Adapt vote reset code into fast campaign resetting

This is kind of a breaking change but the other code was obviously never
released or relied on by anyone - it will be pushed at the same time as
this in fact. It still seems worth having the original committed
separately to show the progression of development of the feature,
however. Technically the standalone vote cooldown resetting could also
be added back if ever desired however there doesn't seem to be that much
of a use case for that at the moment.

This feature ought to be a lot more convenient now as it allows for
resetting back to a set starting point no matter where the player is in
a run. It isn't universally useful as All Campaigns Legacy solo runs
require switching to a different type of server and Main Campaigns co-op
runs require restarting the game after Swamp Fever to work around the
god mode bug, however it is still useful in a good few situations.

Unfortunately this turned out to be pretty complex to implement, first
requiring a bunch of interop with valve's rather wacky KeyValues stuff,
and then requiring a bunch of especially difficult reverse engineering
of L4D1 v1.0.0.5 because it doesn't use said KeyValues stuff and does
something else completely different instead.

A side effect of all this work is that the nag removal hack is now part
of the KeyValues stuff in kvsys.c, which is kind of a comfier place for
it than just kind of dumped in the middle of sst.c.

1 files changed, 243 insertions, 0 deletions

diff --git a/src/l4dreset.c b/src/l4dreset.c
new file mode 100644
index 0000000..4bffa3c
--- /dev/null
+++ b/src/l4dreset.c
@@ -0,0 +1,243 @@
+/*
+ * Copyright © 2023 Willian Henrique <wsimanbrazil@yahoo.com.br>
+ * 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 <string.h>
+
+#include "con_.h"
+#include "engineapi.h"
+#include "ent.h"
+#include "errmsg.h"
+#include "feature.h"
+#include "gamedata.h"
+#include "gametype.h"
+#include "intdefs.h"
+#include "l4dmm.h"
+#include "mem.h"
+#include "vcall.h"
+#include "x86.h"
+#include "x86util.h"
+
+#ifdef _WIN32
+#define strcasecmp _stricmp
+#endif
+
+FEATURE("Left 4 Dead quick resetting")
+REQUIRE(ent)
+REQUIRE(l4dmm)
+
+static void **votecontroller;
+static int off_callerrecords = -1;
+static int off_voteissues;
+
+// Note: the vote callers vector contains these as elements. We don't currently
+// do anything with the structure, but keeping it here for reference.
+/*struct CallerRecord {
+	u32 steamid_trunc;
+	float last_time;
+	int votes_passed;
+	int votes_failed;
+	int last_issueidx;
+	bool last_passed;
+};*/
+
+// XXX: duping this again here... what makes sense to tidy this up?
+#ifdef _WIN32
+#define NVDTOR 1
+#else
+#define NVDTOR 2
+#endif
+
+struct CVoteIssue;
+DECL_VFUNC(const char *, SetIssueDetails, 1 + NVDTOR, const char *)
+DECL_VFUNC(const char *, GetDisplayString, 8 + NVDTOR)
+DECL_VFUNC(const char *, ExecuteCommand, 9 + NVDTOR)
+
+static struct CVoteIssue *getissue(const char *textkey) {
+	struct CUtlVector *issuevec = mem_offset(*votecontroller, off_voteissues);
+	struct CVoteIssue **issues = issuevec->m.mem;
+	for (int i = 0; /*i < issuevec->sz*/; ++i) { // key MUST be valid!
+		if (!strcmp(GetDisplayString(issues[i]), textkey)) return issues[i];
+	}
+}
+
+static void reset(void) {
+	// reset the vote cooldowns if possible (will skip L4D1). only necessary on
+	// versions >2045 and on map 1, but it's easiest to do unconditionally
+	if (off_callerrecords != -1) {
+		// Basically equivalent to CUtlVector::RemoveAll. The elements have no
+		// destructors to call. The resulting state is as if nobody has voted.
+		struct CUtlVector *recordvector = mem_offset(*votecontroller,
+				off_callerrecords);
+		recordvector->sz = 0;
+	}
+	struct CVoteIssue *issue = getissue("#L4D_vote_restart_game");
+	ExecuteCommand(issue);
+}
+
+static void change(const char *missionid) {
+	struct CVoteIssue *issue = getissue("#L4D_vote_mission_change");
+	SetIssueDetails(issue, missionid); // will just nop if invalid
+	ExecuteCommand(issue);
+}
+
+DEF_CCMD_HERE_UNREG(sst_l4d_quickreset,
+		"Reset (or switch) campaign and clear all vote cooldowns", 0) {
+	if (cmd->argc > 2) {
+		con_warn("usage: sst_l4d_quickreset [campaignid]\n");
+		return;
+	}
+	if (!*votecontroller) {
+		con_warn("not hosting a server\n");
+		return;
+	}
+	if (cmd->argc == 2) {
+		const char *cur = l4dmm_curcampaign();
+		if (!cur || strcasecmp(cur, cmd->argv[1])) {
+			change(cmd->argv[1]);
+			return;
+		}
+	}
+	reset();
+}
+
+PREINIT { return GAMETYPE_MATCHES(L4D); }
+
+// This finds the g_voteController variable using the listissues callback, and
+// returns a pointer to the rest of the bytes for find_voteissues() below
+static inline const uchar *find_votecontroller(con_cmdcbv1 listissues_cb) {
+	const uchar *insns = (const uchar *)listissues_cb;
+#ifdef _WIN32
+	// The "listissues" command calls CVoteController::ListIssues, loading
+	// g_voteController into ECX
+	for (const uchar *p = insns; p - insns < 32;) {
+		if (p[0] == X86_MOVRMW && p[1] == X86_MODRM(0, 1, 5)) {
+			votecontroller = mem_loadptr(p + 2);
+			return p;
+		}
+		NEXT_INSN(p, "g_voteController variable");
+	}
+#else
+#warning TODO(linux): this will be different
+#endif
+	return 0;
+}
+
+// This finds ListIssues() using the instruction pointer returned by
+// find_votecontroller() above, and then uses that to find the vote issue list.
+static inline bool find_voteissues(const uchar *insns) {
+#ifdef _WIN32
+	for (const uchar *p = insns; p - insns < 16;) {
+		// Look for the last call before the ret - that has to be ListIssues()
+		if (p[0] == X86_CALL && p[5] == X86_RET) {
+			insns = p + 5 + mem_loadoffset(p + 1);
+			goto ok;
+		}
+		NEXT_INSN(p, "ListIssues call");
+	}
+	return false;
+ok:	for (const uchar *p = insns; p - insns < 96;) {
+		// There's a virtual call on each actual CVoteIssue in the loop over the
+		// list. That entails putting the issue pointer in ECX, which involves
+		// loading that pointer from the vector, which exists at an offset from
+		// `this`, meaning we can find the offset from the mov into ECX.
+		if (p[0] == X86_MOVRMW && (p[1] & 0xF8) == 0x88) {
+			int off = mem_loadoffset(p + 2);
+			if (off > 800) { // sanity check: offset is always fairly high
+				off_voteissues = off;
+				return true;
+			}
+		}
+		// Further complication: at least in 2045 there's a short jmp over some
+		// invalid instruction bytes. I guess there's no reason to ever expect
+		// something interesting after an unconditional jmp, so just follow it.
+		if (p[0] == X86_JMPI8) {
+			p += 2 + ((s8 *)p)[1];
+			continue;
+		}
+		NEXT_INSN(p, "offset to vote issue vector");
+	}
+#else
+#warning TODO(linux): and also this
+#endif
+	return false;
+}
+
+// This finds the caller record vector using a pointer to the
+// CVoteController::Spawn function
+static inline bool find_votecallers(void *votectrlspawn) {
+#ifdef _WIN32
+	const uchar *insns = (const uchar *)votectrlspawn;
+	for (const uchar *p = insns; p - insns < 64;) {
+		// Unsure what the member on this offset actually is (the game seems to
+		// want it to be set to 0 to allow votes to happen), but the vector we
+		// want seems to consistently be 8 bytes after whatever this is
+		// "mov dword ptr [<reg> + off], 0", mod == 0b11
+		if (p[0] == X86_MOVMIW && (p[1] & 0xC0) == 0x80 &&
+				mem_load32(p + 6) == 0) {
+			off_callerrecords = mem_load32(p + 2) + 8;
+			return true;
+		}
+		NEXT_INSN(p, "offset to vote caller record vector");
+	}
+#else
+#warning TODO(linux): this too
+#endif
+	return false;
+}
+
+INIT {
+	struct con_cmd *cmd_listissues = con_findcmd("listissues");
+	if (!cmd_listissues) {
+		errmsg_errorx("couldn't find \"listissues\" command");
+		return false;
+	}
+	con_cmdcbv1 listissues_cb = con_getcmdcbv1(cmd_listissues);
+	const uchar *nextinsns = find_votecontroller(listissues_cb);
+	if (!nextinsns) {
+		errmsg_errorx("couldn't find vote controller variable");
+		return false;
+	}
+	if (!find_voteissues(nextinsns)) {
+		errmsg_errorx("couldn't find vote issues list offset\n");
+		return false;
+	}
+	// only bother with vote cooldown stuff for L4D2, since all versions of L4D1
+	// have unlimited votes anyway. NOTE: assuming L4D2 always has Spawn in
+	// gamedata (which has no reason to stop being true...)
+	if (GAMETYPE_MATCHES(L4D2)) {
+		// g_voteController may have not been initialized yet so we get the
+		// vtable from the ent factory
+		const struct CEntityFactory *factory = ent_getfactory("vote_controller");
+		if (!factory) {
+			errmsg_errorx("couldn't find vote controller entity factory");
+			goto nocd;
+		}
+		void **vtable = ent_findvtable(factory, "CVoteController");
+		if (!vtable) {
+			errmsg_errorx("couldn't find CVoteController vtable");
+			goto nocd;
+		}
+		if (!find_votecallers(vtable[vtidx_Spawn])) {
+			errmsg_errorx("couldn't find vote callers list offset");
+nocd:		errmsg_note("resetting a first map will not clear vote cooldowns");
+		}
+	}
+	con_reg(sst_l4d_quickreset);
+	return true;
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80