tdesktop/Telegram/SourceFiles/media/clip/media_clip_check_streaming.cpp

94 lines
2.3 KiB
C++

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