unix: Initial implementation of FFI module.

Foreign Function Interface module allows to load native dynamic libraries,
call functions and access variables in them. This makes possible to write
interface modules in pure Python.

This module provides thin wrapper around libffi. ctypes compatibility might
be possible to implement on top of this module (though ctypes allow to call
functions without prototypes, which is not supported by libffi (i.e.
implementation would be inefficient))).

unix/Makefile

@@ -11,7 +11,7 @@ include ../py/py.mk
 
 # compiler settings
 CFLAGS = -I. -I$(PY_SRC) -Wall -Werror -ansi -std=gnu99 -DUNIX
-LDFLAGS = -lm
+LDFLAGS = -lm -ldl -lffi
 
 # Debugging/Optimization
 ifdef DEBUG
@@ -25,6 +25,7 @@ SRC_C = \
 	main.c \
 	file.c \
 	socket.c \
+	ffi.c \
 
 OBJ = $(PY_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 LIB = -lreadline

unix/ffi.c

@@ -0,0 +1,330 @@
+#include <assert.h>
+#include <string.h>
+#include <errno.h>
+#include <dlfcn.h>
+#include <ffi.h>
+
+#include "nlr.h"
+#include "misc.h"
+#include "mpconfig.h"
+#include "qstr.h"
+#include "obj.h"
+#include "runtime.h"
+
+typedef struct _mp_obj_opaque_t {
+    mp_obj_base_t base;
+    void *val;
+} mp_obj_opaque_t;
+
+typedef struct _mp_obj_ffimod_t {
+    mp_obj_base_t base;
+    void *handle;
+} mp_obj_ffimod_t;
+
+typedef struct _mp_obj_ffivar_t {
+    mp_obj_base_t base;
+    void *var;
+    char type;
+//    ffi_type *type;
+} mp_obj_ffivar_t;
+
+typedef struct _mp_obj_ffifunc_t {
+    mp_obj_base_t base;
+    void *func;
+    char rettype;
+    ffi_cif cif;
+    ffi_type *params[];
+} mp_obj_ffifunc_t;
+
+typedef struct _mp_obj_fficallback_t {
+    mp_obj_base_t base;
+    void *func;
+    ffi_closure *clo;
+    char rettype;
+    ffi_cif cif;
+    ffi_type *params[];
+} mp_obj_fficallback_t;
+
+static const mp_obj_type_t opaque_type;
+static const mp_obj_type_t ffimod_type;
+static const mp_obj_type_t ffifunc_type;
+static const mp_obj_type_t fficallback_type;
+static const mp_obj_type_t ffivar_type;
+
+static ffi_type *char2ffi_type(char c)
+{
+    switch (c) {
+        case 'b': return &ffi_type_schar;
+        case 'B': return &ffi_type_uchar;
+        case 'i': return &ffi_type_sint;
+        case 'I': return &ffi_type_uint;
+        case 'l': return &ffi_type_slong;
+        case 'L': return &ffi_type_ulong;
+        case 'p':
+        case 's': return &ffi_type_pointer;
+        case 'v': return &ffi_type_void;
+        default: return NULL;
+    }
+}
+
+static ffi_type *get_ffi_type(mp_obj_t o_in)
+{
+    if (MP_OBJ_IS_STR(o_in)) {
+        uint len;
+        const byte *s = mp_obj_str_get_data(o_in, &len);
+        ffi_type *t = char2ffi_type(*s);
+        if (t != NULL) {
+            return t;
+        }
+    }
+    // TODO: Support actual libffi type objects
+
+    nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "Unknown type"));
+}
+
+static mp_obj_t return_ffi_value(int val, char type)
+{
+    switch (type) {
+        case 's': {
+            const char *s = (const char *)val;
+            return mp_obj_new_str((const byte *)s, strlen(s), false);
+        }
+        case 'v':
+            return mp_const_none;
+        default:
+            return mp_obj_new_int(val);
+    }
+}
+
+// FFI module
+
+static void ffimod_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+    mp_obj_ffimod_t *self = self_in;
+    print(env, "<ffimod %p>", self->handle);
+}
+
+static mp_obj_t ffimod_close(mp_obj_t self_in) {
+    mp_obj_ffimod_t *self = self_in;
+    dlclose(self->handle);
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(ffimod_close_obj, ffimod_close);
+
+static mp_obj_t ffimod_func(uint n_args, const mp_obj_t *args) {
+    mp_obj_ffimod_t *self = args[0];
+    const char *rettype = mp_obj_str_get_str(args[1]);
+    const char *symname = mp_obj_str_get_str(args[2]);
+
+    void *sym = dlsym(self->handle, symname);
+    if (sym == NULL) {
+        nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "[Errno %d]", errno));
+    }
+    int nparams = MP_OBJ_SMALL_INT_VALUE(mp_obj_len_maybe(args[3]));
+    mp_obj_ffifunc_t *o = m_new_obj_var(mp_obj_ffifunc_t, ffi_type*, nparams);
+    o->base.type = &ffifunc_type;
+
+    o->func = sym;
+    o->rettype = *rettype;
+
+    mp_obj_t iterable = rt_getiter(args[3]);
+    mp_obj_t item;
+    int i = 0;
+    while ((item = rt_iternext(iterable)) != mp_const_stop_iteration) {
+        o->params[i++] = get_ffi_type(item);
+    }
+
+    int res = ffi_prep_cif(&o->cif, FFI_DEFAULT_ABI, nparams, char2ffi_type(*rettype), o->params);
+    if (res != FFI_OK) {
+        nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "Error in ffi_prep_cif"));
+    }
+
+    return o;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(ffimod_func_obj, 4, 4, ffimod_func);
+
+static void call_py_func(ffi_cif *cif, void *ret, void** args, mp_obj_t func) {
+    mp_obj_t pyargs[cif->nargs];
+    for (int i = 0; i < cif->nargs; i++) {
+        pyargs[i] = mp_obj_new_int(*(int*)args[i]);
+    }
+    mp_obj_t res = rt_call_function_n_kw(func, cif->nargs, 0, pyargs);
+
+    *(ffi_arg*)ret = mp_obj_int_get(res);
+}
+
+static mp_obj_t mod_ffi_callback(mp_obj_t rettype_in, mp_obj_t func_in, mp_obj_t paramtypes_in) {
+    const char *rettype = mp_obj_str_get_str(rettype_in);
+
+    int nparams = MP_OBJ_SMALL_INT_VALUE(mp_obj_len_maybe(paramtypes_in));
+    mp_obj_fficallback_t *o = m_new_obj_var(mp_obj_fficallback_t, ffi_type*, nparams);
+    o->base.type = &fficallback_type;
+
+    o->clo = ffi_closure_alloc(sizeof(ffi_closure), &o->func);
+
+    o->rettype = *rettype;
+
+    mp_obj_t iterable = rt_getiter(paramtypes_in);
+    mp_obj_t item;
+    int i = 0;
+    while ((item = rt_iternext(iterable)) != mp_const_stop_iteration) {
+        o->params[i++] = get_ffi_type(item);
+    }
+
+    int res = ffi_prep_cif(&o->cif, FFI_DEFAULT_ABI, nparams, char2ffi_type(*rettype), o->params);
+    if (res != FFI_OK) {
+        nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "Error in ffi_prep_cif"));
+    }
+
+    res = ffi_prep_closure_loc(o->clo, &o->cif, call_py_func, func_in, o->func);
+    if (res != FFI_OK) {
+        nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "ffi_prep_closure_loc"));
+    }
+
+    return o;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(mod_ffi_callback_obj, mod_ffi_callback);
+
+static mp_obj_t ffimod_var(mp_obj_t self_in, mp_obj_t vartype_in, mp_obj_t symname_in) {
+    mp_obj_ffimod_t *self = self_in;
+    const char *rettype = mp_obj_str_get_str(vartype_in);
+    const char *symname = mp_obj_str_get_str(symname_in);
+
+    void *sym = dlsym(self->handle, symname);
+    if (sym == NULL) {
+        nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "[Errno %d]", errno));
+    }
+    mp_obj_ffivar_t *o = m_new_obj(mp_obj_ffivar_t);
+    o->base.type = &ffivar_type;
+
+    o->var = sym;
+    o->type = *rettype;
+    return o;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(ffimod_var_obj, ffimod_var);
+
+static mp_obj_t ffimod_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
+    const char *fname = mp_obj_str_get_str(args[0]);
+    void *mod = dlopen(fname, RTLD_NOW | RTLD_LOCAL);
+
+    if (mod == NULL) {
+        nlr_jump(mp_obj_new_exception_msg_varg(MP_QSTR_OSError, "[Errno %d]", errno));
+    }
+    mp_obj_ffimod_t *o = m_new_obj(mp_obj_ffimod_t);
+    o->base.type = type_in;
+    o->handle = mod;
+    return o;
+}
+
+static const mp_method_t ffimod_type_methods[] = {
+        { "func", &ffimod_func_obj },
+        { "var", &ffimod_var_obj },
+        { "close", &ffimod_close_obj },
+        { NULL, NULL },
+};
+
+static const mp_obj_type_t ffimod_type = {
+    { &mp_const_type },
+    "ffimod",
+    .print = ffimod_print,
+    .make_new = ffimod_make_new,
+    .methods = ffimod_type_methods,
+};
+
+// FFI function
+
+static void ffifunc_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+    mp_obj_ffifunc_t *self = self_in;
+    print(env, "<ffifunc %p>", self->func);
+}
+
+mp_obj_t ffifunc_call(mp_obj_t self_in, uint n_args, uint n_kw, const mp_obj_t *args) {
+    mp_obj_ffifunc_t *self = self_in;
+    assert(n_kw == 0);
+    assert(n_args == self->cif.nargs);
+
+    int values[n_args];
+    void *valueptrs[n_args];
+    int i;
+    for (i = 0; i < n_args; i++) {
+        mp_obj_t a = args[i];
+        if (a == mp_const_none) {
+            values[i] = 0;
+        } else if (MP_OBJ_IS_INT(a)) {
+            values[i] = mp_obj_int_get(a);
+        } else if (MP_OBJ_IS_STR(a) || MP_OBJ_IS_TYPE(a, &bytes_type)) {
+            const char *s = mp_obj_str_get_str(a);
+            values[i] = (int)s;
+        } else if (MP_OBJ_IS_TYPE(a, &fficallback_type)) {
+            mp_obj_fficallback_t *p = a;
+            values[i] = (int)p->func;
+        } else {
+            assert(0);
+        }
+        valueptrs[i] = &values[i];
+    }
+
+    int retval;
+    ffi_call(&self->cif, self->func, &retval, valueptrs);
+    return return_ffi_value(retval, self->rettype);
+}
+
+static const mp_obj_type_t ffifunc_type = {
+    { &mp_const_type },
+    "ffifunc",
+    .print = ffifunc_print,
+    .call = ffifunc_call,
+};
+
+// FFI callback for Python function
+
+static void fficallback_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+    mp_obj_fficallback_t *self = self_in;
+    print(env, "<fficallback %p>", self->func);
+}
+
+static const mp_obj_type_t fficallback_type = {
+    { &mp_const_type },
+    "fficallback",
+    .print = fficallback_print,
+};
+
+// FFI variable
+
+static void ffivar_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+    mp_obj_ffivar_t *self = self_in;
+    print(env, "<ffivar @%p: 0x%x>", self->var, *(int*)self->var);
+}
+
+static const mp_obj_type_t ffivar_type = {
+    { &mp_const_type },
+    "ffivar",
+    .print = ffivar_print,
+};
+
+// Generic opaque storage object
+
+static const mp_obj_type_t opaque_type = {
+    { &mp_const_type },
+    "opaqueval",
+//    .print = opaque_print,
+};
+
+
+mp_obj_t mod_ffi_open(uint n_args, const mp_obj_t *args) {
+    return ffimod_make_new((mp_obj_t)&ffimod_type, n_args, 0, args);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_ffi_open_obj, 1, 2, mod_ffi_open);
+
+mp_obj_t mod_ffi_as_bytearray(mp_obj_t ptr, mp_obj_t size) {
+    return mp_obj_new_bytearray_by_ref(mp_obj_int_get(size), (void*)mp_obj_int_get(ptr));
+}
+MP_DEFINE_CONST_FUN_OBJ_2(mod_ffi_as_bytearray_obj, mod_ffi_as_bytearray);
+
+
+void ffi_init() {
+    mp_obj_t m = mp_obj_new_module(QSTR_FROM_STR_STATIC("ffi"));
+    rt_store_attr(m, MP_QSTR_open, (mp_obj_t)&mod_ffi_open_obj);
+    rt_store_attr(m, QSTR_FROM_STR_STATIC("callback"), (mp_obj_t)&mod_ffi_callback_obj);
+    // there would be as_bytes, but bytes currently is value, not reference type!
+    rt_store_attr(m, QSTR_FROM_STR_STATIC("as_bytearray"), (mp_obj_t)&mod_ffi_as_bytearray_obj);
+}

unix/main.c

@@ -24,6 +24,7 @@
 extern const mp_obj_fun_native_t mp_builtin_open_obj;
 void file_init();
 void rawsocket_init();
+void ffi_init();
 
 static void execute_from_lexer(mp_lexer_t *lex, mp_parse_input_kind_t input_kind, bool is_repl) {
     if (lex == NULL) {
@@ -227,6 +228,7 @@ int main(int argc, char **argv) {
 
     file_init();
     rawsocket_init();
+    ffi_init();
 
     // Here is some example code to create a class and instance of that class.
     // First is the Python, then the C code.