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// sj.h - v0.4 - rxi 2025
// public domain - no warranty implied, use at your own risk
#ifndef SJ_H
#define SJ_H
#include <stddef.h>
#include <stdbool.h>
typedef struct {
char *data, *cur, *end;
int depth;
char *error;
} sj_Reader;
typedef struct {
int type;
char *start, *end;
int depth;
} sj_Value;
enum { SJ_ERROR, SJ_END, SJ_ARRAY, SJ_OBJECT, SJ_NUMBER, SJ_STRING, SJ_BOOL, SJ_NULL };
sj_Reader sj_reader(char *data, size_t len);
sj_Value sj_read(sj_Reader *r);
bool sj_iter_array(sj_Reader *r, sj_Value arr, sj_Value *val);
bool sj_iter_object(sj_Reader *r, sj_Value obj, sj_Value *key, sj_Value *val);
void sj_location(sj_Reader *r, int *line, int *col);
#endif // #ifndef SJ_H
#ifdef SJ_IMPL
sj_Reader sj_reader(char *data, size_t len) {
return (sj_Reader){ .data = data, .cur = data, .end = data + len };
}
static bool sj__is_number_cont(char c) {
return (c >= '0' && c <= '9')
|| c == 'e' || c == 'E' || c == '.' || c == '-' || c == '+';
}
static bool sj__is_string(char *cur, char *end, char *expect) {
while (*expect) {
if (cur == end || *cur != *expect) {
return false;
}
expect++, cur++;
}
return true;
}
sj_Value sj_read(sj_Reader *r) {
sj_Value res;
top:
if (r->error) { return (sj_Value){ .type = SJ_ERROR, .start = r->cur, .end = r->cur }; }
if (r->cur == r->end) { r->error = "unexpected eof"; goto top; }
res.start = r->cur;
switch (*r->cur) {
case ' ': case '\n': case '\r': case '\t':
case ':': case ',':
r->cur++;
goto top;
case '-': case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
res.type = SJ_NUMBER;
while (r->cur != r->end && sj__is_number_cont(*r->cur)) { r->cur++; }
break;
case '"':
res.type = SJ_STRING;
res.start = ++r->cur;
for (;;) {
if ( r->cur == r->end) { r->error = "unclosed string"; goto top; }
if (*r->cur == '"') { break; }
if (*r->cur == '\\') { r->cur++; }
if ( r->cur != r->end) { r->cur++; }
}
res.end = r->cur++;
return res;
case '{': case '[':
res.type = (*r->cur == '{') ? SJ_OBJECT : SJ_ARRAY;
res.depth = ++r->depth;
r->cur++;
break;
case '}': case ']':
res.type = SJ_END;
if (--r->depth < 0) {
r->error = (*r->cur == '}') ? "stray '}'" : "stray ']'";
goto top;
}
r->cur++;
break;
case 'n': case 't': case 'f':
res.type = (*r->cur == 'n') ? SJ_NULL : SJ_BOOL;
if (sj__is_string(r->cur, r->end, "null")) { r->cur += 4; break; }
if (sj__is_string(r->cur, r->end, "true")) { r->cur += 4; break; }
if (sj__is_string(r->cur, r->end, "false")) { r->cur += 5; break; }
// fallthrough
default:
r->error = "unknown token";
goto top;
}
res.end = r->cur;
return res;
}
static void sj__discard_until(sj_Reader *r, int depth) {
sj_Value val;
val.type = SJ_NULL;
while (r->depth != depth && val.type != SJ_ERROR) {
val = sj_read(r);
}
}
bool sj_iter_array(sj_Reader *r, sj_Value arr, sj_Value *val) {
sj__discard_until(r, arr.depth);
*val = sj_read(r);
if (val->type == SJ_ERROR || val->type == SJ_END) { return false; }
return true;
}
bool sj_iter_object(sj_Reader *r, sj_Value obj, sj_Value *key, sj_Value *val) {
sj__discard_until(r, obj.depth);
*key = sj_read(r);
if (key->type == SJ_ERROR || key->type == SJ_END) { return false; }
*val = sj_read(r);
if (val->type == SJ_END) { r->error = "unexpected object end"; return false; }
if (val->type == SJ_ERROR) { return false; }
return true;
}
void sj_location(sj_Reader *r, int *line, int *col) {
int ln = 1, cl = 1;
for (char *p = r->data; p != r->cur; p++) {
if (*p == '\n') { ln++; cl = 0; }
cl++;
}
*line = ln;
*col = cl;
}
#endif // #ifdef SJ_IMPL
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