/*
 *  Copyright (C) 2009 Gabor Juhos <juhosg@openwrt.org>
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 2 as published
 *  by the Free Software Foundation.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>     /* for unlink() */
#include <libgen.h>
#include <getopt.h>     /* for getopt() */
#include <stdarg.h>
#include <errno.h>
#include <sys/stat.h>

#if (__BYTE_ORDER == __LITTLE_ENDIAN)
#  define HOST_TO_LE16(x)	(x)
#  define HOST_TO_LE32(x)	(x)
#  define LE16_TO_HOST(x)	(x)
#  define LE32_TO_HOST(x)	(x)
#else
#  define HOST_TO_LE16(x)	bswap_16(x)
#  define HOST_TO_LE32(x)	bswap_32(x)
#  define LE16_TO_HOST(x)	bswap_16(x)
#  define LE32_TO_HOST(x)	bswap_32(x)
#endif

uint32_t crc32buf(char *buf, size_t len);

/*
 * Globals
 */
static char *ifname;
static char *progname;
static char *ofname;

/*
 * Message macros
 */
#define ERR(fmt, ...) do { \
	fflush(0); \
	fprintf(stderr, "[%s] *** error: " fmt "\n", \
			progname, ## __VA_ARGS__ ); \
} while (0)

#define ERRS(fmt, ...) do { \
	int save = errno; \
	fflush(0); \
	fprintf(stderr, "[%s] *** error: " fmt "\n", \
			progname, ## __VA_ARGS__, strerror(save)); \
} while (0)

void usage(int status)
{
	FILE *stream = (status != EXIT_SUCCESS) ? stderr : stdout;
	struct board_info *board;

	fprintf(stream, "Usage: %s [OPTIONS...]\n", progname);
	fprintf(stream,
"\n"
"Options:\n"
"  -i <file>       read input from the file <file>\n"
"  -o <file>       write output to the file <file>\n"
"  -h              show this screen\n"
	);

	exit(status);
}

int main(int argc, char *argv[])
{
	int res = EXIT_FAILURE;
	int buflen;
	int err;
	struct stat st;
	char *buf;
	uint32_t *hdr;
	uint32_t crc;

	FILE *outfile, *infile;

	progname = basename(argv[0]);

	while ( 1 ) {
		int c;

		c = getopt(argc, argv, "i:o:h");
		if (c == -1)
			break;

		switch (c) {
		case 'i':
			ifname = optarg;
			break;
		case 'o':
			ofname = optarg;
			break;
		case 'h':
			usage(EXIT_SUCCESS);
			break;
		default:
			usage(EXIT_FAILURE);
			break;
		}
	}

	if (ifname == NULL) {
		ERR("no input file specified");
		goto err;
	}

	if (ofname == NULL) {
		ERR("no output file specified");
		goto err;
	}

	err = stat(ifname, &st);
	if (err){
		ERRS("stat failed on %s", ifname);
		goto err;
	}

	buflen = st.st_size;
	buf = malloc(buflen);
	if (!buf) {
		ERR("no memory for buffer\n");
		goto err;
	}

	infile = fopen(ifname, "r");
	if (infile == NULL) {
		ERRS("could not open \"%s\" for reading", ifname);
		goto err_free;
	}

	errno = 0;
	fread(buf, buflen, 1, infile);
	if (errno != 0) {
		ERRS("unable to read from file %s", ifname);
		goto err_close_in;
	}

	crc = crc32buf(buf, buflen);
	hdr = (uint32_t *)buf;
	*hdr = HOST_TO_LE32(crc);

	outfile = fopen(ofname, "w");
	if (outfile == NULL) {
		ERRS("could not open \"%s\" for writing", ofname);
		goto err_close_in;
	}

	errno = 0;
	fwrite(buf, buflen, 1, outfile);
	if (errno) {
		ERRS("unable to write to file %s", ofname);
		goto err_close_out;
	}

	res = EXIT_SUCCESS;

 out_flush:
	fflush(outfile);

 err_close_out:
	fclose(outfile);
	if (res != EXIT_SUCCESS) {
		unlink(ofname);
	}

 err_close_in:
	fclose(infile);

 err_free:
	free(buf);

 err:
	return res;
}

/**********************************************************************/
/* The following was grabbed and tweaked from the old snippets collection
 * of public domain C code. */

/**********************************************************************\
|* Demonstration program to compute the 32-bit CRC used as the frame  *|
|* check sequence in ADCCP (ANSI X3.66, also known as FIPS PUB 71     *|
|* and FED-STD-1003, the U.S. versions of CCITT's X.25 link-level     *|
|* protocol).  The 32-bit FCS was added via the Federal Register,     *|
|* 1 June 1982, p.23798.  I presume but don't know for certain that   *|
|* this polynomial is or will be included in CCITT V.41, which        *|
|* defines the 16-bit CRC (often called CRC-CCITT) polynomial.  FIPS  *|
|* PUB 78 says that the 32-bit FCS reduces otherwise undetected       *|
|* errors by a factor of 10^-5 over 16-bit FCS.                       *|
\**********************************************************************/

/* Copyright (C) 1986 Gary S. Brown.  You may use this program, or
   code or tables extracted from it, as desired without restriction.*/

/* First, the polynomial itself and its table of feedback terms.  The  */
/* polynomial is                                                       */
/* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
/* Note that we take it "backwards" and put the highest-order term in  */
/* the lowest-order bit.  The X^32 term is "implied"; the LSB is the   */
/* X^31 term, etc.  The X^0 term (usually shown as "+1") results in    */
/* the MSB being 1.                                                    */

/* Note that the usual hardware shift register implementation, which   */
/* is what we're using (we're merely optimizing it by doing eight-bit  */
/* chunks at a time) shifts bits into the lowest-order term.  In our   */
/* implementation, that means shifting towards the right.  Why do we   */
/* do it this way?  Because the calculated CRC must be transmitted in  */
/* order from highest-order term to lowest-order term.  UARTs transmit */
/* characters in order from LSB to MSB.  By storing the CRC this way,  */
/* we hand it to the UART in the order low-byte to high-byte; the UART */
/* sends each low-bit to hight-bit; and the result is transmission bit */
/* by bit from highest- to lowest-order term without requiring any bit */
/* shuffling on our part.  Reception works similarly.                  */

/* The feedback terms table consists of 256, 32-bit entries.  Notes:   */
/*                                                                     */
/*  1. The table can be generated at runtime if desired; code to do so */
/*     is shown later.  It might not be obvious, but the feedback      */
/*     terms simply represent the results of eight shift/xor opera-    */
/*     tions for all combinations of data and CRC register values.     */
/*                                                                     */
/*  2. The CRC accumulation logic is the same for all CRC polynomials, */
/*     be they sixteen or thirty-two bits wide.  You simply choose the */
/*     appropriate table.  Alternatively, because the table can be     */
/*     generated at runtime, you can start by generating the table for */
/*     the polynomial in question and use exactly the same "updcrc",   */
/*     if your application needn't simultaneously handle two CRC       */
/*     polynomials.  (Note, however, that XMODEM is strange.)          */
/*                                                                     */
/*  3. For 16-bit CRCs, the table entries need be only 16 bits wide;   */
/*     of course, 32-bit entries work OK if the high 16 bits are zero. */
/*                                                                     */
/*  4. The values must be right-shifted by eight bits by the "updcrc"  */
/*     logic; the shift must be unsigned (bring in zeroes).  On some   */
/*     hardware you could probably optimize the shift in assembler by  */
/*     using byte-swap instructions.                                   */

static const uint32_t crc_32_tab[] = { /* CRC polynomial 0xedb88320 */
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

#define UPDC32(octet,crc) (crc_32_tab[((crc) ^ (octet)) & 0xff] ^ ((crc) >> 8))

uint32_t crc32buf(char *buf, size_t len)
{
      uint32_t crc;

      crc = 0xFFFFFFFF;

      for ( ; len; --len, ++buf)
      {
            crc = UPDC32(*buf, crc);
      }

      return crc ^ 0xFFFFFFFF;
}

