Small code changes; add ability to find audio functions and data.

Audio is weird. I've been working for a few days to figure out how to
correctly render the audio but in that time I've done some other minor
refactors so I figured I migth as well just push those. Audio should be
coming soon, but no promises.

1 files changed, 115 insertions, 25 deletions

diff --git a/api.c b/api.c
index 0562bba..f2be734 100644
--- a/api.c
+++ b/api.c
@@ -21,14 +21,28 @@
 #include "log.h"
 #include "sst/x86.h"
 
-struct engserver *engserver = NULL;
-struct engclient *engclient = NULL;
-struct engineapi *engineapi = NULL;
-struct enginetools *enginetools = NULL;
-struct demoplayer *demoplayer = NULL;
-struct videomode **videomode = NULL;
-struct movieinfo *movieinfo = NULL;
-void (*cbuf_addtext)(char *) = NULL;
+struct engserver *engserver = 0;
+struct engclient *engclient = 0;
+struct engineapi *engineapi = 0;
+struct enginetools *enginetools = 0;
+struct cvar *cvar = 0;
+struct demoplayer *demoplayer = 0;
+struct videomode **videomode = 0;
+struct movieinfo *movieinfo = 0;
+struct audio_device **audio_device = 0;
+struct soundstate *snd = 0;
+void (*snd_recordbuffer)(void) = 0;
+void (*cbuf_addtext)(char *) = 0;
+
+// This macro is Copyright 2024 Michael Smith under the same license as above.
+#define NEXT_INSN(p, tgt) do { \
+	int _len = x86_len(p); \
+	if (_len == -1) { \
+		bail("unknown or invalid instruction looking for %s", tgt); \
+		return false; \
+	} \
+	(p) += _len; \
+} while (0)
 
 // TODO: should this be split up?
 
@@ -36,15 +50,22 @@ bool api_init(void) {
 	void *engine_dll = os_dlhandle("engine");
 	createinterface_func engine_factory =
 		(createinterface_func)os_dlsym(engine_dll, "CreateInterface");
+
+	void *vstdlib_dll = os_dlhandle("vstdlib");
+	createinterface_func vstdlib_factory =
+		(createinterface_func)os_dlsym(vstdlib_dll, "CreateInterface");
+
 	if (!engine_factory) bail("couldn't get engine factory");
-	engserver = engine_factory(VENGINE_SERVER_INTERFACE_VERSION, NULL);
+	engserver = engine_factory(VENGINE_SERVER_INTERFACE_VERSION, 0);
 	if (!engserver) bail("couldn't get IVEngineServer from engine");
-	engclient = engine_factory(VENGINE_CLIENT_INTERFACE_VERSION, NULL);
+	engclient = engine_factory(VENGINE_CLIENT_INTERFACE_VERSION, 0);
 	if (!engclient) bail("couldn't get IVEngineClient from engine");
-	engineapi = engine_factory(VENGINE_LAUNCHER_INTERFACE_VERSION, NULL);
+	engineapi = engine_factory(VENGINE_LAUNCHER_INTERFACE_VERSION, 0);
 	if (!engineapi) bail("couldn't get IEngineAPI from engine");
-	enginetools = engine_factory(VENGINE_TOOL_INTERFACE_VERSION, NULL);
+	enginetools = engine_factory(VENGINE_TOOL_INTERFACE_VERSION, 0);
 	if (!engineapi) bail("couldn't get IEngineTools from engine");
+	cvar = vstdlib_factory(VENGINE_CVAR_INTERFACE_VERSION, 0);
+	if (!cvar) bail("couldn't get ICVar from vstdlib");
 
 	// find cbuf_addtext
 	const u8 *instr = (const u8 *)engserver->vt->server_command;
@@ -55,10 +76,7 @@ bool api_init(void) {
 			// jump is relative to after the instruction
 			cbuf_addtext = (void (*)(char *))(p + 5 + *(i32 *)(p + 1));
 		}
-		int l = x86_len(p);
-		if (l == -1)
-			bail("invalid instruction looking for cbuf_addtext");
-		p += l;
+		NEXT_INSN(p, "CBuf_AddText");
 	}
 	if (!cbuf_addtext) bail("couldn't find cbuf_addtext");
 
@@ -85,10 +103,7 @@ bool api_init(void) {
 			videomode = *(struct videomode ***)(p + 2);
 			break;
 		}
-		int l = x86_len(p);
-		if (l == -1)
-			bail("invalid instruction looking for videomode");
-		p += l;
+		NEXT_INSN(p, "videomode");
 	}
 	debug("videomode = %p", (void *)videomode);
 
@@ -97,16 +112,13 @@ bool api_init(void) {
 		// step 1: find CL_IsRecordingMovie() in
 		// CEngineTools::StartMovieRecording
 		instr = (const u8 *)enginetools->vt->start_movie_recording;
-		void *cl_isrecordingmovie = NULL;
+		void *cl_isrecordingmovie = 0;
 		for (const u8 *p = instr; p - instr < 64;) {
 			// this is the first call in the function
 			if (*p == X86_CALL) {
 				cl_isrecordingmovie = (void *)(p + 5 + *(i32 *)(p + 1));
 			}
-			int l = x86_len(p);
-			if (l == -1)
-				bail("invalid instruction looking for CL_IsRecordingMovie");
-			p += l;
+			NEXT_INSN(p, "CL_IsRecordingMovie");
 		}
 		if (!cl_isrecordingmovie)
 			bail("couldn't find cbuf_addtext CL_IsRecordingMovie");
@@ -120,6 +132,84 @@ bool api_init(void) {
 		debug("movieinfo = %p", (void *)movieinfo);
 	}
 	
+	// find SND_RecordBuffer... this is something!
+	{
+		// step 1: Find S_Init() in snd_restart
+		struct concommand *snd_restart = cvar->vt->find_command(cvar, "snd_restart");
+		instr = (const u8 *)snd_restart->callback;
+		void *s_init = 0;
+		// S_Init is the 3rd call in Snd_Restart_f
+		int call_count = 0;
+		for (const u8 *p = instr; p - instr < 64;) {
+			if (*p == X86_CALL && ++call_count == 3)
+				s_init = (void *)(p + 5 + *(i32 *)(p + 1));
+			NEXT_INSN(p, "S_Init");
+		}
+		debug("S_Init = %p", (void *)s_init);
+		if (!s_init) bail("couldn't find S_Init");
+		// step 2: find g_AudioDevice in S_Init
+		// g_AudioDevice is the first variable assignment after the check for
+		// the -nosound command line arg. look for that.
+		instr = (const u8 *)s_init;
+		bool nosound_push = false;
+		for (const u8 *p = instr; p - instr < 180;) {
+			if (p[0] == X86_PUSHIW 
+					&& !strcmp(*(const char **)(p + 1), "-nosound"))
+				nosound_push = true;
+			if (nosound_push && p[0] == X86_MOVIIEAX) {
+				audio_device = *(struct audio_device ***)(p + 1);
+				break;
+			}
+			NEXT_INSN(p, "g_AudioDevice");
+		}
+		debug("g_AudioDevice = %p", (void *)audio_device);
+		if (!audio_device) bail("couldn't get ptr to g_AudioDevice");
+	}
+	return true;
+}
+
+bool api_find_snd_recordbuffer(void) {
+	// continuation, we must do this part later
+	// step 3: Find S_TransferStereo16 in CAudioDirectSound::TransferSamples
+	void *transferstereo16 = 0;
+	const u8 *instr = (*audio_device)->vt->transfer_samples;
+	debug("CAudioDirectSound::TransferSamples = %p", (void *)instr);
+	// S_TransferStereo16 is the 8th call in TransferSamples
+	int call_count = 0;
+	for (const u8 *p = instr; p - instr < 384 /* big func! */;) {
+		if (*p == X86_CALL && ++call_count == 8)
+			transferstereo16 = (void *)(p + 5 + *(i32 *)(p + 1));
+		NEXT_INSN(p, "S_TransferStereo16");
+	}
+	if (!transferstereo16)
+		bail("couldn't find transferstereo16");
+	debug("S_TransferStereo16 = %p", transferstereo16);
+	// step 4: find SND_RecordBuffer in S_TransferStereo16
+	// it should be the next call after an 'add ecx, ecx'
+	// We are also going to get Snd_WriteLinearBlastStereo16 to get some other
+	// variables we need.
+	instr = (const u8 *)transferstereo16;
+	bool found_double = false;
+	bool found_recbuf = false;
+	for (const u8 *p = instr; p - instr < 192;) {
+		if (p[0] == X86_ADDRMW && p[1] == X86_MODRM(3, 1, 1))
+			found_double = true;
+		else if (p[0] == X86_CALL && found_double && !found_recbuf) {
+			found_recbuf = true;
+			snd_recordbuffer = (void (*)(void))(p + 5 + *(i32 *)(p + 1));
+		}
+		// this will be the next call
+		else if (p[0] == X86_CALL && found_double && found_recbuf) {
+			// this looks outrageous! that is because it is.
+			snd = (struct soundstate *)(p + 5 + *(i32 *)(p + 1) + 3);
+			break;
+		}
+		NEXT_INSN(p, "SND_RecordBuffer");
+	}
+	if (!snd_recordbuffer)
+		bail("couldn't find snd_recordbuffer");
+	debug("SND_RecordBuffer = %p", (void *)snd_recordbuffer);
+	debug("Snd_WriteLinearBlastStereo16 + 3 = %p", (void *)snd);
 	return true;
 }