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Add JSON_PRECISE_STREAM_POSITION to leave the character that terminates a number in the stream (#5344)

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* docs: qualify the operator>> stream positioning guarantee

operator>>'s notes state that it leaves the stream positioned right
after the parsed value, so that concatenated JSON values can be read
back to back. That does not hold when the value is a number: a number
is only terminated by the character that follows it, and the lexer's
unget() is simulated (it rewinds only the lexer's own bookkeeping),
so that character stays consumed from the stream.

Document the actual behaviour: the guarantee holds for all value types
except numbers, which must be followed by whitespace. Also qualify the
cross-reference on the JSON Lines page, which repeated the unqualified
claim.

Documentation only; the behaviour itself is tracked in #5340.

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

* fix: restore the character that terminates a number (#5340)

operator>> is documented to leave the stream positioned right after the
parsed value, so that concatenated JSON values can be read back to back.
That did not hold for numbers: a number is only terminated by the
character following it, and lexer::scan_number() reads that character
and calls unget() -- which is simulated and rewinds only the lexer's own
bookkeeping. input_stream_adapter consumes via sbumpc() with no matching
sungetc(), so the terminating character stayed consumed and the next
extraction started one byte too late ('1true' left the stream at 'rue').

Propagating unget() to the adapter directly does not work: next_unget
makes the following get() replay the cached character, so the terminator
would be delivered twice. Instead, restore the still-pending character
once at the end of a non-strict parse, where the input is handed back to
the caller:

- input_stream_adapter gains unget_character() (sungetc()) and advertises
  it via supports_unget, detected the same way as supports_seek.
- lexer::restore_pending_unget() turns a pending simulated unget of a
  real (non-EOF) character into a real one and clears next_unget so the
  character is not also replayed. It is a no-op for adapters that cannot
  unget, and reports failure when sungetc() fails, in which case the
  input is left as it was before.
- parser calls it on the three non-strict paths, i.e. for operator>> and
  sax_parse(strict = false).

Strict parse()/accept() are unaffected: they require the input to end
after the value, so the character is consumed by the end-of-input check
anyway. Parse error messages and reported positions are unchanged.

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

* tests: fix CI failures in the #5340 test helpers

Four CI failures, all in the new test code:

- GCC (-Werror=useless-cast): drop the `json(...)` wrapper around
  `json::parse(...)`, which already returns a `json`.
- GCC (-Werror=unused-result): assign the discarded `json::parse()`
  result to a dummy, the idiom used elsewhere in the test suite, and
  catch `json::parse_error&` for consistency.
- clang-tidy (google-default-arguments): remove the default argument
  from the `pbackfail()` override; `sungetc()` supplies the base
  declaration's default.
- MSVC (bad allocation): `no_putback_streambuf::underflow()` set a
  one-character get area without advancing `m_pos`, so an implementation
  whose `istream::get` peeks before it bumps re-read the same character
  forever. Keep no get area at all: `underflow()` peeks, `uflow()`
  consumes, and `sungetc()` still always lands in `pbackfail()`, which
  is what the test needs.

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

* fix: leave the character that terminates a number in the input

Read the character following a number without consuming it, instead of
consuming it and putting it back. input_stream_adapter now peeks with
sgetc() and only steps over the character when the next one is requested
or when the adapter is destroyed, so releasing it cannot fail - no
putback position is required from the streambuf.

Suggested by gregmarr in #5344.

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

* docs: match the version history wording to the peek-based fix

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

* docs: drop the whitespace-separator caveat from the parsing pages

The caveat added in #5343 describes the behavior this branch fixes: a
number no longer consumes the character that terminates it, so
concatenated values need no separator.

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

* refactor: split the strict and non-strict paths in parser

Folding the release_lookahead() call into the existing strict check left
the "in strict mode" comment on an else-if branch, and made the strict
condition in sax_parse() redundant with the branch it followed.

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

* Put the stream position fix behind JSON_PRECISE_STREAM_POSITION

Leaving the character that terminates a number in the stream is observable:
reading "1,2,3" with repeated operator>> works today only because the comma
after each number is swallowed, and std::getline after a number skips the
line break. Both break with the fix, so make it opt-in for 3.x, as suggested
by @gregmarr in the review.

- JSON_PRECISE_STREAM_POSITION (default 0) selects the peek-based
  input_stream_adapter. Without it, the adapter is the consuming one from
  develop and has no supports_lookahead, so lexer::release_lookahead() and
  the parser's calls to it compile to nothing.
- The macro changes input_stream_adapter's layout and member functions, so
  it gets the ABI tag _psp, after _bics. The ABI config tests, the natvis
  generator, and nlohmann_json.natvis (regenerated) know the tag.
- The tests for the fix move to unit-precise-stream-position.cpp, which
  defines the macro itself and runs in every build, and gain the two cases
  above. unit-deserialization.cpp pins the default behavior instead.
- The docs describe the default behavior again and point to the new macro
  page; version history says "added in 3.13.0, planned default in 4.0.0".

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-25 17:56:18 +02:00
committed by GitHub
parent 98278dc3f6
commit abbe52d6de
21 changed files with 1846 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
docs/mkdocs/docs/api/basic_json/sax_parse.md
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@@ -69,7 +69,9 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
[`input_format_t`](input_format_t.md) for more information
`strict` (in)
: whether the input has to be consumed completely (optional, `#!cpp true` by default)
: whether the input has to be consumed completely (optional, `#!cpp true` by default); when `#!cpp false` and the
input is a `#!cpp std::istream`, the character that terminates a number is consumed unless
[`JSON_PRECISE_STREAM_POSITION`](../macros/json_precise_stream_position.md) is defined to `1`; see [`operator>>`](../operator_gtgt.md#notes)
`ignore_comments` (in)
: whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
@@ -136,6 +138,8 @@ A UTF-8 byte order mark is silently ignored.
- Added `ignore_trailing_commas` in version 3.13.0.
- Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
- Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
- `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave a `#!cpp std::istream` positioned right
after the parsed value when `strict` is `#!cpp false`.
!!! warning "Deprecation"

2
docs/mkdocs/docs/api/macros/index.md
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@@ -16,6 +16,8 @@ header. See also the [macro overview page](../../features/macros.md).
## Parsing
- [**JSON_PRECISE_STREAM_POSITION**](json_precise_stream_position.md) - opt in to leaving an input stream positioned
right after a parsed number
- [**JSON_STRICT_NUL_HANDLING**](json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input instead of
treating it as end of input

131
docs/mkdocs/docs/api/macros/json_precise_stream_position.md Normal file
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@@ -0,0 +1,131 @@
# JSON_PRECISE_STREAM_POSITION
```cpp
#define JSON_PRECISE_STREAM_POSITION /* value */
```
When defined to `1`, [`operator>>`](../operator_gtgt.md) and [`sax_parse`](../basic_json/sax_parse.md) with
`strict = false` leave a `#!cpp std::istream` positioned right after the parsed value for every value type. By default,
the character that terminates a number is consumed as well.
The macro only affects reading from a `#!cpp std::istream` when the rest of the stream is not required to be consumed.
[`parse`](../basic_json/parse.md), [`accept`](../basic_json/accept.md), and all other inputs (strings, iterators,
containers, `#!cpp FILE*`) are never affected.
## Default definition
The default value is `0` (disabled — existing behavior is preserved).
```cpp
#define JSON_PRECISE_STREAM_POSITION 0
```
## Notes
!!! note "Background"
A number is the only JSON value whose end can be detected solely by reading the character that follows it. By
default, that character is consumed and not put back, so the stream is left one byte too far after a number, and
only after a number:
```cpp
std::istringstream input("1true");
json j;
input >> j; // j == 1, but the stream now starts at "rue"
```
With this macro, the character is only looked at and left in the stream, so the stream starts at `true`. This
does not require the stream buffer to support putting a character back.
This was not changed unconditionally, because code can depend on the consumed character, even unknowingly (see
[#5340](https://github.com/nlohmann/json/issues/5340)). Both of the following work by default only because the
character after each number is swallowed, and behave differently with this macro:
```cpp
std::istringstream input("1,2,3");
json j1, j2, j3;
input >> j1 >> j2 >> j3; // default: 1, 2, 3
// with the macro: throws parse_error.101 at the ','
```
```cpp
std::istringstream input("42\nfoo");
json j;
std::string line;
input >> j;
std::getline(input, line); // default: "foo"
// with the macro: "" (like after reading an int with >>)
```
In both cases, the behavior with the macro is what you already get today when the value is not a number: `"a","b"`
fails at the `,`, and `std::getline` after `{}` returns an empty string. This macro offers an opt-in path to
the consistent behavior ahead of version 4.0.0, where it is planned to become the default.
!!! warning "Opt-in only"
This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
effect.
!!! note "ABI compatibility"
The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_psp`), 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.
!!! tip "Workaround without the macro"
Separate the values in the stream with whitespace. The character consumed after a number is then the separator,
and whitespace before the next value is skipped anyway.
## Examples
??? example "Default behavior (macro not defined)"
Without the macro, the character after a number is consumed:
```cpp
#include <iostream>
#include <sstream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
std::istringstream input("1true");
json j1, j2;
input >> j1; // j1 == 1
input >> j2; // throws parse_error.101: the stream now starts at "rue"
}
```
??? example "Opt-in precise stream position (macro defined to 1)"
With the macro, the stream is positioned right after the number:
```cpp
#define JSON_PRECISE_STREAM_POSITION 1
#include <iostream>
#include <sstream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
std::istringstream input("1true");
json j1, j2;
input >> j1; // j1 == 1
input >> j2; // j2 == true
}
```
## See also
- [**operator>>**](../operator_gtgt.md) - deserialize from stream
- [**sax_parse**](../basic_json/sax_parse.md) - generate SAX events
## Version history
- Added in version 3.13.0.
- Planned to become the default (with the macro removed) in version 4.0.0.

7
docs/mkdocs/docs/api/operator_gtgt.md
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@@ -67,7 +67,9 @@ input >> j2; // parses the next value
Only numbers are affected. Values ending in a self-delimiting character do not read past themselves, so
`truefalse`, `[1][2]`, `{"a":1}{"b":2}`, and `"a""b"` can be read back to back without a separator.
This is tracked in [#5340](https://github.com/nlohmann/json/issues/5340).
Define [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) to `1` to leave the terminating character in the stream
instead, so that the stream is positioned right after the value for every value type and no separator is
needed. This is tracked in [#5340](https://github.com/nlohmann/json/issues/5340).
Note that reading concatenated values does **not** work for [JSON Lines](../features/parsing/json_lines.md)
(newline-delimited JSON) input -- see that page for why and for the recommended alternative.
@@ -107,9 +109,12 @@ being read.
- [parse](basic_json/parse.md) - deserialize from a compatible input
- [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
instead of treating it as end of input
- [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) - opt in to leaving the stream positioned right after a number
## Version history
- Added in version 1.0.0.
- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
it as end of input; planned to become the default in version 4.0.0.
- `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave the character that terminates a number in
the stream; planned to become the default in version 4.0.0.

9
docs/mkdocs/docs/features/macros.md
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@@ -98,6 +98,15 @@ rather than descending into a bounded number of levels first, which is slower bu
See [full documentation of `JSON_NO_THREAD_LOCAL`](../api/macros/json_no_thread_local.md).
## `JSON_PRECISE_STREAM_POSITION`
When defined to `1`, [`operator>>`](../api/operator_gtgt.md) and non-strict
[`sax_parse`](../api/basic_json/sax_parse.md) leave an input stream positioned right after the parsed value, instead of
also consuming the character that terminates a number. The default value is `0`, which preserves the existing behavior;
this is planned to become the default in version 4.0.0.
See [full documentation of `JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md).
## `JSON_SKIP_LIBRARY_VERSION_CHECK`
When defined, the library will not create a compiler warning when a different version of the library was already

1
docs/mkdocs/docs/features/namespace.md
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@@ -18,6 +18,7 @@ The complete default namespace name is derived as follows:
- [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) defined non-zero appends `_dp`.
- [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) defined non-zero appends
`_bics`.
- [`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md) defined non-zero appends `_psp`.
- The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
underscores. To omit the version component, see [Disabling the version component](#disabling-the-version-component)
below.

3
docs/mkdocs/docs/features/parsing/index.md
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@@ -41,7 +41,8 @@ document followed by trailing bytes" is accepted rather than rejected. If you ar
reject any input that is not exactly one JSON document, prefer `parse`.
When using `operator>>` to read several concatenated values this way, a value that is a number must be followed by
whitespace, because `operator>>` consumes the character that terminates a number — see the
whitespace, because `operator>>` consumes the character that terminates a number, unless
[`JSON_PRECISE_STREAM_POSITION`](../../api/macros/json_precise_stream_position.md) is defined to `1` — see the
[`operator>>` notes](../../api/operator_gtgt.md#notes) for details and examples.
## SAX vs. DOM parsing

1
docs/mkdocs/mkdocs.yml
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@@ -293,6 +293,7 @@ nav:
- 'JSON_NOEXCEPTION': api/macros/json_noexception.md
- 'JSON_NO_IO': api/macros/json_no_io.md
- 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md
- 'JSON_PRECISE_STREAM_POSITION': api/macros/json_precise_stream_position.md
- 'JSON_SKIP_LIBRARY_VERSION_CHECK': api/macros/json_skip_library_version_check.md
- 'JSON_SKIP_UNSUPPORTED_COMPILER_CHECK': api/macros/json_skip_unsupported_compiler_check.md
- 'JSON_STRICT_NUL_HANDLING': api/macros/json_strict_nul_handling.md

19
include/nlohmann/detail/abi_macros.hpp
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@@ -38,6 +38,10 @@
#define JSON_BRACE_INIT_COPY_SEMANTICS 0
#endif
#ifndef JSON_PRECISE_STREAM_POSITION
#define JSON_PRECISE_STREAM_POSITION 0
#endif
#if JSON_DIAGNOSTICS
#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
#else
@@ -62,21 +66,28 @@
#define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
#endif
#if JSON_PRECISE_STREAM_POSITION
#define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION _psp
#else
#define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION
#endif
#ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
#define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
#endif
// Construct the namespace ABI tags component
#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
#define NLOHMANN_JSON_ABI_TAGS \
NLOHMANN_JSON_ABI_TAGS_CONCAT( \
NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS, \
NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS, \
NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS, \
NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION)
// Construct the namespace version component
#define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

82
include/nlohmann/detail/input/input_adapters.hpp
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@@ -101,6 +101,11 @@ class input_stream_adapter
// maintain ifstream flags, except eof
if (is != nullptr)
{
#if JSON_PRECISE_STREAM_POSITION
// consume the character last returned by get_character() unless it
// was given back with release_lookahead()
commit_lookahead();
#endif
is->clear(is->rdstate() & std::ios::eofbit);
}
}
@@ -114,6 +119,58 @@ class input_stream_adapter
input_stream_adapter& operator=(input_stream_adapter&) = delete;
input_stream_adapter& operator=(input_stream_adapter&&) = delete;
#if JSON_PRECISE_STREAM_POSITION
input_stream_adapter(input_stream_adapter&& rhs) noexcept
: is(rhs.is), sb(rhs.sb), lookahead(rhs.lookahead)
{
rhs.is = nullptr;
rhs.sb = nullptr;
rhs.lookahead = false;
}
// Whether the character last returned by get_character() can be given back
// to the input with release_lookahead().
static constexpr bool supports_lookahead = true;
// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
// ensure that std::char_traits<char>::eof() and the character 0xFF do not
// end up as the same value, e.g., 0xFFFFFFFF.
//
// The character is peeked rather than consumed: it is only stepped over
// once the next character is requested, or when the adapter is destroyed.
// Until then, release_lookahead() can leave it in the input.
std::char_traits<char>::int_type get_character()
{
if (lookahead)
{
// step over the character returned by the previous call
sb->sbumpc();
}
auto res = sb->sgetc();
// set eof manually, as we don't use the istream interface.
if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
{
// there is nothing to step over next time
lookahead = false;
is->clear(is->rdstate() | std::ios::eofbit);
}
else
{
lookahead = true;
}
return res;
}
// Leave the character last returned by get_character() in the input, so
// that the next read from the stream - by this adapter or by the caller
// once parsing is done - sees it again. Unlike putting a consumed
// character back, this cannot fail.
void release_lookahead() noexcept
{
lookahead = false;
}
#else
input_stream_adapter(input_stream_adapter&& rhs) noexcept
: is(rhs.is), sb(rhs.sb)
{
@@ -124,6 +181,9 @@ class input_stream_adapter
// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
// ensure that std::char_traits<char>::eof() and the character 0xFF do not
// end up as the same value, e.g., 0xFFFFFFFF.
//
// The character is consumed, so the character that terminates a number
// stays consumed after parsing; see JSON_PRECISE_STREAM_POSITION.
std::char_traits<char>::int_type get_character()
{
auto res = sb->sbumpc();
@@ -134,10 +194,14 @@ class input_stream_adapter
}
return res;
}
#endif
template<class T>
std::size_t get_elements(T* dest, std::size_t count = 1)
{
#if JSON_PRECISE_STREAM_POSITION
commit_lookahead();
#endif
auto res = static_cast<std::size_t>(sb->sgetn(reinterpret_cast<char*>(dest), static_cast<std::streamsize>(count * sizeof(T))));
if (JSON_HEDLEY_UNLIKELY(res < count * sizeof(T)))
{
@@ -147,9 +211,27 @@ class input_stream_adapter
}
private:
#if JSON_PRECISE_STREAM_POSITION
// Step over the character last returned by get_character(). The character
// has already been peeked successfully, so for every streambuf with a get
// area this is a pointer increment that cannot fail.
void commit_lookahead()
{
if (lookahead)
{
lookahead = false;
sb->sbumpc();
}
}
#endif
/// the associated input stream
std::istream* is = nullptr;
std::streambuf* sb = nullptr;
#if JSON_PRECISE_STREAM_POSITION
/// whether get_character() peeked a character that is not consumed yet
bool lookahead = false;
#endif
};
#endif // JSON_NO_IO

65
include/nlohmann/detail/input/lexer.hpp
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@@ -127,6 +127,25 @@ constexpr bool input_adapter_supports_seek(std::false_type /*detected*/)
return false;
}
// Detect whether an input adapter reads with one character of lookahead that
// can be left in the input (see input_stream_adapter::supports_lookahead,
// which is only defined with JSON_PRECISE_STREAM_POSITION), detected like
// supports_seek above.
template<typename InputAdapterType>
using detect_supports_lookahead = decltype(InputAdapterType::supports_lookahead);
template<typename InputAdapterType>
constexpr bool input_adapter_supports_lookahead(std::true_type /*detected*/)
{
return InputAdapterType::supports_lookahead;
}
template<typename InputAdapterType>
constexpr bool input_adapter_supports_lookahead(std::false_type /*detected*/)
{
return false;
}
// Detect whether an input adapter exposes a contiguous byte block that the
// lexer can scan directly (see iterator_input_adapter::supports_bulk_scan).
// Adapters without the flag - file, stream, wide-string, user-defined - fall
@@ -167,6 +186,12 @@ class lexer : public lexer_base<BasicJsonType>
static constexpr bool lazy_token_string =
input_adapter_supports_seek<InputAdapterType>(is_detected<detect_supports_seek, InputAdapterType> {});
/// whether a simulated unget can be passed on to the input adapter, which
/// then leaves the character in the input; see
/// input_adapter_supports_lookahead
static constexpr bool can_release_lookahead =
input_adapter_supports_lookahead<InputAdapterType>(is_detected<detect_supports_lookahead, InputAdapterType> {});
/// whether string scanning may bulk-consume runs of ordinary characters
/// directly from a contiguous input buffer (SWAR fast path). This requires
/// the token to be reconstructible lazily (lazy_token_string), so bypassing
@@ -1898,6 +1923,21 @@ scan_number_done:
uncapture_char(std::integral_constant<bool, lazy_token_string> {});
}
/// adapter without lookahead: nothing to do (see release_lookahead)
void release_lookahead_impl(std::false_type /*can_release*/) const noexcept {}
/// adapter with lookahead: leave the character in the input instead
void release_lookahead_impl(std::true_type /*can_release*/)
{
if (next_unget)
{
// the character is read from the input again rather than replayed
// from current, so the adapter must not step over it
next_unget = false;
ia.release_lookahead();
}
}
/// seekable adapter: nothing was captured, so nothing to undo
void uncapture_char(std::true_type /*lazy*/) const noexcept {}
@@ -1961,6 +2001,31 @@ scan_number_done:
return position;
}
/*!
@brief pass a pending simulated unget on to the input
unget() only rewinds the lexer's own bookkeeping, so the character that
terminated the last token (e.g. the character after a number) would still
be stepped over when the input adapter is done. Callers that hand the
input back to the user afterwards - operator>> and non-strict sax_parse -
call this once when scanning is done, so that the input is positioned
right after the value.
Adapters without lookahead (see input_adapter_supports_lookahead) are not
handed back to the user, so this is a no-op for them. Without
JSON_PRECISE_STREAM_POSITION, no adapter has lookahead, so this is always a
no-op and the terminating character stays consumed.
Scanning may continue after this call: @a next_unget is cleared, and the
character is read from the input again instead of being replayed from
@a current. A pending unget of EOF needs no special case, because reaching
EOF leaves no lookahead to release.
*/
void release_lookahead()
{
release_lookahead_impl(std::integral_constant<bool, can_release_lookahead> {});
}
#if JSON_DIAGNOSTIC_POSITIONS
/// return the offset of the first character of the last read token; unlike
/// the token's parsed value, this accounts for escape sequences

61
include/nlohmann/detail/input/parser.hpp
View File

@@ -100,13 +100,22 @@ class parser
json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
// in strict mode, input must be completely read
if (strict && (get_token() != token_type::end_of_input))
if (strict)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
@@ -128,12 +137,20 @@ class parser
json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
// in strict mode, input must be completely read
if (strict && (get_token() != token_type::end_of_input))
if (strict)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// see above
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
@@ -166,12 +183,24 @@ class parser
(void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
const bool result = sax_parse_internal(sax);
// strict mode: next byte must be EOF
if (result && strict && (get_token() != token_type::end_of_input))
if (result)
{
return sax->parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
if (strict)
{
// strict mode: next byte must be EOF
if (get_token() != token_type::end_of_input)
{
return sax->parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
}
return result;

1
include/nlohmann/detail/macro_unscope.hpp
View File

@@ -45,6 +45,7 @@
#undef JSON_HAS_STATIC_RTTI
#undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
#undef JSON_BRACE_INIT_COPY_SEMANTICS
#undef JSON_PRECISE_STREAM_POSITION
#endif
#include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

960
nlohmann_json.natvis
View File

File diff suppressed because it is too large Load Diff

228
single_include/nlohmann/json.hpp
View File

@@ -95,6 +95,10 @@
#define JSON_BRACE_INIT_COPY_SEMANTICS 0
#endif
#ifndef JSON_PRECISE_STREAM_POSITION
#define JSON_PRECISE_STREAM_POSITION 0
#endif
#if JSON_DIAGNOSTICS
#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
#else
@@ -119,21 +123,28 @@
#define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
#endif
#if JSON_PRECISE_STREAM_POSITION
#define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION _psp
#else
#define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION
#endif
#ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
#define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
#endif
// Construct the namespace ABI tags component
#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
#define NLOHMANN_JSON_ABI_TAGS \
NLOHMANN_JSON_ABI_TAGS_CONCAT( \
NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS, \
NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS, \
NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS, \
NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION)
// Construct the namespace version component
#define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \
@@ -7419,6 +7430,11 @@ class input_stream_adapter
// maintain ifstream flags, except eof
if (is != nullptr)
{
#if JSON_PRECISE_STREAM_POSITION
// consume the character last returned by get_character() unless it
// was given back with release_lookahead()
commit_lookahead();
#endif
is->clear(is->rdstate() & std::ios::eofbit);
}
}
@@ -7432,6 +7448,58 @@ class input_stream_adapter
input_stream_adapter& operator=(input_stream_adapter&) = delete;
input_stream_adapter& operator=(input_stream_adapter&&) = delete;
#if JSON_PRECISE_STREAM_POSITION
input_stream_adapter(input_stream_adapter&& rhs) noexcept
: is(rhs.is), sb(rhs.sb), lookahead(rhs.lookahead)
{
rhs.is = nullptr;
rhs.sb = nullptr;
rhs.lookahead = false;
}
// Whether the character last returned by get_character() can be given back
// to the input with release_lookahead().
static constexpr bool supports_lookahead = true;
// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
// ensure that std::char_traits<char>::eof() and the character 0xFF do not
// end up as the same value, e.g., 0xFFFFFFFF.
//
// The character is peeked rather than consumed: it is only stepped over
// once the next character is requested, or when the adapter is destroyed.
// Until then, release_lookahead() can leave it in the input.
std::char_traits<char>::int_type get_character()
{
if (lookahead)
{
// step over the character returned by the previous call
sb->sbumpc();
}
auto res = sb->sgetc();
// set eof manually, as we don't use the istream interface.
if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
{
// there is nothing to step over next time
lookahead = false;
is->clear(is->rdstate() | std::ios::eofbit);
}
else
{
lookahead = true;
}
return res;
}
// Leave the character last returned by get_character() in the input, so
// that the next read from the stream - by this adapter or by the caller
// once parsing is done - sees it again. Unlike putting a consumed
// character back, this cannot fail.
void release_lookahead() noexcept
{
lookahead = false;
}
#else
input_stream_adapter(input_stream_adapter&& rhs) noexcept
: is(rhs.is), sb(rhs.sb)
{
@@ -7442,6 +7510,9 @@ class input_stream_adapter
// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
// ensure that std::char_traits<char>::eof() and the character 0xFF do not
// end up as the same value, e.g., 0xFFFFFFFF.
//
// The character is consumed, so the character that terminates a number
// stays consumed after parsing; see JSON_PRECISE_STREAM_POSITION.
std::char_traits<char>::int_type get_character()
{
auto res = sb->sbumpc();
@@ -7452,10 +7523,14 @@ class input_stream_adapter
}
return res;
}
#endif
template<class T>
std::size_t get_elements(T* dest, std::size_t count = 1)
{
#if JSON_PRECISE_STREAM_POSITION
commit_lookahead();
#endif
auto res = static_cast<std::size_t>(sb->sgetn(reinterpret_cast<char*>(dest), static_cast<std::streamsize>(count * sizeof(T))));
if (JSON_HEDLEY_UNLIKELY(res < count * sizeof(T)))
{
@@ -7465,9 +7540,27 @@ class input_stream_adapter
}
private:
#if JSON_PRECISE_STREAM_POSITION
// Step over the character last returned by get_character(). The character
// has already been peeked successfully, so for every streambuf with a get
// area this is a pointer increment that cannot fail.
void commit_lookahead()
{
if (lookahead)
{
lookahead = false;
sb->sbumpc();
}
}
#endif
/// the associated input stream
std::istream* is = nullptr;
std::streambuf* sb = nullptr;
#if JSON_PRECISE_STREAM_POSITION
/// whether get_character() peeked a character that is not consumed yet
bool lookahead = false;
#endif
};
#endif // JSON_NO_IO
@@ -8879,6 +8972,25 @@ constexpr bool input_adapter_supports_seek(std::false_type /*detected*/)
return false;
}
// Detect whether an input adapter reads with one character of lookahead that
// can be left in the input (see input_stream_adapter::supports_lookahead,
// which is only defined with JSON_PRECISE_STREAM_POSITION), detected like
// supports_seek above.
template<typename InputAdapterType>
using detect_supports_lookahead = decltype(InputAdapterType::supports_lookahead);
template<typename InputAdapterType>
constexpr bool input_adapter_supports_lookahead(std::true_type /*detected*/)
{
return InputAdapterType::supports_lookahead;
}
template<typename InputAdapterType>
constexpr bool input_adapter_supports_lookahead(std::false_type /*detected*/)
{
return false;
}
// Detect whether an input adapter exposes a contiguous byte block that the
// lexer can scan directly (see iterator_input_adapter::supports_bulk_scan).
// Adapters without the flag - file, stream, wide-string, user-defined - fall
@@ -8919,6 +9031,12 @@ class lexer : public lexer_base<BasicJsonType>
static constexpr bool lazy_token_string =
input_adapter_supports_seek<InputAdapterType>(is_detected<detect_supports_seek, InputAdapterType> {});
/// whether a simulated unget can be passed on to the input adapter, which
/// then leaves the character in the input; see
/// input_adapter_supports_lookahead
static constexpr bool can_release_lookahead =
input_adapter_supports_lookahead<InputAdapterType>(is_detected<detect_supports_lookahead, InputAdapterType> {});
/// whether string scanning may bulk-consume runs of ordinary characters
/// directly from a contiguous input buffer (SWAR fast path). This requires
/// the token to be reconstructible lazily (lazy_token_string), so bypassing
@@ -10650,6 +10768,21 @@ scan_number_done:
uncapture_char(std::integral_constant<bool, lazy_token_string> {});
}
/// adapter without lookahead: nothing to do (see release_lookahead)
void release_lookahead_impl(std::false_type /*can_release*/) const noexcept {}
/// adapter with lookahead: leave the character in the input instead
void release_lookahead_impl(std::true_type /*can_release*/)
{
if (next_unget)
{
// the character is read from the input again rather than replayed
// from current, so the adapter must not step over it
next_unget = false;
ia.release_lookahead();
}
}
/// seekable adapter: nothing was captured, so nothing to undo
void uncapture_char(std::true_type /*lazy*/) const noexcept {}
@@ -10713,6 +10846,31 @@ scan_number_done:
return position;
}
/*!
@brief pass a pending simulated unget on to the input
unget() only rewinds the lexer's own bookkeeping, so the character that
terminated the last token (e.g. the character after a number) would still
be stepped over when the input adapter is done. Callers that hand the
input back to the user afterwards - operator>> and non-strict sax_parse -
call this once when scanning is done, so that the input is positioned
right after the value.
Adapters without lookahead (see input_adapter_supports_lookahead) are not
handed back to the user, so this is a no-op for them. Without
JSON_PRECISE_STREAM_POSITION, no adapter has lookahead, so this is always a
no-op and the terminating character stays consumed.
Scanning may continue after this call: @a next_unget is cleared, and the
character is read from the input again instead of being replayed from
@a current. A pending unget of EOF needs no special case, because reaching
EOF leaves no lookahead to release.
*/
void release_lookahead()
{
release_lookahead_impl(std::integral_constant<bool, can_release_lookahead> {});
}
#if JSON_DIAGNOSTIC_POSITIONS
/// return the offset of the first character of the last read token; unlike
/// the token's parsed value, this accounts for escape sequences
@@ -15960,13 +16118,22 @@ class parser
json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
// in strict mode, input must be completely read
if (strict && (get_token() != token_type::end_of_input))
if (strict)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
@@ -15988,12 +16155,20 @@ class parser
json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
// in strict mode, input must be completely read
if (strict && (get_token() != token_type::end_of_input))
if (strict)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// see above
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
@@ -16026,12 +16201,24 @@ class parser
(void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
const bool result = sax_parse_internal(sax);
// strict mode: next byte must be EOF
if (result && strict && (get_token() != token_type::end_of_input))
if (result)
{
return sax->parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
if (strict)
{
// strict mode: next byte must be EOF
if (get_token() != token_type::end_of_input)
{
return sax->parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
}
return result;
@@ -30765,6 +30952,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
#undef JSON_HAS_STATIC_RTTI
#undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
#undef JSON_BRACE_INIT_COPY_SEMANTICS
#undef JSON_PRECISE_STREAM_POSITION
#endif
// #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

19
single_include/nlohmann/json_fwd.hpp
View File

@@ -56,6 +56,10 @@
#define JSON_BRACE_INIT_COPY_SEMANTICS 0
#endif
#ifndef JSON_PRECISE_STREAM_POSITION
#define JSON_PRECISE_STREAM_POSITION 0
#endif
#if JSON_DIAGNOSTICS
#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
#else
@@ -80,21 +84,28 @@
#define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
#endif
#if JSON_PRECISE_STREAM_POSITION
#define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION _psp
#else
#define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION
#endif
#ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
#define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
#endif
// Construct the namespace ABI tags component
#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
#define NLOHMANN_JSON_ABI_TAGS \
NLOHMANN_JSON_ABI_TAGS_CONCAT( \
NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS, \
NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS, \
NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS, \
NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION)
// Construct the namespace version component
#define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

4
tests/abi/config/default.cpp
View File

@@ -36,6 +36,10 @@ TEST_CASE("default namespace")
expected += "_bics";
#endif
#if JSON_PRECISE_STREAM_POSITION
expected += "_psp";
#endif
expected += "_v" STRINGIZE(NLOHMANN_JSON_VERSION_MAJOR);
expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_MINOR);
expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_PATCH) "::basic_json";

4
tests/abi/config/noversion.cpp
View File

@@ -37,6 +37,10 @@ TEST_CASE("default namespace without version component")
expected += "_bics";
#endif
#if JSON_PRECISE_STREAM_POSITION
expected += "_psp";
#endif
expected += "::basic_json";
// fallback for Clang

52
tests/src/unit-deserialization.cpp
View File

@@ -25,6 +25,7 @@ using nlohmann::json;
#include <iostream>
#include <iterator>
#include <sstream>
#include <string>
#include <valarray>
#if defined(_WIN32)
@@ -1233,6 +1234,57 @@ TEST_CASE("deserialization")
}
}
SECTION("stream position after extraction without JSON_PRECISE_STREAM_POSITION (#5340)")
{
// By default, the character that terminates a number is consumed, so
// the stream is left one byte too far after a number (and only after a
// number). JSON_PRECISE_STREAM_POSITION changes this; see
// unit-precise-stream-position.cpp. These checks pin the default.
const auto remaining = [](std::istream & is)
{
return std::string(std::istreambuf_iterator<char>(is), std::istreambuf_iterator<char>());
};
SECTION("the character after a number is consumed")
{
std::istringstream ss("1true");
json j;
ss >> j;
CHECK(j == 1);
CHECK(remaining(ss) == "rue");
}
SECTION("the character after other values is not consumed")
{
std::istringstream ss("[1]true");
json j;
ss >> j;
CHECK(j == json::parse("[1]"));
CHECK(remaining(ss) == "true");
}
SECTION("comma-separated numbers can be read one by one")
{
std::istringstream ss("1,2,3");
json j1, j2, j3;
ss >> j1 >> j2 >> j3;
CHECK(j1 == 1);
CHECK(j2 == 2);
CHECK(j3 == 3);
}
SECTION("std::getline after a number skips the line break")
{
std::istringstream ss("42\nfoo");
json j;
std::string line;
ss >> j;
std::getline(ss, line);
CHECK(j == 42);
CHECK(line == "foo");
}
}
// build with C++20
// JSON_HAS_CPP_20
#if defined(__cpp_char8_t)

237
tests/src/unit-precise-stream-position.cpp Normal file
View File

@@ -0,0 +1,237 @@
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
#include "doctest_compatibility.h"
// This file tests the opt-in JSON_PRECISE_STREAM_POSITION, so it defines the
// macro itself rather than relying on a -D flag, and runs in every build. The
// default behavior is pinned in unit-deserialization.cpp.
#ifdef JSON_PRECISE_STREAM_POSITION
#undef JSON_PRECISE_STREAM_POSITION
#endif
#define JSON_PRECISE_STREAM_POSITION 1
#include <nlohmann/json.hpp>
using nlohmann::json;
#include <cstddef>
#include <sstream>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#define STRINGIZE_EX(x) #x
#define STRINGIZE(x) STRINGIZE_EX(x)
namespace
{
// A streambuf that keeps no get area at all and refuses every putback: with an
// empty get area, sungetc() always ends up in pbackfail(). Used to check that
// the character terminating a number is left in the input without relying on
// the streambuf being able to put a consumed character back.
class no_putback_streambuf : public std::streambuf
{
public:
explicit no_putback_streambuf(std::string s) : m_data(std::move(s)) {}
protected:
// peek at the next character without consuming it
int_type underflow() override
{
if (m_pos >= m_data.size())
{
return traits_type::eof();
}
return traits_type::to_int_type(m_data[m_pos]);
}
// consume the next character
int_type uflow() override
{
if (m_pos >= m_data.size())
{
return traits_type::eof();
}
return traits_type::to_int_type(m_data[m_pos++]);
}
int_type pbackfail(int_type /*c*/) override
{
return traits_type::eof();
}
private:
std::string m_data;
std::size_t m_pos = 0;
};
// read the characters that are left in a stream
std::string remaining(std::istream& is)
{
std::string result;
char c = 0;
while (is.get(c))
{
result += c;
}
return result;
}
} // namespace
TEST_CASE("JSON_PRECISE_STREAM_POSITION")
{
SECTION("the macro is part of the ABI tag")
{
const std::string ns = STRINGIZE(NLOHMANN_JSON_NAMESPACE);
// other tags may come before it, e.g. json_abi_diag_psp
CHECK(ns.find("_psp") != std::string::npos);
}
SECTION("a number does not consume the character that terminates it")
{
// a number is only terminated by the character following it; that
// character must be given back so the stream is positioned right
// after the value
const std::vector<std::pair<std::string, std::string>> tests =
{
{"1true", "true"},
{"1[2]", "[2]"},
{"1{}", "{}"},
{R"(1"a")", R"("a")"},
{"1 true", " true"},
{"12,", ","},
{"-0.5e3x", "x"},
{"1null", "null"}
};
for (const auto& test : tests)
{
CAPTURE(test.first);
std::istringstream ss(test.first);
json j;
ss >> j;
CHECK(j == json::parse(test.first.substr(0, test.first.size() - test.second.size())));
CHECK(remaining(ss) == test.second);
}
}
SECTION("values that are self-delimiting are unaffected")
{
const std::vector<std::pair<std::string, std::string>> tests =
{
{"truefalse", "false"},
{"[1][2]", "[2]"},
{R"({"a":1}{"b":2})", R"({"b":2})"},
{R"("a""b")", R"("b")"},
{"null null", " null"}
};
for (const auto& test : tests)
{
CAPTURE(test.first);
std::istringstream ss(test.first);
json j;
ss >> j;
CHECK(remaining(ss) == test.second);
}
}
SECTION("a number at the end of the input leaves nothing behind")
{
for (const std::string s :
{"1", "12", "-3.5e2", " 7 "
})
{
CAPTURE(s);
std::istringstream ss(s);
json j;
ss >> j;
CHECK(remaining(ss).find_first_not_of(" \t\n\r") == std::string::npos);
}
}
SECTION("repeated extraction of concatenated values")
{
std::istringstream ss(R"(1true[2]3"x"{"a":4}5)");
const std::vector<json> expected =
{
json(1), json(true), json::parse("[2]"), json(3),
json("x"), json::parse(R"({"a":4})"), json(5)
};
for (const auto& e : expected)
{
json j;
ss >> j;
CHECK(j == e);
}
}
SECTION("differences to the default behavior")
{
// both of these work by accident without the macro, because the
// character after a number is swallowed; see unit-deserialization.cpp
SECTION("a separator after a number is not skipped")
{
std::istringstream ss("1,2");
json j;
ss >> j;
CHECK(j == 1);
CHECK_THROWS_AS(ss >> j, json::parse_error&);
}
SECTION("std::getline after a number sees the line break")
{
std::istringstream ss("42\nfoo");
json j;
std::string line;
ss >> j;
std::getline(ss, line);
CHECK(j == 42);
CHECK(line.empty());
std::getline(ss, line);
CHECK(line == "foo");
}
}
SECTION("sax_parse with strict == false")
{
std::istringstream ss("1true");
json j;
nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::input_stream_adapter> sdp(j, true);
CHECK(json::sax_parse(ss, &sdp, nlohmann::detail::input_format_t::json, false));
CHECK(j == 1);
CHECK(remaining(ss) == "true");
}
SECTION("strict parsing still rejects trailing data")
{
std::istringstream ss("1true");
json _;
CHECK_THROWS_WITH_AS(_ = json::parse(ss),
"[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - unexpected true literal; expected end of input", json::parse_error&);
std::istringstream ss2("1true");
CHECK_FALSE(json::accept(ss2));
}
SECTION("a streambuf that cannot put back is not needed")
{
// the terminating character is never consumed, so no putback
// position is required
no_putback_streambuf buf("1true");
std::istream is(&buf);
json j;
is >> j;
CHECK(j == json(1));
CHECK(remaining(is) == "true");
}
}

2
tools/generate_natvis/generate_natvis.py
View File

@@ -20,7 +20,7 @@ if __name__ == '__main__':
namespaces = ['nlohmann']
abi_prefix = 'json_abi'
abi_tags = ['_diag', '_ldvcmp', '_dp', '_bics']
abi_tags = ['_diag', '_ldvcmp', '_dp', '_bics', '_psp']
version = '_v' + args.version.replace('.', '_')
inline_namespaces = []