/* This exe removes the Copyright-data (CE and AE) from GIF89a
   (as written by Gif Construction Set)...
   Can come in handy when creating CD-roms and stuff.
   J.Thyssen & H.Zimmerman, TC3, 03-97, DOS commandline, 16bit, PKlited.
   Operation= RCMGIF FILE.GIF  Wildcards can also be used)
   Following is code (this txt-file is a C-file) */

#include <io.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys\stat.h>

#define TEMPFILE "!hallo!"
#define MAXBUF 1024

#pragma warn -pia
void main(int argc,char*argv[]){
    FILE *f1,*f2;
    char buf[MAXBUF];
    int done=0,c;

    if(argc!=2){
        printf("RCMGIF FILE.GIF\n");
        exit(1);
    }
    if((f1=fopen(argv[1],"rb"))==NULL){
        printf("Can't open %s\n",argv[1]);
        exit(1);
    }
    /* header and lsd: */
    fread(buf,13,1,f1);
    c=buf[6];
    buf[6]=0;
    if(strcmpi(buf,"GIF89a")){
        fclose(f1);
        printf("%s is not a GIF89a\n",argv[1]);
        exit(1);
    }
    buf[6]=c;
    f2=fopen(TEMPFILE,"wb");
    fwrite(buf,13,1,f2);
    /* do we have a GCT?: */
    if(buf[10]&0x80){ /* yep */
        fread(buf,768,1,f1);
        fwrite(buf,768,1,f2);
    }
    /* rest of GIF has control-bytes: */
    while(!done){
        c=fgetc(f1);
        switch(c){
        case 0x21:/* 89a-extension */
            c=fgetc(f1);
            switch(c){
            case 0xfe:/* CE, throw away! */
            case 0xff:/* AE, we hate that one too... */
                while(c=fgetc(f1)) /* 0 indicates term-block */
                    fread(buf,c,1,f1); /* flush c bytes */
                break;
            default:/* sth else (PTE(0x01) or GCE(0xf9)  keep it */
                fprintf(f2,"%c%c",0x21,c);
                while(c=fgetc(f1)){ /* 0 indicates term-block */
                    fputc(c,f2);
                    fread(buf,1,c,f1); /* copy c bytes */
                    fwrite(buf,1,c,f2);
                }
                /* write termblock: */
                fputc(0,f2);
            }
            break;
        case 0x2c:/* image-data */
            fputc(0x2c,f2);
            fread(buf,10,1,f1); /* GIF87 formal desc. says 9 bytes !?!?! */
            fwrite(buf,10,1,f2);
            /* do we have an LTC: */
            if(buf[8]&0x80){ /* yep */
                fread(buf,768,1,f1);
                fwrite(buf,768,1,f2);
            }
            /* copy rasterdata: */
            while(c=fgetc(f1)){ /* 0 indicates term-block */
                fputc(c,f2);
                fread(buf,1,c,f1); /* copy c bytes */
                fwrite(buf,1,c,f2);
            }
            /* write termblock: */
            fputc(0,f2);
            break;
        case 0x3b:/* GIF-terminator */
            fputc(0x3b,f2);
            done=1;
        }
    }
    fcloseall();
    chmod(argv[1],S_IWRITE);
    unlink(argv[1]);
    rename(TEMPFILE,argv[1]);
}