Azure
diff --git a/‎sdk/storage/azdatalake/file/chunkwriting.go
+193 b/‎sdk/storage/azdatalake/file/chunkwriting.go
+193
@@ -0,0 +1,193 @@
+//go:build go1.18
+// +build go1.18
+
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+package file
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/streaming"
+	"io"
+	"sync"
+)
+
+// chunkWriter provides methods to upload chunks that represent a file to a server.
+// This allows us to provide a local implementation that fakes the server for hermetic testing.
+type chunkWriter interface {
+	AppendData(context.Context, int64, io.ReadSeekCloser, *AppendDataOptions) (AppendDataResponse, error)
+	FlushData(context.Context, int64, *FlushDataOptions) (FlushDataResponse, error)
+}
+
+// bufferManager provides an abstraction for the management of buffers.
+// this is mostly for testing purposes, but does allow for different implementations without changing the algorithm.
+type bufferManager[T ~[]byte] interface {
+	// Acquire returns the channel that contains the pool of buffers.
+	Acquire() <-chan T
+
+	// Release releases the buffer back to the pool for reuse/cleanup.
+	Release(T)
+
+	// Grow grows the number of buffers, up to the predefined max.
+	// It returns the total number of buffers or an error.
+	// No error is returned if the number of buffers has reached max.
+	// This is called only from the reading goroutine.
+	Grow() (int, error)
+
+	// Free cleans up all buffers.
+	Free()
+}
+
+// copyFromReader copies a source io.Reader to file storage using concurrent uploads.
+func copyFromReader[T ~[]byte](ctx context.Context, src io.Reader, dst chunkWriter, options UploadStreamOptions, getBufferManager func(maxBuffers int, bufferSize int64) bufferManager[T]) error {
+	options.setDefaults()
+	actualSize := int64(0)
+	wg := sync.WaitGroup{}       // Used to know when all outgoing chunks have finished processing
+	errCh := make(chan error, 1) // contains the first error encountered during processing
+	var err error
+
+	buffers := getBufferManager(int(options.Concurrency), options.ChunkSize)
+	defer buffers.Free()
+
+	// this controls the lifetime of the uploading goroutines.
+	// if an error is encountered, cancel() is called which will terminate all uploads.
+	// NOTE: the ordering is important here.  cancel MUST execute before
+	// cleaning up the buffers so that any uploading goroutines exit first,
+	// releasing their buffers back to the pool for cleanup.
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	// This goroutine grabs a buffer, reads from the stream into the buffer,
+	// then creates a goroutine to upload/stage the chunk.
+	for chunkNum := uint32(0); true; chunkNum++ {
+		var buffer T
+		select {
+		case buffer = <-buffers.Acquire():
+			// got a buffer
+		default:
+			// no buffer available; allocate a new buffer if possible
+			if _, err := buffers.Grow(); err != nil {
+				return err
+			}
+
+			// either grab the newly allocated buffer or wait for one to become available
+			buffer = <-buffers.Acquire()
+		}
+
+		var n int
+		n, err = io.ReadFull(src, buffer)
+
+		if n > 0 {
+			// some data was read, upload it
+			wg.Add(1) // We're posting a buffer to be sent
+
+			// NOTE: we must pass chunkNum as an arg to our goroutine else
+			// it's captured by reference and can change underneath us!
+			go func(chunkNum uint32) {
+				// Upload the outgoing chunk, matching the number of bytes read
+				offset := int64(chunkNum) * options.ChunkSize
+				appendDataOpts := options.getAppendDataOptions()
+				actualSize += int64(len(buffer[:n]))
+				_, err := dst.AppendData(ctx, offset, streaming.NopCloser(bytes.NewReader(buffer[:n])), appendDataOpts)
+				if err != nil {
+					select {
+					case errCh <- err:
+						// error was set
+					default:
+						// some other error is already set
+					}
+					cancel()
+				}
+				buffers.Release(buffer) // The goroutine reading from the stream can reuse this buffer now
+
+				// signal that the chunk has been staged.
+				// we MUST do this after attempting to write to errCh
+				// to avoid it racing with the reading goroutine.
+				wg.Done()
+			}(chunkNum)
+		} else {
+			// nothing was read so the buffer is empty, send it back for reuse/clean-up.
+			buffers.Release(buffer)
+		}
+
+		if err != nil { // The reader is done, no more outgoing buffers
+			if errors.Is(err, io.EOF) || errors.Is(err, io.ErrUnexpectedEOF) {
+				// these are expected errors, we don't surface those
+				err = nil
+			} else {
+				// some other error happened, terminate any outstanding uploads
+				cancel()
+			}
+			break
+		}
+	}
+
+	wg.Wait() // Wait for all outgoing chunks to complete
+
+	if err != nil {
+		// there was an error reading from src, favor this error over any error during staging
+		return err
+	}
+
+	select {
+	case err = <-errCh:
+		// there was an error during staging
+		return err
+	default:
+		// no error was encountered
+	}
+
+	// All chunks uploaded, return nil error
+	flushOpts := options.getFlushDataOptions()
+	_, err = dst.FlushData(ctx, actualSize, flushOpts)
+	return err
+}
+
+// mmbPool implements the bufferManager interface.
+// it uses anonymous memory mapped files for buffers.
+// don't use this type directly, use newMMBPool() instead.
+type mmbPool struct {
+	buffers chan mmb
+	count   int
+	max     int
+	size    int64
+}
+
+func newMMBPool(maxBuffers int, bufferSize int64) bufferManager[mmb] {
+	return &mmbPool{
+		buffers: make(chan mmb, maxBuffers),
+		max:     maxBuffers,
+		size:    bufferSize,
+	}
+}
+
+func (pool *mmbPool) Acquire() <-chan mmb {
+	return pool.buffers
+}
+
+func (pool *mmbPool) Grow() (int, error) {
+	if pool.count < pool.max {
+		buffer, err := newMMB(pool.size)
+		if err != nil {
+			return 0, err
+		}
+		pool.buffers <- buffer
+		pool.count++
+	}
+	return pool.count, nil
+}
+
+func (pool *mmbPool) Release(buffer mmb) {
+	pool.buffers <- buffer
+}
+
+func (pool *mmbPool) Free() {
+	for i := 0; i < pool.count; i++ {
+		buffer := <-pool.buffers
+		buffer.delete()
+	}
+	pool.count = 0
+}