Commit db2c9308 authored by Eli Zaretskii's avatar Eli Zaretskii

Speed up JSON parsing

Thanks to Dmitry Gutov <> for running many
benchmarks and for useful discussions.
* src/json.c (json_make_string): Speed up parsing of JSON
strings by optimizing the normal case of a valid UTF-8 string
being returned from libjansson.  (Bug#31138)
parent b59429a4
Pipeline #1421 passed with stage
in 53 minutes and 11 seconds
......@@ -217,7 +217,8 @@ json_has_suffix (const char *string, const char *suffix)
/* Create a multibyte Lisp string from the UTF-8 string in
[DATA, DATA + SIZE). If the range [DATA, DATA + SIZE) does not
contain a valid UTF-8 string, an unspecified string is returned.
contain a valid UTF-8 string, the returned string will include raw
Note that all callers below either pass only value UTF-8 strings or
use this function for formatting error messages; in the latter case
correctness isn't critical. */
......@@ -225,8 +226,21 @@ json_has_suffix (const char *string, const char *suffix)
static Lisp_Object
json_make_string (const char *data, ptrdiff_t size)
return code_convert_string (make_specified_string (data, -1, size, false),
Qutf_8_unix, Qt, false, true, true);
ptrdiff_t chars, bytes;
parse_str_as_multibyte ((const unsigned char *) data, size, &chars, &bytes);
/* If DATA is a valid UTF-8 string, we can convert it to a Lisp
string directly. Otherwise, we need to decode it. */
if (chars == size || bytes == size)
return make_specified_string (data, chars, size, true);
struct coding_system coding;
setup_coding_system (Qutf_8_unix, &coding);
coding.mode |= CODING_MODE_LAST_BLOCK;
coding.source = data;
decode_coding_object (&coding, Qnil, 0, 0, size, size, Qt);
return coding.dst_object;
/* Create a multibyte Lisp string from the NUL-terminated UTF-8
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