glib & g_checksum_*

Though I am a glib fan, I really cannot use the g_checksum_* functions to obtain an MD5 string that is compatible with the md5sum command.

Code:

---

gchar *get_hash(const gchar *filepath) {
        FILE *fp;
        if (NULL != (fp = fopen(filepath, "r+b"))) {
                guchar buffer[65536];
                gint read_bytes;
                gchar *result;
                GChecksum *checksum = g_checksum_new(hash_type);
                while ((read_bytes = fread(buffer, sizeof(buffer), 1, fp)) > 0)
                        g_checksum_update(checksum, buffer, read_bytes);

                fclose(fp);
                result = (gchar *) g_checksum_get_string(checksum);
                g_checksum_free(checksum);
                return result;
        }
        return "";
}

---

Any idea on what is wrong with this code?
Thanks in advance for any help and or suggestion

I would say you need to make a COPY of the string returned by g_checksum_get_string(), before you call g_checksum_free()

Yes, you are right.

Code:

---

gchar *get_hash(const gchar *filepath, GChecksumType hash_type) {
    FILE *fp;
    if (NULL != (fp = fopen(filepath, "r+b"))) {
        guchar buffer[65536];
        gint read_bytes;
        gchar *result;
        GChecksum *checksum = g_checksum_new(hash_type);
        while ((read_bytes = fread(buffer, sizeof(buffer), 1, fp)) > 0)
            g_checksum_update(checksum, buffer, read_bytes);

        fclose(fp);
        result = g_strdup((gchar *) g_checksum_get_string(checksum));
        g_checksum_free(checksum);
        return result;
    }
    return g_strdup("");
}

---

Unfortunately, the returned array contains a different hash value from that returned by md5sum

Your fread parameters are the wrong way round.

That is, if you're wanting to return the number of bytes, as opposed to the number of buffers.

** Thank you so much!!

Code:

---

gchar *get_hash(const gchar *filepath, GChecksumType hash_type) {
        FILE *fp;
        if (NULL != (fp = fopen(filepath, "rb"))) {
                guchar buffer[65536];
                gint read_bytes;
                gchar *result;
                GChecksum *checksum = g_checksum_new(hash_type);
                while ((read_bytes = fread(buffer, 1, sizeof(buffer), fp)) > 0)
                        g_checksum_update(checksum, buffer, read_bytes);

                result = g_strdup((gchar *) g_checksum_get_string(checksum));

                fclose(fp);
                g_checksum_free(checksum);

                return result;
        }
        return g_strdup("");
}

---

> guchar buffer[65536];
If you're stuck for choosing a buffer size, then the macro BUFSIZ (in stdio.h) is a good alternative.

> result = g_strdup((gchar *) g_checksum_get_string(checksum));
I can't see how this cast was necessary.