81 lines
2.2 KiB
C++
81 lines
2.2 KiB
C++
/*
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Copyright (c) 2019 yvt
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This file is part of OpenSpades.
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OpenSpades is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenSpades is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with OpenSpades. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "RandomAccessAdaptor.h"
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#include <Core/Debug.h>
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#include <Core/Exception.h>
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#include <Core/IStream.h>
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#include <cstring>
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namespace spades {
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RandomAccessAdaptor::RandomAccessAdaptor(IStream &inner) : inner{inner} {}
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RandomAccessAdaptor::~RandomAccessAdaptor() {
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// Do nothing - the buffer is automatically taken care of
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}
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void RandomAccessAdaptor::ExpandTo(std::size_t newBufferSize) {
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if (newBufferSize <= buffer.size()) {
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return;
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}
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SPADES_MARK_FUNCTION();
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std::size_t numAdditionalBytes = newBufferSize - buffer.size();
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std::size_t originalSize = buffer.size();
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try {
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// Expand the internal buffer
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buffer.resize(newBufferSize);
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// Read additional bytes from the underlying stream to the newly
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// allocated space of the internal buffer
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std::size_t numBytesRead = inner.Read(buffer.data() + originalSize, numAdditionalBytes);
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// Shrink the buffer to the actual read size
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buffer.resize(originalSize + numBytesRead);
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} catch (...) {
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// Roll back to the original state
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buffer.resize(originalSize);
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throw;
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}
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}
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bool RandomAccessAdaptor::TryRead(std::size_t offset, std::size_t size, char *output) {
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SPADES_MARK_FUNCTION();
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std::size_t newLen = offset + size;
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if (newLen < offset) {
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// `newLen` overflowed `size_t`.
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SPRaise("integer overflow");
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}
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ExpandTo(newLen);
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if (buffer.size() < newLen) {
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// Reached EOF
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return false;
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}
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std::memcpy(output, buffer.data() + offset, size);
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return true;
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}
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} // namespace spades
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