circuitpython/py/modstruct.c

#include <assert.h>
#include <string.h>
#include "misc.h"
#include "mpconfig.h"
#include "qstr.h"
#include "obj.h"
#include "builtin.h"
#include "objtuple.h"
#include "objstr.h"
#include "binary.h"

#if MICROPY_ENABLE_MOD_STRUCT

STATIC char get_fmt_type(const char **fmt) {
    char t = **fmt;
    switch (t) {
        case '!':
            t = '>';
            break;
        case '@':
        case '=':
        case '<':
        case '>':
            break;
        default:
            return '@';
    }
    // Skip type char
    (*fmt)++;
    return t;
}

STATIC uint calcsize_items(const char *fmt) {
    // TODO
    return strlen(fmt);
}

STATIC mp_obj_t struct_calcsize(mp_obj_t fmt_in) {
    const char *fmt = mp_obj_str_get_str(fmt_in);
    char fmt_type = get_fmt_type(&fmt);
    machine_uint_t size;
    for (size = 0; *fmt; fmt++) {
        uint align;
        int sz = mp_binary_get_size(fmt_type, *fmt, &align);
        // TODO
        assert(sz != -1);
        // Apply alignment
        size = (size + align - 1) & ~(align - 1);
        size += sz;
    }
    return MP_OBJ_NEW_SMALL_INT(size);
}
MP_DEFINE_CONST_FUN_OBJ_1(struct_calcsize_obj, struct_calcsize);

STATIC mp_obj_t struct_unpack(mp_obj_t fmt_in, mp_obj_t data_in) {
    // TODO: "The buffer must contain exactly the amount of data required by the format (len(bytes) must equal calcsize(fmt))."
    const char *fmt = mp_obj_str_get_str(fmt_in);
    char fmt_type = get_fmt_type(&fmt);
    uint size = calcsize_items(fmt);
    mp_obj_tuple_t *res = mp_obj_new_tuple(size, NULL);
    mp_buffer_info_t bufinfo;
    mp_get_buffer_raise(data_in, &bufinfo, MP_BUFFER_READ);
    byte *p = bufinfo.buf;

    for (uint i = 0; i < size; i++) {
        mp_obj_t item = mp_binary_get_val(fmt_type, *fmt++, &p);
        res->items[i] = item;
    }
    return res;
}
MP_DEFINE_CONST_FUN_OBJ_2(struct_unpack_obj, struct_unpack);

STATIC mp_obj_t struct_pack(uint n_args, mp_obj_t *args) {
    // TODO: "The arguments must match the values required by the format exactly."
    const char *fmt = mp_obj_str_get_str(args[0]);
    char fmt_type = get_fmt_type(&fmt);
    int size = MP_OBJ_SMALL_INT_VALUE(struct_calcsize(args[0]));
    byte *p;
    mp_obj_t res = mp_obj_str_builder_start(&mp_type_bytes, size, &p);
    memset(p, 0, size);

    for (uint i = 1; i < n_args; i++) {
        mp_binary_set_val(fmt_type, *fmt++, args[i], &p);
    }
    return res;
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(struct_pack_obj, 1, -1, struct_pack);

STATIC const mp_map_elem_t mp_module_struct_globals_table[] = {
    { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_struct) },
    { MP_OBJ_NEW_QSTR(MP_QSTR_calcsize), (mp_obj_t)&struct_calcsize_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_pack), (mp_obj_t)&struct_pack_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_unpack), (mp_obj_t)&struct_unpack_obj },
};

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

const mp_obj_module_t mp_module_struct = {
    .base = { &mp_type_module },
    .name = MP_QSTR_struct,
    .globals = (mp_obj_dict_t*)&mp_module_struct_globals,
};

#endif