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Source/Engine/Serialization/FileReadStream.cpp

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+// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.
+
+#include "FileReadStream.h"
+#include "Engine/Core/Log.h"
+#include "Engine/Platform/File.h"
+
+FileReadStream* FileReadStream::Open(const StringView& path)
+{
+    const auto file = File::Open(path, FileMode::OpenExisting, FileAccess::Read, FileShare::Read);
+    if (file == nullptr)
+    {
+        LOG(Warning, "Cannot open file '{0}'", path);
+        return nullptr;
+    }
+    return New<FileReadStream>(file);
+}
+
+void FileReadStream::Unlink()
+{
+    _file = nullptr;
+}
+
+FileReadStream::FileReadStream(File* file)
+    : _file(file)
+    , _virtualPosInBuffer(0)
+    , _bufferSize(0)
+{
+    ASSERT_LOW_LAYER(_file);
+}
+
+FileReadStream::~FileReadStream()
+{
+    // Ensure to be file closed and deleted
+    if (_file)
+        Delete(_file);
+}
+
+void FileReadStream::Flush()
+{
+    // Check if need to flush
+    /*if (_virtualPosInBuffer > 0)
+    {
+        // Update buffer
+        uint32 bytesRead;
+        _hasError |= _file->Read(_buffer, FILESTREAM_BUFFER_SIZE, &bytesRead) != 0;
+        _virtualPosInBuffer = 0;
+    }*/
+}
+
+void FileReadStream::Close()
+{
+    if (_file)
+    {
+        _file->Close();
+    }
+}
+
+uint32 FileReadStream::GetLength()
+{
+    return _file->GetSize();
+}
+
+uint32 FileReadStream::GetPosition()
+{
+    return _file->GetPosition() - _bufferSize + _virtualPosInBuffer;
+}
+
+void FileReadStream::SetPosition(uint32 seek)
+{
+    // Seek
+    _file->SetPosition(seek);
+
+    // Update buffer
+    _hasError |= _file->Read(_buffer, FILESTREAM_BUFFER_SIZE, &_bufferSize) != 0;
+    _virtualPosInBuffer = 0;
+}
+
+void FileReadStream::ReadBytes(void* data, uint32 bytes)
+{
+    // Skip if nothing to read
+    if (bytes == 0)
+    {
+        return;
+    }
+
+    // Ensure to flush the buffer if it's empty
+    if (_bufferSize == 0)
+    {
+        CHECK(_virtualPosInBuffer == 0);
+        _hasError |= _file->Read(_buffer, FILESTREAM_BUFFER_SIZE, &_bufferSize) != 0;
+    }
+
+    // Check if buffer has enough data for this read
+    const uint32 bufferBytesLeft = static_cast<uint32>(_bufferSize - _virtualPosInBuffer);
+    if (bytes <= bufferBytesLeft)
+    {
+        Platform::MemoryCopy(data, _buffer + _virtualPosInBuffer, bytes);
+        _virtualPosInBuffer += bytes;
+    }
+    else
+    {
+        // Flush already buffered bytes and read more it the buffer (reduce amount of flushes)
+        if (_virtualPosInBuffer > 0)
+        {
+            Platform::MemoryCopy(data, _buffer + _virtualPosInBuffer, bufferBytesLeft);
+            data = (byte*)data + bufferBytesLeft;
+            bytes -= bufferBytesLeft;
+            _virtualPosInBuffer = 0;
+            _hasError |= _file->Read(_buffer, FILESTREAM_BUFFER_SIZE, &_bufferSize) != 0;
+        }
+
+        // Read as much as can using whole buffer
+        while (bytes >= FILESTREAM_BUFFER_SIZE)
+        {
+            Platform::MemoryCopy(data, _buffer, FILESTREAM_BUFFER_SIZE);
+            data = (byte*)data + FILESTREAM_BUFFER_SIZE;
+            bytes -= FILESTREAM_BUFFER_SIZE;
+            _hasError |= _file->Read(_buffer, FILESTREAM_BUFFER_SIZE, &_bufferSize) != 0;
+        }
+
+        // Read the rest of the buffer but without flushing its data
+        if (bytes > 0)
+        {
+            Platform::MemoryCopy(data, _buffer, bytes);
+            _virtualPosInBuffer = bytes;
+        }
+    }
+}