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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2018 Scott Shawcroft for Adafruit Industries
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef MICROPY_INCLUDED_SUPERVISOR_TRANSLATE_H
#define MICROPY_INCLUDED_SUPERVISOR_TRANSLATE_H
#include <stdint.h>
// The format of the compressed data is:
// - the size of the uncompressed string in UTF-8 bytes, encoded as a
// (compress_max_length_bits)-bit number. compress_max_length_bits is
// computed during dictionary generation time, and happens to be 8
// for all current platforms. However, it'll probably end up being
// 9 in some translations sometime in the future. This length excludes
// the trailing NUL, though notably decompress_length includes it.
//
// - followed by the huffman encoding of the individual UTF-16 code
// points that make up the string. The trailing "\0" is not
// represented by a huffman code, but is implied by the length.
// (building the huffman encoding on UTF-16 code points gave better
// compression than building it on UTF-8 bytes)
//
// - code points starting at 128 (word_start) and potentially extending
// to 255 (word_end) (but never interfering with the target
// language's used code points) stand for dictionary entries in a
// dictionary with size up to 256 code points. The dictionary entries
// are computed with a heuristic based on frequent substrings of 2 to
// 9 code points. These are called "words" but are not, grammatically
// speaking, words. They're just spans of code points that frequently
// occur together. They are ordered shortest to longest.
//
// - dictionary entries are non-overlapping, and the _ending_ index of each
// entry is stored in an array. A count of words of each length, from
// minlen to maxlen, is given in the array called wlencount. From
// this small array, the start and end of the N'th word can be
// calculated by an efficient, small loop. (A bit of time is traded
// to reduce the size of this table indicating lengths)
//
// The "data" / "tail" construct is so that the struct's last member is a
// "flexible array". However, the _only_ member is not permitted to be
// a flexible member, so we have to declare the first byte as a separte
// member of the structure.
//
// For translations where length needs 8 bits, this saves about 1.5
// bytes per string on average compared to a structure of {uint16_t,
// flexible array}, but is also future-proofed against strings with
// UTF-8 length above 256, with a savings of about 1.375 bytes per
// string.
typedef struct compressed_string {
uint8_t data;
const uint8_t tail[];
} compressed_string_t;
// Return the compressed, translated version of a source string
// Usually, due to LTO, this is optimized into a load of a constant
// pointer.
const compressed_string_t *translate(const char *c);
void serial_write_compressed(const compressed_string_t *compressed);
char *decompress(const compressed_string_t *compressed, char *decompressed);
uint16_t decompress_length(const compressed_string_t *compressed);
// Map MicroPython's error messages to our translations.
#if defined(MICROPY_ENABLE_DYNRUNTIME) && MICROPY_ENABLE_DYNRUNTIME
#define MP_ERROR_TEXT(x) (x)
#else
#define MP_ERROR_TEXT(x) translate(x)
#endif
#endif // MICROPY_INCLUDED_SUPERVISOR_TRANSLATE_H
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