#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;

}