94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
/*
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This file is part of Telegram Desktop,
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the official desktop application for the Telegram messaging service.
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For license and copyright information please follow this link:
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https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
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*/
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#include "media/clip/media_clip_check_streaming.h"
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#include <QtCore/QBuffer>
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#include <QtCore/QtEndian>
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namespace Media {
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namespace Clip {
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namespace {
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constexpr auto kHeaderSize = 8;
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constexpr auto kFindMoovBefore = 128 * 1024;
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template <typename Type>
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Type ReadBigEndian(bytes::const_span data) {
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const auto bytes = data.subspan(0, sizeof(Type)).data();
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return qFromBigEndian(*reinterpret_cast<const Type*>(bytes));
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}
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bool IsAtom(bytes::const_span header, const char (&atom)[5]) {
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const auto check = header.subspan(4, 4);
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return bytes::compare(
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header.subspan(4, 4),
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bytes::make_span(atom).subspan(0, 4)) == 0;
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}
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} // namespace
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bool CheckStreamingSupport(
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const FileLocation &location,
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QByteArray data) {
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QBuffer buffer;
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QFile file;
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if (data.isEmpty()) {
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file.setFileName(location.name());
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} else {
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buffer.setBuffer(&data);
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}
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const auto size = data.isEmpty()
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? file.size()
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: data.size();
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const auto device = data.isEmpty()
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? static_cast<QIODevice*>(&file)
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: static_cast<QIODevice*>(&buffer);
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if (size < kHeaderSize || !device->open(QIODevice::ReadOnly)) {
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return false;
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}
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auto lastReadPosition = 0;
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char atomHeader[kHeaderSize] = { 0 };
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auto atomHeaderBytes = bytes::make_span(atomHeader);
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while (true) {
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const auto position = device->pos();
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if (device->read(atomHeader, kHeaderSize) != kHeaderSize) {
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break;
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}
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if (lastReadPosition >= kFindMoovBefore) {
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return false;
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} else if (IsAtom(atomHeaderBytes, "moov")) {
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return true;
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}
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const auto length = [&] {
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const auto result = ReadBigEndian<uint32>(atomHeaderBytes);
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if (result != 1) {
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return uint64(result);
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}
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char atomSize64[kHeaderSize] = { 0 };
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if (device->read(atomSize64, kHeaderSize) != kHeaderSize) {
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return uint64(-1);
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}
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auto atomSize64Bytes = bytes::make_span(atomSize64);
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return ReadBigEndian<uint64>(atomSize64Bytes);
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}();
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if (position + length > size) {
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break;
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}
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device->seek(position + length);
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lastReadPosition = position;
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}
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return false;
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}
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} // namespace Clip
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} // namespace Media
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