protected async Task <InternalPageBlobSizeInfo> PreparePageBlobAsync(CloudPageBlob pageBlob,
int sourceBufferByteCountToWrite, CancellationToken cancellationToken)
{
EnsureBlobExistsResult result = await this.EnsureBlobExistsAsync(pageBlob, byteCountToWrite : sourceBufferByteCountToWrite);
InternalPageBlobSizeInfo sizeInfo;
switch (result)
{
case EnsureBlobExistsResult.Created:
sizeInfo = new InternalPageBlobSizeInfo();
break;
case EnsureBlobExistsResult.AlreadyExisted:
sizeInfo = await this.ResizePageBlobIfNeededAsync(pageBlob, sourceBufferByteCountToWrite,
cancellationToken);
break;
default:
throw new NotSupportedException($"Unrecognized enum value ({result}) returned from the method {nameof(this.EnsureBlobExistsAsync)}.");
}
return(sizeInfo);
}
protected async Task <InternalPageBlobSizeInfo> ResizePageBlobIfNeededAsync(CloudPageBlob pageBlob,
int sourceBufferByteCountToWrite, CancellationToken cancellationToken)
{
BlobProperties blobProperties = await this.GetPropertiesAsync(pageBlob, cancellationToken);
int offsetOfLastPage = CalculateOffsetOfLastPage((int)blobProperties.Length);
byte[] usedBytesFromLastPage =
await this.GetUsedBytesWrittenToLastPageAsync(pageBlob, offsetOfLastPage, cancellationToken);
var sizeInfo = new InternalPageBlobSizeInfo(offsetOfLastPage, usedBytesFromLastPage);
int currentTotalBytesUsed =
CalculateTotalBytesUsed((int)blobProperties.Length, usedBytesFromLastPage.Length);
await this.ResizePageBlobIfNeededAsync(pageBlob, (int)blobProperties.Length, currentTotalBytesUsed,
sourceBufferByteCountToWrite, cancellationToken);
return(sizeInfo);
}
internal async Task <BlobSegmentInfo> AppendImplAsync(Stream sourceStreamToWrite, CancellationToken?cancellationToken = null, Func <Task> concurrencyTestFunc = null)
{
if (cancellationToken == null)
{
cancellationToken = CancellationToken.None;
}
this.EnsureInitialized();
CloudPageBlob pageBlob = this.BlobContainer.GetPageBlobReference(this.BlobPath);
// Note: We only force the use of a buffer here if the stream that is passed cannot seek. We need the
// length to fill out the page with null characters, so it must support seeking unless we find a
// different algorithm.
if (!sourceStreamToWrite.CanSeek)
{
sourceStreamToWrite =
await BuildMemoryStreamThatCanSeekAsync(sourceStreamToWrite, cancellationToken.Value);
}
InternalPageBlobSizeInfo pageBlobSizeInfo = await this.PreparePageBlobAsync(pageBlob,
(int)sourceStreamToWrite.Length, cancellationToken.Value);
Stream streamToWrite = BuildStreamOfPagesToWrite(sourceStreamToWrite, pageBlobSizeInfo);
int byteOffset = pageBlobSizeInfo.OffsetOfLastPage + pageBlobSizeInfo.UsedBytesFromLastPage.Length;
int streamLength = (int)sourceStreamToWrite.Length;
if (concurrencyTestFunc != null)
{
await concurrencyTestFunc();
}
await pageBlob.WritePagesAsync(streamToWrite, pageBlobSizeInfo.OffsetOfLastPage, null,
CreateAccessCondition(pageBlob), this.RequestOptions, this.OperationContext, cancellationToken.Value);
return(new BlobSegmentInfo(byteOffset, streamLength));
}
protected static Stream BuildStreamOfPagesToWrite(Stream sourceStreamToWrite, InternalPageBlobSizeInfo sizeInfo)
{
int updatedUsedByteCount = sizeInfo.UsedBytesFromLastPage.Length + (int)sourceStreamToWrite.Length;
int updatedUsedToFullPageByteCount = CalculateBlobLengthThroughEndOfPage(updatedUsedByteCount);
var streamForPreviouslyUsedBytes = new MemoryStream(sizeInfo.UsedBytesFromLastPage, false);
if (updatedUsedByteCount == updatedUsedToFullPageByteCount)
{
return(new ConcatenatedStream(new[] { streamForPreviouslyUsedBytes, sourceStreamToWrite }));
}
var streamToFillOutLastPage = new MemoryStream(FullPageOfNullChars, 0,
(int)(updatedUsedToFullPageByteCount - updatedUsedByteCount));
return(new ConcatenatedStream(new[] { streamForPreviouslyUsedBytes, sourceStreamToWrite, streamToFillOutLastPage }));
}
