/* sha1.c - Interfaces to SHA-1 hash for the notmuch mail system
 *
 * Copyright © 2009 Carl Worth
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see http://www.gnu.org/licenses/ .
 *
 * Author: Carl Worth <cworth@cworth.org>
 */

#include "notmuch-private.h"

#include <gcrypt.h>

/* Just some simple interfaces on top of libgcrypt */

static char *
_hex_of_sha1_digest (gcry_md_hd_t c)
{
    char *result, *r;
    unsigned char *digest;
    int i;
    int digest_size;

    digest_size = gcry_md_get_algo_dlen(gcry_md_get_algo(c));
    digest = gcry_md_read(c, 0);
    result = xcalloc (digest_size * 2 + 1, 1);

    for (r = result, i = 0;
	 i < digest_size;
	 r += 2, i++)
    {
	sprintf (r, "%02x", digest[i]);
    }

    return result;
}

/* Create a hexadecimal string version of the SHA-1 digest of 'str'
 * (including its null terminating character).
 *
 * This function returns a newly allocated string which the caller
 * should free() when finished.
 */
char *
notmuch_sha1_of_string (const char *str)
{
    char *result;
    gcry_md_hd_t c;

    gcry_md_open (&c, GCRY_MD_SHA1, 0);
    gcry_md_write (c, str, strlen (str) + 1);
    gcry_md_final (c);
    result = _hex_of_sha1_digest (c);
    gcry_md_close (c);

    return result;
}

/* Create a hexadecimal string version of the SHA-1 digest of the
 * contents of the named file.
 *
 * This function returns a newly allocated string which the caller
 * should free() when finished.
 *
 * If any error occurs while reading the file, (permission denied,
 * file not found, etc.), this function returns NULL.
 */
char *
notmuch_sha1_of_file (const char *filename)
{
    FILE *file;
#define BLOCK_SIZE 4096
    unsigned char block[BLOCK_SIZE];
    size_t bytes_read;
    gcry_md_hd_t c;
    char *result;

    file = fopen (filename, "r");
    if (file == NULL)
	return NULL;

    gcry_md_open(&c, GCRY_MD_SHA1, 0);

    while (1) {
	bytes_read = fread (block, 1, 4096, file);
	if (bytes_read == 0) {
	    if (feof (file)) {
		break;
	    } else if (ferror (file)) {
		fclose (file);
		return NULL;
	    }
	} else {
	    gcry_md_write (c, block, bytes_read);
	}
    }

    gcry_md_final (c);

    result = _hex_of_sha1_digest (c);

    gcry_md_close (c);

    fclose (file);

    return result;
}