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tdlib-fork/tdutils/td/utils/find_boundary.cpp

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include "td/utils/find_boundary.h"
#include <cstring>
namespace td {
bool find_boundary(ChainBufferReader range, Slice boundary, size_t &already_read) {
range.advance(already_read);
const int MAX_BOUNDARY_LENGTH = 70;
CHECK(boundary.size() <= MAX_BOUNDARY_LENGTH + 4);
while (!range.empty()) {
Slice ready = range.prepare_read();
if (ready[0] == boundary[0]) {
if (range.size() < boundary.size()) {
return false;
}
auto save_range = range.clone();
char x[MAX_BOUNDARY_LENGTH + 4];
range.advance(boundary.size(), {x, sizeof(x)});
if (Slice(x, boundary.size()) == boundary) {
return true;
}
// not a boundary, restoring previous state and skip one symbol
range = std::move(save_range);
range.advance(1);
already_read++;
} else {
const char *ptr = static_cast<const char *>(std::memchr(ready.data(), boundary[0], ready.size()));
size_t shift;
if (ptr == nullptr) {
shift = ready.size();
} else {
shift = ptr - ready.data();
}
already_read += shift;
range.advance(shift);
}
}
return false;
}
} // namespace td