State the exact input size limit of json_document

The check rejects inputs of 0xFFFFFFF0 bytes or more, but the exception
message and the documentation said 4 GiB. Name the limit once
(max_input_size), and state 4 GiB minus 16 bytes in the message and the
documentation. Test the limit with a container that only claims the size.

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

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

@@ -79,8 +79,8 @@ discarded; see [`is_discarded`](is_discarded.md).
 Throws the same exception [`BasicJsonType::parse()`](../basic_json/parse.md) throws for the same input and options --
 the same exception id, message, and position -- because on a failing input the library's own parser is run on the
 same bytes to produce the diagnostic. Additionally throws
-[`out_of_range.416`](../../home/exceptions.md#jsonexceptionout_of_range416) if the input is 4 GiB or larger, a size
-[`BasicJsonType::parse()`](../basic_json/parse.md) does not reject.
+[`out_of_range.416`](../../home/exceptions.md#jsonexceptionout_of_range416) if the input is 4294967280 bytes (4 GiB
+minus 16 bytes) or larger, a size [`BasicJsonType::parse()`](../basic_json/parse.md) does not reject.
 
 ## Complexity
 

docs/mkdocs/docs/features/json_view.md

@@ -111,7 +111,7 @@ document: `#!cpp auto v = json_document::parse(text).root();` does not compile.
 
 - **Only 64-bit integers.** `basic_json_document<BasicJsonType>` requires `BasicJsonType::number_integer_t` and
   `number_unsigned_t` to both be 64 bits wide; this is a compile-time `#!cpp static_assert`.
-- **A 4 GiB input limit.** An input of 4 GiB or more throws
+- **A 4 GiB input limit.** An input of 4294967280 bytes (4 GiB minus 16 bytes) or more throws
   [`out_of_range.416`](../home/exceptions.md#jsonexceptionout_of_range416), a limit
   `#!cpp basic_json::parse()` does not have.
 - **A stream is always read to its end.** There is no partial/streaming read of an `#!cpp std::istream`.

docs/mkdocs/docs/home/architecture.md

@@ -210,7 +210,8 @@ packet-beta
 - **Navigation** needs no pointers: the elements of an array or object follow its node, and the node after a value's
   subtree is `next` nodes further for an array or object, and the next node otherwise (`document_data::after`). Views
   step from element to element this way and skip whole subtrees in constant time.
-- **Offsets** are 32 bits wide, so a document is limited to 4 GiB (`out_of_range.416`).
+- **Offsets** are 32 bits wide, so a document is limited to 4294967279 bytes, 4 GiB minus 16 bytes (a margin below
+  2^32 for positions one scanner step past the end of the text; `out_of_range.416`).
 
 For example, `#!json {"a": [1, 2.5]}` becomes five nodes. Each node's elements follow it, and `next` leads from an
 array or object past its subtree:

docs/mkdocs/docs/home/exceptions.md

@@ -1048,12 +1048,12 @@ MessagePack's ext type and BSON's binary subtype are each stored in a single byt
 
 [`basic_json_document::parse()`](../api/basic_json_document/parse.md) and the other parsing functions of
 [`basic_json_document`](../api/basic_json_document/index.md) index a value's position in the source text in 32 bits,
-so they do not support an input of 4 GiB or more.
+so they do not support an input of 4294967280 bytes (4 GiB minus 16 bytes) or more.
 
 !!! failure "Example message"
 
     ```
-    [json.exception.out_of_range.416] input of 4 GiB or more is not supported by json_document
+    [json.exception.out_of_range.416] input of 4294967280 bytes or more is not supported by json_document
     ```
 
 !!! note