public void Flush()
{
lock (locker)
{
foreach (var dirtyRegion in writtenRegions)
{
BasePageStorage.WriteTo(PageIndex, dirtyRegion.FirstIndex, this.cacheBuffer, dirtyRegion.FirstIndex, dirtyRegion.Length);
}
}
}
public void Write(long dstOffset, byte[] buffer, long srcOffset, long length)
{
if (BasePageStorage.IsReadOnly)
{
throw new InvalidOperationException("Cannot write to a read-only " + nameof(CachedPage) + ".");
}
if (dstOffset < 0)
{
throw new ArgumentOutOfRangeException(nameof(dstOffset), "The destination offset cannot be less than zero.");
}
if (srcOffset < 0)
{
throw new ArgumentOutOfRangeException(nameof(srcOffset), "The source offset cannot be less than zero.");
}
if (length < 0)
{
throw new ArgumentOutOfRangeException(nameof(length), "The length cannot be less than zero.");
}
if (dstOffset + length > BasePageStorage.PageSize)
{
throw new ArgumentOutOfRangeException(nameof(dstOffset), "The sum of the destination offset and length cannot be greater than the page size.");
}
if (srcOffset + length > buffer.Length)
{
throw new ArgumentOutOfRangeException(nameof(srcOffset), "The sum of the source offset and length cannot be greater than the size of the source buffer.");
}
lock (locker)
{
DataRegion dstRegion = new DataRegion(dstOffset, (dstOffset + length) - 1 /*-1 to go from count to index*/);
//Copy the data to the cached buffer
Buffer.BlockCopy(buffer, (int)srcOffset, cacheBuffer, (int)dstOffset, (int)length);
//Writes affect read cache too
readRegions.Add(dstRegion);
if (WriteMode == CachedPageStorage.CacheWriteMode.WriteThrough)
{
//Write directly to the base storage
BasePageStorage.WriteTo(PageIndex, dstOffset, buffer, srcOffset, length);
}
else
{
//Update the 'dirty' write regions
writtenRegions.Add(dstRegion);
}
}
//Mark this page as more recent
UpdateUseCounter();
}
/// <summary>
/// Reads from the page, updating cache where necessary.
/// </summary>
/// <param name="srcOffset">The source offset within the page's payload.</param>
/// <param name="buffer">The destination buffer.</param>
/// <param name="dstOffset">The offset within the destination <paramref name="buffer"/>.</param>
/// <param name="length">The number of bytes to read.</param>
public void Read(long srcOffset, byte[] buffer, long dstOffset, long length)
{
if (buffer == null)
{
throw new ArgumentNullException(nameof(buffer));
}
if (srcOffset < 0)
{
throw new ArgumentOutOfRangeException(nameof(srcOffset), "The source offset cannot be less than zero.");
}
if (dstOffset < 0)
{
throw new ArgumentOutOfRangeException(nameof(dstOffset), "The destination offset cannot be less than zero.");
}
if (length < 0)
{
throw new ArgumentOutOfRangeException(nameof(length), "The length cannot be less than zero.");
}
if (srcOffset + length > BasePageStorage.PageSize)
{
throw new ArgumentOutOfRangeException(nameof(srcOffset), "The sum of the source offset and length cannot be greater than the size of each page.");
}
if (dstOffset + length > buffer.Length)
{
throw new ArgumentOutOfRangeException(nameof(dstOffset), "The sum of the destination offset and length cannot be greater than the size of the destination buffer.");
}
lock (locker)
{
if (length != 0)
{
DataRegion srcRegion = new DataRegion(srcOffset, (srcOffset + length) - 1 /*-1 to go from count to index*/);
//Determine which DataRegions are not currently cached (if any), and load them into cache
foreach (var missing in readRegions.GetMissingRegions(srcRegion))
{
//Read this missing DataRegion into cache
BasePageStorage.ReadFrom(PageIndex, missing.FirstIndex, cacheBuffer, missing.FirstIndex, missing.Length);
readRegions.Add(missing);
}
//Copy the data from the cached buffer
Buffer.BlockCopy(cacheBuffer, (int)srcOffset, buffer, (int)dstOffset, (int)length);
}
//Else we don't need to do anything, read 0 bytes is meaningless
}
//Mark this page as more recent
UpdateUseCounter();
}
