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/*

** Universal IPS patch create/apply utility

** Written by Neill Corlett - Copyright 1999

** See UIPS.TXT for terms of use and disclaimer.

**

** To compile this, if you have gcc installed:

**

**    gcc uips.c -o uips

**

** (Add optimization options to taste.)

**

** If you don't have gcc, figure something else out.

*/

#include <stdio.h>

#include <stdlib.h>

/* Define truncate(2) for systems that don't have it */

#if defined(__MSDOS__) && defined(__TURBOC__)

#include <dos.h>

#include <io.h>

#include <fcntl.h>

static void truncate(const char *filename, long size) {

  int handle;

  unsigned nwritten;

  if(_dos_open(filename, O_WRONLY, &handle)) return;

  if(lseek(handle, size, SEEK_SET) != -1L) {

    _dos_write(handle, (void far*)(&handle), 0, &nwritten);

  }

  _dos_close(handle);

}

#elif defined(__WIN32__)

#include <windows.h>

static void truncate(const char *filename, long size) {

  HANDLE f = CreateFile(

    filename,

    GENERIC_WRITE,

    0,

    NULL,

    OPEN_EXISTING,

    FILE_ATTRIBUTE_NORMAL,

    NULL

  );

  if(f == INVALID_HANDLE_VALUE) return;

  SetFilePointer(f, size, NULL, FILE_BEGIN);

  if(GetLastError() == NO_ERROR) SetEndOfFile(f);

  CloseHandle(f);

}

#else

#include <unistd.h>

#endif

#define IPS_EOF   (0x00454F46l)

#define IPS_LIMIT (0x01000000l)

/* Show program banner */

static void banner(void) {

  fprintf(stderr,

    "Universal IPS create/apply utility\n"

    "Written by Neill Corlett - Copyright 1999\n"

  );

}

/* Show usage info */

static void usage(const char *prgname) {

  fprintf(stderr,

    "Usage:\n"

    "To create an IPS patch:\n"

    "  %s c patch_file source_file(s) target_file\n"

    "To apply an IPS patch:\n"

    "  %s a patch_file target_file\n",

    prgname, prgname

  );

}

/* Wrapper for fopen that does various things */

static FILE *my_fopen(const char *filename, const char *mode, long *size) {

  FILE *f = fopen(filename, mode);

  if(!f) {

    perror(filename);

    return NULL;

  }

  if(size) {

    fseek(f, 0, SEEK_END);

    *size = ftell(f);

    fseek(f, 0, SEEK_SET);

  }

  return f;

}

/* Read a number from a file, MSB first */

static long readvalue(FILE *f, unsigned nbytes) {

  long v = 0;

  while(nbytes--) {

    int c = fgetc(f);

    if(c == EOF) return -1;

    v = (v << 8) | (c & 0xFF);

  }

  return v;

}

/* Write a number to a file, MSB first */

static void writevalue(long value, FILE *f, unsigned nbytes) {

  unsigned i = nbytes << 3;

  while(nbytes--) {

    i -= 8;

    fputc(value >> i, f);

  }

}

/* Search for the next difference between the target file and a number of

** source files */

static long get_next_difference(

        long       ofs,

        FILE     **source_file,

  const long      *source_size,

        unsigned   source_nfiles,

        FILE      *target_file,

        long       target_size

) {

  unsigned i;

  if(ofs >= target_size) return target_size;

  fseek(target_file, ofs, SEEK_SET);

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

    if(ofs >= source_size[i]) return ofs;

  }

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

    fseek(source_file[i], ofs, SEEK_SET);

  }

  for(;;) {

    int tc = fgetc(target_file);

    if(tc == EOF) return target_size;

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

      if(fgetc(source_file[i]) != tc) return ofs;

    }

    ofs++;

  }

}

/* Search for the end of a difference block */

static long get_difference_end(

        long       ofs,

        int        similar_limit,

        FILE     **source_file,

  const long      *source_size,

        unsigned   source_nfiles,

        FILE      *target_file,

        long       target_size

) {

  unsigned i;

  int      similar_rl = 0;

  if(ofs >= target_size) return target_size;

  fseek(target_file, ofs, SEEK_SET);

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

    if(ofs >= source_size[i]) return target_size;

  }

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

    fseek(source_file[i], ofs, SEEK_SET);

  }

  for(;;) {

    char is_different = 0;

    int tc = fgetc(target_file);

    if(tc == EOF) return target_size;

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

      int fc = fgetc(source_file[i]);

      if(fc == EOF) return target_size;

      if(fc != tc) is_different = 1;

    }

    ofs++;

    if(is_different) {

      similar_rl = 0;

    } else {

      similar_rl++;

      if(similar_rl == similar_limit) break;

    }

  }

  return ofs - similar_limit;

}

/* Encode a difference block into a patch file */

static void encode_patch_block(

  FILE *patch_file,

  FILE *target_file,

  long  ofs,

  long  ofs_end

) {

  while(ofs < ofs_end) {

    long ofs_block_end, rl;

    int c;

    /* Avoid accidental "EOF" marker */

    if(ofs == IPS_EOF) ofs--;

    /* Write the offset to the patch file */

    writevalue(ofs, patch_file, 3);

    fseek(target_file, ofs, SEEK_SET);

    /* If there is a beginning run of at least 9 bytes, use it */

    c = fgetc(target_file);

    rl = 1;

    while(

      (fgetc(target_file) == c) &&

      (rl < 0xFFFF) &&

      ((ofs + rl) < ofs_end)

    ) rl++;

    /* Encode a run, if the run was long enough */

    if(rl >= 9) {

      writevalue( 0, patch_file, 2);

      writevalue(rl, patch_file, 2);

      writevalue( c, patch_file, 1);

      ofs += rl;

      continue;

    }

    /* Search for the end of the block.

    ** The block ends if there's an internal run of at least 14, or an ending

    ** run of at least 9, or the block length == 0xFFFF, or the block reaches

    ** ofs_end. */

    fseek(target_file, ofs, SEEK_SET);

    ofs_block_end = ofs;

    c = -1;

    while(

      (ofs_block_end < ofs_end) &&

      ((ofs_block_end - ofs) < 0xFFFF)

    ) {

      int c2 = fgetc(target_file);

      ofs_block_end++;

      if(c == c2) {

        rl++;

        if(rl == 14) {

          ofs_block_end -= 14;

          break;

        }

      } else {

        rl = 1;

        c = c2;

      }

    }

    /* Look for a sufficiently long ending run */

    if((ofs_block_end == ofs_end) && (rl >= 9)) {

      ofs_block_end -= rl;

      if(ofs_block_end == IPS_EOF) ofs_block_end++;

    }

    /* Encode a regular patch block */

    writevalue(ofs_block_end - ofs, patch_file, 2);

    fseek(target_file, ofs, SEEK_SET);

    while(ofs < ofs_block_end) {

      fputc(fgetc(target_file), patch_file);

      ofs++;

    }

  }

}

/* Create a patch given a list of source filenames and a target filename.

** Returns 0 on success. */

static int create_patch(

  const char  *patch_filename,

  unsigned     source_nfiles,

  const char **source_filename,

  const char  *target_filename

) {

  FILE    *patch_file  = NULL;

  FILE   **source_file = NULL;

  long    *source_size = NULL;

  FILE    *target_file = NULL;

  long     target_size;

  long     ofs;

  int      e = 0;

  unsigned i;

  char     will_truncate = 0;

  /* Allocate memory for list of source file streams and sizes */

  if(

    (!(source_file = malloc(sizeof(FILE*) * source_nfiles))) ||

    (!(source_size = malloc(sizeof(long)  * source_nfiles)))

  ) {

    fprintf(stderr, "Out of memory\n");

    goto err;

  }

  for(i = 0; i < source_nfiles; i++) source_file[i] = NULL;

  /* Open target file */

  target_file = my_fopen(target_filename, "rb", &target_size);

  if(!target_file) goto err;

  /* Open source files */

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

    source_file[i] = my_fopen(source_filename[i], "rb", source_size + i);

    if(!source_file[i]) goto err;

    if(source_size[i] > target_size) will_truncate = 1;

  }

  /* Create patch file */

  patch_file = my_fopen(patch_filename, "wb", NULL);

  if(!patch_file) goto err;

  fprintf(stderr, "Creating %s...\n", patch_filename);

  /* Write "PATCH" signature */

  if(fwrite("PATCH", 1, 5, patch_file) != 5) {

    perror(patch_filename);

    goto err;

  }

  /* Main patch creation loop */

  ofs = 0;

  for(;;) {

    long ofs_end;

    /* Search for next difference */

    ofs = get_next_difference(

      ofs,

      source_file,

      source_size,

      source_nfiles,

      target_file,

      target_size

    );

    if(ofs == target_size) break;

    if(ofs >= IPS_LIMIT) {

      fprintf(stderr, "Warning: Differences beyond 16MB were ignored\n");

      break;

    }

    /* Determine the length of the difference block */

    ofs_end = get_difference_end(

      ofs,

      6,

      source_file,

      source_size,

      source_nfiles,

      target_file,

      target_size

    );

    /* Progress indicator */

    fprintf(stderr, "%06lX %06lX\r", ofs, ofs_end - ofs);

    /* Encode the difference block into the patch file */

    encode_patch_block(patch_file, target_file, ofs, ofs_end);

    ofs = ofs_end;

  }

  /* Write EOF marker */

  writevalue(IPS_EOF, patch_file, 3);

  if(will_truncate) {

    if(target_size >= IPS_LIMIT) {

      fprintf(stderr, "Warning: Can't truncate beyond 16MB\n");

    } else {

      writevalue(target_size, patch_file, 3);

    }

  }

  /* Finished */

  fprintf(stderr, "\nDone\n");

  goto no_err;

  err:

  e = 1;

  no_err:

  if(patch_file) fclose(patch_file);

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

    if(source_file[i]) fclose(source_file[i]);

  }

  if(target_file) fclose(target_file);

  if(source_file) free(source_file);

  if(source_size) free(source_size);

  return e;

}

/* Apply a patch to a given target.

** Returns 0 on success. */

static int apply_patch(

  const char *patch_filename,

  const char *target_filename

) {

  FILE *patch_file  = NULL;

  FILE *target_file = NULL;

  long  target_size;

  long  ofs;

  int   e = 0;

  /* Open patch file */

  patch_file = my_fopen(patch_filename, "rb", NULL);

  if(!patch_file) goto err;

  /* Verify first five characters */

  if(

    (fgetc(patch_file) != 'P') ||

    (fgetc(patch_file) != 'A') ||

    (fgetc(patch_file) != 'T') ||

    (fgetc(patch_file) != 'C') ||

    (fgetc(patch_file) != 'H')

  ) {

    fprintf(stderr, "%s: Invalid patch file format\n", patch_filename);

    goto err;

  }

  /* Open target file */

  target_file = my_fopen(target_filename, "r+b", &target_size);

  if(!target_file) goto err;

  fprintf(stderr, "Applying %s...\n", patch_filename);

  /* Main patch application loop */

  for(;;) {

    long ofs, len;

    long rlen  = 0;

    int  rchar = 0;

    /* Read the beginning of a patch record */

    ofs = readvalue(patch_file, 3);

    if(ofs == -1) goto err_eof;

    if(ofs == IPS_EOF) break;

    len = readvalue(patch_file, 2);

    if(len == -1) goto err_eof;

    if(!len) {

      rlen = readvalue(patch_file, 2);

      if(rlen == -1) goto err_eof;

      rchar = fgetc(patch_file);

      if(rchar == EOF) goto err_eof;

    }

    /* Seek to the appropriate position in the target file */

    if(ofs <= target_size) {

      fseek(target_file, ofs, SEEK_SET);

    } else {

      fseek(target_file, 0, SEEK_END);

      while(target_size < ofs) {

        fputc(0, target_file);

        target_size++;

      }

    }

    /* Apply patch block */

    if(len) {

      fprintf(stderr, "regular  %06lX %04lX\r", ofs, len);

      ofs += len;

      if(ofs > target_size) target_size = ofs;

      while(len--) {

        rchar = fgetc(patch_file);

        if(rchar == EOF) goto err_eof;

        fputc(rchar, target_file);

      }

    } else {

      fprintf(stderr, "run      %06lX %04lX\r", ofs, rlen);

      ofs += rlen;

      if(ofs > target_size) target_size = ofs;

      while(rlen--) fputc(rchar, target_file);

    }

  }

  /* Perform truncation if necessary */

  fclose(target_file);

  target_file = NULL;

  ofs = readvalue(patch_file, 3);

  if(ofs != -1) {

    fprintf(stderr, "truncate %06lX     ", ofs);

    truncate(target_filename, ofs);

  }

  /* Finished */

  fprintf(stderr, "\nDone\n");

  goto no_err;

  err_eof:

  fprintf(stderr,

    "%s: Unexpected end-of-file, patch incomplete\n",

    patch_filename

  );

  err:

  e = 1;

  no_err:

  if(target_file) fclose(target_file);

  if(patch_file) fclose(patch_file);

  return e;

}

int main(

  int argc,

  char **argv

) {

  char cmd;

  if(argc < 2) {

    banner();

    usage(argv[0]);

    return 1;

  }

  cmd = argv[1][0];

  if(cmd && argv[1][1]) cmd = 0;

  switch(cmd) {

  case 'c':

  case 'C':

    if(argc < 5) {

      fprintf(stderr, "Not enough parameters\n");

      usage(argv[0]);

      return 1;

    }

    if(create_patch(

      argv[2],

      argc - 4,

      (const char**)(argv + 3),

      argv[argc - 1]

    )) return 1;

    break;

  case 'a':

  case 'A':

    if(argc < 4) usage(argv[0]);

    if(apply_patch(argv[2], argv[3])) return 1;

    break;

  default:

    fprintf(stderr, "Unknown command: %s\n", argv[1]);

    usage(argv[0]);

    return 1;

  }

  return 0;

}