docs: fix article before std::istream in FAQ

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/basic_json/accept.md

@@ -23,6 +23,9 @@ Checks whether the input is valid JSON.
     respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
     the iterator type with `operator!=`.
     
+    Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its
+    low surrogate, and a code point above `U+10FFFF` all make this function return `false`.
+
 Unlike the [`parse()`](parse.md) function, this function neither throws an exception in case of invalid JSON input
 (i.e., a parse error) nor creates diagnostic information.
 
@@ -35,9 +38,12 @@ Unlike the [`parse()`](parse.md) function, this function neither throws an excep
     - a `#!c FILE` pointer (throws if null)
     - a C-style array of characters
     - a pointer to a null-terminated string of single byte characters (throws if null)
-    - a `std::string`
+    - a `std::string` or a `std::string_view` (C++17)
     - a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
       (as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
+    - wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide string object
+      (`std::wstring`, `std::u16string`, `std::u32string`) or an array (e.g. a wide string literal); a pointer to a
+      null-terminated wide string (e.g. `std::u16string::c_str()`) is not supported
 
 `IteratorType`
 :   a compatible iterator type, for instance.
@@ -125,6 +131,21 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
     --8<-- "examples/accept__iterator_pair.output"
     ```
 
+??? example "Example: (3) reading from UTF-16 strings"
+
+    The encoding is deduced from the character type of the input. String literals like `u"..."`, `U"..."`, and
+    `L"..."` work as well.
+
+    ```cpp
+    --8<-- "examples/accept__wide_string.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/accept__wide_string.output"
+    ```
+
 ## See also
 
 - [parse](parse.md) - deserialize from a compatible input
@@ -151,6 +172,9 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
   ([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
 - Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
   ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
+- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
+  a code point above `U+10FFFF`) is rejected in version 3.13.0; before that, some such sequences were accepted or
+  ended the input silently.
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/basic_json/index.md

@@ -44,6 +44,22 @@ are collected in [Template Parameter Requirements](../../features/types/template
 - [**json**](../json.md) - default specialization
 - [**ordered_json**](../ordered_json.md) - a specialization that maintains the insertion order of object keys
 
+## Documents and views
+
+Besides `basic_json`, the library offers a second way to hold a parsed JSON text: a
+[`basic_json_document`](../basic_json_document/index.md), which owns or borrows the text and holds a flat index of the
+values in it, and a [`basic_json_view`](../basic_json_view/index.md), a read-only handle to one value of such a document.
+Both are defined in the header `<nlohmann/json_view.hpp>`; see
+[Zero-copy JSON views](../../features/json_view.md) for the concept and the trade-offs.
+
+- [**json_document**](../json_document.md) / [**ordered_json_document**](../ordered_json_document.md) - read-only
+  documents of the `basic_json` specialization they belong to
+- [**json_editable_document**](../json_editable_document.md) /
+  [**ordered_json_editable_document**](../ordered_json_editable_document.md) - documents that can be modified in place
+- [**json_view**](../json_view.md) / [**ordered_json_view**](../ordered_json_view.md) - views of a document
+- [**json_editable_view**](../json_editable_view.md) /
+  [**ordered_json_editable_view**](../ordered_json_editable_view.md) - views of an editable document
+
 ## Iterator invalidation
 
 All operations that add values to an **array** ([`push_back`](push_back.md) , [`operator+=`](operator+=.md),
@@ -343,6 +359,9 @@ Access to the JSON value
 ## See also
 
 - [RFC 8259: The JavaScript Object Notation (JSON) Data Interchange Format](https://tools.ietf.org/html/rfc8259)
+- [basic_json_document](../basic_json_document/index.md) / [basic_json_view](../basic_json_view/index.md) - parse a JSON
+  text into a flat index and read it through a view
+- [Zero-copy JSON views](../../features/json_view.md) - when to use a document and a view instead of a `basic_json`
 
 ## Version history
 

docs/mkdocs/docs/api/basic_json/parse.md

@@ -25,6 +25,10 @@ static basic_json parse(IteratorType first, SentinelType last,
     respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
     the iterator type with `operator!=`.
 
+    Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its
+    low surrogate, and a code point above `U+10FFFF` all yield a
+    [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101).
+
 ## Template parameters
 
 `InputType`
@@ -34,9 +38,12 @@ static basic_json parse(IteratorType first, SentinelType last,
     - a `FILE` pointer (throws if null)
     - a C-style array of characters
     - a pointer to a null-terminated string of single byte characters (throws if null)
-    - a `std::string`
+    - a `std::string` or a `std::string_view` (C++17)
     - a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
       (as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
+    - wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide string object
+      (`std::wstring`, `std::u16string`, `std::u32string`) or an array (e.g. a wide string literal); a pointer to a
+      null-terminated wide string (e.g. `std::u16string::c_str()`) is not supported
 
 `IteratorType`
 :   a compatible iterator type, for instance.
@@ -112,6 +119,13 @@ By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input
 outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
 [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
 
+!!! tip "Parsing into a document instead of a value"
+
+    [`basic_json_document::parse`](../basic_json_document/parse.md) accepts the same inputs and the same options, but
+    keeps the result as a flat index of the parsed values instead of a tree of `basic_json` values. It is faster and uses
+    less memory when only parts of the document are read, and it also accepts a pointer to a null-terminated wide string,
+    which `parse()` does not. See [Zero-copy JSON views](../../features/json_view.md).
+
 !!! tip "Performance"
 
     Contiguous inputs (strings, string views, vectors, arrays, pointer ranges) are the fastest to parse. A
@@ -250,6 +264,22 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
     --8<-- "examples/trailing_commas.output"
     ```
 
+??? example "Example: parse from UTF-16, UTF-32, and wide strings"
+
+    The encoding is deduced from the character type of the input; `std::u16string` and `std::u32string` are interpreted
+    as UTF-16 and UTF-32, and `std::wstring` uses the platform's `wchar_t` width. String literals like `u"..."`,
+    `U"..."`, and `L"..."` work as well, as do iterators over wide characters.
+
+    ```cpp
+    --8<-- "examples/parse__wide_string.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/parse__wide_string.output"
+    ```
+
 ## See also
 
 - [accept](accept.md) - check if the input is valid JSON
@@ -280,6 +310,9 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
   time).
 - Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
   ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) restores `std::fgetc`).
+- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
+  a code point above `U+10FFFF`) is rejected with `parse_error.101` in version 3.13.0; before that, some such
+  sequences were accepted or ended the input silently.
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/basic_json/sax_parse.md

@@ -31,6 +31,10 @@ Read from input and generate SAX events
     respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
     the iterator type with `operator!=`.
 
+    Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its
+    low surrogate, and a code point above `U+10FFFF` all yield a
+    [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101).
+
 The SAX event lister must follow the interface of [`json_sax`](../json_sax/index.md).
 
 ## Template parameters
@@ -42,8 +46,12 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
     - a `FILE` pointer
     - a C-style array of characters
     - a pointer to a null-terminated string of single byte characters
+    - a `std::string` or a `std::string_view` (C++17)
     - a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
       (as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
+    - wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide string object
+      (`std::wstring`, `std::u16string`, `std::u32string`) or an array (e.g. a wide string literal); a pointer to a
+      null-terminated wide string (e.g. `std::u16string::c_str()`) is not supported
 
 `IteratorType`
 :   a compatible iterator type for overload (2); a pair of character iterators whose `value_type` is an integral type
@@ -160,6 +168,9 @@ use the same file with stdio functions, but it must not wait for another thread
   ([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
 - Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
   ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
+- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
+  a code point above `U+10FFFF`) is rejected with `parse_error.101` in version 3.13.0; before that, some such
+  sequences were accepted or ended the input silently.
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/basic_json_document/index.md

@@ -115,6 +115,12 @@ points apply to every edit:
   [`source_offset()`](../basic_json_view/source_offset.md) of a value introduced by an edit is
   `#!cpp static_cast<std::size_t>(-1)`, the same value it reports for a decoded string.
 
+## See also
+
+- [basic_json_view](../basic_json_view/index.md) - the read-only handle to a value of a document
+- [json_document](../json_document.md) - the document type of the default specialization
+- [Zero-copy JSON views](../../features/json_view.md) - the concept behind documents and views
+
 ## Version history
 
 - Added in version 3.13.0.

docs/mkdocs/docs/api/basic_json_document/parse.md

@@ -21,17 +21,18 @@ static basic_json_document parse(IteratorType first, IteratorType last,
 
 Both overloads accept the same JSON text as [`BasicJsonType::parse()`](../basic_json/parse.md), with the same
 `ignore_comments`/`ignore_trailing_commas` options, but build a [`basic_json_document`](index.md) (a flat index into
-the input) instead of a tree of `BasicJsonType` values. They take the same inputs as `BasicJsonType::parse()`. Byte
+the input) instead of a tree of `BasicJsonType` values. They take the same inputs as `BasicJsonType::parse()`, plus a
-inputs that stay alive can be borrowed; all others (streams, `#!cpp FILE*`, wide characters, non-contiguous
+pointer to a null-terminated wide string, which `BasicJsonType::parse()` does not accept. Byte inputs that stay alive
-iterators) are read into a copy that the document owns -- see the Notes. Use [`parse_copy()`](parse_copy.md) to get an
+can be borrowed; all others (streams, `#!cpp FILE*`, wide characters, non-contiguous iterators) are read into a copy
-owned copy of a borrowable input as well.
+that the document owns -- see the Notes. Use [`parse_copy()`](parse_copy.md) to get an owned copy of a borrowable input
+as well.
 
 ## Template parameters
 
 `InputType`
 :   A compatible input, for instance:
 
-    - a `#!cpp std::string`, `#!cpp std::string_view`, or a C-style array of single-byte characters
+    - a `#!cpp std::string`, a `#!cpp std::string_view` (C++17), or a C-style array of single-byte characters
     - a pointer to a null-terminated string of single-byte characters (`#!cpp char`, `#!cpp signed char`,
       `#!cpp unsigned char`, `#!cpp std::uint8_t`)
     - a container for which `#!cpp obj.data()` and `#!cpp obj.size()` give contiguous single-byte access, e.g.
@@ -47,6 +48,10 @@ owned copy of a borrowable input as well.
     `#!cpp std::string::iterator`; the iterators of single-byte characters are borrowed or read like the byte inputs
     above, those of wide characters are converted to UTF-8
 
+Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its low
+surrogate, and a code point above `U+10FFFF` all yield a
+[`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101).
+
 ## Parameters
 
 `input` (in)
@@ -155,3 +160,5 @@ buffer of a given length, pass a pair of pointers: `#!cpp parse(ptr, ptr + len)`
 ## Version history
 
 - Added in version 3.13.0.
+- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
+  a code point above `U+10FFFF`) is rejected with `parse_error.101`.

docs/mkdocs/docs/api/basic_json_view/index.md

@@ -143,6 +143,12 @@ still refers to it -- including ones taken before the change -- reads the new va
 
 - [**source_offset**](source_offset.md) - byte offset of this value in the document's source text
 
+## See also
+
+- [basic_json_document](../basic_json_document/index.md) - the document a view refers into
+- [materialize](materialize.md) - build the `BasicJsonType` value of a subtree
+- [Zero-copy JSON views](../../features/json_view.md) - the concept behind documents and views
+
 ## Version history
 
 - Added in version 3.13.0.

docs/mkdocs/docs/examples/accept__wide_string.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a valid JSON text, given as UTF-16
+    const std::u16string valid_text = u"{\"name\":\"\u00e9\"}";
+
+    // an invalid JSON text, given as UTF-16
+    const std::u16string invalid_text = u"{\"name\":\"\u00e9\",}";
+
+    std::cout << std::boolalpha
+              << json::accept(valid_text) << ' '
+              << json::accept(invalid_text) << '\n';
+}

docs/mkdocs/docs/examples/accept__wide_string.output

@@ -0,0 +1 @@
+true false

docs/mkdocs/docs/examples/parse__wide_string.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // the same JSON text, given in different encodings
+    const std::string utf8 = "{\"name\":\"\u00e9\"}";
+    const std::u16string utf16 = u"{\"name\":\"\u00e9\"}";
+    const std::u32string utf32 = U"{\"name\":\"\u00e9\"}";
+    const std::wstring wide = L"{\"name\":\"\u00e9\"}";
+
+    // the encoding is deduced from the character type of the input, and all
+    // of them yield the same value
+    std::cout << json::parse(utf8) << '\n'
+              << json::parse(utf16) << '\n'
+              << json::parse(utf32) << '\n'
+              << json::parse(wide) << '\n';
+
+    // a wide string literal works as well: u"..." is UTF-16, U"..." is UTF-32
+    std::cout << json::parse(u"[1, 2, 3]") << '\n';
+
+    // iterators over wide characters work as well
+    std::cout << json::parse(utf16.begin(), utf16.end()) << '\n';
+}

docs/mkdocs/docs/examples/parse__wide_string.output

@@ -0,0 +1,6 @@
+{"name":"é"}
+{"name":"é"}
+{"name":"é"}
+{"name":"é"}
+[1,2,3]
+{"name":"é"}

docs/mkdocs/docs/features/conversions.md

@@ -38,6 +38,16 @@ which avoids repeating it:
     --8<-- "examples/get_to.output"
     ```
 
+!!! info "Getting values out of a document or a view"
+
+    A [view](../api/basic_json_view/index.md) offers the same `get<T>()` conversion, but reads it straight from the
+    document's index, without building a `basic_json` value first. Two conversions never copy at all:
+    [`get_string()`](../api/basic_json_view/get_string.md) returns a string as a view into the source text, and
+    [`number_token()`](../api/basic_json_view/number_token.md) returns a number exactly as it was written. Every other
+    type is obtained from a subtree that is built on demand with
+    [`materialize()`](../api/basic_json_view/materialize.md). See
+    [Zero-copy JSON views](json_view.md#getting-values-out-without-copying).
+
 The library already knows how to convert to and from the scalar types and the STL containers (such as
 `#!cpp std::vector`, `#!cpp std::map`, `#!cpp std::array`, `#!cpp std::optional`, and many more). Converting a JSON
 object back to a `#!cpp std::map` or a JSON array back to a `#!cpp std::vector` therefore works without any extra code:
@@ -234,3 +244,4 @@ The conversions above are built in for standard types. To make the same syntax w
 - [`get_ref`](../api/basic_json/get_ref.md) / [`get_ptr`](../api/basic_json/get_ptr.md) - access the stored value without copying
 - [Arbitrary types conversions](arbitrary_types.md) - support your own types
 - [`JSON_USE_IMPLICIT_CONVERSIONS`](../api/macros/json_use_implicit_conversions.md) - toggle implicit conversions
+- [Zero-copy JSON views](json_view.md) - get values out of a document or a view

docs/mkdocs/docs/features/creating_values.md

@@ -1,7 +1,9 @@
 # Creating JSON values
 
 There are several ways to create a JSON value in memory. This page gives an overview; to read a value from JSON text
-instead, see [parsing](parsing/index.md).
+instead, see [parsing](parsing/index.md). A JSON text can also be parsed into a
+[document](../api/basic_json_document/index.md) and read through a [view](../api/basic_json_view/index.md) instead of
+into a value; see [Zero-copy JSON views](json_view.md).
 
 ## From C++ values
 
@@ -101,3 +103,4 @@ string `#!json "42"`.
 - [`operator""_json`](../api/operator_literal_json.md) - the `_json` literal
 - [Converting values](conversions.md) - which C++ types can be used
 - [Parsing](parsing/index.md) - create a value from JSON text
+- [Zero-copy JSON views](json_view.md) - create a document and a view from JSON text instead of a value

docs/mkdocs/docs/features/macros.md

@@ -287,6 +287,23 @@ external dependency and is not defined by default.
 
 See [full documentation of `JSON_USE_SIMDUTF`](../api/macros/json_use_simdutf.md).
 
+## `JSON_VIEW_NO_SIMD`
+
+When defined, the parser of [`basic_json_document`](../api/basic_json_document/index.md)
+(`<nlohmann/json_view.hpp>`) uses only portable C++ to scan strings, instead of vector instructions (SSE2 on x86-64,
+NEON on AArch64). The same input is accepted or rejected either way; only the speed differs. It is not defined by
+default.
+
+See [full documentation of `JSON_VIEW_NO_SIMD`](../api/macros/json_view_no_simd.md).
+
+## `JSON_VIEW_USE_SSSE3`
+
+When defined on x86-64, the parser of [`basic_json_document`](../api/basic_json_document/index.md)
+(`<nlohmann/json_view.hpp>`) validates non-ASCII text in strings with SSSE3 without asking the CPU first. It is not
+defined by default.
+
+See [full documentation of `JSON_VIEW_USE_SSSE3`](../api/macros/json_view_use_ssse3.md).
+
 ## `NLOHMANN_DEFINE_TYPE_*(...)`, `NLOHMANN_DEFINE_DERIVED_TYPE_*(...)`
 
 The library defines 12 macros to simplify the serialization/deserialization of types. See the page on

docs/mkdocs/docs/features/modifying_values.md

@@ -85,6 +85,16 @@ json a = {1, 2, 3, 4};
 a.erase(1);             // [1,3,4]  (erase by index)
 ```
 
+## Editing a document
+
+The operations above work on a `basic_json` value. A JSON text that was parsed into a
+[document](json_view.md#editing-a-document) can also be changed in place, without building a `basic_json` tree for the
+parts that are not touched: [`set`](../api/basic_json_document/set.md) replaces a value or an object member,
+[`push_back`](../api/basic_json_document/push_back.md) appends to an array,
+[`insert`](../api/basic_json_document/insert.md) inserts into an array, and
+[`erase`](../api/basic_json_document/erase.md) removes a member or an element. These functions are available on the
+editable document types, such as [`json_editable_document`](../api/json_editable_document.md).
+
 ## See also
 
 - [`push_back`](../api/basic_json/push_back.md) / [`emplace_back`](../api/basic_json/emplace_back.md) - append to an array
@@ -93,3 +103,4 @@ a.erase(1);             // [1,3,4]  (erase by index)
 - [`merge_patch`](../api/basic_json/merge_patch.md) - apply an RFC 7396 merge patch
 - [`erase`](../api/basic_json/erase.md) / [`clear`](../api/basic_json/clear.md) - remove elements
 - [JSON Patch and Diff](json_patch.md) and [JSON Merge Patch](merge_patch.md) - structured modifications
+- [Editing a document](json_view.md#editing-a-document) - change a parsed document in place

docs/mkdocs/docs/features/parsing/index.md

@@ -18,6 +18,7 @@ flowchart LR
 The [`parse`](../../api/basic_json/parse.md) function reads a JSON value from an input. The input can be
 
 - a string (`#!cpp std::string`, C string, or string literal),
+- a wide string (`#!cpp std::u16string`, `#!cpp std::u32string`, or `#!cpp std::wstring`, or a wide string literal),
 - a `#!cpp std::istream` (e.g., an `#!cpp std::ifstream` reading from a file),
 - a `#!cpp FILE*` pointer,
 - a pair of iterators over a contiguous range (e.g., a `#!cpp std::vector<std::uint8_t>`), or
@@ -32,12 +33,18 @@ std::ifstream f("example.json");
 json data = json::parse(f);
 ```
 
-The input must be encoded in UTF-8; other encodings are not supported. A single input may contain only one JSON value.
+The input must be encoded in UTF-8; other encodings are not supported. The exception is wide-character input, which
+is read as UTF-16 or UTF-32 -- depending on the character type -- and converted to UTF-8; see the
+[`parse`](../../api/basic_json/parse.md) page for an example. A single input may contain only one JSON value.
 Inputs consisting of multiple values separated by newlines are handled by the [JSON Lines](json_lines.md) format.
 
 By default, the library rejects comments and trailing commas. Both can be enabled with parameters of the `parse`
 function — see [comments](../comments.md) and [trailing commas](../trailing_commas.md).
 
+[`basic_json_document::parse`](../../api/basic_json_document/parse.md) accepts the same inputs with the same options,
+but keeps the result in a document rather than in a `basic_json` value; see
+[Documents and views](#documents-and-views) below.
+
 ## Strictness and trailing data
 
 [`parse`](../../api/basic_json/parse.md) reads a single JSON value and requires the whole input to be consumed: any
@@ -98,6 +105,24 @@ The library offers two parsing models:
 You can influence a DOM parse without switching to the SAX interface by passing a
 [parser callback](parser_callbacks.md), which is called during parsing and can, for example, discard parts of the input.
 
+## Documents and views
+
+A third model sits between DOM and SAX: [`basic_json_document::parse`](../../api/basic_json_document/parse.md) parses
+the input into a document that keeps the text and a flat index of the values in it, and
+[`basic_json_view`](../../api/basic_json_view/index.md) gives read-only access to the values through that index.
+Strings and numbers stay in the source text and are only decoded when they are read, which is faster and uses less
+memory than building a tree of `basic_json` values when only parts of the document are needed. A document can also be
+modified in place, and it can be saved and loaded again without parsing it.
+
+```cpp
+#include <nlohmann/json_view.hpp>
+
+json_document doc = json_document::parse(R"({"happy": true, "pi": 3.141})");
+std::cout << doc.root()["happy"].get<bool>() << '\n';
+```
+
+See [Zero-copy JSON views](../json_view.md) for the concept and the trade-offs.
+
 ## Exceptions
 
 When the input is not valid JSON, the `parse` function throws an exception by default. If exceptions are undesired or
@@ -108,6 +133,7 @@ options.
 ## See also
 
 - [`parse`](../../api/basic_json/parse.md) - deserialize from a compatible input
+- [`basic_json_document::parse`](../../api/basic_json_document/parse.md) - deserialize into a document instead of a value
 - [`accept`](../../api/basic_json/accept.md) - check if the input is valid JSON
 - [`sax_parse`](../../api/basic_json/sax_parse.md) - generate SAX events
 - [JSON Lines](json_lines.md) - parse newline-delimited JSON
@@ -115,3 +141,4 @@ options.
 - [SAX interface](sax_interface.md) - implement a custom SAX handler
 - [parsing and exceptions](parse_exceptions.md) - control error handling
 - [parsing untrusted input](untrusted_input.md) - what to consider when parsing input from untrusted sources
+- [Zero-copy JSON views](../json_view.md) - parse into a document and read it through a view

docs/mkdocs/docs/features/parsing/untrusted_input.md

@@ -81,6 +81,9 @@ Invalid UTF-8 is rejected while parsing, not just while serializing:
 
 - In JSON text, an ill-formed UTF-8 byte in a string is a
   [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) ("invalid string: ill-formed UTF-8 byte").
+- In UTF-16 or UTF-32 input, an ill-formed sequence is a
+  [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) as well: a lone surrogate, a high surrogate
+  that is not followed by its low surrogate, and a code point above `U+10FFFF` are all rejected.
 - In a binary format, a string that is not valid UTF-8 is a
   [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113).
 

docs/mkdocs/docs/home/debugging.md

@@ -1,7 +1,7 @@
 # Debugging
 
-This page collects the library's built-in debugger integrations and other debugging-related features. They are
+This page collects the library's built-in debugger integrations and other debugging-related features. They are not
-not linked from a single place elsewhere in the docs, so are collected here.
+covered by any single page elsewhere in the docs, so they are collected here.
 
 ## Visual Studio (natvis)
 

docs/mkdocs/docs/home/exceptions.md

@@ -99,7 +99,8 @@ As this global context comes at the price of storing one additional pointer per
 
     Now the exception message contains a JSON Pointer `/address/housenumber` that indicates which value has the wrong type.
 
-See [documentation of `JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) for more information.
+See [documentation of `JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) for more information, and
+[Debugging](debugging.md) for the debugger integrations of the library.
 
 ## Parse errors
 

docs/mkdocs/docs/home/faq.md

@@ -81,8 +81,9 @@ rejected by default, and the library never adds them when serializing.
 
 The library supports **Unicode input** as follows:
 
-- Only **UTF-8** encoded input is supported, which is the default encoding for JSON, according to [RFC 8259](https://tools.ietf.org/html/rfc8259.html#section-8.1).
+- **UTF-8** encoded input is supported, which is the default encoding for JSON, according to [RFC 8259](https://tools.ietf.org/html/rfc8259.html#section-8.1).
-- `std::u16string` and `std::u32string` can be parsed, assuming UTF-16 and UTF-32 encoding, respectively. These encodings are not supported when reading from files or other input containers.
+- `std::u16string` and `std::u32string` can be parsed, assuming UTF-16 and UTF-32 encoding, respectively; `std::wstring` works as well and is interpreted as UTF-16 or UTF-32, depending on the width of the platform's `wchar_t`. These encodings cannot be read from a `FILE*` or a `std::istream`, which carry bytes only.
+- Ill-formed UTF-16 or UTF-32 input is rejected: a lone surrogate, a high surrogate that is not followed by its low surrogate, and a code point above `U+10FFFF` all yield a parse error. The same holds for iterators over 2- or 4-byte characters.
 - Other encodings such as Latin-1 or ISO 8859-1 are **not** supported and will yield parse or serialization errors.
 - The library will not replace [Unicode noncharacters](http://www.unicode.org/faq/private_use.html#nonchar1).
 - Invalid surrogates (e.g., incomplete pairs such as `\uDEAD`) will yield parse errors.
@@ -146,7 +147,7 @@ json::parse(std::string("\"") + '\0' + "\""); // throws parse_error.101: control
 
     Why are wide strings (e.g., `std::wstring`) dumped as arrays of numbers?
 
-As described [above](#parse-errors-reading-non-ascii-characters), the library assumes UTF-8 as encoding.  To store a wide string, you need to change the encoding.
+As described [above](#parse-errors-reading-non-ascii-characters), the library stores its strings as UTF-8. To store a wide string, you need to change the encoding.
 
 !!! example
 

docs/mkdocs/docs/index.md

@@ -6,7 +6,9 @@ JSON for Modern C++ is a header-only C++11 library that turns JSON into a first-
 magic of modern C++ so that creating, reading, and modifying JSON values feels as natural as it does in languages like
 Python. The whole library is available as a single header, `json.hpp`, with no dependencies, no subproject, and no
 complex build system to set up; a companion header, `json_fwd.hpp`, provides forward declarations to keep compile times
-down. See [header-only integration](integration/index.md) for details. It is heavily unit-tested with 100% code
+down, `<nlohmann/json_literals.hpp>` holds the user-defined string literals on their own, and
+`<nlohmann/json_view.hpp>` adds zero-copy views and editable documents. See
+[header-only integration](integration/index.md) for details. It is heavily unit-tested with 100% code
 coverage, checked with Valgrind and the Clang Sanitizers for memory leaks, and continuously fuzz-tested by Google
 OSS-Fuzz.
 
@@ -58,7 +60,8 @@ Conda, and more), and pkg-config.
 
     ---
 
-    Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, and more.
+    Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, zero-copy views,
+    and more.
 
     [:octicons-arrow-right-24: Features](features/index.md)
 
@@ -74,7 +77,8 @@ Conda, and more), and pkg-config.
 
     ---
 
-    The complete reference for `basic_json` and its member functions, types, and related classes.
+    The complete reference for `basic_json` and its member functions, types, and related classes, as well as for
+    `json_document` and `json_view`.
 
     [:octicons-arrow-right-24: API documentation](api/basic_json/index.md)