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Telegram/SourceFiles/media/clip/media_clip_check_streaming.cpp

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+/*
+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 "core/file_location.h"
+#include "base/bytes.h"
+#include "logs.h"
+
+#include <QtCore/QtEndian>
+#include <QtCore/QBuffer>
+#include <QtCore/QFile>
+
+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]) {
+	return bytes::compare(
+		header.subspan(4, 4),
+		bytes::make_span(atom).subspan(0, 4)) == 0;
+}
+
+} // namespace
+
+bool CheckStreamingSupport(
+		const Core::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