/*
	iwad64ex.c : Extracts the embedded IWAD in Hexen 64.
	Currently does not decompress the data (or fix the endianness in data).
	(C)2019 Marisa Kirisame, UnSX Team.
	Released under the MIT license.
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <errno.h>

typedef struct
{
	char sig[4];
	uint32_t nlumps;
	uint32_t dirpos;
} wad_t;

typedef struct
{
	uint32_t filepos, size;
	char name[8];
} lump_t;

char *data;
wad_t *wad;
lump_t *lumps;

uint32_t btl( uint32_t b )
{
	return ((b>>24)&0xff)|((b<<8)&0xff0000)
		|((b>>8)&0xff00)|((b<<24)&0xff000000);
}

int main( int argc, char **argv )
{
	if ( argc < 3 )
	{
		fprintf(stderr,"usage: iwad64ex <romfile> <wadfile>\n");
		return 1;
	}
	FILE *romfile = fopen(argv[1],"rb");
	if ( !romfile )
	{
		fprintf(stderr,"failed to open %s for reading: %s\n",
			argv[1],strerror(errno));
		return 2;
	}
	ssize_t fpos = 0;
	char buf[4096];
	ssize_t found = 0;
	while ( !feof(romfile) )
	{
		memset(buf,0,4096);
		int bsiz = fread(buf,1,4096,romfile);
		// to avoid GNU-exclusive memmem function I'll just roll out
		// my own thing here (fuckin' GNU and their exclusives...)
		for ( int i=0; i<bsiz-5; i++ )
		{
			if ( !memcmp(buf+i,"IWAD",4)
				|| !memcmp(buf+i,"PWAD",4) )
			{
				fpos += i;
				found = 1;
				break;
			}
		}
		if ( found ) break;
		fpos += bsiz;
	}
	if ( !found )
	{
		fclose(romfile);
		fprintf(stderr,"WAD signature not found in ROM\n");
		return 8;
	}
	printf("Embedded wad found at %#zx\n",fpos);
	data = malloc(12);
	if ( !data )
	{
		fclose(romfile);
		fprintf(stderr,"cannot allocate 12 bytes for wad header: %s",
			strerror(errno));
		return 16;
	}
	fseek(romfile,fpos,SEEK_SET);
	fread(data,1,12,romfile);
	wad = (wad_t*)data;
	// fix endianness
	wad->nlumps = btl(wad->nlumps);
	wad->dirpos = btl(wad->dirpos);
	// reallocate to fit
	size_t fullsiz = wad->dirpos+wad->nlumps*16;
	data = realloc(data,fullsiz);
	wad = (wad_t*)data;
	if ( errno )
	{
		fclose(romfile);
		free(data);
		fprintf(stderr,"cannot allocate %zd bytes for full wad: %s",
			fullsiz,strerror(errno));
		return 32;
	}
	fread(data+12,1,fullsiz-12,romfile);
	lumps = (lump_t*)(data+wad->dirpos);
	// loop and fix endianness
	for ( int i=0; i<wad->nlumps; i++ )
	{
		lumps[i].filepos = btl(lumps[i].filepos);
		lumps[i].size = btl(lumps[i].size);
		printf("%.8s %d %d\n",lumps[i].name,lumps[i].size,
			lumps[i].filepos);
	}
	fclose(romfile);
	FILE *wadfile = fopen(argv[2],"wb");
	if ( !wadfile )
	{
		fprintf(stderr,"failed to open %s for writing: %s\n",
			argv[2],strerror(errno));
		return 4;
	}
	fwrite(data,1,fullsiz,wadfile);
	fclose(wadfile);
	free(data);
	printf("wrote %s, %d bytes\n",argv[2],fullsiz);
	return 0;
}