gistfile1.cpp

/*
 * Lag compensation has a bug where animation cycletime is off by two ticks,
 * which makes it difficult to hit people jumping or transitioning to a duck.
 * Altimor has taken a break from his Persona 3 toaster waifu to correct this
 * catastrophe. APPLAUSE
 */
#include "util.h"
#include "plugin.h"
#include "lagcomp.h"
#include "baseanimating.h"

#include <stdexcept>
#include <cstdint>
#include <Windows.h>
#include <detours.h>

// Returns in xmm0
using SequenceDuration_t = __m128(__thiscall*)(
		const CBaseAnimating *base_animating,
		const void *studiohdr,
		const int sequence);

// CBaseAnimating::SequenceDuration
static SequenceDuration_t SequenceDuration;

/**
 * SequenceDuration_wrap - Make SequenceDuration usable from C++ code
 * @base_animating:	Pointer to the CBaseAnimating
 * @sequence:		Sequence number
 *
 * Return a 32 bit float instead of a 128 bit xmm register
 */
static float SequenceDuration_wrap(
		const CBaseAnimating *base_animating,
		const int sequence)
{
	const auto *studiohdr = *(void**)((uintptr_t)(base_animating) + 0x490);
	const auto xmm0 = SequenceDuration(base_animating, studiohdr, sequence);

	float result;
	_mm_store_ss(&result, xmm0);
	return result;
}

ConVar cycle_offset("sv_lagcomp_anim_offset", "2");

using UpdateLagRecords_t = void(__stdcall*)(
		const CBaseAnimating *player,
		CUtlFixedLinkedList<LagRecord> *track,
		const int a3);

static UpdateLagRecords_t orig_UpdateLagRecords;

/**
 * hook_UpdateLagRecords - Hook for CLagCompensationManager::UpdateLagRecords
 * @player:	Pointer to player to be updated
 * @track:	Pointer to list of LagRecords
 * @a3:		Never used in the original function, great job Valve
 *
 * Advance the master cycle and layer cycles by the desired number of ticks
 */
static void __stdcall hook_UpdateLagRecords(
		const CBaseAnimating *player,
		CUtlFixedLinkedList<LagRecord> *track,
		const int a3)
{
	orig_UpdateLagRecords(player, track, a3);

	const auto apply_fix = [player](float *cycle, const int sequence)
	{
		const auto duration = SequenceDuration_wrap(player, sequence);
		*cycle += cycle_offset.GetFloat() / duration / 64.f;
	};
	auto &record = track->Element(track->Head());
	apply_fix(&record.m_masterCycle, record.m_masterSequence);

	for(auto &layer : record.m_layerRecords)
		apply_fix(&layer.m_cycle, layer.m_sequence);
}

/**
 * plugin::Load - Valve plugin load method override
 * @interfaceFactory:	engine.dll factory
 * @gameServerFactory:	server.dll factory
 *
 * Grab offsets and detour the function where anim cycletime is saved
 */
bool plugin::Load(
		CreateInterfaceFn interfaceFactory,
		CreateInterfaceFn gameServerFactory)
{
	ConnectTier1Libraries(&interfaceFactory, 1);
	ConnectTier2Libraries(&interfaceFactory, 1);
	ConVar_Register(0);

	uintptr_t start, end;
	get_module_bounds("server.dll", &start, &end);

	// Scan for CLagCompensationManager::UpdateLagRecords
	uintptr_t UpdateLagRecords;
	try {
		const auto *UpdateLagRecords_sig = "\x53\x56\x57\x81\xF9";
		const auto *UpdateLagRecords_mask = "xxxxx";
		UpdateLagRecords = sigscan(
				start,
				end,
				UpdateLagRecords_sig,
				UpdateLagRecords_mask) - 0xF;

		const auto *SequenceDuration_sig = "\x85\xF6\x75\x2F\x8B\x47\x5C";
		const auto *SequenceDuration_mask = "xxxxxxx";
		SequenceDuration = (SequenceDuration_t)(sigscan(
				start,
				end,
				SequenceDuration_sig,
				SequenceDuration_mask) - 0xA);
	} catch(...) {
		Error("Sigscans failed!\n");
		return false;
	}
	orig_UpdateLagRecords = (UpdateLagRecords_t)(DetourFunction(
			(byte*)(UpdateLagRecords),
			(byte*)(hook_UpdateLagRecords)));

	return true;
}

/**
 * plugin::Unload - Valve plugin unload method override
 *
 * Unregister the ICVar and disconnect libraries
 */
void plugin::Unload()
{
	ConVar_Unregister();
	DisconnectTier2Libraries();
	DisconnectTier1Libraries();
}