circuitpython/unix/modffi.c

#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"
#include "binary.h"

/*
 * modffi uses character codes to encode a value type, based on "struct"
 * module type codes, with some extensions and overridings.
 *
 * Extra/overridden typecodes:
 *      v - void, can be used only as return type
 *      P - const void*, pointer to read-only memory
 *      p - void*, meaning pointer to a writable memory (note that this
 *          clashes with struct's "p" as "Pascal string").
 *      s - as argument, the same as "p", as return value, causes string
 *          to be allocated and returned, instead of pointer value.
 *
 * Note: all constraint specified by typecode can be not enforced at this time,
 * but may be later.
 */

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 'f': return &ffi_type_float;
        case 'd': return &ffi_type_double;
        case 'P': // const void*
        case 'p': // void*
        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 char *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_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "Unknown type"));
}

STATIC mp_obj_t return_ffi_value(ffi_arg 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;
        case 'f': {
            float *p = (float*)&val;
            return mp_obj_new_float(*p);
        }
        case 'd': {
            double *p = (double*)&val;
            return mp_obj_new_float(*p);
        }
        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_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT((machine_int_t)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 = mp_getiter(args[3]);
    mp_obj_t item;
    int i = 0;
    while ((item = mp_iternext(iterable)) != MP_OBJ_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_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "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 = mp_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 = mp_getiter(paramtypes_in);
    mp_obj_t item;
    int i = 0;
    while ((item = mp_iternext(iterable)) != MP_OBJ_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_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "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_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "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_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT((machine_int_t)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_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT((machine_int_t)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_map_elem_t ffimod_locals_dict_table[] = {
    { MP_OBJ_NEW_QSTR(MP_QSTR_func), (mp_obj_t) &ffimod_func_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_var), (mp_obj_t) &ffimod_var_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t) &ffimod_close_obj },
};

STATIC MP_DEFINE_CONST_DICT(ffimod_locals_dict, ffimod_locals_dict_table);

STATIC const mp_obj_type_t ffimod_type = {
    { &mp_type_type },
    .name = MP_QSTR_ffimod,
    .print = ffimod_print,
    .make_new = ffimod_make_new,
    .locals_dict = (mp_obj_t)&ffimod_locals_dict,
};

// 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);

    ffi_arg 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)) {
            const char *s = mp_obj_str_get_str(a);
            values[i] = (ffi_arg)s;
        } else if (((mp_obj_base_t*)a)->type->buffer_p.get_buffer != NULL) {
            mp_obj_base_t *o = (mp_obj_base_t*)a;
            mp_buffer_info_t bufinfo;
            int ret = o->type->buffer_p.get_buffer(o, &bufinfo, MP_BUFFER_READ); // TODO: MP_BUFFER_READ?
            if (ret != 0 || bufinfo.buf == NULL) {
                goto error;
            }
            values[i] = (ffi_arg)bufinfo.buf;
        } else if (MP_OBJ_IS_TYPE(a, &fficallback_type)) {
            mp_obj_fficallback_t *p = a;
            values[i] = (ffi_arg)p->func;
        } else {
            goto error;
        }
        valueptrs[i] = &values[i];
    }

    ffi_arg retval;
    ffi_call(&self->cif, self->func, &retval, valueptrs);
    return return_ffi_value(retval, self->rettype);

error:
    nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "Don't know how to pass object to native function"));
}

STATIC const mp_obj_type_t ffifunc_type = {
    { &mp_type_type },
    .name = MP_QSTR_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_type_type },
    .name = MP_QSTR_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 mp_obj_t ffivar_get(mp_obj_t self_in) {
    mp_obj_ffivar_t *self = self_in;
    return mp_binary_get_val_array(self->type, self->var, 0);
}
MP_DEFINE_CONST_FUN_OBJ_1(ffivar_get_obj, ffivar_get);

STATIC mp_obj_t ffivar_set(mp_obj_t self_in, mp_obj_t val_in) {
    mp_obj_ffivar_t *self = self_in;
    mp_binary_set_val_array(self->type, self->var, 0, val_in);
    return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_2(ffivar_set_obj, ffivar_set);

STATIC const mp_map_elem_t ffivar_locals_dict_table[] = {
    { MP_OBJ_NEW_QSTR(MP_QSTR_get), (mp_obj_t)&ffivar_get_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_set), (mp_obj_t)&ffivar_set_obj },
};

STATIC MP_DEFINE_CONST_DICT(ffivar_locals_dict, ffivar_locals_dict_table);

STATIC const mp_obj_type_t ffivar_type = {
    { &mp_type_type },
    .name = MP_QSTR_ffivar,
    .print = ffivar_print,
    .locals_dict = (mp_obj_t)&ffivar_locals_dict,
};

// Generic opaque storage object (unused)

/*
STATIC const mp_obj_type_t opaque_type = {
    { &mp_type_type },
    .name = MP_QSTR_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);

STATIC const mp_map_elem_t mp_module_ffi_globals_table[] = {
    { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_ffi) },
    { MP_OBJ_NEW_QSTR(MP_QSTR_open), (mp_obj_t)&mod_ffi_open_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_callback), (mp_obj_t)&mod_ffi_callback_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_as_bytearray), (mp_obj_t)&mod_ffi_as_bytearray_obj },
};

STATIC const mp_obj_dict_t mp_module_ffi_globals = {
    .base = {&mp_type_dict},
    .map = {
        .all_keys_are_qstrs = 1,
        .table_is_fixed_array = 1,
        .used = ARRAY_SIZE(mp_module_ffi_globals_table),
        .alloc = ARRAY_SIZE(mp_module_ffi_globals_table),
        .table = (mp_map_elem_t*)mp_module_ffi_globals_table,
    },
};

const mp_obj_module_t mp_module_ffi = {
    .base = { &mp_type_module },
    .name = MP_QSTR_ffi,
    .globals = (mp_obj_dict_t*)&mp_module_ffi_globals,
};