Split buffer and file download options into their own types (#18896)

* Split buffer and file download options into their own types

This allows the options for each API to independently evolve over time.
Fixed potential panic in some helper methods.

* type-o

sdk/storage/azblob/blob/client.go

@@ -269,10 +269,7 @@ func (b *Client) GetSASToken(permissions SASPermissions, start time.Time, expiry
 // Concurrent Download Functions -----------------------------------------------------------------------------------------
 
 // download downloads an Azure blob to a WriterAt in parallel.
-func (b *Client) download(ctx context.Context, writer io.WriterAt, o *downloadOptions) (int64, error) {
-	if o == nil {
-		o = &downloadOptions{}
-	}
+func (b *Client) download(ctx context.Context, writer io.WriterAt, o downloadOptions) (int64, error) {
 	if o.BlockSize == 0 {
 		o.BlockSize = DefaultDownloadBlockSize
 	}
@@ -372,24 +369,32 @@ func (b *Client) DownloadStream(ctx context.Context, o *DownloadStreamOptions) (
 
 // DownloadBuffer downloads an Azure blob to a buffer with parallel.
 func (b *Client) DownloadBuffer(ctx context.Context, buffer []byte, o *DownloadBufferOptions) (int64, error) {
-	return b.download(ctx, shared.NewBytesWriter(buffer), o)
+	if o == nil {
+		o = &DownloadBufferOptions{}
+	}
+	return b.download(ctx, shared.NewBytesWriter(buffer), (downloadOptions)(*o))
 }
 
 // DownloadFile downloads an Azure blob to a local file.
 // The file would be truncated if the size doesn't match.
 func (b *Client) DownloadFile(ctx context.Context, file *os.File, o *DownloadFileOptions) (int64, error) {
+	if o == nil {
+		o = &DownloadFileOptions{}
+	}
+	do := (*downloadOptions)(o)
+
 	// 1. Calculate the size of the destination file
 	var size int64
 
-	count := o.Count
+	count := do.Count
 	if count == CountToEnd {
 		// Try to get Azure blob's size
-		getBlobPropertiesOptions := o.getBlobPropertiesOptions()
+		getBlobPropertiesOptions := do.getBlobPropertiesOptions()
 		props, err := b.GetProperties(ctx, getBlobPropertiesOptions)
 		if err != nil {
 			return 0, err
 		}
-		size = *props.ContentLength - o.Offset
+		size = *props.ContentLength - do.Offset
 	} else {
 		size = count
 	}
@@ -406,7 +411,7 @@ func (b *Client) DownloadFile(ctx context.Context, file *os.File, o *DownloadFil
 	}
 
 	if size > 0 {
-		return b.download(ctx, file, o)
+		return b.download(ctx, file, *do)
 	} else { // if the blob's size is 0, there is no need in downloading it
 		return 0, nil
 	}

sdk/storage/azblob/blob/models.go

@@ -109,7 +109,7 @@ func (o *DownloadStreamOptions) format() (*generated.BlobClientDownloadOptions,
 
 // ---------------------------------------------------------------------------------------------------------------------
 
-// downloadOptions identifies options used by the DownloadBuffer and DownloadFile functions.
+// downloadOptions contains common options used by the DownloadBuffer and DownloadFile functions.
 type downloadOptions struct {
 	// Count is the number of bytes to download.  Specify 0 to download the entire blob (this is the default).
 	Count int64
@@ -138,13 +138,19 @@ type downloadOptions struct {
 }
 
 func (o *downloadOptions) getBlobPropertiesOptions() *GetPropertiesOptions {
+	if o == nil {
+		return nil
+	}
 	return &GetPropertiesOptions{
 		AccessConditions: o.AccessConditions,
 		CpkInfo:          o.CpkInfo,
 	}
 }
 
 func (o *downloadOptions) getDownloadBlobOptions(offSet, count int64, rangeGetContentMD5 *bool) *DownloadStreamOptions {
+	if o == nil {
+		return nil
+	}
 	return &DownloadStreamOptions{
 		AccessConditions:   o.AccessConditions,
 		CpkInfo:            o.CpkInfo,
@@ -155,11 +161,61 @@ func (o *downloadOptions) getDownloadBlobOptions(offSet, count int64, rangeGetCo
 	}
 }
 
-// DownloadBufferOptions identifies options used by the DownloadBuffer and DownloadFile functions.
-type DownloadBufferOptions = downloadOptions
+// DownloadBufferOptions contains the optional parameters for the DownloadBuffer method.
+type DownloadBufferOptions struct {
+	// Count is the number of bytes to download.  Specify 0 to download the entire blob (this is the default).
+	Count int64
+
+	// Offset is the byte offset within the blob to start the download.  The default value is zero.
+	Offset int64
+
+	// BlockSize specifies the block size to use for each parallel download; the default size is DefaultDownloadBlockSize.
+	BlockSize int64
+
+	// Progress is a function that is invoked periodically as bytes are received.
+	Progress func(bytesTransferred int64)
+
+	// BlobAccessConditions indicates the access conditions used when making HTTP GET requests against the blob.
+	AccessConditions *AccessConditions
+
+	// ClientProvidedKeyOptions indicates the client provided key by name and/or by value to encrypt/decrypt data.
+	CpkInfo      *CpkInfo
+	CpkScopeInfo *CpkScopeInfo
+
+	// Parallelism indicates the maximum number of blocks to download in parallel (0=default)
+	Parallelism uint16
+
+	// RetryReaderOptionsPerBlock is used when downloading each block.
+	RetryReaderOptionsPerBlock RetryReaderOptions
+}
+
+// DownloadFileOptions contains the optional parameters for the DownloadFile method.
+type DownloadFileOptions struct {
+	// Count is the number of bytes to download.  Specify 0 to download the entire blob (this is the default).
+	Count int64
+
+	// Offset is the byte offset within the blob to start the download.  The default value is zero.
+	Offset int64
+
+	// BlockSize specifies the block size to use for each parallel download; the default size is DefaultDownloadBlockSize.
+	BlockSize int64
+
+	// Progress is a function that is invoked periodically as bytes are received.
+	Progress func(bytesTransferred int64)
 
-// DownloadFileOptions identifies options used by the DownloadBuffer and DownloadFile functions.
-type DownloadFileOptions = downloadOptions
+	// BlobAccessConditions indicates the access conditions used when making HTTP GET requests against the blob.
+	AccessConditions *AccessConditions
+
+	// ClientProvidedKeyOptions indicates the client provided key by name and/or by value to encrypt/decrypt data.
+	CpkInfo      *CpkInfo
+	CpkScopeInfo *CpkScopeInfo
+
+	// Parallelism indicates the maximum number of blocks to download in parallel (0=default)
+	Parallelism uint16
+
+	// RetryReaderOptionsPerBlock is used when downloading each block.
+	RetryReaderOptionsPerBlock RetryReaderOptions
+}
 
 // ---------------------------------------------------------------------------------------------------------------------