Function append_json_string

src/pipeline/pass_definitions.c:175–199

Appends are ATOMIC: a field is emitted only if the WHOLE serialized form * fits (with PD_ESC_SPACE bytes reserved for the closing '}' + NUL). Cutting a * field mid-value produced unterminated strings/arrays — malformed properties * JSON that aborts every json_extract()-based consumer downstream (seen on the * Linux kernel: 50-param functions truncated at the 2 KB cap). Dropping an * oversized

 * Linux kernel: 50-param functions truncated at the 2 KB cap). Dropping an
 * oversized optional field whole keeps the JSON valid. */
static void append_json_string(char *buf, size_t bufsize, size_t *pos, const char *key,
                               const char *val) {
    if (!val || val[0] == '\0') {
        return;
    }
    /* ,"key":"<escaped>" — comma + 2 key quotes + colon + 2 value quotes */
    size_t required = strlen(key) + def_json_escaped_len(val) + PD_JSON_FIELD_OVERHEAD;
    if (*pos + required + PD_ESC_SPACE > bufsize) {
        return; /* whole field would not fit — skip it atomically */
    }
    size_t p = *pos;
    int w = snprintf(buf + p, bufsize - p, ",\"%s\":\"", key);
    if (w <= 0 || (size_t)w >= bufsize - p) {
        return;
    }
    p += (size_t)w;
    for (const char *s = val; *s && p < bufsize - PD_ESC_MARGIN; s++) {
        p += (size_t)def_json_escape_char(buf + p, bufsize - p - PD_ESC_SPACE, *s);
    }
    if (p < bufsize - SKIP_ONE) {
        buf[p++] = '"';
    }
    buf[p] = '\0';
    *pos = p;
}

/* Append a JSON array of strings: ,"key":["a","b","c"]. Atomic like
 * append_json_string: emitted only if the whole array fits. */