add modtrezorutils

Contains a memcpy helper for zero-cost copying between two buffers (bytearray or memoryview).

extmod/modtrezorutils/modtrezorutils.c

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) Jan Pochyla, SatoshiLabs
+ *
+ * Licensed under TREZOR License
+ * see LICENSE file for details
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include "py/nlr.h"
+#include "py/runtime.h"
+#include "py/binary.h"
+#include "py/objstr.h"
+
+#if MICROPY_PY_TREZORUTILS
+
+/// def trezor.utils.memcpy(dst: bytearray, dst_ofs: int,
+///                         src: bytearray, src_ofs: int,
+//                          n: int) -> int:
+///     '''
+///     Copies at most `n` bytes from `src` at offset `src_ofs` to
+///     `dst` at offset `dst_ofs`.  Returns the number of actually
+///     copied bytes.
+///     '''
+STATIC mp_obj_t mod_TrezorUtils_memcpy(size_t n_args, const mp_obj_t *args) {
+    mp_arg_check_num(n_args, 0, 5, 5, false);
+
+    mp_buffer_info_t dst;
+    mp_get_buffer_raise(args[0], &dst, MP_BUFFER_WRITE);
+    int dst_ofs = mp_obj_get_int(args[1]);
+    if (dst_ofs < 0) {
+        mp_raise_ValueError("Invalid dst offset (has to be >= 0)");
+    }
+
+    mp_buffer_info_t src;
+    mp_get_buffer_raise(args[2], &src, MP_BUFFER_READ);
+    int src_ofs = mp_obj_get_int(args[3]);
+    if (src_ofs < 0) {
+        mp_raise_ValueError("Invalid src offset (has to be >= 0)");
+    }
+
+    int n = mp_obj_get_int(args[4]);
+    if (n < 0) {
+        mp_raise_ValueError("Invalid byte count (has to be >= 0)");
+    }
+    size_t dst_rem = (dst_ofs < dst.len) ? dst.len - dst_ofs : 0;
+    size_t src_rem = (src_ofs < src.len) ? src.len - src_ofs : 0;
+    size_t ncpy = MIN(n, MIN(src_rem, dst_rem));
+
+    memmove(((char*)dst.buf) + dst_ofs, ((const char*)src.buf) + src_ofs, ncpy);
+
+    return mp_obj_new_int(ncpy);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_TrezorUtils_memcpy_obj, 5, 5, mod_TrezorUtils_memcpy);
+
+STATIC const mp_rom_map_elem_t mp_module_TrezorUtils_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_TrezorUtils) },
+    { MP_ROM_QSTR(MP_QSTR_memcpy), MP_ROM_PTR(&mod_TrezorUtils_memcpy_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(mp_module_TrezorUtils_globals, mp_module_TrezorUtils_globals_table);
+
+const mp_obj_module_t mp_module_TrezorUtils = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&mp_module_TrezorUtils_globals,
+};
+
+#endif // MICROPY_PY_TREZORUTILS