A function to stringify the newline character.

stringify_newline.c

/** @brief Stringify the newline character of a string.
 *
 * In detail, the newline character, '\n' is not supported on
 * json string, so it needs to split in two characters "\n".
 *
 * @param [in] src The string to stringify
 * @return the stringified string on success<br>
 *         NULL otherwise
 *
 */
static char *
stringify_newline (char *src)
{
    char *dst, *str;
    size_t count_newline = 0;
    size_t src_sz, dst_sz, i, j;

    if (!src)
        return NULL;

    src_sz = strlen (src);

    /* count newline characters */
    for (str = src; *str != '\0'; str++)
        if (*str == '\n') count_newline++;

    dst_sz = src_sz + count_newline + 1;
    dst = malloc (dst_sz);
    if (!dst)
        return NULL;

    for (i = 0, j = 0; i < src_sz; i++) {
        if (src[i] == '\n') {
            dst[j++] = '\\';
            dst[j++] = 'n';
        } else
            dst[j++] = src[i];
    }
    dst[j] = '\0';

    return dst;

}