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/*
* Copyright © 2023 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 "bitbuf.h"
#include "con_.h"
#include "democustom.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"
FEATURE()
REQUIRE(demorec)
REQUIRE_GAMEDATA(vtidx_GetEngineBuildNumber)
REQUIRE_GAMEDATA(vtidx_RecordPacket)
static int nbits_msgtype, nbits_datalen;
// The engine allows usermessages up to 255 bytes, we add 2 bytes of overhead,
// and then there's the leading bits before that too (see create_message)
static char bb_buf[DEMOCUSTOM_MSG_MAX + 4];
static struct bitbuf bb = {
bb_buf, sizeof(bb_buf), sizeof(bb_buf) * 8, 0, false, false, "SST"
};
static void create_message(struct bitbuf *msg, const void *buf, int len) {
// The way we pack our custom demo data is via a user message packet with
// type "HudText" - this causes the client to do a text lookup which will
// simply silently fail on invalid keys. By making the first byte null
// (creating an empty string), we get the rest of the packet to stick in
// whatever other data we want.
//
// Notes from Uncrafted:
// > But yeah the data you want to append is as follows:
// > - 6 bits (5 bits in older versions) for the message type - should be 23
// > for user message
bitbuf_appendbits(msg, 23, nbits_msgtype);
// > - 1 byte for the user message type - should be 2 for HudText
bitbuf_appendbyte(msg, 2);
// > - ~~an int~~ 11 or 12 bits for the length of your data in bits,
bitbuf_appendbits(msg, len * 8, nbits_datalen); // NOTE: assuming len <= 254
// > - your data
// [first the aforementioned null byte, plus an arbitrary marker byte to
// avoid confusion when parsing the demo later...
bitbuf_appendbyte(msg, 0);
bitbuf_appendbyte(msg, 0xAC);
// ... and then just the data itself]
bitbuf_appendbuf(msg, buf, len);
// Thanks Uncrafted, very cool!
}
typedef void (*VCALLCONV WriteMessages_func)(void *this, struct bitbuf *msg);
static WriteMessages_func WriteMessages = 0;
void democustom_write(const void *buf, int len) {
create_message(&bb, buf, len);
WriteMessages(demorecorder, &bb);
bitbuf_reset(&bb);
}
// This finds the CDemoRecorder::WriteMessages() function, which takes a raw
// network packet, wraps it up in the appropriate demo framing format and writes
// it out to the demo file being recorded.
static bool find_WriteMessages(void) {
// TODO(compat): probably rewrite this to just scan for a call instruction!
const uchar *insns = (*(uchar ***)demorecorder)[vtidx_RecordPacket];
// RecordPacket calls WriteMessages pretty much right away:
// 56 push esi
// 57 push edi
// 8B F1 mov esi,ecx
// 8D BE lea edi,[esi + 0x68c]
// 8C 06 00 00
// 57 push edi
// E8 call CDemoRecorder_WriteMessages
// B0 EF FF FF
// So we just double check the byte pattern...
static const uchar bytes[] =
#ifdef _WIN32
HEXBYTES(56, 57, 8B, F1, 8D, BE, 8C, 06, 00, 00, 57, E8);
#else
#warning This is possibly different on Linux too, have a look!
{-1, -1, -1, -1, -1, -1};
#endif
if (!memcmp(insns, bytes, sizeof(bytes))) {
ssize off = mem_loadoffset(insns + sizeof(bytes));
// ... and then offset is relative to the address of whatever is _after_
// the call instruction... because x86.
WriteMessages = (WriteMessages_func)(insns + sizeof(bytes) + 4 + off);
return true;
}
return false;
}
DECL_VFUNC_DYN(int, GetEngineBuildNumber)
INIT {
// More UncraftedkNowledge:
// > yeah okay so [the usermessage length is] 11 bits if the demo protocol
// > is 11 or if the game is l4d2 and the network protocol is 2042.
// > otherwise it's 12 bits
// > there might be some other l4d2 versions where it's 11 but idk
// 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);
// condition is redundant until other GetEngineBuildNumber offsets are added
// if (GAMETYPE_MATCHES(L4D2)) {
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 >=. No big deal
// really.
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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