/*
  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * FFmpeg 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 

 #include "config.h"

 #include "common.h"

 #include "bswap.h"

 #include "crc.h"
 

 #if CONFIG_HARDCODED_TABLES

 #include "crc_data.h"

 #else

 static struct {
     uint8_t  le;
     uint8_t  bits;
     uint32_t poly;
 } av_crc_table_params[AV_CRC_MAX] = {
     [AV_CRC_8_ATM]      = { 0,  8,       0x07 },
     [AV_CRC_16_ANSI]    = { 0, 16,     0x8005 },
     [AV_CRC_16_CCITT]   = { 0, 16,     0x1021 },
     [AV_CRC_32_IEEE]    = { 0, 32, 0x04C11DB7 },
     [AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
 };
 static AVCRC av_crc_table[AV_CRC_MAX][257];

 #endif

 
 /**

  * Initialize a CRC table.

  * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
  * @param le If 1, the lowest bit represents the coefficient for the highest
  *           exponent of the corresponding polynomial (both for poly and
  *           actual CRC).
  *           If 0, you must swap the CRC parameter and the result of av_crc

  *           if you need the standard representation (can be simplified in
  *           most cases to e.g. bswap16):

  *           av_bswap32(crc << (32-bits))

  * @param bits number of bits for the CRC
  * @param poly generator polynomial without the x**bits coefficient, in the
  *             representation as specified by le

  * @param ctx_size size of ctx in bytes

  * @return <0 on failure
  */

 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
 {

     unsigned i, j;

     uint32_t c;
 

     if (bits < 8 || bits > 32 || poly >= (1LL << bits))

         return -1;

     if (ctx_size != sizeof(AVCRC) * 257 && ctx_size != sizeof(AVCRC) * 1024)

         return -1;
 
     for (i = 0; i < 256; i++) {
         if (le) {
             for (c = i, j = 0; j < 8; j++)

                 c = (c >> 1) ^ (poly & (-(c & 1)));

             ctx[i] = c;
         } else {
             for (c = i << 24, j = 0; j < 8; j++)

                 c = (c << 1) ^ ((poly << (32 - bits)) & (((int32_t) c) >> 31));

             ctx[i] = av_bswap32(c);

         }
     }

     ctx[256] = 1;

 #if !CONFIG_SMALL

     if (ctx_size >= sizeof(AVCRC) * 1024)

         for (i = 0; i < 256; i++)

             for (j = 0; j < 3; j++)
                 ctx[256 *(j + 1) + i] =
                     (ctx[256 * j + i] >> 8) ^ ctx[ctx[256 * j + i] & 0xFF];

 #endif

 
     return 0;
 }
 

 /**

  * Get an initialized standard CRC table.

  * @param crc_id ID of a standard CRC
  * @return a pointer to the CRC table or NULL on failure
  */

 const AVCRC *av_crc_get_table(AVCRCId crc_id)
 {

 #if !CONFIG_HARDCODED_TABLES

     if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id]) - 1])

         if (av_crc_init(av_crc_table[crc_id],
                         av_crc_table_params[crc_id].le,
                         av_crc_table_params[crc_id].bits,
                         av_crc_table_params[crc_id].poly,
                         sizeof(av_crc_table[crc_id])) < 0)
             return NULL;
 #endif
     return av_crc_table[crc_id];
 }
 
 /**

  * Calculate the CRC of a block.

  * @param crc CRC of previous blocks if any or initial value for CRC

  * @return CRC updated with the data from the given block
  *
  * @see av_crc_init() "le" parameter
  */

 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
                 const uint8_t *buffer, size_t length)
 {
     const uint8_t *end = buffer + length;

 #if !CONFIG_SMALL

     if (!ctx[256]) {
         while (((intptr_t) buffer & 3) && buffer < end)
             crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8);

         while (buffer < end - 3) {
             crc ^= av_le2ne32(*(const uint32_t *) buffer); buffer += 4;
             crc = ctx[3 * 256 + ( crc        & 0xFF)] ^
                   ctx[2 * 256 + ((crc >> 8 ) & 0xFF)] ^
                   ctx[1 * 256 + ((crc >> 16) & 0xFF)] ^
                   ctx[0 * 256 + ((crc >> 24)       )];

         }

     }

 #endif

     while (buffer < end)
         crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8);

 
     return crc;
 }
 
 #ifdef TEST
 #undef printf

 int main(void)
 {

     uint8_t buf[1999];
     int i;

     int p[4][3] = { { AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04 },
                     { AV_CRC_32_IEEE   , 0x04C11DB7, 0xC0F5BAE0 },
                     { AV_CRC_16_ANSI   , 0x8005    , 0x1FBB     },
                     { AV_CRC_8_ATM     , 0x07      , 0xE3       }
     };

     const AVCRC *ctx;

     for (i = 0; i < sizeof(buf); i++)
         buf[i] = i + i * i;

     for (i = 0; i < 4; i++) {

         ctx = av_crc_get_table(p[i][0]);

         printf("crc %08X = %X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));

     }

     return 0;

 }
 #endif