/*
  * 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 <math.h>
 #include <float.h>

 #include <limits.h>

 #include "libavutil/intfloat.h"

 #include "libavutil/intreadwrite.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;
     uint64_t ret_sq = 0;

     int s;
 

     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;
 }
 

 static int16_t get_s16l(uint8_t *p)
 {
     union {
         uint16_t u;
         int16_t  s;
     } v;
     v.u = p[0] | p[1] << 8;
     return v.s;
 }
 
 static float get_f32l(uint8_t *p)
 {
     union av_intfloat32 v;
     v.i = p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
     return v.f;
 }
 

 static double get_f64l(uint8_t *p)
 {
     return av_int2double(AV_RL64(p));
 }
 

 static int run_psnr(FILE *f[2], int len, int shift, int skip_bytes)

 {

     int i, j;

     uint64_t sse = 0;

     double sse_d = 0.0;

     uint8_t buf[2][SIZE];

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

     int size0      = 0;
     int size1      = 0;

     uint64_t maxdist = 0;
     double maxdist_d = 0.0;

     int noseek;

     noseek = fseek(f[0], 0, SEEK_SET) ||
              fseek(f[1], 0, SEEK_SET);

     if (!noseek) {

         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 += len) {

             switch (len) {
             case 1:
             case 2: {
                 int64_t a = buf[0][j];
                 int64_t b = buf[1][j];
                 int dist;
                 if (len == 2) {
                     a = get_s16l(buf[0] + j);
                     b = get_s16l(buf[1] + j);
                 } else {
                     a = buf[0][j];
                     b = buf[1][j];
                 }
                 sse += (a - b) * (a - b);
                 dist = abs(a - b);
                 if (dist > maxdist)
                     maxdist = dist;
                 break;
             }
             case 4:
             case 8: {
                 double dist, a, b;
                 if (len == 8) {
                     a = get_f64l(buf[0] + j);
                     b = get_f64l(buf[1] + j);
                 } else {
                     a = get_f32l(buf[0] + j);
                     b = get_f32l(buf[1] + j);
                 }
                 dist = fabs(a - b);
                 sse_d += (a - b) * (a - b);
                 if (dist > maxdist_d)
                     maxdist_d = dist;
                 break;
             }

             }

         }

         size0 += s0;
         size1 += s1;

         if (s0 + s1 <= 0)

             break;

     }

     i = FFMIN(size0, size1) / len;
     if (!i)
         i = 1;

     switch (len) {
     case 1:
     case 2: {
         uint64_t psnr;
         uint64_t 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:%5"PRIu64" bytes:%9d/%9d\n",
                (int)(dev / F), (int)(dev % F),
                (int)(psnr / F), (int)(psnr % F),
                maxdist, size0, size1);

         return psnr;

         }
     case 4:
     case 8: {
         char psnr_str[64];

         double psnr = INT_MAX;

         double dev = sqrt(sse_d / i);
         uint64_t scale = (len == 4) ? (1ULL << 24) : (1ULL << 32);
 
         if (sse_d) {

             psnr = 2 * log(DBL_MAX) - log(i / sse_d);

             snprintf(psnr_str, sizeof(psnr_str), "%5.02f", psnr);
         } else
             snprintf(psnr_str, sizeof(psnr_str), "inf");
 
         maxdist = maxdist_d * scale;
 
         printf("stddev:%10.2f PSNR:%s MAXDIFF:%10"PRIu64" bytes:%9d/%9d\n",
                dev * scale, psnr_str, maxdist, size0, size1);

         return psnr;
     }

     }

     return -1;

 }
 
 int main(int argc, char *argv[])
 {
     FILE *f[2];

     int len = 1;

     int shift_first= argc < 5 ? 0 : atoi(argv[4]);
     int skip_bytes = argc < 6 ? 0 : atoi(argv[5]);
     int shift_last = shift_first + (argc < 7 ? 0 : atoi(argv[6]));
     int shift;
     int max_psnr   = -1;
     int max_psnr_shift = 0;
 

     if (argc > 3) {
         if (!strcmp(argv[3], "u8")) {
             len = 1;
         } else if (!strcmp(argv[3], "s16")) {
             len = 2;
         } else if (!strcmp(argv[3], "f32")) {
             len = 4;

         } else if (!strcmp(argv[3], "f64")) {
             len = 8;

         } else {
             char *end;
             len = strtol(argv[3], &end, 0);

             if (*end || len < 1 || len > 2) {

                 fprintf(stderr, "Unsupported sample format: %s\n", argv[3]);
                 return 1;
             }
         }
     }
 

     if (argc < 3) {
         printf("tiny_psnr <file1> <file2> [<elem size> [<shift> [<skip bytes> [<shift search range>]]]]\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 (shift = shift_first; shift <= shift_last; shift++) {
         int psnr = run_psnr(f, len, shift, skip_bytes);
         if (psnr > max_psnr || (shift < 0 && psnr == max_psnr)) {
             max_psnr = psnr;
             max_psnr_shift = shift;
         }
     }
     if (shift_last > shift_first)
         printf("Best PSNR is %3d.%02d for shift %i\n", (int)(max_psnr / F), (int)(max_psnr % F), max_psnr_shift);

     return 0;
 }