/*
  * Copyright (c) 2003 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 <stdio.h>

 #include <stdlib.h>

 #include <string.h>

 #include <inttypes.h>

 #include <assert.h>

 #define FFMIN(a,b) ((a) > (b) ? (b) : (a))

 #define F 100
 #define SIZE 2048
 

 uint64_t exp16_table[21]={

      65537,
      65538,
      65540,
      65544,
      65552,
      65568,
      65600,
      65664,
      65793,
      66050,
      66568,
      67616,
      69763,
      74262,
      84150,
     108051,
     178145,
     484249,
    3578144,
  195360063,

  582360139072LL,

 };

 
 #if 0

 // 16.16 fixpoint exp()
 static unsigned int exp16(unsigned int a){
     int i;
     int out= 1<<16;
 
     for(i=19;i>=0;i--){
         if(a&(1<<i))
             out= (out*exp16_table[i] + (1<<15))>>16;
     }

     return out;
 }

 #endif
 

 // 16.16 fixpoint log()

 static int64_t log16(uint64_t a){

     int i;
     int out=0;

 
     if(a < 1<<16)
         return -log16((1LL<<32) / a);

     a<<=16;

     for(i=20;i>=0;i--){

         int64_t b= exp16_table[i];
         if(a<(b<<16)) continue;

         out |= 1<<i;

         a = ((a/b)<<16) + (((a%b)<<16) + b/2)/b;

     }
     return out;
 }
 

 static uint64_t int_sqrt(uint64_t a)
 {
     uint64_t ret=0;
     int s;
     uint64_t ret_sq=0;
 
     for(s=31; s>=0; s--){
         uint64_t b= ret_sq + (1ULL<<(s*2)) + (ret<<s)*2;
         if(b<=a){
             ret_sq=b;
             ret+= 1ULL<<s;
         }
     }
     return ret;
 }
 
 int main(int argc,char* argv[]){
     int i, j;
     uint64_t sse=0;
     uint64_t dev;
     FILE *f[2];
     uint8_t buf[2][SIZE];

     uint64_t psnr;

     int len= argc<4 ? 1 : atoi(argv[3]);

     int64_t max= (1<<(8*len))-1;

     int shift= argc<5 ? 0 : atoi(argv[4]);

     int skip_bytes = argc<6 ? 0 : atoi(argv[5]);

     int size0=0;
     int size1=0;

     int maxdist = 0;

     if(argc<3){

         printf("tiny_psnr <file1> <file2> [<elem size> [<shift> [<skip bytes>]]]\n");

         printf("WAV headers are skipped automatically.\n");

         return 1;

     }

     f[0]= fopen(argv[1], "rb");
     f[1]= fopen(argv[2], "rb");

     if(!f[0] || !f[1]){

         fprintf(stderr, "Could not open input files.\n");

         return 1;

     }

 
     for (i = 0; i < 2; i++) {
         uint8_t *p = buf[i];

         if (fread(p, 1, 12, f[i]) != 12)
             return 1;

         if (!memcmp(p,   "RIFF", 4) &&
             !memcmp(p+8, "WAVE", 4)) {

             if (fread(p, 1, 8, f[i]) != 8)
                 return 1;

             while (memcmp(p, "data", 4)) {
                 int s = p[4] | p[5]<<8 | p[6]<<16 | p[7]<<24;
                 fseek(f[i], s, SEEK_CUR);

                 if (fread(p, 1, 8, f[i]) != 8)
                     return 1;

             }
         } else {
             fseek(f[i], -12, SEEK_CUR);
         }
     }
 

     fseek(f[shift<0], abs(shift), SEEK_CUR);

     fseek(f[0],skip_bytes,SEEK_CUR);
     fseek(f[1],skip_bytes,SEEK_CUR);
 

     for(;;){
         int s0= fread(buf[0], 1, SIZE, f[0]);
         int s1= fread(buf[1], 1, SIZE, f[1]);

         for(j=0; j<FFMIN(s0,s1); j++){

             int64_t a= buf[0][j];
             int64_t b= buf[1][j];

             int dist;

             if(len==2){
                 a= (int16_t)(a | (buf[0][++j]<<8));
                 b= (int16_t)(b | (buf[1][  j]<<8));
             }

             sse += (a-b) * (a-b);

             dist = abs(a-b);
             if (dist > maxdist) maxdist = dist;

         }

         size0 += s0;
         size1 += s1;
         if(s0+s1<=0)
             break;

     }

     i= FFMIN(size0,size1)/len;

     if(!i) i=1;

     dev= int_sqrt( ((sse/i)*F*F) + (((sse%i)*F*F) + i/2)/i );

     if(sse)

         psnr= ((2*log16(max<<16) + log16(i) - log16(sse))*284619LL*F + (1LL<<31)) / (1LL<<32);

     else

         psnr= 1000*F-1; //floating point free infinity :)

     printf("stddev:%5d.%02d PSNR:%3d.%02d MAXDIFF:%5d bytes:%9d/%9d\n",

         (int)(dev/F), (int)(dev%F),

         (int)(psnr/F), (int)(psnr%F),

         maxdist,

         size0, size1);

     return 0;
 }