#include <stdio.h>

 #include <dlfcn.h>

 #include "string.h"

 #include "malloc.h"

 extern "C" char * cplus_demangle(const char *, int);

 #define DMGL_PARAMS	 (1 << 0)

 struct VOffset

 {

 	int linux_offset;

 	int windows_offset;

 };

 static bool FindVFunc(void *handle, void **vtable, const char* vtable_end, const char *class_function, const char *params, VOffset *offsets);

 int main(int argc, char **argv)

 {

 	void *handle;

 	void **pVtable;

 	VOffset offsets;

 	char *params = NULL;

 	bool ret;

 	if (argc < 4)

 	{

 		fprintf(stderr, "Usage: <binary> <vtable start symbol> <function> <optional: params> <optional: vtable end symbol>\n");

 		return -1;

 	}

 	handle = dlopen(argv[1], RTLD_NOW);

 	if (handle == NULL)

 	{

 		fprintf(stderr, "Failed to open server image, error [%s]\n", dlerror());

 		return -1;

 	}

 	pVtable = (void **)dlsym(handle, argv[2]);

 	if (pVtable == NULL)

 	{

 		char startSym[128];

 		snprintf(startSym, sizeof(startSym), "_ZTV%d%s", strlen(argv[2]), argv[2]);

 		pVtable = (void **)dlsym(handle, startSym);

 	}

 	if (pVtable == NULL)

 	{

 		fprintf(stderr, "Invalid vtable symbol \"%s\"\n", argv[2]);

 		dlclose(handle);

 		return -1;

 	}

 	if (argc >= 5)

 	{

 		params = argv[4];

 		if (params[0] == '"')

 		{

 			params++;

 		}

 		int len = strlen(params)-1;

 		if (params[len] == '"')

 		{

 			params[len] = '\0';

 		}

 		if (params[0] == 0)

 		{

 			params = NULL;

 		}

 	}

 	if (argc == 6)

 	{

 		ret = FindVFunc(handle, pVtable, argv[5], argv[3], params, &offsets);

 	}

 	else

 	{

 		ret = FindVFunc(handle, pVtable, "_ZTI", argv[3], params, &offsets);

 	}

 	if (ret)

 	{

 		if (params != NULL)

 		{

 			printf("%s%s - Win: %i  Linux : %i\n", argv[3], params, offsets.windows_offset, offsets.linux_offset);

 		}

 		else

 		{

 			printf("%s - Win: %i  Linux : %i\n", argv[3], offsets.windows_offset, offsets.linux_offset);

 		}

 		dlclose(handle);

 		return 0;

 	}

 	fprintf(stderr, "Failed to find function!");

 	dlclose(handle);

 	return -1;

 }

 static bool FindVFunc(void *handle, void **vtable, const char* vtable_end, const char *class_function, const char *params, VOffset *offsets)

 {

 	Dl_info d;

 	int linux_offset = -1;

 	int windows_offset = -1;

 	int overloads = 0;

 	int location = 0;

 	int start_offset = -1;

 	for (int i=0; i< 1000; i++)

 	{

 		void *FuncPtr = vtable[i];

 		int status = dladdr(FuncPtr, &d);

 		if (!status)

 		{

 			continue;

 		}

 		if (i > 1 && strncmp(d.dli_sname, vtable_end, strlen(vtable_end)) == 0)

 		{

 			break;

 		}

 		char *name = cplus_demangle(d.dli_sname, DMGL_PARAMS);

 		if (name == NULL)

 		{

 			printf("Demangling failed\n");

 			continue;

 		}

 		char *foundfunction = strpbrk(name, ":");

 		if (foundfunction == NULL)

 		{

 			//printf("Couldnt split function\n");

 			free(name);

 			continue;

 		}

 		//Skip both ':' chars

 		foundfunction += 2;

 		if (strncmp(foundfunction, class_function, strlen(class_function)) == 0 && foundfunction[strlen(class_function)] == '(')

 		{

 			//printf("Symbol: %s Demangled: %s Offset: %i\n", d.dli_sname, name, i);

 			//We have a pointer to a function, but it may be overloaded.

 			overloads++;

 			if (start_offset == -1)

 			{

 				start_offset = i-1;

 			}

 			char *foundparams = strpbrk(foundfunction, "(");

 			if (foundparams == NULL)

 			{

 				printf("ARGH\n");

 				free(name);

 				continue;

 			}

 			if(params == NULL || strcmp(foundparams, params) == 0)

 			{

 				//This is actually our function - So this is the linux offset

 				linux_offset = i;

 				location = overloads;

 			}

 		}

 		free(name);

 	}

 	windows_offset = (overloads-location) + start_offset;

 	offsets->linux_offset = linux_offset - 2;

 	offsets->windows_offset = windows_offset - 2;

 	return true;

 }