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/*
* Copyright © 2024 Michael Smith <mikesmiffy128@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
#include <string.h>
#include "bitbuf.h"
#include "con_.h"
#include "demorec.h"
#include "engineapi.h"
#include "errmsg.h"
#include "feature.h"
#include "gamedata.h"
#include "intdefs.h"
#include "mem.h"
#include "ppmagic.h"
#include "vcall.h"
#include "x86.h"
#include "x86util.h"
FEATURE()
REQUIRE(demorec)
REQUIRE_GAMEDATA(vtidx_GetEngineBuildNumber)
REQUIRE_GAMEDATA(vtidx_RecordPacket)
static int nbits_msgtype, nbits_datalen;
// engine limit is 255, we use 2 bytes for header + round the bitstream to the
// next whole byte, which gives 3 bytes overhead hence 252 here.
#define CHUNKSZ 252
static union {
char x[CHUNKSZ + /*7*/ 8]; // needs to be multiple of of 4!
bitbuf_cell _align; // just in case...
} bb_buf;
static struct bitbuf bb = {
{bb_buf.x}, sizeof(bb_buf), sizeof(bb_buf) * 8, 0, false, false, "SST"
};
static const void *createhdr(struct bitbuf *msg, int len, bool last) {
// We pack custom data into user message packets of type "HudText," with a
// leading null byte which the engine treats as an empty string. On demo
// playback, the client does a text lookup which fails silently on invalid
// keys, giving us the rest of the packet to stick in whatever data we want.
//
// Big thanks to our resident demo expert, Uncrafted, for explaining what to
// do here way back when this was first being figured out!
bitbuf_appendbits(msg, 23, nbits_msgtype); // type: 23 is user message
bitbuf_appendbyte(msg, 2); // user message type: 2 is HudText
bitbuf_appendbits(msg, len * 8, nbits_datalen); // our data length in bits
bitbuf_appendbyte(msg, 0); // aforementionied null byte
bitbuf_appendbyte(msg, 0xAC + last); // arbitrary marker byte to aid parsing
// store the data itself byte-aligned so there's no need to bitshift the
// universe (which would be both slower and more annoying to do)
bitbuf_roundup(msg);
return msg->buf + (msg->nbits >> 3);
}
typedef void (*VCALLCONV WriteMessages_func)(void *this, struct bitbuf *msg);
static WriteMessages_func WriteMessages = 0;
void democustom_write(const void *buf, int len) {
for (; len > CHUNKSZ; len -= CHUNKSZ) {
createhdr(&bb, CHUNKSZ, false);
memcpy(bb.buf + (bb.nbits >> 3), buf, CHUNKSZ);
bb.nbits += CHUNKSZ << 3;
WriteMessages(demorecorder, &bb);
bitbuf_reset(&bb);
}
createhdr(&bb, len, true);
memcpy(bb.buf + (bb.nbits >> 3), buf, len);
bb.nbits += len << 3;
WriteMessages(demorecorder, &bb);
bitbuf_reset(&bb);
}
static bool find_WriteMessages(void) {
const uchar *insns = (*(uchar ***)demorecorder)[vtidx_RecordPacket];
// RecordPacket calls WriteMessages right away, so just look for a call
for (const uchar *p = insns; p - insns < 32;) {
if (*p == X86_CALL) {
WriteMessages = (WriteMessages_func)(p + 5 + mem_loads32(p + 1));
return true;
}
NEXT_INSN(p, "WriteMessages function");
}
return false;
}
DECL_VFUNC_DYN(int, GetEngineBuildNumber)
INIT {
// More UncraftedkNowledge:
// - usermessage length is:
// - 11 bits in protocol 11, or l4d2 protocol 2042
// - otherwise 12 bits
// So here we have to figure out the network protocol version!
// NOTE: assuming engclient != null as GEBN index relies on client version
int buildnum = GetEngineBuildNumber(engclient);
//if (GAMETYPE_MATCHES(L4D2)) { // redundant until we add more GEBN offsets!
nbits_msgtype = 6;
// based on Some Code I Read, buildnum *should* be the protocol version,
// however L4D2 returns the actual game version instead, because sure
// why not. The only practical difference though is that the network
// protocol froze after 2042, so we just have to do a >=. Fair enough!
// TODO(compat): how does TLS affect this? no idea yet
if (buildnum >= 2042) nbits_datalen = 11; else nbits_datalen = 12;
//}
return find_WriteMessages();
}
// vi: sw=4 ts=4 noet tw=80 cc=80
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