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// by jeremie miller - 2014
// public domain or MIT license, contributions/improvements welcome via github at https://github.com/quartzjer/js0n
#include <string.h> // one strncmp() is used to do key comparison, and a strlen(key) if no len passed in
// gcc started warning for the init syntax used here, is not helpful so don't generate the spam, suppressing the warning is really inconsistently supported across versions
#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
#pragma GCC diagnostic push
#endif
#pragma GCC diagnostic ignored "-Wunknown-pragmas"
#pragma GCC diagnostic ignored "-Wpragmas"
#pragma GCC diagnostic ignored "-Winitializer-overrides"
#pragma GCC diagnostic ignored "-Woverride-init"
// only at depth 1, track start pointers to match key/value
#define PUSH(i) if(depth == 1) { if(!index) { val = cur+i; }else{ if(klen && index == 1) start = cur+i; else index--; } }
// determine if key matches or value is complete
#define CAP(i) if(depth == 1) { if(val && !index) {*vlen = (size_t)((cur+i+1) - val); return val;}; if(klen && start) {index = (klen == (size_t)(cur-start) && strncmp(key,start,klen)==0) ? 0 : 2; start = 0;} }
// this makes a single pass across the json bytes, using each byte as an index into a jump table to build an index and transition state
const char *js0n(const char *key, size_t klen,
const char *json, size_t jlen, size_t *vlen)
{
const char *val = 0;
const char *cur, *end, *start;
size_t index = 1;
int depth = 0;
int utf8_remain = 0;
static void *gostruct[] =
{
[0 ... 255] = &&l_bad,
['\t'] = &&l_loop, [' '] = &&l_loop, ['\r'] = &&l_loop, ['\n'] = &&l_loop,
['"'] = &&l_qup,
[':'] = &&l_loop,[','] = &&l_loop,
['['] = &&l_up, [']'] = &&l_down, // tracking [] and {} individually would allow fuller validation but is really messy
['{'] = &&l_up, ['}'] = &&l_down,
['-'] = &&l_bare, [48 ... 57] = &&l_bare, // 0-9
[65 ... 90] = &&l_bare, // A-Z
[97 ... 122] = &&l_bare // a-z
};
static void *gobare[] =
{
[0 ... 31] = &&l_bad,
[32 ... 126] = &&l_loop, // could be more pedantic/validation-checking
['\t'] = &&l_unbare, [' '] = &&l_unbare, ['\r'] = &&l_unbare, ['\n'] = &&l_unbare,
[','] = &&l_unbare, [']'] = &&l_unbare, ['}'] = &&l_unbare, [':'] = &&l_unbare,
[127 ... 255] = &&l_bad
};
static void *gostring[] =
{
[0 ... 31] = &&l_bad, [127] = &&l_bad,
[32 ... 126] = &&l_loop,
['\\'] = &&l_esc, ['"'] = &&l_qdown,
[128 ... 191] = &&l_bad,
[192 ... 223] = &&l_utf8_2,
[224 ... 239] = &&l_utf8_3,
[240 ... 247] = &&l_utf8_4,
[248 ... 255] = &&l_bad
};
static void *goutf8_continue[] =
{
[0 ... 127] = &&l_bad,
[128 ... 191] = &&l_utf_continue,
[192 ... 255] = &&l_bad
};
static void *goesc[] =
{
[0 ... 255] = &&l_bad,
['"'] = &&l_unesc, ['\\'] = &&l_unesc, ['/'] = &&l_unesc, ['b'] = &&l_unesc,
['f'] = &&l_unesc, ['n'] = &&l_unesc, ['r'] = &&l_unesc, ['t'] = &&l_unesc, ['u'] = &&l_unesc
};
void **go = gostruct;
if(!json || jlen <= 0 || !vlen) return 0;
*vlen = 0;
// no key is array mode, klen provides requested index
if(!key)
{
index = klen;
klen = 0;
}else{
if(klen <= 0) klen = strlen(key); // convenience
}
for(start=cur=json,end=cur+jlen; cur<end; cur++)
{
goto *go[(unsigned char)*cur];
l_loop:;
}
if(depth) *vlen = jlen; // incomplete
return 0;
l_bad:
*vlen = cur - json; // where error'd
return 0;
l_up:
PUSH(0);
++depth;
goto l_loop;
l_down:
--depth;
CAP(0);
goto l_loop;
l_qup:
PUSH(1);
go=gostring;
goto l_loop;
l_qdown:
CAP(-1);
go=gostruct;
goto l_loop;
l_esc:
go = goesc;
goto l_loop;
l_unesc:
go = gostring;
goto l_loop;
l_bare:
PUSH(0);
go = gobare;
goto l_loop;
l_unbare:
CAP(-1);
go = gostruct;
goto *go[(unsigned char)*cur];
l_utf8_2:
go = goutf8_continue;
utf8_remain = 1;
goto l_loop;
l_utf8_3:
go = goutf8_continue;
utf8_remain = 2;
goto l_loop;
l_utf8_4:
go = goutf8_continue;
utf8_remain = 3;
goto l_loop;
l_utf_continue:
if (!--utf8_remain)
go=gostring;
goto l_loop;
}
#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
#pragma GCC diagnostic pop
#endif
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