Function extract_json_field

src/cli/progress_sink.c:95–154

Extract one string field from the logger's compact JSON format. Keys are * accepted only at object boundaries so worker-controlled values cannot spoof * a progress event by merely containing a key-shaped substring. */

 * accepted only at object boundaries so worker-controlled values cannot spoof
 * a progress event by merely containing a key-shaped substring. */
static const char *extract_json_field(const char *line, const char *key, char *buf, int buf_len) {
    char needle[CBM_SZ_64];
    int needle_len = snprintf(needle, sizeof(needle), "\"%s\":", key);
    if (needle_len <= 0 || needle_len >= (int)sizeof(needle)) {
        return NULL;
    }
    const char *candidate = line;
    while ((candidate = strstr(candidate, needle)) != NULL) {
        const char *before = candidate;
        while (before > line && (before[-1] == ' ' || before[-1] == '\t')) {
            before--;
        }
        if (before == line || (before[-1] != '{' && before[-1] != ',')) {
            candidate += needle_len;
            continue;
        }
        const char *value = candidate + needle_len;
        while (*value == ' ' || *value == '\t') {
            value++;
        }
        if (*value++ != '\"') {
            return NULL;
        }
        int offset = 0;
        bool escaped = false;
        while (*value && offset < buf_len - 1) {
            if (!escaped && *value == '\"') {
                buf[offset] = '\0';
                return buf;
            }
            if (!escaped && *value == '\\') {
                escaped = true;
                value++;
                continue;
            }
            if (escaped) {
                switch (*value) {
                case 'n':
                    buf[offset++] = '\n';
                    break;
                case 'r':
                    buf[offset++] = '\r';
                    break;
                case 't':
                    buf[offset++] = '\t';
                    break;
                default:
                    buf[offset++] = *value;
                    break;
                }
                escaped = false;
            } else {
                buf[offset++] = *value;
            }
            value++;
        }
        return NULL;
    }