ffi.c
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ffi.c
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	#ifdef _WIN32
	#include <windows.h>
	#define dlopen(name, flags) ((void*)LoadLibraryA(name))
	#define dlsym(handle, name) ((void*)GetProcAddress((HMODULE)(handle), (name)))
	#define dlclose(handle) FreeLibrary((HMODULE)(handle))
	#define dlerror() "LoadLibrary failed"
	#define RTLD_LAZY 0
	#else
	#include <dlfcn.h>
	#endif
	#include <ffi.h>
	#include <pthread.h>
	#include <stdlib.h>
	#include <string.h>
	#include <utarray.h>
	#include <uthash.h>

	#include "errors.h"
	#include "internal.h"

	#include "modules/ffi.h"
	#include "modules/symbol.h"

	typedef struct ffi_lib {
	char name[256];
	void *handle;
	jsval_t js_obj;
	UT_hash_handle hh;
	} ffi_lib_t;

	typedef struct ffi_func {
	char name[256];
	void *func_ptr;
	ffi_cif cif;
	ffi_type **arg_types;
	ffi_type *ret_type;
	char ret_type_str[32];
	int arg_count;
	bool is_variadic;
	UT_hash_handle hh;
	} ffi_func_t;

	typedef struct ffi_ptr {
	void *ptr;
	size_t size;
	bool is_managed;
	uint64_t ptr_key;
	UT_hash_handle hh;
	} ffi_ptr_t;

	typedef struct ffi_callback {
	ffi_closure *closure;
	void *code_ptr;
	ffi_cif cif;
	ffi_type **arg_types;
	ffi_type *ret_type;
	char ret_type_str[32];
	char **arg_type_strs;
	int arg_count;
	struct js *js;
	jsval_t js_func;
	uint64_t cb_key;
	UT_hash_handle hh;
	} ffi_callback_t;

	static ffi_lib_t *ffi_libraries = NULL;
	static ffi_ptr_t *ffi_pointers = NULL;
	static ffi_callback_t *ffi_callbacks = NULL;
	static UT_array *ffi_functions_array = NULL;

	static pthread_mutex_t ffi_libraries_mutex = PTHREAD_MUTEX_INITIALIZER;
	static pthread_mutex_t ffi_functions_mutex = PTHREAD_MUTEX_INITIALIZER;
	static pthread_mutex_t ffi_pointers_mutex = PTHREAD_MUTEX_INITIALIZER;
	static pthread_mutex_t ffi_callbacks_mutex = PTHREAD_MUTEX_INITIALIZER;

	static const UT_icd ffi_func_icd = {
	.sz = sizeof(ffi_func_t *),
	.init = NULL,
	.copy = NULL,
	.dtor = NULL,
	};

	static jsval_t ffi_dlopen(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_define(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_lib_call(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_call_function(struct js js, ffi_func_t func, jsval_t *args, int nargs);
	static jsval_t ffi_alloc_memory(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_free_memory(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_read_memory(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_write_memory(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_get_pointer(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_create_callback(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_free_callback(struct js js, jsval_t args, int nargs);
	static jsval_t ffi_read_ptr(struct js js, jsval_t args, int nargs);

	static ffi_type get_ffi_type(const char type_str);
	static void js_to_ffi_value(struct js js, jsval_t val, ffi_type type, void buffer);
	static jsval_t ffi_to_js_value(struct js js, void val, ffi_type type, const char type_str);
	static void ffi_callback_handler(ffi_cif cif, void ret, void *args, void user_data);

	jsval_t ffi_library(struct js *js) {
	jsval_t ffi_obj = js_mkobj(js);

	js_set(js, ffi_obj, "dlopen", js_mkfun(ffi_dlopen));
	js_set(js, ffi_obj, "alloc", js_mkfun(ffi_alloc_memory));
	js_set(js, ffi_obj, "free", js_mkfun(ffi_free_memory));
	js_set(js, ffi_obj, "read", js_mkfun(ffi_read_memory));
	js_set(js, ffi_obj, "write", js_mkfun(ffi_write_memory));
	js_set(js, ffi_obj, "pointer", js_mkfun(ffi_get_pointer));
	js_set(js, ffi_obj, "callback", js_mkfun(ffi_create_callback));
	js_set(js, ffi_obj, "freeCallback", js_mkfun(ffi_free_callback));
	js_set(js, ffi_obj, "readPtr", js_mkfun(ffi_read_ptr));

	const char *suffix;
	#ifdef __APPLE__
	suffix = "dylib";
	#elif defined(__linux__)
	suffix = "so";
	#elif defined(_WIN32)
	suffix = "dll";
	#else
	suffix = "so";
	#endif
	js_set(js, ffi_obj, "suffix", js_mkstr(js, suffix, strlen(suffix)));

	jsval_t ffi_types = js_mkobj(js);
	js_set(js, ffi_types, "void", js_mkstr(js, "void", 4));
	js_set(js, ffi_types, "int8", js_mkstr(js, "int8", 4));
	js_set(js, ffi_types, "int16", js_mkstr(js, "int16", 5));
	js_set(js, ffi_types, "int", js_mkstr(js, "int", 3));
	js_set(js, ffi_types, "int64", js_mkstr(js, "int64", 5));
	js_set(js, ffi_types, "uint8", js_mkstr(js, "uint8", 5));
	js_set(js, ffi_types, "uint16", js_mkstr(js, "uint16", 6));
	js_set(js, ffi_types, "uint64", js_mkstr(js, "uint64", 6));
	js_set(js, ffi_types, "float", js_mkstr(js, "float", 5));
	js_set(js, ffi_types, "double", js_mkstr(js, "double", 6));
	js_set(js, ffi_types, "pointer", js_mkstr(js, "pointer", 7));
	js_set(js, ffi_types, "string", js_mkstr(js, "string", 6));
	js_set(js, ffi_types, "spread", js_mkstr(js, "...", 3));
	js_set(js, ffi_obj, "FFIType", ffi_types);
	js_set(js, ffi_obj, get_toStringTag_sym_key(), js_mkstr(js, "FFI", 3));

	return ffi_obj;
	}

	static void ffi_init_array(void) {
	static int initialized = 0;
	if (initialized)
	return;
	initialized = 1;
	if (!ffi_functions_array)
	utarray_new(ffi_functions_array, &ffi_func_icd);
	}

	static jsval_t ffi_dlopen(struct js js, jsval_t args, int nargs) {
	if (nargs < 1 \|\| vtype(args[0]) != T_STR) {
	return js_mkerr(js, "dlopen() requires library name string");
	}

	ffi_init_array();

	size_t lib_name_len;
	const char *lib_name = js_getstr(js, args[0], &lib_name_len);

	pthread_mutex_lock(&ffi_libraries_mutex);

	ffi_lib_t *lib = NULL;
	HASH_FIND_STR(ffi_libraries, lib_name, lib);
	if (lib) {
	jsval_t result = lib->js_obj;
	pthread_mutex_unlock(&ffi_libraries_mutex);
	return result;
	}

	pthread_mutex_unlock(&ffi_libraries_mutex);

	void *handle = dlopen(lib_name, RTLD_LAZY);
	if (!handle) {
	return js_mkerr(js, "Failed to load library: %s", dlerror());
	}

	lib = (ffi_lib_t *)malloc(sizeof(ffi_lib_t));
	if (!lib) {
	dlclose(handle);
	return js_mkerr(js, "Out of memory");
	}

	strncpy(lib->name, lib_name, sizeof(lib->name) - 1);
	lib->name[sizeof(lib->name) - 1] = '\0';
	lib->handle = handle;

	lib->js_obj = js_mkobj(js);
	js_set(js, lib->js_obj, "__lib_ptr", js_mknum((double)(uint64_t)lib));
	js_set(js, lib->js_obj, "define", js_mkfun(ffi_define));
	js_set(js, lib->js_obj, "call", js_mkfun(ffi_lib_call));

	pthread_mutex_lock(&ffi_libraries_mutex);
	HASH_ADD_STR(ffi_libraries, name, lib);
	pthread_mutex_unlock(&ffi_libraries_mutex);

	return lib->js_obj;
	}

	static jsval_t ffi_define(struct js js, jsval_t args, int nargs) {
	if (nargs < 2 \|\| vtype(args[0]) != T_STR) {
	return js_mkerr(js, "define() requires function name string and signature");
	}

	jsval_t this_obj = js_getthis(js);
	jsval_t lib_ptr_val = js_get(js, this_obj, "__lib_ptr");
	if (vtype(lib_ptr_val) != T_NUM) {
	return js_mkerr(js, "Invalid library object");
	}

	size_t func_name_len;
	const char *func_name = js_getstr(js, args[0], &func_name_len);

	jsval_t sig = args[1];
	int sig_type = vtype(sig);
	if (sig_type == T_STR \|\| sig_type == T_NUM \|\| sig_type == T_NULL \|\|
	sig_type == T_UNDEF) {
	return js_mkerr(js,
	"Signature must be an array [returnType, [argTypes...]] or "
	"an object {args: [...], returns: type}");
	}

	const char *ret_type_str;
	jsval_t arg_types_arr;
	int arg_count;

	jsval_t returns_val = js_get(js, sig, "returns");
	jsval_t args_val = js_get(js, sig, "args");

	if (vtype(returns_val) != T_UNDEF && vtype(args_val) != T_UNDEF) {
	if (vtype(returns_val) != T_STR) {
	return js_mkerr(js, "Return type must be a string");
	}
	ret_type_str = js_getstr(js, returns_val, NULL);
	arg_types_arr = args_val;

	if (vtype(arg_types_arr) == T_STR \|\| vtype(arg_types_arr) == T_NUM \|\|
	vtype(arg_types_arr) == T_NULL \|\|
	vtype(arg_types_arr) == T_UNDEF) {
	return js_mkerr(js, "Argument types must be an array");
	}

	jsval_t length_val = js_get(js, arg_types_arr, "length");
	arg_count = (int)js_getnum(length_val);
	} else {
	jsval_t ret_type_val = js_get(js, sig, "0");
	if (vtype(ret_type_val) != T_STR) {
	return js_mkerr(js, "Return type must be a string");
	}

	ret_type_str = js_getstr(js, ret_type_val, NULL);
	arg_types_arr = js_get(js, sig, "1");

	int arg_arr_type = vtype(arg_types_arr);
	if (arg_arr_type == T_STR \|\| arg_arr_type == T_NUM \|\|
	arg_arr_type == T_NULL \|\| arg_arr_type == T_UNDEF) {
	return js_mkerr(js, "Argument types must be an array");
	}

	jsval_t length_val = js_get(js, arg_types_arr, "length");
	arg_count = (int)js_getnum(length_val);
	}

	ffi_type *ret_type = get_ffi_type(ret_type_str);
	if (!ret_type) {
	return js_mkerr(js, "Unknown return type: %s", ret_type_str);
	}

	ffi_lib_t lib = (ffi_lib_t )(uint64_t)js_getnum(lib_ptr_val);
	void *func_ptr = dlsym(lib->handle, func_name);
	if (!func_ptr) {
	return js_mkerr(js, "Function '%s' not found", func_name);
	}

	ffi_func_t func = (ffi_func_t )malloc(sizeof(ffi_func_t));
	if (!func) {
	return js_mkerr(js, "Out of memory");
	}

	strncpy(func->name, func_name, sizeof(func->name) - 1);
	func->name[sizeof(func->name) - 1] = '\0';
	func->func_ptr = func_ptr;
	func->ret_type = ret_type;
	strncpy(func->ret_type_str, ret_type_str, sizeof(func->ret_type_str) - 1);
	func->ret_type_str[sizeof(func->ret_type_str) - 1] = '\0';
	func->arg_count = arg_count;
	func->is_variadic = false;

	if (arg_count > 0) {
	func->arg_types = (ffi_type *)malloc(sizeof(ffi_type ) * arg_count);
	if (!func->arg_types) {
	free(func);
	return js_mkerr(js, "Out of memory");
	}

	for (int i = 0; i < arg_count; i++) {
	char idx_str[16];
	snprintf(idx_str, sizeof(idx_str), "%d", i);
	jsval_t arg_type_val = js_get(js, arg_types_arr, idx_str);

	if (vtype(arg_type_val) != T_STR) {
	free(func->arg_types);
	free(func);
	return js_mkerr(js, "Argument type must be a string");
	}

	const char *arg_type_str = js_getstr(js, arg_type_val, NULL);

	if (strcmp(arg_type_str, "...") == 0) {
	func->is_variadic = true;
	func->arg_count = i;
	break;
	}

	func->arg_types[i] = get_ffi_type(arg_type_str);
	if (!func->arg_types[i]) {
	free(func->arg_types);
	free(func);
	return js_mkerr(js, "Unknown argument type: %s", arg_type_str);
	}
	}
	} else {
	func->arg_types = NULL;
	}

	if (!func->is_variadic) {
	ffi_status status =
	ffi_prep_cif(&func->cif, FFI_DEFAULT_ABI, func->arg_count, ret_type, func->arg_types);
	if (status != FFI_OK) {
	if (func->arg_types)
	free(func->arg_types);
	free(func);
	return js_mkerr(js, "Failed to prepare function call (status=%d, argc=%d)", status, func->arg_count);
	}
	}

	pthread_mutex_lock(&ffi_functions_mutex);
	utarray_push_back(ffi_functions_array, &func);
	unsigned int func_index = utarray_len(ffi_functions_array) - 1;
	pthread_mutex_unlock(&ffi_functions_mutex);

	js_set(js, this_obj, func_name, js_mkffi(func_index));

	return js_mkundef();
	}

	static jsval_t ffi_lib_call(struct js js, jsval_t args, int nargs) {
	jsval_t lib_obj = js_getthis(js);
	if (nargs < 1 \|\| vtype(args[0]) != T_STR)
	return js_mkerr(js, "call() requires function name string");

	size_t func_name_len;
	const char *func_name = js_getstr(js, args[0], &func_name_len);

	jsval_t ffi_val = js_get(js, lib_obj, func_name);
	int func_index = js_getffi(ffi_val);
	if (func_index < 0) {
	return js_mkerr(js, "Function '%s' not defined", func_name);
	}

	return ffi_call_by_index(js, (unsigned int)func_index, args + 1, nargs - 1);
	}

	static jsval_t ffi_call_function(struct js js, ffi_func_t func, jsval_t *args,int nargs) {
	if (!func->is_variadic && nargs != func->arg_count) {
	return js_mkerr(js, "Function '%s' expects %d arguments, got %d", func->name, func->arg_count, nargs);
	}

	if (func->is_variadic && nargs < func->arg_count) {
	return js_mkerr(js, "Function '%s' expects at least %d arguments, got %d", func->name, func->arg_count, nargs);
	}

	#define MAX_ARGS 32
	void *arg_values_buf[MAX_ARGS];
	ffi_arg arg_buffers_buf[MAX_ARGS];

	int actual_arg_count = func->is_variadic ? nargs : func->arg_count;

	if (actual_arg_count > MAX_ARGS) {
	return js_mkerr(js, "Too many arguments");
	}

	void **arg_values = arg_values_buf;
	memset(arg_values, 0, sizeof(arg_values_buf));

	for (int i = 0; i < actual_arg_count; i++) {
	arg_values[i] = &arg_buffers_buf[i];
	memset(arg_values[i], 0, sizeof(ffi_arg));

	ffi_type *arg_type;
	if (i < func->arg_count) {
	arg_type = func->arg_types[i];
	} else arg_type = &ffi_type_sint32;

	js_to_ffi_value(js, args[i], arg_type, arg_values[i]);
	}

	ffi_arg result;
	memset(&result, 0, sizeof(result));

	if (func->is_variadic) {
	#define MAX_VARIADIC_ARGS 32
	ffi_type *all_arg_types[MAX_VARIADIC_ARGS];

	if (actual_arg_count > MAX_VARIADIC_ARGS) {
	return js_mkerr(js, "Too many variadic arguments");
	}

	for (int i = 0; i < func->arg_count; i++) all_arg_types[i] = func->arg_types[i];
	for (int i = func->arg_count; i < actual_arg_count; i++) all_arg_types[i] = &ffi_type_sint32;

	ffi_cif call_cif;
	ffi_status status =
	ffi_prep_cif_var(&call_cif, FFI_DEFAULT_ABI, func->arg_count,
	actual_arg_count, func->ret_type, all_arg_types);

	if (status != FFI_OK) {
	return js_mkerr(js, "Failed to prepare variadic call CIF (status=%d)", status);
	}

	ffi_call(&call_cif, func->func_ptr, &result, arg_values);
	} else {
	ffi_call(&func->cif, func->func_ptr, &result, arg_values);
	}

	return ffi_to_js_value(js, &result, func->ret_type, func->ret_type_str);
	}

	jsval_t ffi_call_by_index(struct js js, unsigned int func_index, jsval_t args, int nargs) {
	pthread_mutex_lock(&ffi_functions_mutex);
	if (func_index >= utarray_len(ffi_functions_array)) {
	pthread_mutex_unlock(&ffi_functions_mutex);
	return js_mkerr(js, "Invalid FFI function index");
	}

	ffi_func_t func = (ffi_func_t **)utarray_eltptr(ffi_functions_array, func_index);
	pthread_mutex_unlock(&ffi_functions_mutex);

	return ffi_call_function(js, func, args, nargs);
	}

	static jsval_t ffi_alloc_memory(struct js js, jsval_t args, int nargs) {
	if (nargs < 1 \|\| vtype(args[0]) != T_NUM) {
	return js_mkerr(js, "alloc() requires size");
	}

	size_t size = (size_t)js_getnum(args[0]);
	if (size == 0) {
	return js_mkerr(js, "alloc() requires non-zero size");
	}

	void *ptr = malloc(size);
	if (!ptr) {
	return js_mkerr(js, "alloc() failed to allocate memory");
	}

	ffi_ptr_t ffi_ptr = (ffi_ptr_t )malloc(sizeof(ffi_ptr_t));
	if (!ffi_ptr) {
	free(ptr);
	return js_mkerr(js, "Out of memory");
	}

	ffi_ptr->ptr = ptr;
	ffi_ptr->size = size;
	ffi_ptr->is_managed = true;
	ffi_ptr->ptr_key = (uint64_t)ptr;

	pthread_mutex_lock(&ffi_pointers_mutex);
	HASH_ADD(hh, ffi_pointers, ptr_key, sizeof(uint64_t), ffi_ptr);
	pthread_mutex_unlock(&ffi_pointers_mutex);

	return js_mknum((double)ffi_ptr->ptr_key);
	}

	static jsval_t ffi_free_memory(struct js js, jsval_t args, int nargs) {
	if (nargs < 1 \|\| vtype(args[0]) != T_NUM) {
	return js_mkerr(js, "free() requires pointer");
	}

	uint64_t ptr_key = (uint64_t)js_getnum(args[0]);

	pthread_mutex_lock(&ffi_pointers_mutex);
	ffi_ptr_t *ffi_ptr = NULL;
	HASH_FIND(hh, ffi_pointers, &ptr_key, sizeof(uint64_t), ffi_ptr);

	if (!ffi_ptr) {
	pthread_mutex_unlock(&ffi_pointers_mutex);
	return js_mkerr(js, "Invalid pointer");
	}

	if (ffi_ptr->is_managed) {
	free(ffi_ptr->ptr);
	}

	HASH_DEL(ffi_pointers, ffi_ptr);
	free(ffi_ptr);
	pthread_mutex_unlock(&ffi_pointers_mutex);

	return js_mkundef();
	}

	static jsval_t ffi_read_memory(struct js js, jsval_t args, int nargs) {
	if (nargs < 2 \|\| vtype(args[0]) != T_NUM \|\| vtype(args[1]) != T_STR) {
	return js_mkerr(js, "read() requires pointer and type");
	}

	uint64_t ptr_key = (uint64_t)js_getnum(args[0]);

	pthread_mutex_lock(&ffi_pointers_mutex);
	ffi_ptr_t *ffi_ptr = NULL;
	HASH_FIND(hh, ffi_pointers, &ptr_key, sizeof(uint64_t), ffi_ptr);

	if (!ffi_ptr) {
	pthread_mutex_unlock(&ffi_pointers_mutex);
	return js_mkerr(js, "Invalid pointer");
	}

	void *ptr = ffi_ptr->ptr;
	pthread_mutex_unlock(&ffi_pointers_mutex);

	const char *type_str = js_getstr(js, args[1], NULL);
	ffi_type *type = get_ffi_type(type_str);
	if (!type) {
	return js_mkerr(js, "Unknown type: %s", type_str);
	}

	return ffi_to_js_value(js, ptr, type, type_str);
	}

	static jsval_t ffi_write_memory(struct js js, jsval_t args, int nargs) {
	if (nargs < 3 \|\| vtype(args[0]) != T_NUM \|\| vtype(args[1]) != T_STR) {
	return js_mkerr(js, "write() requires pointer, type, and value");
	}

	uint64_t ptr_key = (uint64_t)js_getnum(args[0]);

	pthread_mutex_lock(&ffi_pointers_mutex);
	ffi_ptr_t *ffi_ptr = NULL;
	HASH_FIND(hh, ffi_pointers, &ptr_key, sizeof(uint64_t), ffi_ptr);

	if (!ffi_ptr) {
	pthread_mutex_unlock(&ffi_pointers_mutex);
	return js_mkerr(js, "Invalid pointer");
	}

	void *ptr = ffi_ptr->ptr;
	pthread_mutex_unlock(&ffi_pointers_mutex);

	const char *type_str = js_getstr(js, args[1], NULL);
	ffi_type *type = get_ffi_type(type_str);
	if (!type) {
	return js_mkerr(js, "Unknown type: %s", type_str);
	}

	js_to_ffi_value(js, args[2], type, ptr);

	return js_mkundef();
	}

	static jsval_t ffi_get_pointer(struct js js, jsval_t args, int nargs) {
	if (nargs < 1 \|\| vtype(args[0]) != T_NUM) return js_mkerr(js, "pointer() requires pointer");
	uint64_t ptr_key = (uint64_t)js_getnum(args[0]);

	pthread_mutex_lock(&ffi_pointers_mutex);
	ffi_ptr_t *ffi_ptr = NULL;
	HASH_FIND(hh, ffi_pointers, &ptr_key, sizeof(uint64_t), ffi_ptr);
	bool exists = ffi_ptr != NULL;
	pthread_mutex_unlock(&ffi_pointers_mutex);

	return js_bool(exists);
	}

	static jsval_t ffi_read_ptr(struct js js, jsval_t args, int nargs) {
	if (nargs < 2 \|\| vtype(args[0]) != T_NUM \|\| vtype(args[1]) != T_STR) {
	return js_mkerr(js, "readPtr() requires pointer and type");
	}

	void ptr = (void )(uint64_t)js_getnum(args[0]);
	if (!ptr) return js_mknull();

	const char *type_str = js_getstr(js, args[1], NULL);

	if (strcmp(type_str, "string") == 0) {
	const char str = (const char )ptr;
	return js_mkstr(js, str, strlen(str));
	}

	ffi_type *type = get_ffi_type(type_str);
	if (!type) return js_mkerr(js, "Unknown type: %s", type_str);

	return ffi_to_js_value(js, ptr, type, type_str);
	}

	static void ffi_callback_handler(ffi_cif cif, void ret, void *args, void user_data) {
	(void)cif;
	ffi_callback_t cb = (ffi_callback_t )user_data;
	struct js *js = cb->js;

	jsval_t js_args[32];
	int arg_count = cb->arg_count > 32 ? 32 : cb->arg_count;

	for (int i = 0; i < arg_count; i++) {
	js_args[i] = ffi_to_js_value(js, args[i], cb->arg_types[i], cb->arg_type_strs[i]);
	}

	jsval_t result = js_call(js, cb->js_func, js_args, arg_count);

	if (cb->ret_type != &ffi_type_void) {
	if (cb->ret_type == &ffi_type_sint8) {
	(int8_t )ret = (int8_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_sint16) {
	(int16_t )ret = (int16_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_sint32) {
	(int32_t )ret = (int32_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_sint64) {
	(int64_t )ret = (int64_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_uint8) {
	(uint8_t )ret = (uint8_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_uint16) {
	(uint16_t )ret = (uint16_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_uint64) {
	(uint64_t )ret = (uint64_t)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_float) {
	(float )ret = (float)js_getnum(result);
	} else if (cb->ret_type == &ffi_type_double) {
	(double )ret = js_getnum(result);
	} else if (cb->ret_type == &ffi_type_pointer) {
	if (vtype(result) == T_NUM) {
	(void )ret = (void )(uint64_t)js_getnum(result);
	} else {
	(void *)ret = NULL;
	}
	}
	}
	}

	static jsval_t ffi_create_callback(struct js js, jsval_t args, int nargs) {
	if (nargs < 2) return js_mkerr(js, "callback() requires function and signature");

	jsval_t js_func = args[0];
	jsval_t sig = args[1];
	int sig_type = vtype(sig);
	if (sig_type == T_STR \|\| sig_type == T_NUM \|\| sig_type == T_NULL \|\| sig_type == T_UNDEF) {
	return js_mkerr(js, "Signature must be an object {args: [...], returns: type}");
	}

	const char *ret_type_str;
	jsval_t arg_types_arr;
	int arg_count;

	jsval_t returns_val = js_get(js, sig, "returns");
	jsval_t args_val = js_get(js, sig, "args");

	if (vtype(returns_val) != T_UNDEF && vtype(args_val) != T_UNDEF) {
	if (vtype(returns_val) != T_STR) return js_mkerr(js, "Return type must be a string");
	ret_type_str = js_getstr(js, returns_val, NULL);
	arg_types_arr = args_val;
	jsval_t length_val = js_get(js, arg_types_arr, "length");
	arg_count = (int)js_getnum(length_val);
	} else {
	jsval_t ret_type_val = js_get(js, sig, "0");
	if (vtype(ret_type_val) != T_STR) return js_mkerr(js, "Return type must be a string");
	ret_type_str = js_getstr(js, ret_type_val, NULL);
	arg_types_arr = js_get(js, sig, "1");
	jsval_t length_val = js_get(js, arg_types_arr, "length");
	arg_count = (int)js_getnum(length_val);
	}

	ffi_type *ret_type = get_ffi_type(ret_type_str);
	if (!ret_type) return js_mkerr(js, "Unknown return type: %s", ret_type_str);

	ffi_callback_t cb = (ffi_callback_t )malloc(sizeof(ffi_callback_t));
	if (!cb) return js_mkerr(js, "Out of memory");

	cb->js = js;
	cb->js_func = js_func;
	cb->ret_type = ret_type;
	strncpy(cb->ret_type_str, ret_type_str, sizeof(cb->ret_type_str) - 1);
	cb->ret_type_str[sizeof(cb->ret_type_str) - 1] = '\0';
	cb->arg_count = arg_count;

	if (arg_count > 0) {
	cb->arg_types = (ffi_type *)malloc(sizeof(ffi_type ) * arg_count);
	cb->arg_type_strs = (char *)malloc(sizeof(char ) * arg_count);
	if (!cb->arg_types \|\| !cb->arg_type_strs) {
	if (cb->arg_types) free(cb->arg_types);
	if (cb->arg_type_strs) free(cb->arg_type_strs);
	free(cb);
	return js_mkerr(js, "Out of memory");
	}

	for (int i = 0; i < arg_count; i++) {
	char idx_str[16];
	snprintf(idx_str, sizeof(idx_str), "%d", i);
	jsval_t arg_type_val = js_get(js, arg_types_arr, idx_str);

	if (vtype(arg_type_val) != T_STR) {
	for (int j = 0; j < i; j++) free(cb->arg_type_strs[j]);
	free(cb->arg_types);
	free(cb->arg_type_strs);
	free(cb);
	return js_mkerr(js, "Argument type must be a string");
	}

	const char *arg_type_str = js_getstr(js, arg_type_val, NULL);
	cb->arg_types[i] = get_ffi_type(arg_type_str);
	if (!cb->arg_types[i]) {
	for (int j = 0; j < i; j++) free(cb->arg_type_strs[j]);
	free(cb->arg_types);
	free(cb->arg_type_strs);
	free(cb);
	return js_mkerr(js, "Unknown argument type: %s", arg_type_str);
	}
	cb->arg_type_strs[i] = strdup(arg_type_str);
	}
	} else {
	cb->arg_types = NULL;
	cb->arg_type_strs = NULL;
	}

	ffi_status status = ffi_prep_cif(&cb->cif, FFI_DEFAULT_ABI, arg_count, ret_type, cb->arg_types);
	if (status != FFI_OK) {
	for (int i = 0; i < arg_count; i++) free(cb->arg_type_strs[i]);
	if (cb->arg_types) free(cb->arg_types);
	if (cb->arg_type_strs) free(cb->arg_type_strs);
	free(cb);
	return js_mkerr(js, "Failed to prepare callback CIF (status=%d)", status);
	}

	cb->closure = (ffi_closure *)ffi_closure_alloc(sizeof(ffi_closure), &cb->code_ptr);
	if (!cb->closure) {
	for (int i = 0; i < arg_count; i++) free(cb->arg_type_strs[i]);
	if (cb->arg_types) free(cb->arg_types);
	if (cb->arg_type_strs) free(cb->arg_type_strs);
	free(cb);
	return js_mkerr(js, "Failed to allocate closure");
	}

	status = ffi_prep_closure_loc(cb->closure, &cb->cif, ffi_callback_handler, cb, cb->code_ptr);
	if (status != FFI_OK) {
	ffi_closure_free(cb->closure);
	for (int i = 0; i < arg_count; i++) free(cb->arg_type_strs[i]);
	if (cb->arg_types) free(cb->arg_types);
	if (cb->arg_type_strs) free(cb->arg_type_strs);
	free(cb);
	return js_mkerr(js, "Failed to prepare closure (status=%d)", status);
	}

	cb->cb_key = (uint64_t)cb->code_ptr;

	pthread_mutex_lock(&ffi_callbacks_mutex);
	HASH_ADD(hh, ffi_callbacks, cb_key, sizeof(uint64_t), cb);
	pthread_mutex_unlock(&ffi_callbacks_mutex);

	return js_mknum((double)cb->cb_key);
	}

	static jsval_t ffi_free_callback(struct js js, jsval_t args, int nargs) {
	if (nargs < 1 \|\| vtype(args[0]) != T_NUM) {
	return js_mkerr(js, "freeCallback() requires callback pointer");
	}

	uint64_t cb_key = (uint64_t)js_getnum(args[0]);

	pthread_mutex_lock(&ffi_callbacks_mutex);
	ffi_callback_t *cb = NULL;
	HASH_FIND(hh, ffi_callbacks, &cb_key, sizeof(uint64_t), cb);

	if (!cb) {
	pthread_mutex_unlock(&ffi_callbacks_mutex);
	return js_mkerr(js, "Invalid callback pointer");
	}

	HASH_DEL(ffi_callbacks, cb);
	pthread_mutex_unlock(&ffi_callbacks_mutex);

	ffi_closure_free(cb->closure);
	for (int i = 0; i < cb->arg_count; i++) free(cb->arg_type_strs[i]);
	if (cb->arg_types) free(cb->arg_types);
	if (cb->arg_type_strs) free(cb->arg_type_strs);
	free(cb);

	return js_mkundef();
	}

	typedef enum {
	JS_FFI_VOID = 0,
	JS_FFI_INT8,
	JS_FFI_INT16,
	JS_FFI_INT,
	JS_FFI_INT64,
	JS_FFI_UINT8,
	JS_FFI_UINT16,
	JS_FFI_UINT64,
	JS_FFI_FLOAT,
	JS_FFI_DOUBLE,
	JS_FFI_POINTER,
	JS_FFI_STRING,
	JS_FFI_UNKNOWN,
	JS_FFI_COUNT
	} js_ffi_type_id;

	static js_ffi_type_id get_ffi_type_id(const char *type_str) {
	if (!type_str) return JS_FFI_UNKNOWN;

	switch (type_str[0]) {
	case 'v': if (strcmp(type_str, "void") == 0) return JS_FFI_VOID; break;
	case 'i':
	if (type_str[1] == 'n' && type_str[2] == 't') {
	if (type_str[3] == '\0') return JS_FFI_INT;
	if (strcmp(type_str + 3, "8") == 0) return JS_FFI_INT8;
	if (strcmp(type_str + 3, "16") == 0) return JS_FFI_INT16;
	if (strcmp(type_str + 3, "64") == 0) return JS_FFI_INT64;
	}
	break;
	case 'u':
	if (type_str[1] == 'i' && type_str[2] == 'n' && type_str[3] == 't') {
	if (strcmp(type_str + 4, "8") == 0) return JS_FFI_UINT8;
	if (strcmp(type_str + 4, "16") == 0) return JS_FFI_UINT16;
	if (strcmp(type_str + 4, "64") == 0) return JS_FFI_UINT64;
	}
	break;
	case 'f': if (strcmp(type_str, "float") == 0) return JS_FFI_FLOAT; break;
	case 'd': if (strcmp(type_str, "double") == 0) return JS_FFI_DOUBLE; break;
	case 'p': if (strcmp(type_str, "pointer") == 0) return JS_FFI_POINTER; break;
	case 's': if (strcmp(type_str, "string") == 0) return JS_FFI_STRING; break;
	}
	return JS_FFI_UNKNOWN;
	}

	static ffi_type get_ffi_type(const char type_str) {
	static ffi_type *type_map[] = {
	[JS_FFI_VOID] = &ffi_type_void,
	[JS_FFI_INT8] = &ffi_type_sint8,
	[JS_FFI_INT16] = &ffi_type_sint16,
	[JS_FFI_INT] = &ffi_type_sint32,
	[JS_FFI_INT64] = &ffi_type_sint64,
	[JS_FFI_UINT8] = &ffi_type_uint8,
	[JS_FFI_UINT16] = &ffi_type_uint16,
	[JS_FFI_UINT64] = &ffi_type_uint64,
	[JS_FFI_FLOAT] = &ffi_type_float,
	[JS_FFI_DOUBLE] = &ffi_type_double,
	[JS_FFI_POINTER] = &ffi_type_pointer,
	[JS_FFI_STRING] = &ffi_type_pointer,
	[JS_FFI_UNKNOWN] = NULL,
	};

	js_ffi_type_id id = get_ffi_type_id(type_str);
	return type_map[id];
	}

	static void js_to_ffi_value(struct js js, jsval_t val, ffi_type type, void buffer) {
	static const void *dispatch[] = {
	&&do_sint8, &&do_sint16, &&do_sint32, &&do_sint64,
	&&do_uint8, &&do_uint16, &&do_uint64,
	&&do_float, &&do_double, &&do_pointer, &&do_done
	};

	int idx;
	if (type == &ffi_type_sint8) idx = 0;
	else if (type == &ffi_type_sint16) idx = 1;
	else if (type == &ffi_type_sint32) idx = 2;
	else if (type == &ffi_type_sint64) idx = 3;
	else if (type == &ffi_type_uint8) idx = 4;
	else if (type == &ffi_type_uint16) idx = 5;
	else if (type == &ffi_type_uint64) idx = 6;
	else if (type == &ffi_type_float) idx = 7;
	else if (type == &ffi_type_double) idx = 8;
	else if (type == &ffi_type_pointer) idx = 9;
	else idx = 10;

	goto *dispatch[idx];

	do_sint8: {
	int8_t v = (int8_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_sint16: {
	int16_t v = (int16_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_sint32: {
	int32_t v = (int32_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_sint64: {
	int64_t v = (int64_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_uint8: {
	uint8_t v = (uint8_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_uint16: {
	uint16_t v = (uint16_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_uint64: {
	uint64_t v = (uint64_t)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_float: {
	float v = (float)js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_double: {
	double v = js_getnum(val);
	memcpy(buffer, &v, sizeof(v));
	goto do_done;
	}
	do_pointer: {
	if (vtype(val) == T_STR) {
	size_t str_len;
	const char *str = js_getstr(js, val, &str_len);
	void ptr = (void )str;
	memcpy(buffer, &ptr, sizeof(ptr));
	} else {
	void ptr = (void )(uint64_t)js_getnum(val);
	memcpy(buffer, &ptr, sizeof(ptr));
	}
	goto do_done;
	}
	do_done:
	return buffer;
	}

	static jsval_t ffi_to_js_value(struct js js, void val, ffi_type type, const char type_str) {
	static const void *dispatch[] = {
	&&ret_void, &&ret_sint8, &&ret_sint16, &&ret_sint32, &&ret_sint64,
	&&ret_uint8, &&ret_uint16, &&ret_uint64,
	&&ret_float, &&ret_double, &&ret_pointer, &&ret_undef
	};

	int idx;
	if (type == &ffi_type_void) idx = 0;
	else if (type == &ffi_type_sint8) idx = 1;
	else if (type == &ffi_type_sint16) idx = 2;
	else if (type == &ffi_type_sint32) idx = 3;
	else if (type == &ffi_type_sint64) idx = 4;
	else if (type == &ffi_type_uint8) idx = 5;
	else if (type == &ffi_type_uint16) idx = 6;
	else if (type == &ffi_type_uint64) idx = 7;
	else if (type == &ffi_type_float) idx = 8;
	else if (type == &ffi_type_double) idx = 9;
	else if (type == &ffi_type_pointer) idx = 10;
	else idx = 11;

	goto *dispatch[idx];

	ret_void:
	return js_mkundef();
	ret_sint8:
	return js_mknum((double)((int8_t )val));
	ret_sint16:
	return js_mknum((double)((int16_t )val));
	ret_sint32:
	return js_mknum((double)((int32_t )val));
	ret_sint64:
	return js_mknum((double)((int64_t )val));
	ret_uint8:
	return js_mknum((double)((uint8_t )val));
	ret_uint16:
	return js_mknum((double)((uint16_t )val));
	ret_uint64:
	return js_mknum((double)((uint64_t )val));
	ret_float:
	return js_mknum((double)((float )val));
	ret_double:
	return js_mknum((double)((double )val));
	ret_pointer: {
	void ptr = (void **)val;
	if (type_str && strcmp(type_str, "string") == 0 && ptr) {
	const char str = (const char )ptr;
	if (str && strlen(str) < 1024) return js_mkstr(js, str, strlen(str));
	}
	return js_mknum((double)(uint64_t)ptr);
	}
	ret_undef:
	return js_mkundef();
	}

	void ffi_gc_update_roots(GC_OP_VAL_ARGS) {
	pthread_mutex_lock(&ffi_callbacks_mutex);
	ffi_callback_t cb, tmp;
	HASH_ITER(hh, ffi_callbacks, cb, tmp) {
	op_val(ctx, &cb->js_func);
	}
	pthread_mutex_unlock(&ffi_callbacks_mutex);
	}

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