52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#include "td/utils/find_boundary.h"
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#include <cstring>
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namespace td {
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bool find_boundary(ChainBufferReader range, Slice boundary, size_t &already_read) {
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range.advance(already_read);
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const int MAX_BOUNDARY_LENGTH = 70;
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CHECK(boundary.size() <= MAX_BOUNDARY_LENGTH + 4);
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while (!range.empty()) {
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Slice ready = range.prepare_read();
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if (ready[0] == boundary[0]) {
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if (range.size() < boundary.size()) {
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return false;
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}
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auto save_range = range.clone();
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char x[MAX_BOUNDARY_LENGTH + 4];
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range.advance(boundary.size(), {x, sizeof(x)});
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if (std::memcmp(x, boundary.data(), boundary.size()) == 0) {
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return true;
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}
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// not a boundary, restoring previous state and skip one symbol
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range = std::move(save_range);
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range.advance(1);
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already_read++;
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} else {
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const char *ptr = static_cast<const char *>(std::memchr(ready.data(), boundary[0], ready.size()));
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size_t shift;
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if (ptr == nullptr) {
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shift = ready.size();
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} else {
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shift = ptr - ready.data();
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}
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already_read += shift;
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range.advance(shift);
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}
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}
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return false;
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}
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} // namespace td
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