mbn96 / json-parser

Very low footprint JSON parser written in portable ANSI C

Very low footprint JSON parser written in portable C89 (sometimes referred to as ANSI C).

• BSD licensed with no dependencies (i.e. just drop the C file into your project)
• Never recurses or allocates more memory than it needs
• Very simple API with operator sugar for C++

Want to serialize? Check out json-builder!

Installing

There is now a makefile which will produce a libjsonparser static and dynamic library. However, this is not required to build json-parser, and the source files (json.c and json.h) should be happy in any build system you already have in place.

API

json_value * json_parse (const json_char * json,
                         size_t length);

json_value * json_parse_ex (json_settings * settings,
                            const json_char * json,
                            size_t length,
                            char * error);

void json_value_free (json_value *);

The type field of json_value is one of:

• json_object (see u.object.length, u.object.values[x].name, u.object.values[x].value)
• json_array (see u.array.length, u.array.values)
• json_integer (see u.integer)
• json_double (see u.dbl)
• json_string (see u.string.ptr, u.string.length)
• json_boolean (see u.boolean)
• json_null

Compile-Time Options

Unless otherwise specified, compile definitions must be provided both when compiling json.c and when compiling any of your own source files that include json.h.

JSON_TRACK_SOURCE

Stores the source location (line and column number) inside each json_value.

This is useful for application-level error reporting.

json_int_t

By default, json_int_t is defined as long under C89 and int_fast64_t otherwise. For MSVC it is defined as __int64 regardless of language standard support.

Optionally, you may define json_int_t to be your own preferred type name for integer types parsed from JSON documents. It must be a signed integer type, there is no support for unsigned types. If you specify a raw primitive type without signed or unsigned (and not a typdef), JSON_INT_MAX will be calculated for you. Otherwise, you must provide your own definition of JSON_INT_MAX as the highest positive integer value that can be represented by json_int_t.

Example usage:

• -Djson_int_t=short
• "-Djson_int_t=signed char" -DJSON_INT_MAX=127
• "-Djson_int_t=long long"
• -Djson_int_t=__int128

Runtime Options

settings |= json_enable_comments;

Enables C-style // line and /* block */ comments.

size_t value_extra

The amount of space (if any) to allocate at the end of each json_value, in order to give the application space to add metadata.

void * (* mem_alloc) (size_t, int zero, void * user_data);
void (* mem_free) (void *, void * user_data);

Custom allocator routines. If NULL, the default malloc and free will be used.

The user_data pointer will be forwarded from json_settings to allow application context to be passed.

Changes in version 1.1.0

• UTF-8 byte order marks are now skipped if present

• Allows cross-compilation by honoring --host if given (@wkz)

• Maximum size for error buffer is now exposed in header (@LB--)

• GCC warning for static after const fixed (@batrick)

• Optional support for C-style line and block comments added (@Jin-W-FS)

• name_length field added to object values

• It is now possible to retrieve the source line/column number of a parsed json_value when JSON_TRACK_SOURCE is enabled

• The application may now extend json_value using the value_extra setting

• Un-ambiguate pow call in the case of C++ overloaded pow (@fcartegnie)

• Fix null pointer de-reference when a non-existing array is closed and no root value is present