use-integer-sign-comparison,
         -modernize-use-nodiscard,
         -modernize-use-ranges,
-         -modernize-use-string-view,
         -modernize-use-std-numbers,
         -modernize-use-trailing-return-type,
         -performance-enum-size,
         -portability-avoid-pragma-once,
         -readability-function-cognitive-complexity,
+         -readability-function-size,
         -readability-identifier-length,
         -readability-magic-numbers,
         -readability-redundant-access-specifiers,
         -readability-redundant-parentheses,
         -readability-redundant-typename,
         -readability-simplify-boolean-expr,
-         -readability-trailing-comma,
         -readability-uppercase-literal-suffix,
         -readability-use-concise-preprocessor-directives'

@@ -163,9 +163,9 @@ jobs:
          python3 $GENERATOR --list-tags
          TAG_COUNT=$(python3 $GENERATOR --list-tags | wc -l)

-          python3 $GENERATOR --abi-tags diag,_dp,_vns --abi-tags _diag --output $RUNNER_TEMP/abi_tags.natvis
-          grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_vns -->' $RUNNER_TEMP/abi_tags.natvis
-          grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_vns_v[0-9_]* -->' $RUNNER_TEMP/abi_tags.natvis
+          python3 $GENERATOR --abi-tags diag,_dp,_ns --abi-tags _diag --output $RUNNER_TEMP/abi_tags.natvis
+          grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_ns -->' $RUNNER_TEMP/abi_tags.natvis
+          grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_ns_v[0-9_]* -->' $RUNNER_TEMP/abi_tags.natvis
          test $(grep -c '<!-- Namespace ' $RUNNER_TEMP/abi_tags.natvis) -eq $(( $(grep -c '<!-- Namespace ' nlohmann_json.natvis) + 2 ))

          python3 $GENERATOR --all --output $RUNNER_TEMP/all.natvis
@@ -43,8 +43,7 @@ jobs:
      - name: flawfinder_scan
        uses: david-a-wheeler/flawfinder@c4216b74cf2639ffa98503768bd6e4299b5440c9 # v2.0.20
        with:
-          # single_include/ is omitted: it is generated from include/ and would report every finding twice
-          arguments: '--sarif ./cmake ./docs ./include ./src ./tests ./tools'
+          arguments: '--sarif ./'
          output: 'flawfinder_results.sarif'

      - name: Upload analysis results to GitHub Security tab
@@ -90,6 +90,7 @@ cc_library(
        "include/nlohmann/detail/view/simd.hpp",
        "include/nlohmann/detail/view/string_ref.hpp",
        "include/nlohmann/detail/view/value.hpp",
+        "include/nlohmann/detail/view/view_mode.hpp",
        "include/nlohmann/json.hpp",
        "include/nlohmann/json_fwd.hpp",
        "include/nlohmann/json_literals.hpp",
@@ -309,7 +309,7 @@ The "Check amalgamation" workflow fails if the file is out of date.

 The file covers the namespace variants with up to two ABI tags. A Natvis file for other configurations can be
 generated with the `--abi-tags` or `--all` options, for example
-`make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my_nlohmann_json.natvis"`; see
+`make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_ns --output my_nlohmann_json.natvis"`; see
 [`tools/generate_natvis`](tools/generate_natvis/README.md). With MSVC, CMake adds the file to the `nlohmann_json`
 target and installs it.

@@ -120,7 +120,7 @@ $(AMALGAMATED_VIEW_FILE): $(SRCS)
 	tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json_view.json -s . --verbose=yes

 NATVIS_VENV=tools/generate_natvis/venv
-# extra options for generate_natvis.py, e.g. NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my.natvis"
+# extra options for generate_natvis.py, e.g. NATVIS_ARGS="--abi-tags _diag,_dp,_ns --output my.natvis"
 NATVIS_ARGS=

 # regenerate nlohmann_json.natvis from the ABI tags and version in include/nlohmann/detail/abi_macros.hpp
@@ -151,7 +151,7 @@ The `json` class provides an API for manipulating a JSON value. To create a `jso
 ```cpp
 #include <fstream>
 #include <nlohmann/json.hpp>
-using nlohmann::json;
+using json = nlohmann::json;

 // ...

@@ -164,7 +164,7 @@ If using modules (enabled with `NLOHMANN_JSON_BUILD_MODULES`), this example beco
 import std;
 import nlohmann.json;

-using nlohmann::json;
+using json = nlohmann::json;

 // ...

@@ -842,7 +842,7 @@ assert(p == p2);
 To make this work with one of your types, you only need to provide two functions:

 ```cpp
-using nlohmann::json;
+using json = nlohmann::json;

 namespace ns {
    void to_json(json& j, const person& p) {
@@ -1257,7 +1257,7 @@ See the page [quality assurance](https://json.nlohmann.me/community/quality_assu
 #include <nlohmann/json.hpp>

 // for convenience
-using nlohmann::json;
+using json = nlohmann::json;
 ```

 to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).
@@ -113,15 +113,15 @@ basic_json(basic_json&& other) noexcept;

    ```mermaid
    flowchart TD
-        A(["initializer_list init"]) --> B{{"empty, or every element is a 2-element<br/>array whose first element is a string?"}}
-        B -->|"yes"| C{{"type_deduction"}}
-        B -->|"no"| D{{"type_deduction"}}
+        A(["initializer_list init"]) --> B{"empty, or every element is a 2-element<br/>array whose first element is a string?"}
+        B -->|"yes"| C{"type_deduction"}
+        B -->|"no"| D{"type_deduction"}
        C -->|"true"| OBJ["create object"]
-        C -->|"false"| E{{"manual_type"}}
+        C -->|"false"| E{"manual_type"}
        E -->|"object"| OBJ
        E -->|"array"| ARR["create array"]
        D -->|"true"| ARR
-        D -->|"false"| F{{"manual_type"}}
+        D -->|"false"| F{"manual_type"}
        F -->|"array"| ARR
        F -->|"object"| ERR["throw type_error.301"]
    ```
@@ -7,9 +7,7 @@ const_iterator begin() const noexcept;

 Returns an iterator to the first element.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-begin-end.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-begin-end.svg)

 ## Return value

@@ -6,9 +6,7 @@ const_iterator cbegin() const noexcept;

 Returns an iterator to the first element.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-begin-end.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-begin-end.svg)

 ## Return value

@@ -6,9 +6,7 @@ const_iterator cend() const noexcept;

 Returns an iterator to one past the last element.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-begin-end.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-begin-end.svg)

 ## Return value

@@ -6,9 +6,7 @@ const_reverse_iterator crbegin() const noexcept;

 Returns an iterator to the reverse-beginning; that is, the last element.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-rbegin-rend.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-rbegin-rend.svg)

 ## Return value

@@ -7,9 +7,7 @@ const_reverse_iterator crend() const noexcept;
 Returns an iterator to the reverse-end; that is, one before the first element. This element acts as a placeholder,
 attempting to access it results in undefined behavior.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-rbegin-rend.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-rbegin-rend.svg)

 ## Return value

@@ -7,9 +7,7 @@ const_iterator end() const noexcept;

 Returns an iterator to one past the last element.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-begin-end.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-begin-end.svg)

 ## Return value

@@ -45,7 +45,7 @@ Constant.
    #include <iostream>
    #include <nlohmann/json.hpp>
    
-    using nlohmann::json;
+    using json = nlohmann::json;
    
    int main()
    {
@@ -22,9 +22,7 @@ The parser callback distinguishes the following events:

 ## Examples

-<div class="nj-fig-wrap" markdown>
--8<-- "images/callback_events.svg"
-</div>
+![Example when certain parse events are triggered](../../images/callback_events.png)

 ??? example

@@ -23,9 +23,7 @@ table describes the values of the parameters `depth`, `event`, and `parsed`.
 | `parse_event_t::array_end`    | the parser read `]` and finished processing a JSON array  | depth of the parent of the JSON array     | the parsed JSON array            |
 | `parse_event_t::value`        | the parser finished reading a JSON value                  | depth of the value                        | the parsed JSON value            |

-<div class="nj-fig-wrap" markdown>
--8<-- "images/callback_events.svg"
-</div>
+![Example when certain parse events are triggered](../../images/callback_events.png)

 Discarding a value (i.e., returning `#!cpp false`) has different effects depending on the context in which function was
 called:
@@ -7,9 +7,7 @@ const_reverse_iterator rbegin() const noexcept;

 Returns an iterator to the reverse-beginning; that is, the last element.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-rbegin-rend.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-rbegin-rend.svg)

 ## Return value

@@ -8,9 +8,7 @@ const_reverse_iterator rend() const noexcept;
 Returns an iterator to the reverse-end; that is, one before the first element. This element acts as a placeholder,
 attempting to access it results in undefined behavior.

-<div class="nj-fig-wrap" markdown>
--8<-- "images/range-rbegin-rend.svg"
-</div>
+![Illustration from cppreference.com](../../images/range-rbegin-rend.svg)

 ## Return value

@@ -12,7 +12,7 @@ void erase(view_type array, I idx);
 std::size_t erase(const json_pointer& ptr);
 ```

-Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
+Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
 has `erase`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).

 1. Removes every member of `object` whose key is `key` (see [Notes](#notes) on duplicate keys) and returns how many
@@ -3,7 +3,7 @@
 <small>Defined in header `<nlohmann/json_view.hpp>`</small>

 ```cpp
-template<typename BasicJsonType, bool Editable = false>
+template<typename BasicJsonType, view_mode Mode = view_mode::read_only>
 class basic_json_document;
 ```

@@ -20,9 +20,9 @@ is move-only: a copy would duplicate the whole index, the decoded-string buffer,
 enough in every use we know of. The index, the decoded strings, and the owned text live in one heap block that the
 document holds through a `#!cpp std::unique_ptr`; this is also why views survive a move of the document.

-With `#!cpp Editable == true`, the document also offers [`set`](set.md), [`push_back`](push_back.md),
+With `#!cpp Mode == view_mode::editable`, the document also offers [`set`](set.md), [`push_back`](push_back.md),
 [`insert`](insert.md), and [`erase`](erase.md) to change values in place, see [Edits](#edits) below. The source text
-itself is never written; a read-only document (`#!cpp Editable == false`, the default) does not carry any of the
+itself is never written; a read-only document (`#!cpp view_mode::read_only`, the default) does not carry any of the
 bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp static_assert`).

 ## Template parameters
@@ -32,9 +32,10 @@ bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp
    [`ordered_json`](../ordered_json.md). Only 64-bit `number_integer_t`/`number_unsigned_t` types are supported; this
    is checked with a `static_assert`.

-`Editable`
-:   whether the document supports [`set`](set.md), [`push_back`](push_back.md), [`insert`](insert.md), and
-    [`erase`](erase.md) (optional, `#!cpp false` by default). See [Edits](#edits) below.
+`Mode`
+:   a [`view_mode`](../view_mode.md): `#!cpp view_mode::editable` if the document supports [`set`](set.md),
+    [`push_back`](push_back.md), [`insert`](insert.md), and [`erase`](erase.md) (optional, `#!cpp view_mode::read_only`
+    by default). See [Edits](#edits) below.

 ## Specializations

@@ -47,7 +48,7 @@ bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp

 ## Member types

- **view_type** - the type of view returned by [`root()`](root.md) (`#!cpp basic_json_view<BasicJsonType, Editable>`)
+- **view_type** - the type of view returned by [`root()`](root.md) (`#!cpp basic_json_view<BasicJsonType, Mode>`)
 - **value_t** - the JSON type enumeration, see [`basic_json::value_t`](../basic_json/value_t.md)
 - **image_check** - how [`load()`](load.md) validates an image (`full`, `bounds`, `none`), see [`image_check`](load.md#image_check)

@@ -80,15 +81,15 @@ bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp
 ### Edits

 - [**set**](set.md) - replace a value, or set an object member, an array element, or the value a JSON pointer refers
-  to (`#!cpp Editable` documents only)
- [**push_back**](push_back.md) - append to an array (`#!cpp Editable` documents only)
- [**insert**](insert.md) - insert an element into an array before a given position (`#!cpp Editable` documents only)
+  to (editable documents only)
+- [**push_back**](push_back.md) - append to an array (editable documents only)
+- [**insert**](insert.md) - insert an element into an array before a given position (editable documents only)
 - [**erase**](erase.md) - remove an object member, an array element, or the value a JSON pointer refers to
-  (`#!cpp Editable` documents only)
+  (editable documents only)

 ## Edits

-An editable document (`#!cpp Editable == true`) can be changed after parsing, with [`set`](set.md),
+An editable document (`#!cpp view_mode::editable`) can be changed after parsing, with [`set`](set.md),
 [`push_back`](push_back.md), [`insert`](insert.md), and [`erase`](erase.md);
 [`json_editable_document`](../json_editable_document.md) and
 [`ordered_json_editable_document`](../ordered_json_editable_document.md) are the corresponding specializations. A few
@@ -5,7 +5,7 @@ template<typename I, typename V>
 view_type insert(view_type array, I idx, V&& value);
 ```

-Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
+Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
 has `insert`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).

 Inserts `value` into `array` as a new element before position `idx`, which must not be past the end
@@ -55,10 +55,7 @@ validate with overload 2 first, if the original vector must survive a failed loa

 ## Exceptions

-On a big-endian target, throws [`type_error.320`](../../home/exceptions.md#jsonexceptiontype_error320) -- the same
-exception [`save()`](save.md#exceptions) throws there, since the image format is little-endian only.
-
-Otherwise throws [`parse_error.116`](../../home/exceptions.md#jsonexceptionparse_error116) if `image` is not one
+Throws [`parse_error.116`](../../home/exceptions.md#jsonexceptionparse_error116) if `image` is not one
 `save()` could have written, or fails the requested `check`:

 | message               | when                                                                                                |
@@ -95,6 +92,9 @@ are checked once, however many nodes refer to it.

 ## Notes

+**Little-endian targets only.** On a big-endian target, `load()` does not exist, just like
+[`save()`](save.md#notes): the image format is little-endian, so a call fails to compile.
+
 ### `image_check` { #image_check }

 ```cpp
@@ -13,7 +13,7 @@ editable, and it does not have to be `array`'s own document -- which is copied s
 source document afterward; a `BasicJsonType` value; or anything `BasicJsonType` can be constructed from (numbers,
 strings, `#!cpp bool`, `#!cpp nullptr`, containers, ...).

-Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
+Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
 has `push_back`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).

 ## Template parameters
@@ -12,7 +12,7 @@ An edited document is written in its *current* state, with its values in documen
 parser would have produced them for that JSON text: a member [`set`](set.md) added goes at the end, an
 [`erase`](erase.md)d member leaves no trace, and a float that is not finite (NaN or positive/negative infinity)
 becomes null, the same substitution [`dump()`](../basic_json_view/dump.md) makes. The same document always saves to
-the same bytes -- also across `BasicJsonType` and `#!cpp Editable`, since the image reflects document order and
+the same bytes -- also across `BasicJsonType` and the [`view_mode`](../view_mode.md), since the image reflects document order and
 values only, not which specialization produced them.

 ## Return value
@@ -31,9 +31,6 @@ Throws [`type_error.320`](../../home/exceptions.md#jsonexceptiontype_error320) i
 [discarded](is_discarded.md) -- a default-constructed document, or one a failed [`parse()`](parse.md)/
 [`read()`](read.md) with `allow_exceptions == false` left discarded.

-On a big-endian target, throws `type_error.320` with a different message instead: the image format is little-endian
-only (see [Notes](#notes)).
-
 Throws [`out_of_range.416`](../../home/exceptions.md#jsonexceptionout_of_range416) if the node count, the text, or
 the decoded strings of the image would individually reach 4 GiB -- the same 32-bit offsets
 [`parse()`](parse.md#exceptions) and, for edits, [`set`](set.md)/[`push_back`](push_back.md) are already limited to.
@@ -44,9 +41,6 @@ the decoded strings of the image would individually reach 4 GiB -- the same 32-b
    [json.exception.type_error.320] cannot save a discarded json_document
    ```
    ```
-    [json.exception.type_error.320] json_document images need a little-endian target
-    ```
-    ```
    [json.exception.out_of_range.416] images of 4 GiB or more are not supported by json_document
    ```

@@ -70,9 +64,9 @@ else -- see [`load`'s Exceptions](load.md#exceptions).
    the *same* build on the *same* (little-endian) machine -- not as a long-term storage format. Keep the original
    JSON text if you need to read a saved document back with a future library version.

-**Little-endian only.** The image is written as raw little-endian bytes, with no byte-swapping. `save()` (and
-[`load`](load.md)) throw `type_error.320` on a big-endian target rather than silently produce bytes a big-endian
-reader could not interpret correctly.
+**Little-endian targets only.** The image is written as raw little-endian bytes, with no byte-swapping. On a
+big-endian target, `save()` and [`load`](load.md) do not exist: a call fails to compile rather than produce bytes a
+big-endian reader could not interpret correctly.

 ## Examples

@@ -18,7 +18,7 @@ template<typename V>
 view_type set(const json_pointer& ptr, V&& value);
 ```

-Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
+Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
 has `set`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).

 1. Replaces the value `target` refers to with `value`.
@@ -19,16 +19,36 @@ For the types below, the conversion works directly on the flat index -- no `Basi
  document's own buffer of decoded strings (see [`get_string()`](get_string.md))
 - `BasicJsonType` -- equivalent to [`materialize()`](materialize.md)
 - `basic_json_view` -- returns `#!cpp *this`
- `#!cpp std::vector<U, A>` -- from an array, element by element, each converted with `#!cpp get<U>()`; `#!cpp
-  std::vector<basic_json_view>` keeps a view of every element instead of a value
- `#!cpp std::map<K, V, C, A>` and `#!cpp std::unordered_map<K, V, H, E, A>`, if `K` is constructible from a `#!cpp
-  (const char*, std::size_t)` pair -- from an object, member by member, each value converted with `#!cpp get<V>()`; with a repeated
-  key, the *last* value is kept, as [`BasicJsonType::parse()`](../basic_json/parse.md) (and
-  [`materialize()`](materialize.md)) does; `#!cpp std::map<std::string, basic_json_view>` keeps views of the members
-  instead of values
+- `#!cpp std::vector<U, A>` of the types above -- from an array, element by element, each converted with
+  `#!cpp get<U>()`; `#!cpp std::vector<basic_json_view>` keeps a view of every element instead of a value
+- `#!cpp std::map<K, basic_json_view, C, A>` and `#!cpp std::unordered_map<K, basic_json_view, H, E, A>`, if `K` is
+  constructible from a `#!cpp (const char*, std::size_t)` pair -- views of the members of an object; with a repeated
+  key, the view of the *last* member is kept, as [`BasicJsonType::parse()`](../basic_json/parse.md) keeps its value

-Every other `T` -- `#!cpp std::list`, `#!cpp std::pair`, `#!cpp std::array`, enumerations, user types with a
-`from_json()`, ... -- is converted by `#!cpp materialize().get<T>()`: the subtree is built into a real `BasicJsonType`
+A default-constructible `T` whose `from_json()` accepts views reads the view directly as well, without building a
+`BasicJsonType` value. This covers the library's own conversions of the standard library types -- all other
+`#!cpp std::vector`s, `#!cpp std::map`/`#!cpp std::unordered_map` (also with other key types), `#!cpp std::list`,
+`#!cpp std::deque`, `#!cpp std::set`, `#!cpp std::forward_list`, `#!cpp std::valarray`, `#!cpp std::array`, C arrays,
+`#!cpp std::pair`, `#!cpp std::tuple`, `#!cpp std::optional`, enumerations, `#!cpp std::filesystem::path`, ... --
+which give the same values as `#!cpp materialize().get<T>()` (from an object, a repeated key keeps the *last* value,
+as [`BasicJsonType::parse()`](../basic_json/parse.md) does), as well as the types of the
+[`NLOHMANN_DEFINE_TYPE_*`](../macros/nlohmann_define_type_intrusive.md) and
+[`NLOHMANN_DEFINE_DERIVED_TYPE_*`](../macros/nlohmann_define_derived_type.md) macros and the enumerations of
+[`NLOHMANN_JSON_SERIALIZE_ENUM`](../macros/nlohmann_json_serialize_enum.md), and any `from_json()` constrained to
+accept views, e.g. with [`is_json_view`](../is_json_view.md). A `from_json()` that also accepts types that are no JSON
+values at all, such as the unconstrained `#!cpp template<typename BasicJsonType> void from_json(const BasicJsonType&,
+T&)` of [arbitrary type conversions](../../features/arbitrary_types.md), is not called with a view: it may use
+`BasicJsonType` functions a view does not have. See [Writing generic code](../../features/json_view.md#writing-generic-code).
+
+!!! warning "Duplicate keys"
+
+    Such a `from_json()` looks members up in the view, where a repeated key finds the **first** member, while
+    `#!cpp materialize().get<T>()` sees the **last** one, as [`BasicJsonType::parse()`](../basic_json/parse.md)
+    keeps it: for `#!cpp {"x":1,"x":2}`, `#!cpp get<point>()` reads `#!cpp x == 1`. See
+    [Duplicate keys](../../features/json_view.md#duplicate-keys).
+
+Every other `T` -- user types whose `from_json()` is written for `BasicJsonType` only, types without a default
+constructor, `#!cpp std::tuple`s holding references, ... -- is converted by `#!cpp materialize().get<T>()`: the subtree is built into a real `BasicJsonType`
 value first (as [`BasicJsonType::parse()`](../basic_json/parse.md) would), and converted from there exactly as
 [`BasicJsonType::get<T>()`](../basic_json/get.md) would convert it.

@@ -53,12 +73,15 @@ Strong guarantee: there are no changes to the view or the document it refers to.
  throws for the same JSON type and `T`.
 - For `#!cpp std::vector<U, A>`: throws `type_error.302` if the value is not an array; otherwise, whatever converting
  an element to `U` throws.
- For `#!cpp std::map`/`#!cpp std::unordered_map`: throws `type_error.302` if the value is not an object; otherwise,
-  whatever converting a member to the mapped type throws.
+- For `#!cpp std::map`/`#!cpp std::unordered_map` of views: throws `type_error.302` if the value is not an object.
+- For a `T` whose `from_json()` reads the view: whatever that `from_json()` throws; for the library's conversions and
+  the macros, the same exceptions with the same messages as [`BasicJsonType::get<T>()`](../basic_json/get.md) of the
+  same value.
 - For every other `T`: whatever [`materialize().get<T>()`](../basic_json/get.md) throws -- typically `type_error.302`,
  or whatever a user-provided `from_json()` throws.

-None of the exceptions thrown directly by this function (the first three bullets above) carry a
+None of the exceptions thrown directly by this function or by a `from_json()` that reads the view (the first four
+bullets above) carry a
 [`JSON_DIAGNOSTICS`](../macros/json_diagnostics.md) path: the view has no `BasicJsonType` value to point at. An
 exception thrown while converting through `materialize()` (the last bullet) is different: it is thrown by a real
 `BasicJsonType` value, so it **does** carry a `JSON_DIAGNOSTICS` path if `BasicJsonType` was built with it enabled.
@@ -76,6 +99,8 @@ document.
 - `#!cpp std::map`/`#!cpp std::unordered_map`: linear in the number of members for walking them, plus the container's
  own insertion cost per member (logarithmic for `#!cpp std::map`, amortized constant for `#!cpp
  std::unordered_map`), times the complexity of converting one member to the mapped type.
+- a `T` whose `from_json()` reads the view: the cost of that `from_json()`; for the macros, linear in the number of
+  members times the cost of a lookup, plus the cost of converting the members.
 - every other `T`: the cost of [`materialize()`](materialize.md) and of destroying the `BasicJsonType` value
  afterwards, plus that of [`BasicJsonType::get<T>()`](../basic_json/get.md).

@@ -5,12 +5,13 @@ template<typename T>
 T& get_to(T& v) const;
 ```

-Converts the value to `T` and stores it in `v`, in one of two ways:
+Converts the value to `T` and stores it in `v`, in one of three ways:

 - For the types that [`get<T>()`](get.md) converts directly -- arithmetic types, `#!cpp bool`,
  `#!cpp std::nullptr_t`, [`string_view_t`](index.md#member-types), `#!cpp std::basic_string`, `BasicJsonType`,
-  `basic_json_view`, `#!cpp std::vector`, and `#!cpp std::map`/`#!cpp std::unordered_map` with string keys -- `v` is
-  assigned: `#!cpp v = get<T>()`.
+  `basic_json_view`, vectors of these, and maps of views -- `v` is assigned: `#!cpp v = get<T>()`.
+- For a type whose `from_json()` accepts views (see [`get<T>()`](get.md)), that `from_json()` is called with the
+  view and the existing `v`, without building a `BasicJsonType` value.
 - For every other type, the subtree is built into a `BasicJsonType` value and `#!cpp materialize().get_to(v)` is
  called, i.e. `from_json()` is invoked with the existing `v`, exactly as
  [`BasicJsonType::get_to()`](../basic_json/get_to.md) does.
@@ -3,7 +3,7 @@
 <small>Defined in header `<nlohmann/json_view.hpp>`</small>

 ```cpp
-template<typename BasicJsonType, bool Editable = false>
+template<typename BasicJsonType, view_mode Mode = view_mode::read_only>
 class basic_json_view;
 ```

@@ -37,7 +37,7 @@ Moving the document itself does not invalidate its views: the index is heap-allo
 `#!cpp operator ValueType()`), and no `#!cpp get_ptr()` or `#!cpp get_ref()`; see [`get`](get.md).

 `basic_json_view` itself is always read-only -- it never has a `set` or `push_back` of its own. A view of an
-**editable** document (`#!cpp Editable == true`) sees every edit made through
+**editable** document (`#!cpp view_mode::editable`) sees every edit made through
 [`basic_json_document::set`](../basic_json_document/set.md) and
 [`basic_json_document::push_back`](../basic_json_document/push_back.md): once a value is changed, every view that
 still refers to it -- including ones taken before the change -- reads the new value. See
@@ -49,9 +49,10 @@ still refers to it -- including ones taken before the change -- reads the new va
 :   a specialization of [`basic_json`](../basic_json/index.md), matching the
    [`basic_json_document`](../basic_json_document/index.md) the view was taken from.

-`Editable`
-:   whether the view is of an editable document, matching the [`basic_json_document`](../basic_json_document/index.md)
-    it was taken from (optional, `#!cpp false` by default). See [Edits](../basic_json_document/index.md#edits).
+`Mode`
+:   a [`view_mode`](../view_mode.md): whether the view is of an editable document, matching the
+    [`basic_json_document`](../basic_json_document/index.md) it was taken from (optional, `#!cpp view_mode::read_only` by
+    default). See [Edits](../basic_json_document/index.md#edits).

 ## Specializations

@@ -63,6 +64,7 @@ still refers to it -- including ones taken before the change -- reads the new va

 ## Member types

+- **basic_json_type** - `BasicJsonType` (it also marks the class for [`is_json_view`](../is_json_view.md))
 - **value_t** - the JSON type enumeration, see [`basic_json::value_t`](../basic_json/value_t.md)
 - **string_t**, **number_integer_t**, **number_unsigned_t**, **number_float_t**, **json_pointer** - the corresponding
  member types of `BasicJsonType`
@@ -0,0 +1,56 @@
+# <small>nlohmann::</small>is_json_view
+
+<small>Defined in header `<nlohmann/json_view.hpp>`</small>
+
+```cpp
+template<typename T>
+struct is_json_view;
+```
+
+A type trait: `#!cpp is_json_view<T>::value` is `#!cpp true` if `T` is a [`basic_json_view`](basic_json_view/index.md)
+of any `BasicJsonType` and any [`view_mode`](view_mode.md) -- [`json_view`](json_view.md),
+[`json_editable_view`](json_editable_view.md), [`ordered_json_view`](ordered_json_view.md), ... -- and
+`#!cpp false` otherwise, for [`basic_json`](basic_json/index.md) as well.
+
+It is meant for constraining templates that accept views, in particular a `from_json()` that should read views
+directly: [`get<T>()`](basic_json_view/get.md) on a view calls a `from_json()` with the view only if that `from_json()`
+accepts views but not arbitrary types.
+
+## Template parameters
+
+`T`
+:   the type to check (without cv-qualifiers or references)
+
+## Notes
+
+A view is recognized by its member type `basic_json_type` (a [`basic_json`](basic_json/index.md) specialization) and
+its [`materialize()`](basic_json_view/materialize.md) returning that type, so the trait needs no declaration of the
+view class.
+
+## Examples
+
+??? example
+
+    The example below shows the trait, and a `from_json()` constrained to `json` values and views: `get<T>()` on a view
+    reads the view directly.
+
+    ```cpp
+    --8<-- "examples/is_json_view.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/is_json_view.output"
+    ```
+
+## See also
+
+- [basic_json_view](basic_json_view/index.md) - a handle to one value of a document
+- [get](basic_json_view/get.md) - which conversions read the view directly
+- [view_mode](view_mode.md) - read-only or editable
+- [Writing generic code](../features/json_view.md#writing-generic-code) - functions and `from_json()` for views
+
+## Version history
+
+Added in version 3.13.0.
@@ -3,7 +3,7 @@
 <small>Defined in header `<nlohmann/json_view.hpp>`</small>

 ```cpp
-using json_editable_document = basic_json_document<json, true>;
+using json_editable_document = basic_json_document<json, view_mode::editable>;
 ```

 This type is an **editable** [`basic_json_document`](basic_json_document/index.md) of the default
@@ -3,7 +3,7 @@
 <small>Defined in header `<nlohmann/json_view.hpp>`</small>

 ```cpp
-using json_editable_view = basic_json_view<json, true>;
+using json_editable_view = basic_json_view<json, view_mode::editable>;
 ```

 This type is a [`basic_json_view`](basic_json_view/index.md) of a value of a
@@ -43,8 +43,6 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
 - [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
 - [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
- [**JSON_VIEW_NO_SIMD**](json_view_no_simd.md) - use only portable code in the parser of `json_view.hpp`
- [**JSON_VIEW_USE_SSSE3**](json_view_use_ssse3.md) - validate non-ASCII strings with SSSE3 in the parser of `json_view.hpp`

 ## Library version

@@ -38,7 +38,7 @@ Therefore, assertions can be switched off by defining `NDEBUG`.
    ```cpp
    #include <nlohmann/json.hpp>
    
-    using nlohmann::json;
+    using json = nlohmann::json;
    
    int main()
    {
@@ -64,7 +64,7 @@ Therefore, assertions can be switched off by defining `NDEBUG`.
    
    #include <nlohmann/json.hpp>
    
-    using nlohmann::json;
+    using json = nlohmann::json;
    
    int main()
    {
@@ -79,7 +79,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    ```cpp
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -98,7 +98,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #define JSON_BRACE_INIT_COPY_SEMANTICS 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -54,7 +54,7 @@ The default value is `0` (disabled, the deprecated functions can still be called
    ```cpp
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -72,7 +72,7 @@ The default value is `0` (disabled, the deprecated functions can still be called
    #define JSON_DELETE_DEPRECATED_FUNCTIONS 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -39,7 +39,7 @@ The default value is `0`.
    #define JSON_DISABLE_ENUM_SERIALIZATION 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    enum class Choice
    {
@@ -66,7 +66,7 @@ The default value is `0`.
    #define JSON_DISABLE_ENUM_SERIALIZATION 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    enum class Choice
    {
@@ -99,7 +99,7 @@ The default value is `0`.
    #define JSON_DISABLE_ENUM_SERIALIZATION 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    enum class Choice
    {
@@ -92,7 +92,7 @@ The default value is `0`: streams are scanned in bulk.
    #include <sstream>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -115,7 +115,7 @@ The default value is `0`: streams are scanned in bulk.
    #include <sstream>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -72,7 +72,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    ```cpp
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -89,7 +89,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -73,7 +73,7 @@ The default value is `0`: the file is locked once and read with the unlocked std
    #include <cstdio>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -92,7 +92,7 @@ The default value is `0`: the file is locked once and read with the unlocked std
    #include <cstdio>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -5,7 +5,8 @@
 ```

 When defined, the library uses only portable C++ code where it would otherwise use vector instructions: when scanning
-strings during parsing, and when writing floating-point numbers during serialization.
+strings during parsing, and when writing floating-point numbers during serialization. This includes the parser of
+[`basic_json_document`](../basic_json_document/index.md) (`<nlohmann/json_view.hpp>`).

 The macro is an escape hatch, for example for toolchains that cannot compile the vector code, for sanitizers or
 analyzers that do not understand it, or to compare the speed of both variants. It does not change any result: values,
@@ -61,7 +62,7 @@ By default, `#!cpp JSON_NO_SIMD` is not defined, and vector instructions are use
    #include <iostream>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -77,6 +78,7 @@ By default, `#!cpp JSON_NO_SIMD` is not defined, and vector instructions are use
 - [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
 - [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a time
 - [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
+- [json_view](../../features/json_view.md) - the zero-copy view, whose parser the macro also affects

 ## Version history

@@ -94,7 +94,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #include <sstream>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -115,7 +115,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #include <sstream>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -64,7 +64,7 @@ The default value is `0` (disabled, the behavior of version 3.12.0 and earlier i
    ```cpp
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -81,7 +81,7 @@ The default value is `0` (disabled, the behavior of version 3.12.0 and earlier i
    #define JSON_STRICT_BINARY_UTF8 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -92,7 +92,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    ```cpp
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -109,7 +109,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #define JSON_STRICT_NUL_HANDLING 1
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    int main()
    {
@@ -77,7 +77,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #include <map>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    enum TaskState { TS_STOPPED, TS_RUNNING, TS_COMPLETED };

@@ -105,7 +105,7 @@ The default value is `0` (disabled — existing behavior is preserved).
    #include <map>
    #include <nlohmann/json.hpp>

-    using nlohmann::json;
+    using json = nlohmann::json;

    enum TaskState { TS_STOPPED, TS_RUNNING, TS_COMPLETED };

@@ -1,52 +0,0 @@
-# JSON_VIEW_NO_SIMD
-
-```cpp
-#define JSON_VIEW_NO_SIMD
-```
-
-When defined, the parser of [`basic_json_document`](../basic_json_document/index.md) (`<nlohmann/json_view.hpp>`)
-uses only portable C++ to scan strings. By default, it scans long runs of string bytes 16 at a time with NEON on
-AArch64 (with GCC and Clang) and SSE2 on x86-64, which are part of the baseline instruction sets of these
-architectures, and validates non-ASCII text with NEON (or SSSE3, see
-[`JSON_VIEW_USE_SSSE3`](json_view_use_ssse3.md)).
-
-The same input is accepted or rejected either way, with the same values, and errors are reported the same way; only
-the speed differs. The macro exists for platforms whose compilers lack the intrinsics headers, and to test the portable
-code.
-
-!!! note "ABI compatibility"
-
-    The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the
-    [namespace](../../features/namespace.md) (tag `_vns`), resulting in distinct symbol names. Translation units
-    compiled with and without it can therefore be linked into the same program without One Definition Rule (ODR)
-    violations, but they cannot exchange instances of library types.
-
-## Default definition
-
-By default, `#!cpp JSON_VIEW_NO_SIMD` is not defined, and the vector code is used where available.
-
-```cpp
-#undef JSON_VIEW_NO_SIMD
-```
-
-## Examples
-
-??? example
-
-    The code below uses the portable string scanning of the view.
-
-    ```cpp
-    #define JSON_VIEW_NO_SIMD
-    #include <nlohmann/json_view.hpp>
-
-    ...
-    ```
-
-## See also
-
- [JSON_VIEW_USE_SSSE3](json_view_use_ssse3.md) - validate non-ASCII strings with SSSE3 on x86-64
- [json_view](../../features/json_view.md) - the zero-copy view
-
-## Version history
-
- Added in version 3.13.0.
@@ -1,53 +0,0 @@
-# JSON_VIEW_USE_SSSE3
-
-```cpp
-#define JSON_VIEW_USE_SSSE3
-```
-
-When defined on x86-64, the parser of [`basic_json_document`](../basic_json_document/index.md)
-(`<nlohmann/json_view.hpp>`) validates non-ASCII text in strings with SSSE3 without asking the CPU first.
-
-By default, the parser checks once at run time whether the CPU has SSSE3 (all x86-64 CPUs since about 2011 have it)
-and then validates non-ASCII text 16 bytes at a time, using the "lookup4" algorithm of
-[simdjson](https://github.com/simdjson/simdjson); on CPUs without SSSE3, it validates one UTF-8 sequence at a time.
-The vector check is compiled for SSSE3 with a function attribute (GCC 4.9 and later, Clang), so this needs no compiler
-option. With MSVC, the check uses `__cpuid`. On AArch64, the vector check uses NEON and is always on.
-
-Define the macro only together with a compiler option that enables SSSE3 (e.g. `-mssse3`, or `-march=` with a CPU that
-has it), and only for programs that run on such CPUs. It saves the check of the CPU, which costs little. The same
-input is accepted or rejected either way; only the speed of non-ASCII text differs.
-
-!!! note "ABI compatibility"
-
-    The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the
-    [namespace](../../features/namespace.md) (tag `_vssse3`, on every architecture), resulting in distinct symbol
-    names. Translation units compiled with and without it can therefore be linked into the same program without One
-    Definition Rule (ODR) violations, but they cannot exchange instances of library types.
-
-## Default definition
-
-By default, `#!cpp JSON_VIEW_USE_SSSE3` is not defined.
-
-```cpp
-#undef JSON_VIEW_USE_SSSE3
-```
-
-## Examples
-
-??? example
-
-    With CMake, for a program that only runs on CPUs with SSSE3:
-
-    ```cmake
-    target_compile_definitions(your_target PRIVATE JSON_VIEW_USE_SSSE3)
-    target_compile_options(your_target PRIVATE -mssse3)
-    ```
-
-## See also
-
- [JSON_VIEW_NO_SIMD](json_view_no_simd.md) - use only portable code in the view's parser
- [JSON_USE_SIMDUTF](json_use_simdutf.md) - validate UTF-8 with simdutf in `basic_json`'s parser
-
-## Version history
-
- Added in version 3.13.0.
@@ -147,6 +147,13 @@ void to_json(BasicJsonType& j, const B& b) {
    See Implementation limits for [NLOHMANN_DEFINE_TYPE_INTRUSIVE](nlohmann_define_type_intrusive.md) and
    [NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE](nlohmann_define_type_non_intrusive.md), respectively.

+!!! info "Views"
+
+    The generated `from_json()` also reads the views of [`json_document`](../json_document.md)s
+    (`<nlohmann/json_view.hpp>`): [`get<T>()`](../basic_json_view/get.md) on a view looks the members up in the
+    view, without building a `json` value first. The base part is read from the view as well if the base's
+    `from_json()` accepts views, and from [`materialize()`](../basic_json_view/materialize.md) otherwise.
+
 ## Examples

 ??? example "Example: (1) NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE"
@@ -192,3 +199,5 @@ void to_json(BasicJsonType& j, const B& b) {
 6. Added in version 3.12.0.

 All six macros were changed to allow an empty member list in version 3.13.0.
+
+The generated `from_json()` reads the views of `json_document`s since version 3.13.0.
@@ -81,6 +81,12 @@ See the examples below for the concrete generated code.
      that serializes a struct's members positionally into a JSON array; for that, write `to_json`/`from_json` by
      hand, building/reading a `json::array()` of the members in order.

+!!! info "Views"
+
+    The generated `from_json()` also reads the views of [`json_document`](../json_document.md)s
+    (`<nlohmann/json_view.hpp>`): [`get<T>()`](../basic_json_view/get.md) on a view looks the members up in the
+    view, without building a `json` value first.
+
 ## Examples

 ??? example "Example: (1) NLOHMANN_DEFINE_TYPE_INTRUSIVE"
@@ -189,3 +195,5 @@ See the examples below for the concrete generated code.

 All three macros were changed to work with any `basic_json` specialization (not only `nlohmann::json`) in version 3.12.0,
 and to allow an empty member list in version 3.13.0.
+
+The generated `from_json()` reads the views of `json_document`s since version 3.13.0.
@@ -80,6 +80,12 @@ See the examples below for the concrete generated code.
      that serializes a struct's members positionally into a JSON array; for that, write `to_json`/`from_json` by
      hand, building/reading a `json::array()` of the members in order.

+!!! info "Views"
+
+    The generated `from_json()` also reads the views of [`json_document`](../json_document.md)s
+    (`<nlohmann/json_view.hpp>`): [`get<T>()`](../basic_json_view/get.md) on a view looks the members up in the
+    view, without building a `json` value first.
+
 ## Examples

 ??? example "Example: (1) NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE"
@@ -188,3 +194,5 @@ See the examples below for the concrete generated code.

 All three macros were changed to work with any `basic_json` specialization (not only `nlohmann::json`) in version 3.12.0,
 and to allow an empty member list in version 3.13.0.
+
+The generated `from_json()` reads the views of `json_document`s since version 3.13.0.
@@ -39,6 +39,6 @@ the library.
 ## Version history

 - Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag `_dp` in
-  version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_ns`, `_vns`,
-  and `_vssse3` in version 3.13.0; see
+  version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, and `_ns` in
+  version 3.13.0; see
  [`nlohmann` Namespace](../../features/namespace.md#structure).
@@ -45,6 +45,12 @@ inline void from_json(const BasicJsonType& j, type& e);
      Define [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](json_use_objects_for_enum_keyed_maps.md) to store them as objects
      with the converted keys. Such maps can be read from both forms.

+!!! info "Views"
+
+    The generated `from_json()` also reads the views of [`json_document`](../json_document.md)s
+    (`<nlohmann/json_view.hpp>`), comparing the view with the entries of the mapping, without building a `json` value
+    first.
+
 ## Examples

 ??? example "Example: Basic usage"
@@ -88,3 +94,5 @@ inline void from_json(const BasicJsonType& j, type& e);
 ## Version history

 Added in version 3.4.0.
+
+The generated `from_json()` reads the views of `json_document`s since version 3.13.0.
@@ -48,6 +48,12 @@ inline void from_json(const BasicJsonType& j, type& e);
      Define [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](json_use_objects_for_enum_keyed_maps.md) to store them as objects
      with the converted keys. Such maps can be read from both forms.

+!!! info "Views"
+
+    The generated `from_json()` also reads the views of [`json_document`](../json_document.md)s
+    (`<nlohmann/json_view.hpp>`), comparing the view with the entries of the mapping, without building a `json` value
+    first.
+
 ## Examples

 ??? example "Example: Basic usage"
@@ -3,7 +3,7 @@
 <small>Defined in header `<nlohmann/json_view.hpp>`</small>

 ```cpp
-using ordered_json_editable_document = basic_json_document<ordered_json, true>;
+using ordered_json_editable_document = basic_json_document<ordered_json, view_mode::editable>;
 ```

 This type is an **editable** [`basic_json_document`](basic_json_document/index.md) of the
@@ -3,7 +3,7 @@
 <small>Defined in header `<nlohmann/json_view.hpp>`</small>

 ```cpp
-using ordered_json_editable_view = basic_json_view<ordered_json, true>;
+using ordered_json_editable_view = basic_json_view<ordered_json, view_mode::editable>;
 ```

 This type is a [`basic_json_view`](basic_json_view/index.md) of a value of an
@@ -0,0 +1,81 @@
+# <small>nlohmann::</small>view_mode
+
+<small>Defined in header `<nlohmann/json_view.hpp>`</small>
+
+```cpp
+enum class view_mode : std::uint8_t
+{
+    read_only,
+    editable
+};
+```
+
+The second template parameter of [`basic_json_document`](basic_json_document/index.md) and
+[`basic_json_view`](basic_json_view/index.md): whether a document can be changed after parsing, and whether a view is
+of such a document.
+
+`read_only`
+:   the default: the document is parsed once and then only read. It carries none of the bookkeeping edits need, and
+    calling [`set`](basic_json_document/set.md), [`push_back`](basic_json_document/push_back.md),
+    [`insert`](basic_json_document/insert.md), or [`erase`](basic_json_document/erase.md) on it fails to compile.
+
+`editable`
+:   the document also offers [`set`](basic_json_document/set.md), [`push_back`](basic_json_document/push_back.md),
+    [`insert`](basic_json_document/insert.md), and [`erase`](basic_json_document/erase.md); its views see every edit,
+    see [Edits](basic_json_document/index.md#edits).
+
+The shortcuts name both modes: [`json_document`](json_document.md) and [`json_view`](json_view.md) are read-only,
+[`json_editable_document`](json_editable_document.md) and [`json_editable_view`](json_editable_view.md) are editable
+(and likewise for `ordered_json`).
+
+## Notes
+
+The mode is part of the view's type, and there is no conversion between the two modes: a read-only view reads a
+container in place, while a view of an editable document follows the links that edits leave behind. A function that
+accepts views therefore names the modes it accepts in its signature:
+
+```cpp
+// views of editable documents only
+template<typename BasicJsonType>
+void f(basic_json_view<BasicJsonType, view_mode::editable> v);
+
+// views of read-only documents only
+template<typename BasicJsonType>
+void f(basic_json_view<BasicJsonType, view_mode::read_only> v);
+
+// either
+template<typename BasicJsonType, view_mode Mode>
+void f(basic_json_view<BasicJsonType, Mode> v);
+```
+
+A function that takes a [`json_view`](json_view.md) accepts neither an [`ordered_json_view`](ordered_json_view.md)
+nor a [`json_editable_view`](json_editable_view.md). Views of the two modes still compare with
+[`operator==`](basic_json_view/operator_eq.md).
+
+## Examples
+
+??? example
+
+    The example below shows a function template that accepts the views of both modes, and one that accepts only
+    views of editable documents.
+
+    ```cpp
+    --8<-- "examples/view_mode.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/view_mode.output"
+    ```
+
+## See also
+
+- [basic_json_document](basic_json_document/index.md) - a parsed JSON text
+- [basic_json_view](basic_json_view/index.md) - a handle to one value of a document
+- [json_editable_document](json_editable_document.md) - an editable document of `json`
+- [Writing generic code](../features/json_view.md#writing-generic-code) - functions that accept views
+
+## Version history
+
+Added in version 3.13.0.
@@ -188,13 +188,10 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
        ```

 - [x] The code is checked with the latest [Cppcheck](https://cppcheck.sourceforge.io) with all warnings enabled.
- [x] The code is checked with the latest [Clang Static Analyzer](https://clang-analyzer.llvm.org) with 52 enabled
-  checkers.
+- [x] The code is checked with the latest [Clang Static Analyzer](https://clang-analyzer.llvm.org) with 89 enabled
+  rules.
 - [x] The code is checked with [Infer](https://fbinfer.com).
 - [x] The code is checked with [Codacy](https://app.codacy.com/gh/nlohmann/json/dashboard).
- [x] The code is scanned with [CodeQL](https://codeql.github.com), [Semgrep](https://semgrep.dev), and
-  [Flawfinder](https://dwheeler.com/flawfinder/) on every push and pull request and on a schedule; the findings are
-  reported to GitHub's code scanning.

 ## Dynamic analysis

@@ -207,8 +204,6 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
 - [x] The test suite is executed with [Valgrind](https://valgrind.org) (Memcheck) to detect memory leaks.
 - [x] The test suite is executed with [Sanitizers](https://github.com/google/sanitizers) (address sanitizer, undefined
  behavior sanitizer, integer overflow detection, nullability violations).
- [x] The fuzz targets are run with [CIFuzz](https://google.github.io/oss-fuzz/getting-started/continuous-integration/)
-  on every pull request to catch regressions before they are merged.

 ## Dependencies

@@ -228,8 +223,6 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
  No release is made while such an alert is open.
 - [x] Third-party code included in the repository for testing, such as [doctest](https://github.com/doctest/doctest),
  is updated manually.
- [x] The repository is evaluated with the [OpenSSF Scorecard](https://securityscorecards.dev) on a schedule and on
-  every push to the default branch, and the results are reported to GitHub's code scanning.

 ## Style check

@@ -265,21 +258,4 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
 - [x] The library is tested against relevant CMake versions:
  - CMake 3.5 (the earliest supported)
  - CMake 3.31.6 (the latest 3.x release)
-  - CMake 4.0.0 (the first 4.x release)
-!!! success "Requirement: Other build systems"
-
-    The library can be used with build systems and package managers other than CMake.
-
- [x] The library can be consumed with [Meson](https://json.nlohmann.me/integration/package_managers/) and the Swift
-  Package Manager; the installation with Meson and the resolution of `Package.swift` are tested in the CI.
-
-!!! success "Requirement: Reproducible and verifiable builds"
-
-    The library can be built and tested without network access or a Git checkout, and its licensing is machine-readable.
-
- [x] The test suite is executed from an exported source tree without the `.git` directory and with the test data
-  being available offline.
- [x] The test suite is executed without the tests that change installed files to check that builds are reproducible.
- [x] The repository is checked for compliance with the [REUSE specification](https://reuse.software) so that the
-  license and copyright of every file is machine-readable.
- [x] The documentation is built with warnings treated as errors, and its links are checked regularly.
+  - CMake 4.0.0 (a very recent release)
@@ -1,739 +0,0 @@
-/* nlohmann/json brand for Material for MkDocs (values from brand/kit/tokens.css) */
-
-@font-face {
-    font-family: "Inter";
-    src: url("fonts/Inter.woff2") format("woff2");
-    font-weight: 100 900;
-    font-display: swap;
-}
-@font-face {
-    font-family: "Inter";
-    src: url("fonts/Inter-Italic.woff2") format("woff2");
-    font-style: italic;
-    font-weight: 100 900;
-    font-display: swap;
-}
-@font-face {
-    font-family: "JetBrains Mono";
-    src: url("fonts/JetBrainsMono.woff2") format("woff2");
-    font-weight: 100 800;
-    font-display: swap;
-}
-@font-face {
-    font-family: "JetBrains Mono";
-    src: url("fonts/JetBrainsMono-Italic.woff2") format("woff2");
-    font-style: italic;
-    font-weight: 400;
-    font-display: swap;
-}
-
-:root {
-    --md-text-font: "Inter";
-    --md-code-font: "JetBrains Mono";
-}
-
-/* light */
-[data-md-color-scheme="default"] {
-    --nj-blue: #1747a6;
-    --nj-blue-deep: #10357d;
-    --nj-blue-soft: #eaf1fd;
-    --nj-band: #1747a6;
-    --nj-red: #d93a3f;
-    --nj-red-soft: #fdeced;
-    --nj-string: #b4322a;
-    --nj-comment: #646d7a;
-
-    --md-primary-fg-color: var(--nj-band);
-    --md-primary-fg-color--light: #1d55c4;
-    --md-primary-fg-color--dark: #10357d;
-    --md-accent-fg-color: var(--nj-blue-deep);
-    --md-accent-fg-color--transparent: rgba(23, 71, 166, .1);
-    --md-typeset-a-color: var(--nj-blue);
-    --md-default-fg-color: #0f1419;
-    --md-default-fg-color--light: #4a515c;
-    --md-default-fg-color--lighter: #8a919c;
-    --md-default-fg-color--lightest: #e3e6eb;
-    --md-typeset-color: #0f1419;
-    --md-code-bg-color: #f5f7fa;
-    --md-code-fg-color: #0f1419;
-}
-
-/* dark */
-[data-md-color-scheme="slate"] {
-    --nj-blue: #7aa7f5;
-    --nj-blue-deep: #a9c6f8;
-    --nj-blue-soft: #16233b;
-    --nj-band: #173e8c;
-    --nj-red: #f06a6e;
-    --nj-red-soft: #3a1c1e;
-    --nj-string: #f08a7e;
-    --nj-comment: #8b929e;
-
-    --md-hue: 220;
-    --md-primary-fg-color: var(--nj-band);
-    --md-primary-fg-color--light: #163f93;
-    --md-primary-fg-color--dark: #0c2556;
-    --md-accent-fg-color: var(--nj-blue-deep);
-    --md-accent-fg-color--transparent: rgba(122, 167, 245, .12);
-    --md-typeset-a-color: var(--nj-blue);
-    --md-default-bg-color: #0f1218;
-    --md-default-fg-color: #f2f4f7;
-    --md-default-fg-color--light: #b3b9c4;
-    --md-default-fg-color--lighter: #7b828e;
-    --md-default-fg-color--lightest: #272c36;
-    --md-typeset-color: #f2f4f7;
-    --md-code-bg-color: #171b23;
-    --md-code-fg-color: #f2f4f7;
-    --md-footer-bg-color: #0b0e13;
-    --md-footer-bg-color--dark: #08090d;
-}
-
-/* syntax colours (all at least 4.5:1 on the code panel in both schemes) */
-[data-md-color-scheme="default"] {
-    --nj-hl-keyword: #1747a6;
-    --nj-hl-type: #0d6e72;
-    --nj-hl-function: #6b3fb8;
-    --nj-hl-string: #23793a;
-    --nj-hl-escape: #0f5d2a;
-    --nj-hl-key: #10357d;
-    --nj-hl-number: #b04a07;
-    --nj-hl-preproc: #a3247a;
-}
-[data-md-color-scheme="slate"] {
-    --nj-hl-keyword: #7aa7f5;
-    --nj-hl-type: #4fd1c5;
-    --nj-hl-function: #c4a3ff;
-    --nj-hl-string: #7ed491;
-    --nj-hl-escape: #b2ecc0;
-    --nj-hl-key: #a9c6f8;
-    --nj-hl-number: #f5a65b;
-    --nj-hl-preproc: #f48fc8;
-}
-.md-typeset .highlight :is(.k, .kd, .kn, .kr, .kp, .kv, .ow) { color: var(--nj-hl-keyword); font-weight: 600; }
-.md-typeset .highlight :is(.kt, .nc, .nn, .na) { color: var(--nj-hl-type); }
-.md-typeset .highlight :is(.nf, .fm, .nb, .bp) { color: var(--nj-hl-function); }
-.md-typeset .highlight :is(.s, .s1, .s2, .sb, .sc, .sd, .sh, .sx, .sr, .ss, .sa, .dl, .cpf) { color: var(--nj-hl-string); }
-.md-typeset .highlight :is(.se, .si) { color: var(--nj-hl-escape); font-weight: 600; }
-.md-typeset .highlight .nt { color: var(--nj-hl-key); }
-.md-typeset .highlight :is(.m, .mi, .mf, .mh, .mo, .mb, .il, .kc) { color: var(--nj-hl-number); }
-.md-typeset .highlight .kc { font-weight: 500; }
-.md-typeset .highlight .cp { color: var(--nj-hl-preproc); }
-.md-typeset .highlight :is(.c, .c1, .cm, .ch, .cs) { color: var(--nj-comment); font-style: italic; }
-.md-typeset .highlight :is(.o, .p) { color: var(--md-default-fg-color--light); }
-.md-typeset .highlight :is(.n, .nx, .nv, .no, .ni, .nl, .py) { color: var(--md-code-fg-color); }
-.md-typeset .highlight .err { color: inherit; background: none; }
-
-/* typography: Inter with cv11/ss03, bold headlines with negative tracking */
-body {
-    font-feature-settings: "cv11", "ss03";
-}
-.md-typeset {
-    font-size: .85rem;          /* 17 px body */
-    line-height: 1.65;
-}
-.md-typeset h1 {
-    color: var(--md-typeset-color);
-    font-weight: 800;
-    letter-spacing: -.035em;
-    line-height: 1.1;
-}
-.md-typeset h2 {
-    font-weight: 800;
-    letter-spacing: -.025em;
-    line-height: 1.15;
-}
-.md-typeset h3 {
-    font-weight: 700;
-    letter-spacing: -.015em;
-}
-.md-typeset table:not([class]) {
-    font-variant-numeric: tabular-nums;
-}
-
-/* header and tabs: one blue band with the faint syntax pattern; wordmark instead of the site name.
-   A veil over the tile keeps the glyphs from running through the navigation text; the hero shows the pattern at full strength. */
-.md-header, .md-tabs {
-    --nj-veil: linear-gradient(color-mix(in srgb, var(--md-primary-fg-color) 62%, transparent), color-mix(in srgb, var(--md-primary-fg-color) 62%, transparent));
-    background-color: var(--md-primary-fg-color);
-    background-image: var(--nj-veil), url("pattern-on-blue.svg");
-    background-size: auto, 160px 160px;
-    background-position: 0 0, 0 0;
-}
-.md-tabs {
-    background-position: 0 0, 0 -48px;     /* continue the header's tile */
-}
-.md-header__button.md-logo img {
-    width: auto;
-    height: 1.5rem;
-}
-.md-header__topic:first-child .md-ellipsis {   /* the wordmark replaces the site name at every width */
-    display: none;
-}
-@media screen and (max-width: 76.234375em) {   /* Material hides the header logo here: show the wordmark on phones, too */
-    .md-header__button.md-logo {
-        display: block;
-        margin: 0 0 0 .2rem;
-        padding: .4rem .2rem;
-    }
-    .md-header__button[for="__drawer"] {
-        order: -1;
-    }
-}
-.md-nav__button.md-logo img {
-    width: auto;
-    height: 1.4rem;
-}
-
-/* shapes: 6 px corners on blocks, 4 px on inline code */
-.md-typeset pre > code, .md-typeset .highlight, .md-typeset .highlighttable,
-.md-typeset .admonition, .md-typeset details, .md-typeset .tabbed-set,
-.md-typeset .grid.cards > ul > li, .md-typeset .md-button {
-    border-radius: 6px;
-}
-.md-typeset code {
-    border-radius: 4px;
-}
-
-/* inline code: the font alone marks it, no grey box; linked code keeps the link colour */
-.md-typeset :not(pre) > code {
-    padding: 0;
-    background-color: transparent;
-    box-shadow: none;
-    color: inherit;
-    font-size: .88em;
-}
-.md-typeset .highlight pre > code, .md-typeset .highlighttable {
-    border: 1px solid var(--md-default-fg-color--lightest);
-}
-
-/* callouts: 3 px left border; note/info/tip in blue on blue-soft, danger/bug in red on red-soft */
-.md-typeset .admonition, .md-typeset details {
-    border-width: 0 0 0 3px;
-    box-shadow: none;
-    font-size: .8rem;
-}
-.md-typeset :is(.admonition, details):is(.note, .info, .tip, .abstract, .example, .question) {
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-
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-        padding: .55em .75em;
-    }
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-
-/* more room before headings (Material: h2 1.6em, h3 1.6em, h4-h6 1-1.25em) and at the end of each page (1.2rem) */
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-    margin-bottom: 4.8rem;      /* 96 px */
-}
-
-/* Mermaid diagrams: white boxes with a blue outline, grey lines, Inter; shapes and spacing in js/mermaid-brand.js */
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-    --md-mermaid-font-family: var(--md-text-font-family), sans-serif;
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-/* a diagram wider than the column scrolls sideways (js/mermaid-brand.js stops shrinking it at 80 %) */
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-
-/* ---- polish pass ---- */
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-/* header: a search field that reads as a field on the band, tabs with an active marker, readable GitHub facts */
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-}
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-    display: block;
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-.nj-fig .fg-note { fill: currentColor; fill-opacity: .7; font-size: 13.5px; text-anchor: middle; }
-.nj-fig .fg-note--r { text-anchor: end; }
-.nj-fig .fg-note--l { text-anchor: start; }
-.nj-fig .fg-h { fill: currentColor; fill-opacity: .7; font-size: 15px; font-weight: 600; }
-.nj-fig .fg-code { fill: currentColor; font-family: var(--md-code-font-family), monospace; font-size: 16px; white-space: pre; }
-.nj-fig .fg-leg { font-size: 15px; }
-.nj-fig { --cb-os: #4eb05a; --cb-oe: #1a6b34; --cb-k: #e5534b; --cb-as: #f0c000; --cb-ae: #b07d00; --cb-v: #1f6fd1; }
-[data-md-color-scheme="slate"] .nj-fig { --cb-os: #7ee787; --cb-oe: #2ea043; --cb-k: #ff7b72; --cb-as: #f2cc60; --cb-ae: #c69026; --cb-v: #58a6ff; }
-.nj-fig .cb-os { fill: var(--cb-os); }
-.nj-fig .cb-oe { fill: var(--cb-oe); }
-.nj-fig .cb-k { fill: var(--cb-k); }
-.nj-fig .cb-as { fill: var(--cb-as); }
-.nj-fig .cb-ae { fill: var(--cb-ae); }
-.nj-fig .cb-v { fill: var(--cb-v); }
-.md-typeset img[src*="json-light"], .md-typeset img[src*="json-dark"] {
-    border-radius: 8px;
-}
-.md-typeset img {
-    max-width: 100%;
-    height: auto;
-}
-
-/* home page: content uses the same column as every other page */
-body:has(.nj-hero) .md-content {
-    max-width: none;
-    margin: 0;
-}
-.md-typeset .grid.cards {
-    width: auto;
-}
-
-/* 404 page (overrides/404.html) */
-.nj-404 {
-    max-width: 30rem;
-    padding: 2rem 0 3rem;
-}
-.nj-404__code {
-    margin: 0 0 .4rem;
-    color: var(--nj-blue);
-    font-family: var(--md-code-font-family);
-    font-size: .8rem;
-    font-weight: 500;
-}
-.md-typeset .nj-404 h1 {
-    margin-bottom: .8rem;
-}
-.nj-404 .md-button {
-    margin: .4rem .4rem 0 0;
-}
-
-/* touch targets and phones */
-@media screen and (max-width: 59.984375em) {
-    .md-nav__link {
-        padding-block: .2rem;
-    }
-}
-@media screen and (max-width: 29.984375em) {
-    .md-typeset h1 {
-        font-size: 1.7em;
-    }
-    .md-typeset .highlight pre > code {
-        font-size: .68rem;
-    }
-}
@@ -1 +0,0 @@
-<svg xmlns='http://www.w3.org/2000/svg' width='160' height='160'><g font-family='Menlo,monospace' font-size='26' font-weight='600' fill='#ffffff' fill-opacity='0.10'><text x='14' y='34'>{</text><text x='92' y='22'>]</text><text x='136' y='60'>:</text><text x='52' y='82'>[</text><text x='118' y='112'>,</text><text x='20' y='140'>}</text><text x='78' y='150'>:</text><text x='140' y='158'>{</text></g></svg>
@@ -2,7 +2,7 @@
 #include <iomanip>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -2,7 +2,7 @@
 #include <vector>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -2,19 +2,19 @@
 #include <iomanip>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
    // a valid JSON text
-    const auto* valid_text = R"(
+    auto valid_text = R"(
    {
        "numbers": [1, 2, 3]
    }
    )";

    // an invalid JSON text
-    const auto* invalid_text = R"(
+    auto invalid_text = R"(
    {
        "strings": ["extra", "comma", ]
    }
@@ -2,7 +2,7 @@
 #include <string>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -2,9 +2,9 @@
 #include <iomanip>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
-    std::cout << std::boolalpha << std::is_same<std::vector<json>, json::array_t>::value << '\n';
+    std::cout << std::boolalpha << std::is_same<std::vector<json>, json::array_t>::value << std::endl;
 }
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;
 using namespace nlohmann::literals;

 int main()
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;
 using namespace nlohmann::literals;

 int main()
@@ -3,7 +3,7 @@
 #include <nlohmann/json.hpp>

 using namespace std::string_view_literals;
-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -3,7 +3,7 @@
 #include <nlohmann/json.hpp>

 using namespace std::string_view_literals;
-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,8 +1,8 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
-using nlohmann::ordered_json;
+using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;

 int main()
 {
@@ -8,7 +8,7 @@
 #include <valarray>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>

-using nlohmann::json;
+using json = nlohmann::json;

 int main()
 {
@@ -2,7 +2,7 @@
 #include <nlohmann/json.hpp>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -2,7 +2,7 @@
 #include <utility>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -1,9 +1,9 @@
 #include <iostream>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json;
-using nlohmann::json_editable_document;
-using nlohmann::json_editable_view;
+using json = nlohmann::json;
+using json_editable_document = nlohmann::json_editable_document;
+using json_editable_view = nlohmann::json_editable_view;

 int main()
 {
@@ -1,9 +1,9 @@
 #include <iostream>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json;
-using nlohmann::json_editable_document;
-using nlohmann::json_editable_view;
+using json = nlohmann::json;
+using json_editable_document = nlohmann::json_editable_document;
+using json_editable_view = nlohmann::json_editable_view;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -4,8 +4,8 @@
 #include <vector>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json;
-using nlohmann::json_document;
+using json = nlohmann::json;
+using json_document = nlohmann::json_document;
 using image_check = json_document::image_check;

 int main()
@@ -2,7 +2,7 @@
 #include <string>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -2,7 +2,7 @@
 #include <string>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -3,7 +3,7 @@
 #include <nlohmann/json.hpp>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
@@ -1,7 +1,7 @@
 #include <iostream>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 json_document parse_from_temporary_buffer()
 {
@@ -2,7 +2,7 @@
 #include <vector>
 #include <nlohmann/json_view.hpp>

-using nlohmann::json_document;
+using json_document = nlohmann::json_document;

 int main()
 {
Author	SHA1	Message	Date
Niels Lohmann	e73ed66ac1	json_view: check_utf8 skips well-formed runs with the parser's string scan Strings of 32 bytes or more that are written into an editable document are validated with scan_string_run(), which skips well-formed UTF-8 16 bytes at a time; the byte-wise check runs only from where the scan found ill-formed UTF-8, to report the same type_error.316. Shorter strings keep the byte-wise check (inlined with a constant start, so that this path is the code it was), where the vector scan costs more than it saves. set()/push_back() of strings of 32 bytes or more take 0.29-0.76 of the time (x86-64 GCC, averaged over code layouts) and 0.25-0.80 (AArch64 clang); shorter strings take 1.5-4 % fewer instructions; the json_view rows of bench_edit execute at most 0.04 % more instructions. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:42:02 +01:00
Niels Lohmann	ea5125f7fd	docs: writing generic code for json_view A "Writing generic code" section on the json_view page: why a function taking json_view accepts no other view, the three signatures for editable, read-only, or either kind of view (passed by value), why the modes do not convert, is_json_view, and how a from_json() reads views (constrained to json values and views; the macros and the library's conversions do it already) with what differs then (duplicate keys, JSON_DIAGNOSTICS paths). Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:41:59 +01:00
Niels Lohmann	e25817c437	json_view: the library's std conversions read views directly The library's from_json() overloads (containers, maps, std::array, C arrays, pairs, tuples, optional, valarray, forward_list, enums, binary, paths, and scalars) accept views: their traits use the view's basic_json type, and the few accesses that differ (get_ptr) go through small helpers. from_json() of a view now finds them; only the probe still looks up by ADL only. get<T>() of a view thus converts these types without materialize(), with the same values and exceptions; from an object, a repeated key keeps the last value, as parse() does. The view keeps its direct paths for vectors of the types it converts directly (faster than from_json()) and for containers of views; its other vector and map paths are replaced by from_json(). For basic_json, std::valarray and std::forward_list are read in one pass (40 % and 3.5 % fewer instructions); all other conversions are unchanged. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:41:56 +01:00
Niels Lohmann	b9030ba4a1	json_view: from_json() of the macros reads views directly get<T>() and get_to() of a view call T's from_json() with the view itself when that from_json() accepts views but not an unrelated probe type, and fall back to materialize() otherwise. The from_json() functions of the NLOHMANN_DEFINE_TYPE_, NLOHMANN_DEFINE_DERIVED_TYPE_ and NLOHMANN_JSON_SERIALIZE_ENUM(_STRICT) macros accept basic_json values and views; a derived type whose base reads only json reads the base part through materialize(). The library's own from_json() overloads are not called with views: from_json() of a view (and of the probe) only looks up functions by ADL. New public trait nlohmann::is_json_view<T>, and the member type basic_json_type of basic_json_view. With duplicate keys, the members of such a T are those the view's lookups find (the first ones). bench_decode.cpp measures decoding into structs (4-6x faster than materialize().get<T>() on twitter, citm_catalog, and synthetic records). Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:41:54 +01:00
Niels Lohmann	367bf19bc2	json_view: one SIMD macro set with the library The view's vector code follows JSON_NO_SIMD, like the lexer and the float writer, and skips the CPU check of SSSE3 when the code is compiled for SSSE3 anyway (__SSSE3__), like the lexer. JSON_VIEW_NO_SIMD and JSON_VIEW_USE_SSSE3 and their ABI tags _vns and _vssse3 are removed; they were never released. JSON_NO_SIMD keeps its tag _ns. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:41:51 +01:00
Niels Lohmann	f0e049e7ae	json_view: no save() and load() on big-endian targets The image format is little-endian only. Instead of throwing type_error.320 at runtime, save_image(), load_image() and the members save() and load() do not exist on a big-endian target, so a call fails to compile, like set() on a read-only document. type_error.320 remains for saving a discarded document. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:41:48 +01:00
Niels Lohmann	266432ea65	json_view: view_mode enum instead of bool Editable, node_kind for node::kind basic_json_document and basic_json_view take a view_mode (read_only, the default, or editable) instead of a bool: basic_json_document<json, true> did not say what true means. The shortcut aliases are unchanged. The kind of a node is a node_kind (the value_t values plus link, 10 as before), which removes the static_cast<std::uint8_t>(value_t::...) of every comparison. The node and image layouts are unchanged. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-25 20:41:47 +01:00
				`@@ -1 +0,0 @@`
				`<svg xmlns='http://www.w3.org/2000/svg' width='160' height='160'><g font-family='Menlo,monospace' font-size='26' font-weight='600' fill='#ffffff' fill-opacity='0.10'><text x='14' y='34'>{</text><text x='92' y='22'>]</text><text x='136' y='60'>:</text><text x='52' y='82'>[</text><text x='118' y='112'>,</text><text x='20' y='140'>}</text><text x='78' y='150'>:</text><text x='140' y='158'>{</text></g></svg>`