Fetching ETag directly from metadata (#157)

Added support for fetching ETag directly from metadata when doing upload with Aws Transfer
Only set Etag to handle's metadata when part is the last part

Author: singku

aws-cpp-sdk-transfer/include/aws/transfer/TransferHandle.h

@@ -54,7 +54,7 @@ namespace Aws
         {
             public:
                 PartState();
-                PartState(int partId, size_t bestProgressInBytes, size_t sizeInBytes);
+                PartState(int partId, size_t bestProgressInBytes, size_t sizeInBytes, bool lastPart = false);
 
                 int GetPartId() const { return m_partId; }
 
@@ -80,6 +80,9 @@ namespace Aws
                 void SetRangeBegin(size_t rangeBegin) { m_rangeBegin = rangeBegin; }
                 size_t GetRangeBegin() const { return m_rangeBegin; }
 
+                bool IsLastPart() { return m_lastPart; }
+                void SetLastPart() { m_lastPart = true; }
+
             private:
 
                 int m_partId;
@@ -92,6 +95,7 @@ namespace Aws
 
                 std::atomic<Aws::IOStream *> m_downloadPartStream;
                 std::atomic<Aws::Utils::Array<unsigned char> *> m_downloadBuffer;
+                bool m_lastPart;
         };
 
         using PartPointer = std::shared_ptr< PartState >;
@@ -298,6 +302,11 @@ namespace Aws
             */
             inline void SetMetadata(const Aws::Map<Aws::String, Aws::String>& value) { m_metadata = value; }
 
+            /**
+             * Add a new entry to or update an existed entry of m_metadata, useful when users want to get ETag directly from metadata.
+             */
+            inline void AddMetadataEntry(const Aws::String& key, const Aws::String& value) { m_metadata[key] = value; }
+
             /**
              * The current status of the operation
              */

aws-cpp-sdk-transfer/source/transfer/TransferHandle.cpp

@@ -30,18 +30,20 @@ namespace Aws
             m_sizeInBytes(0),
             m_rangeBegin(0),
             m_downloadPartStream(nullptr),
-            m_downloadBuffer(nullptr)
+            m_downloadBuffer(nullptr),
+            m_lastPart(false)
         {}
 
-        PartState::PartState(int partId, size_t bestProgressInBytes, size_t sizeInBytes) :
+        PartState::PartState(int partId, size_t bestProgressInBytes, size_t sizeInBytes, bool lastPart) :
             m_partId(partId),
             m_eTag(""),
             m_currentProgressInBytes(0),
             m_bestProgressInBytes(bestProgressInBytes),
             m_sizeInBytes(sizeInBytes),
             m_rangeBegin(0),
             m_downloadPartStream(nullptr),
-            m_downloadBuffer(nullptr)
+            m_downloadBuffer(nullptr),
+            m_lastPart(lastPart)
         {}
 
 
@@ -128,6 +130,10 @@ namespace Aws
             }
 
             partState->SetETag(eTag);
+            if (partState->IsLastPart()) 
+            {
+                AddMetadataEntry("ETag", eTag);
+            }
             m_completedParts[partState->GetPartId()] = partState;
         }
 

aws-cpp-sdk-transfer/source/transfer/TransferManager.cpp

@@ -243,7 +243,8 @@ namespace Aws
                     for (uint64_t i = 0; i < partCount; ++i)
                     {
                         uint64_t partSize = std::min(totalSize - i * m_transferConfig.bufferSize, m_transferConfig.bufferSize);
-                        handle->AddQueuedPart(Aws::MakeShared<PartState>(CLASS_TAG, static_cast<int>(i + 1), 0, static_cast<size_t>(partSize)));
+                        bool lastPart = (i == partCount - 1) ? true : false;
+                        handle->AddQueuedPart(Aws::MakeShared<PartState>(CLASS_TAG, static_cast<int>(i + 1), 0, static_cast<size_t>(partSize), lastPart));
                     }                    
                 }
                 else
@@ -339,7 +340,7 @@ namespace Aws
 
         void TransferManager::DoSinglePartUpload(Aws::IOStream* streamToPut, const std::shared_ptr<TransferHandle>& handle)
         {
-            auto partState = Aws::MakeShared<PartState>(CLASS_TAG, 1, 0, static_cast<size_t>(handle->GetBytesTotalSize()));
+            auto partState = Aws::MakeShared<PartState>(CLASS_TAG, 1, 0, static_cast<size_t>(handle->GetBytesTotalSize()), true);
 
             handle->UpdateStatus(TransferStatus::IN_PROGRESS);
             handle->SetIsMultipart(false);
@@ -609,7 +610,8 @@ namespace Aws
                 for(std::size_t i = 0; i < partCount; ++i)
                 {
                     std::size_t partSize = (i + 1 < partCount ) ? bufferSize : (downloadSize - bufferSize * (partCount - 1));
-                    auto partState = Aws::MakeShared<PartState>(CLASS_TAG, static_cast<int>(i + 1), 0, partSize);
+                    bool lastPart = (i == partCount - 1) ? true : false;
+                    auto partState = Aws::MakeShared<PartState>(CLASS_TAG, static_cast<int>(i + 1), 0, partSize, lastPart);
                     partState->SetRangeBegin(i * bufferSize);
                     handle->AddQueuedPart(partState);
                 }