Tool for stripping stringtable data out of SourceTV demos

sourcetv_fixer_v2.c

#include <stdio.h>
#include <err.h>
#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>


struct demo_header {
	char header[8];
	int32_t demo_proto_version;
	int32_t net_proto_version;
	char server_name[260];
	char client_name[260];
	char map_name[260];
	char game_dir[260];
	float playback_time;
	int32_t ticks;
	int32_t frames;
	int32_t signon_length;
};


enum {
	DEM_SIGNON       = 1,
	DEM_PACKET       = 2,
	DEM_SYNCTICK     = 3,
	DEM_CONSOLECMD   = 4,
	DEM_USERCMD      = 5,
	DEM_DATATABLES   = 6,
	DEM_STOP         = 7,
	DEM_STRINGTABLES = 8,
};


static const char *msgtypenames[] = {
	"0",
	"SIGNON",
	"PACKET",
	"SYNCTICK",
	"CONSOLECMD",
	"USERCMD",
	"DATATABLES",
	"STOP",
	"STRINGTABLES",
};


char path_in[1024];
char path_out[1024];

FILE *f_in  = NULL;
FILE *f_out = NULL;

struct demo_header hdr;



int main(int argc, char **argv)
{
	fprintf(stderr, "SourceTV demo stringtable remover (by sigsegv)\n\n");
	fprintf(stderr,
		"WARNING: this is a hacky tool meant solely for use as a temporary workaround;\n"
		"         make sure to keep your original demo file (it won't be overwritten)\n\n");
	
	if (argc != 2) {
		fprintf(stderr, "usage: %s <demoname>\n"
			"(reads from demoname.dem, writes to demoname_fixed.dem)\n",
			argv[0]);
		return 1;
	}
	
	
	const char *path_base = argv[1];
	
	snprintf(path_in, sizeof(path_in), "%s.dem", path_base);
	snprintf(path_out, sizeof(path_out), "%s_fixed.dem", path_base);
	
	
	f_in = fopen(path_in, "r");
	if (f_in == NULL) {
		err(1, "could not open '%s'", path_in);
	}
	
	
	if (fread(&hdr, 1, sizeof(hdr), f_in) != sizeof(hdr)) {
		err(1, "could not read header from '%s'", path_in);
	}
	
	
	bool    strtab_found = false;
	int32_t strtab_off   = -1;
	int32_t strtab_len   = 0;
	
	
	int32_t stop_at = hdr.signon_length;
	if (stop_at == 0) {
		stop_at = INT32_MAX;
	}
	
	int32_t off = sizeof(hdr);
	while (!strtab_found && off < stop_at) {
		int msg_type;
		if ((msg_type = fgetc(f_in)) == EOF) {
			if (feof(f_in)) {
				break;
			} else {
				err(1, "could not read msg type from '%s', offset %x",
					path_in, off);
			}
		}
		++off;
		
		warnx("off 0x%x: msg_type %d %s",
			off, msg_type, msgtypenames[msg_type]);
		
		if (msg_type == DEM_STOP) {
			break;
		}
		
		int32_t msg_tick;
		if (fread(&msg_tick, 1, sizeof(msg_tick), f_in) != sizeof(msg_tick)) {
			err(1, "could not read msg tick from '%s', "
				"msg_type %d, offset 0x%x",
				path_in, msg_type, off);
		}
		off += 4;
		
		if (msg_type == DEM_SYNCTICK) {
			continue;
		}
		
		int skip = 0;
		if (msg_type == DEM_SIGNON || msg_type == DEM_PACKET) {
			skip = 0x54;
		} else if (msg_type == DEM_USERCMD) {
			skip = 0x4;
		}
		
		if (skip != 0) {
			if (fseek(f_in, skip, SEEK_CUR) != 0) {
				err(1, "could not seek 0x%x bytes forward in '%s', "
					"msg_type %d, offset 0x%x",
					skip, path_in, msg_type, off);
			}
		}
		off += skip;
		
		int32_t msg_len;
		if (fread(&msg_len, 1, sizeof(msg_len), f_in) != sizeof(msg_len)) {
			err(1, "could not read msg len from '%s', "
				"msg_type %d, offset 0x%x",
				path_in, msg_type, off);
		}
		off += 4;
		
		if (msg_type == DEM_STRINGTABLES) {
			strtab_off = off - 9;
			strtab_len = msg_len + 9;
			strtab_found = true;
			
			warnx("found DEM_STRINGTABLES: offset 0x%x, total len %d",
				strtab_off, strtab_len);
		}
		
		if (fseek(f_in, msg_len, SEEK_CUR) != 0) {
			err(1, "could not seek 0x%x bytes forward in '%s', "
				"msg_type %d, offset 0x%x",
				msg_len, path_in, msg_type, off);
		}
		off += msg_len;
	}
	
	
	if (strtab_found) {
		warnx("will now write '%s'", path_out);
		
		f_out = fopen(path_out, "w");
		if (f_out == NULL) {
			err(1, "could not open '%s'", path_out);
		}
		
		
		if (hdr.signon_length != 0) {
			warnx("adjusting demo header for changed signon length\n"
				"  was: %d\n"
				"  now: %d",
				hdr.signon_length,
				hdr.signon_length - strtab_len);
			hdr.signon_length -= strtab_len;
		}
		
		
		if (fwrite(&hdr, 1, sizeof(hdr), f_out) != sizeof(hdr)) {
			err(1, "could not write header to '%s'", path_out);
		}
		
		
		char buf[4096];
		
		/* data copy:
		 * from: right after the header
		 * to:   right before DEM_STRINGTABLES
		 */
		
		if (fseek(f_in, sizeof(hdr), SEEK_SET) != 0) {
			err(1, "could not seek back to the header in '%s'", path_in);
		}
		
		int32_t len = strtab_off - sizeof(hdr);
		int32_t off = sizeof(hdr);
		while (len > 0) {
			int32_t this_len = sizeof(buf);
			if (len < this_len) {
				this_len = len;
			}
			
			if (fread(buf, 1, this_len, f_in) != this_len) {
				err(1, "could not read %d bytes from '%s' at offset 0x%x",
					this_len, path_in, off);
			}
			if (fwrite(buf, 1, this_len, f_out) != this_len) {
				err(1, "could not write %d bytes to '%s' at offset 0x%x",
					this_len, path_out, off);
			}
			
			len -= this_len;
			off += this_len;
		}
		
		
		/* data copy:
		 * from: right after DEM_STRINGTABLES
		 * to:   end-of-file
		 */
		
		if (fseek(f_in, strtab_off + strtab_len, SEEK_SET) != 0) {
			err(1, "could not seek to post-DEM_STRINGTABLES location in '%s'",
				path_in);
		}
		
		bool done = false;
		do {
			int32_t this_len;
			if ((this_len = fread(buf, 1, sizeof(buf), f_in)) != sizeof(buf)) {
				if (feof(f_in)) {
					done = true;
				} else {
					err(1, "could not read %d bytes from '%s' at offset 0x%x",
						sizeof(buf), path_in, off);
				}
			}
			if (fwrite(buf, 1, this_len, f_out) != this_len) {
				err(1, "could not write %d bytes to '%s' at offset 0x%x",
					this_len, path_out, off);
			}
			
			len -= this_len;
			off += this_len;
		} while (!done);
		
		
		fclose(f_out);
	} else {
		warnx("no DEM_STRINGTABLES msg found, no need to write a new file");
	}
	
	
	fclose(f_in);
	
	warnx("success");
	return 0;
}