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author | nkozlovskiy <nmk@ydb.tech> | 2023-10-11 19:11:46 +0300 |
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committer | nkozlovskiy <nmk@ydb.tech> | 2023-10-11 19:33:28 +0300 |
commit | 61b3971447e473726d6cdb23fc298e457b4d973c (patch) | |
tree | e2a2a864bb7717f7ae6138f6a3194a254dd2c7bb /contrib/libs/clang14-rt/lib/sanitizer_common/sanitizer_lzw.h | |
parent | a674dc57d88d43c2e8e90a6084d5d2c988e0402c (diff) | |
download | ydb-61b3971447e473726d6cdb23fc298e457b4d973c.tar.gz |
add sanitizers dependencies
Diffstat (limited to 'contrib/libs/clang14-rt/lib/sanitizer_common/sanitizer_lzw.h')
-rw-r--r-- | contrib/libs/clang14-rt/lib/sanitizer_common/sanitizer_lzw.h | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/contrib/libs/clang14-rt/lib/sanitizer_common/sanitizer_lzw.h b/contrib/libs/clang14-rt/lib/sanitizer_common/sanitizer_lzw.h new file mode 100644 index 0000000000..42acfbdcea --- /dev/null +++ b/contrib/libs/clang14-rt/lib/sanitizer_common/sanitizer_lzw.h @@ -0,0 +1,159 @@ +//===-- sanitizer_lzw.h -----------------------------------------*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// Lempel–Ziv–Welch encoding/decoding +// +//===----------------------------------------------------------------------===// + +#ifndef SANITIZER_LZW_H +#define SANITIZER_LZW_H + +#include "sanitizer_dense_map.h" + +namespace __sanitizer { + +using LzwCodeType = u32; + +template <class T, class ItIn, class ItOut> +ItOut LzwEncode(ItIn begin, ItIn end, ItOut out) { + using Substring = + detail::DenseMapPair<LzwCodeType /* Prefix */, T /* Next input */>; + + // Sentinel value for substrings of len 1. + static constexpr LzwCodeType kNoPrefix = + Min(DenseMapInfo<Substring>::getEmptyKey().first, + DenseMapInfo<Substring>::getTombstoneKey().first) - + 1; + DenseMap<Substring, LzwCodeType> prefix_to_code; + { + // Add all substring of len 1 as initial dictionary. + InternalMmapVector<T> dict_len1; + for (auto it = begin; it != end; ++it) + if (prefix_to_code.try_emplace({kNoPrefix, *it}, 0).second) + dict_len1.push_back(*it); + + // Slightly helps with later delta encoding. + Sort(dict_len1.data(), dict_len1.size()); + + // For large sizeof(T) we have to store dict_len1. Smaller types like u8 can + // just generate them. + *out = dict_len1.size(); + ++out; + + for (uptr i = 0; i != dict_len1.size(); ++i) { + // Remap after the Sort. + prefix_to_code[{kNoPrefix, dict_len1[i]}] = i; + *out = dict_len1[i]; + ++out; + } + CHECK_EQ(prefix_to_code.size(), dict_len1.size()); + } + + if (begin == end) + return out; + + // Main LZW encoding loop. + LzwCodeType match = prefix_to_code.find({kNoPrefix, *begin})->second; + ++begin; + for (auto it = begin; it != end; ++it) { + // Extend match with the new item. + auto ins = prefix_to_code.try_emplace({match, *it}, prefix_to_code.size()); + if (ins.second) { + // This is a new substring, but emit the code for the current match + // (before extend). This allows LZW decoder to recover the dictionary. + *out = match; + ++out; + // Reset the match to a single item, which must be already in the map. + match = prefix_to_code.find({kNoPrefix, *it})->second; + } else { + // Already known, use as the current match. + match = ins.first->second; + } + } + + *out = match; + ++out; + + return out; +} + +template <class T, class ItIn, class ItOut> +ItOut LzwDecode(ItIn begin, ItIn end, ItOut out) { + if (begin == end) + return out; + + // Load dictionary of len 1 substrings. Theses correspont to lowest codes. + InternalMmapVector<T> dict_len1(*begin); + ++begin; + + if (begin == end) + return out; + + for (auto& v : dict_len1) { + v = *begin; + ++begin; + } + + // Substrings of len 2 and up. Indexes are shifted because [0, + // dict_len1.size()) stored in dict_len1. Substings get here after being + // emitted to the output, so we can use output position. + InternalMmapVector<detail::DenseMapPair<ItOut /* begin. */, ItOut /* end */>> + code_to_substr; + + // Copies already emitted substrings into the output again. + auto copy = [&code_to_substr, &dict_len1](LzwCodeType code, ItOut out) { + if (code < dict_len1.size()) { + *out = dict_len1[code]; + ++out; + return out; + } + const auto& s = code_to_substr[code - dict_len1.size()]; + + for (ItOut it = s.first; it != s.second; ++it, ++out) *out = *it; + return out; + }; + + // Returns lens of the substring with the given code. + auto code_to_len = [&code_to_substr, &dict_len1](LzwCodeType code) -> uptr { + if (code < dict_len1.size()) + return 1; + const auto& s = code_to_substr[code - dict_len1.size()]; + return s.second - s.first; + }; + + // Main LZW decoding loop. + LzwCodeType prev_code = *begin; + ++begin; + out = copy(prev_code, out); + for (auto it = begin; it != end; ++it) { + LzwCodeType code = *it; + auto start = out; + if (code == dict_len1.size() + code_to_substr.size()) { + // Special LZW case. The code is not in the dictionary yet. This is + // possible only when the new substring is the same as previous one plus + // the first item of the previous substring. We can emit that in two + // steps. + out = copy(prev_code, out); + *out = *start; + ++out; + } else { + out = copy(code, out); + } + + // Every time encoded emits the code, it also creates substing of len + 1 + // including the first item of the just emmited substring. Do the same here. + uptr len = code_to_len(prev_code); + code_to_substr.push_back({start - len, start + 1}); + + prev_code = code; + } + return out; +} + +} // namespace __sanitizer +#endif |