ips.c

/* tiny simple in-memory ips-patcher */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>

uint32_t read24(FILE *fp) {
  return  ((fgetc(fp) << 16) & 0xff0000)
         |((fgetc(fp) <<  8) & 0x00ff00)
         |((fgetc(fp)      ) & 0x0000ff);
}

uint16_t read16(FILE *fp) {
  return  ((fgetc(fp) <<  8) & 0xff00)
         |((fgetc(fp)      ) & 0x00ff);
}

int main(int argc, char **argv) {
  FILE *fd, *ips;
  char *buffer;
  char ipsbuf[5];
  long offset = 0;
  size_t cursize, lastsize;
  char *off_endptr;

  int32_t ipsaddr;
  size_t ipsflen;
  uint16_t ipssize;
  uint32_t ipsrlen;

  /* display usage */
  if(argc < 4 || argc > 5) {
    fprintf(stderr, "Usage: %s <infile> <ipsfile> <outfile> [offset]\n", argv[0]);
    fprintf(stderr, "offset is a signed offset applied to all addresses specified in the patch\n");
    fprintf(stderr, "it may be given in decimal (-512), hex (-0x200), or octal (-01000)\n");
    exit(1);
  }
  /* parse offset option */
  if(argc >= 5) {
    offset = strtol(argv[4], &off_endptr, 0);
    if(*off_endptr) {
      fprintf(stderr, "Invalid offset: %s (first invalid char: '%c')\n", argv[4], *off_endptr);
      exit(1);
    }
    printf("using offset: %s\n", argv[4]);
  }
  /* open input file */
  if((fd=fopen(argv[1], "rb")) == NULL) {
    perror("cannot open input file");
    exit(1);
  }
  /* open IPS file */
  if((ips=fopen(argv[2], "rb")) == NULL) {
    perror("cannot open IPS file");
    exit(1);
  }
  /* get IPS file size */
  fseek(ips, 0, SEEK_END);
  ipsflen = ftell(ips);
  fseek(ips, 0, SEEK_SET);

  /* check if the IPS header is valid */
  fread(ipsbuf, 5, 1, ips);
  if(memcmp("PATCH", ipsbuf, 5)) {
    fprintf(stderr, "Invalid IPS file\n");
    exit(1);
  }
  /* read entire input file into memory */
  fseek(fd, 0, SEEK_END);
  cursize = ftell(fd);
  lastsize = cursize;
  fseek(fd, 0, SEEK_SET);
  if((buffer = malloc(cursize)) == NULL) {
    fprintf(stderr, "could not reserve memory\n");
    exit(1);
  }
  fread(buffer, cursize, 1, fd);
  fclose(fd);

  /* perform IPS patching */
  while(1) {
    ipsaddr = read24(ips);
    if(feof(ips)) {
      fprintf(stderr, "unexpected end of IPS file\n");
      break;
    }
    /* end tag */
    if(ipsaddr == 0x454f46 && ftell(ips) >= (ipsflen - 3)) {
      printf("EOF");
      if(ftell(ips) == (ipsflen - 3)) {
        lastsize = cursize;
        cursize = read24(ips);
        printf(", padding to size %06lx\n", cursize);
        if((buffer = realloc(buffer, cursize)) == NULL) {
          fprintf(stderr, "could not reserve more memory\n");
          break;
        }
        memset(buffer+lastsize, 0xff, cursize-lastsize);
      } else {
        printf("\n");
      }
      break;
    } else {
      if((ipsaddr + offset) < 0) {
        printf("offset %c%lx cannot be applied to address %06x, ignoring\n", offset < 0 ? '-' : '+', labs(offset), (uint32_t)ipsaddr);
      }
      ipsaddr += offset;
      ipssize = read16(ips);
      if(ipssize) {
        if(ipsaddr >= 0) {
          /* regular chunk */
          printf("std patch @%06x, size %04x\n", (uint32_t)ipsaddr, ipssize);
          /* extend memory if needed + initialize it */
          if((ipsaddr + ipssize) > cursize) {
            lastsize = cursize;
            cursize = ipsaddr + ipssize;
            if((buffer = realloc(buffer, cursize)) == NULL) {
              fprintf(stderr, "could not reserve more memory\n");
              break;
            }
            memset(buffer+lastsize, 0xff, cursize-lastsize);
          }
          fread(buffer+ipsaddr, ipssize, 1, ips);
        } else {
          fseek(ips, ipssize, SEEK_CUR);
        }
      } else {
        /* RLE chunk */
        ipsrlen = read16(ips);
        if(ipsaddr >= 0) {
          printf("RLE patch @%06x, size %04x\n", (uint32_t)ipsaddr, ipsrlen);
          /* extend memory if needed + initialize it */
          if((ipsaddr + ipsrlen) > cursize) {
            lastsize = cursize;
            cursize = ipsaddr + ipsrlen;
            if((buffer = realloc(buffer, cursize)) == NULL) {
              fprintf(stderr, "could not reserve more memory\n");
              break;
            }
            memset(buffer+lastsize, 0xff, cursize-lastsize);
          }
          memset(buffer+ipsaddr, fgetc(ips), ipsrlen);
        } else {
          fgetc(ips);
        }
      }
    }
  }
  if((fd = fopen(argv[3], "wb")) == NULL) {
    perror("cannot open output file");
    exit(1);
  }
  fwrite(buffer, cursize, 1, fd);
  printf("done\n");
  fclose(ips);
  fclose(fd);
  free(buffer);
  return 0;
}