/* patcher.c - patches files using patchfile */
/* Version 1.1 25-JAN-96 */
/* Copyright © 1996 Sean Riddle */

/* Freely distributable on any medium given all copyrights are retained */
/* by the author and no charge greater than $7.00 is made for obtaining */
/* this software */

/* Please send all bug reports and update ideas to: */
/* sriddle@ionet.net */

/* latest version at: */
/* <a href="http://www.ionet.net/~sriddle">Please don't hurl on my URL!</a> */

/* usage: patcher <file> <patch file> */

/* the patchfile format is as follows: */
/* Offset $0: From $7E To $23 */
/* comments have ; in first position of line */

/* compiled on Amiga SAS/C 6.56 */

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

void main(int argc,char *argv[]) {
   FILE *fpin,*fppat;
   char line[256];
   int i;
   int offset,from,to,was;
   int err=0;
   int ap=1;
   
   if(argc==3) {
      if(fpin=fopen(argv[1],"rb+")) {
         if(fppat=fopen(argv[2],"rb")) {
            while(fgets(line,255,fppat)) {
               if(line[0]!=';') {
                  for(i=0;(i<strlen(line))&&(line[i]!='O');i++)
                     ;
                  if(!strncmp(&line[i],"Offset $",8)) {
                     offset=strtol(&line[i+8],NULL,16);
                     for(;(i<strlen(line))&&!((line[i]=='F')&&(line[i+1]=='r'))
                           ;i++)
                        ;
                     if(!strncmp(&line[i],"From $",6)) {
                        from=strtol(&line[i+6],NULL,16);
                        for(;(i<strlen(line))&&(line[i]!='T');i++)
                           ;
                        if(!strncmp(&line[i],"To $",4)) {
                           to=strtol(&line[i+4],NULL,16);
                           if(!fseek(fpin,offset,SEEK_SET)) {
                              was=fgetc(fpin);
                              if(was!=EOF) {
                                 fseek(fpin,offset,SEEK_SET);
                                 fputc(to,fpin);
                                 if(was!=to)
                                    ap=0;
                                 if(was!=from) {
                                    printf("Offset $%04.4X was $%02.2X, should have been $%02.2X\n",
                                          offset,was,from);
                                    err=1;
                                 }
                              } else {
                                 printf("Offset $%04.4X EOF\n");
                                 err=2;
                              }
                           } else {
                              printf("Offset $%04.4X seek error\n");
                              err=3;
                           }
                        }else
                        printf("No `To' line: `%s'\n",line);
                     } else
                        printf("No `From' line: `%s'\n",line);
                  }
               }
            }
            fclose(fppat);
            switch(err) {
               case 0:
                  printf("File patched OK\n");
                  break;
               case 1:
                  if(ap==0)
                     printf("Incorrect file for this patch!\n");
                  else
                     printf("File already patched\n");
                  break;
               case 2:
                  printf("End of file error\n");
                  break;
               case 3:
                  printf("Seek error\n");
                  break;
            }
         } else
            printf("Can't open patch file\n");
         fclose(fpin);
      } else
         printf("Can't open file\n");
   } else
      printf("Usage: `%s <file> <patch file>'\n",argv[0]);
}