#include <stdio.h>#include <stdlib.h>#define MAXCHUNK (2048*1024)static unsigned int seed;void my_srand(unsigned int n){  seed = n & 0xffff;}unsigned int my_rand(){  seed = (seed * 2109 + 9273) & 0x7fff;  return (seed + 0xc000) & 0xffff;}void load(FILE *fh, unsigned char *ptr, unsigned long sz){  if(fread(ptr, 1, sz, fh) != sz)    {      fprintf(stderr, "Read error!\n");      exit(1);    }}void load_chunk(FILE *fh, unsigned char *ptr, unsigned long sz){  static int idx[MAXCHUNK/32];  int i;  /* Convert chunk size to number of slices */  sz /= 32;  /* Initialize index table with unity,     so that each slice gets loaded exactly once */  for(i = 0; i < sz; i++)    idx[i] = i;  for(i = sz-1; i >= 0; --i)    {      /* Select a replacement index */      int x = (my_rand() * i) >> 16;      /* Swap */      int tmp = idx[i];      idx[i] = idx[x];      idx[x] = tmp;      /* Load resulting slice */      load(fh, ptr+32*idx[i], 32);    }}void load_file(FILE *fh, unsigned char *ptr, unsigned long filesz){  unsigned long chunksz;  my_srand(filesz);  /* Descramble 2 meg blocks for as long as possible, then     gradually reduce the window down to 32 bytes (1 slice) */  for(chunksz = MAXCHUNK; chunksz >= 32; chunksz >>= 1)    while(filesz >= chunksz)      {	load_chunk(fh, ptr, chunksz);	filesz -= chunksz;	ptr += chunksz;      }  /* Load final incomplete slice */  if(filesz)    load(fh, ptr, filesz);}void read_file(char *filename, unsigned char **ptr, unsigned long *sz){  FILE *fh = fopen(filename, "rb");  if(fh == NULL)    {      fprintf(stderr, "Can't open \"%s\".\n", filename);      exit(1);    }  if(fseek(fh, 0, SEEK_END)<0)    {      fprintf(stderr, "Seek error.\n");      exit(1);    }  *sz = ftell(fh);  *ptr = malloc(*sz);  if( *ptr == NULL )    {      fprintf(stderr, "Out of memory.\n");      exit(1);    }  if(fseek(fh, 0, SEEK_SET)<0)    {      fprintf(stderr, "Seek error.\n");      exit(1);    }  load_file(fh, *ptr, *sz);  fclose(fh);}void save(FILE *fh, unsigned char *ptr, unsigned long sz){  if(fwrite(ptr, 1, sz, fh) != sz)    {      fprintf(stderr, "Write error!\n");      exit(1);    }}void save_chunk(FILE *fh, unsigned char *ptr, unsigned long sz){  static int idx[MAXCHUNK/32];  int i;  /* Convert chunk size to number of slices */  sz /= 32;  /* Initialize index table with unity,     so that each slice gets saved exactly once */  for(i = 0; i < sz; i++)    idx[i] = i;  for(i = sz-1; i >= 0; --i)    {      /* Select a replacement index */      int x = (my_rand() * i) >> 16;      /* Swap */      int tmp = idx[i];      idx[i] = idx[x];      idx[x] = tmp;      /* Save resulting slice */      save(fh, ptr+32*idx[i], 32);    }}void save_file(FILE *fh, unsigned char *ptr, unsigned long filesz){  unsigned long chunksz;  my_srand(filesz);  /* Descramble 2 meg blocks for as long as possible, then     gradually reduce the window down to 32 bytes (1 slice) */  for(chunksz = MAXCHUNK; chunksz >= 32; chunksz >>= 1)    while(filesz >= chunksz)      {	save_chunk(fh, ptr, chunksz);	filesz -= chunksz;	ptr += chunksz;      }  /* Save final incomplete slice */  if(filesz)    save(fh, ptr, filesz);}void write_file(char *filename, unsigned char *ptr, unsigned long sz){  FILE *fh = fopen(filename, "wb");  if(fh == NULL)    {      fprintf(stderr, "Can't open \"%s\".\n", filename);      exit(1);    }  save_file(fh, ptr, sz);  fclose(fh);}void descramble(char *src, char *dst){  unsigned char *ptr = NULL;  unsigned long sz = 0;  FILE *fh;  read_file(src, &ptr, &sz);  fh = fopen(dst, "wb");  if(fh == NULL)    {      fprintf(stderr, "Can't open \"%s\".\n", dst);      exit(1);    }  if( fwrite(ptr, 1, sz, fh) != sz )    {      fprintf(stderr, "Write error.\n");      exit(1);    }  fclose(fh);  free(ptr);}void scramble(char *src, char *dst){  unsigned char *ptr = NULL;  unsigned long sz = 0;  FILE *fh;  fh = fopen(src, "rb");  if(fh == NULL)    {      fprintf(stderr, "Can't open \"%s\".\n", src);      exit(1);    }  if(fseek(fh, 0, SEEK_END)<0)    {      fprintf(stderr, "Seek error.\n");      exit(1);    }  sz = ftell(fh);  ptr = malloc(sz);  if( ptr == NULL )    {      fprintf(stderr, "Out of memory.\n");      exit(1);    }  if(fseek(fh, 0, SEEK_SET)<0)    {      fprintf(stderr, "Seek error.\n");      exit(1);    }  if( fread(ptr, 1, sz, fh) != sz )    {      fprintf(stderr, "Read error.\n");      exit(1);    }  fclose(fh);  write_file(dst, ptr, sz);  free(ptr);}int main(int argc, char *argv[]){  int opt = 0;  if(argc > 1 && !strcmp(argv[1], "-d"))    opt ++;  if(argc != 3+opt)    {      fprintf(stderr, "Usage: %s [-d] from to\n", argv[0]);      exit(1);    }    if(opt)    descramble(argv[2], argv[3]);  else    scramble(argv[1], argv[2]);  return 0;}