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