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accept_encoding_gzip.go
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accept_encoding_gzip.go
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package acceptencoding
import (
"compress/gzip"
"context"
"fmt"
"io"
"github.com/aws/smithy-go"
"github.com/aws/smithy-go/middleware"
smithyhttp "github.com/aws/smithy-go/transport/http"
)
const acceptEncodingHeaderKey = "Accept-Encoding"
const contentEncodingHeaderKey = "Content-Encoding"
// AddAcceptEncodingGzipOptions provides the options for the
// AddAcceptEncodingGzip middleware setup.
type AddAcceptEncodingGzipOptions struct {
Enable bool
}
// AddAcceptEncodingGzip explicitly adds handling for accept-encoding GZIP
// middleware to the operation stack. This allows checksums to be correctly
// computed without disabling GZIP support.
func AddAcceptEncodingGzip(stack *middleware.Stack, options AddAcceptEncodingGzipOptions) error {
if options.Enable {
if err := stack.Finalize.Add(&EnableGzip{}, middleware.Before); err != nil {
return err
}
if err := stack.Deserialize.Insert(&DecompressGzip{}, "OperationDeserializer", middleware.After); err != nil {
return err
}
return nil
}
return stack.Finalize.Add(&DisableGzip{}, middleware.Before)
}
// DisableGzip provides the middleware that will
// disable the underlying http client automatically enabling for gzip
// decompress content-encoding support.
type DisableGzip struct{}
// ID returns the id for the middleware.
func (*DisableGzip) ID() string {
return "DisableAcceptEncodingGzip"
}
// HandleFinalize implements the FinalizeMiddleware interface.
func (*DisableGzip) HandleFinalize(
ctx context.Context, input middleware.FinalizeInput, next middleware.FinalizeHandler,
) (
output middleware.FinalizeOutput, metadata middleware.Metadata, err error,
) {
req, ok := input.Request.(*smithyhttp.Request)
if !ok {
return output, metadata, &smithy.SerializationError{
Err: fmt.Errorf("unknown request type %T", input.Request),
}
}
// Explicitly enable gzip support, this will prevent the http client from
// auto extracting the zipped content.
req.Header.Set(acceptEncodingHeaderKey, "identity")
return next.HandleFinalize(ctx, input)
}
// EnableGzip provides a middleware to enable support for
// gzip responses, with manual decompression. This prevents the underlying HTTP
// client from performing the gzip decompression automatically.
type EnableGzip struct{}
// ID returns the id for the middleware.
func (*EnableGzip) ID() string {
return "AcceptEncodingGzip"
}
// HandleFinalize implements the FinalizeMiddleware interface.
func (*EnableGzip) HandleFinalize(
ctx context.Context, input middleware.FinalizeInput, next middleware.FinalizeHandler,
) (
output middleware.FinalizeOutput, metadata middleware.Metadata, err error,
) {
req, ok := input.Request.(*smithyhttp.Request)
if !ok {
return output, metadata, &smithy.SerializationError{
Err: fmt.Errorf("unknown request type %T", input.Request),
}
}
// Explicitly enable gzip support, this will prevent the http client from
// auto extracting the zipped content.
req.Header.Set(acceptEncodingHeaderKey, "gzip")
return next.HandleFinalize(ctx, input)
}
// DecompressGzip provides the middleware for decompressing a gzip
// response from the service.
type DecompressGzip struct{}
// ID returns the id for the middleware.
func (*DecompressGzip) ID() string {
return "DecompressGzip"
}
// HandleDeserialize implements the DeserializeMiddlware interface.
func (*DecompressGzip) HandleDeserialize(
ctx context.Context, input middleware.DeserializeInput, next middleware.DeserializeHandler,
) (
output middleware.DeserializeOutput, metadata middleware.Metadata, err error,
) {
output, metadata, err = next.HandleDeserialize(ctx, input)
if err != nil {
return output, metadata, err
}
resp, ok := output.RawResponse.(*smithyhttp.Response)
if !ok {
return output, metadata, &smithy.DeserializationError{
Err: fmt.Errorf("unknown response type %T", output.RawResponse),
}
}
if v := resp.Header.Get(contentEncodingHeaderKey); v != "gzip" {
return output, metadata, err
}
// Clear content length since it will no longer be valid once the response
// body is decompressed.
resp.Header.Del("Content-Length")
resp.ContentLength = -1
resp.Body = wrapGzipReader(resp.Body)
return output, metadata, err
}
type gzipReader struct {
reader io.ReadCloser
gzip *gzip.Reader
}
func wrapGzipReader(reader io.ReadCloser) *gzipReader {
return &gzipReader{
reader: reader,
}
}
// Read wraps the gzip reader around the underlying io.Reader to extract the
// response bytes on the fly.
func (g *gzipReader) Read(b []byte) (n int, err error) {
if g.gzip == nil {
g.gzip, err = gzip.NewReader(g.reader)
if err != nil {
g.gzip = nil // ensure uninitialized gzip value isn't used in close.
return 0, fmt.Errorf("failed to decompress gzip response, %w", err)
}
}
return g.gzip.Read(b)
}
func (g *gzipReader) Close() error {
if g.gzip == nil {
return nil
}
if err := g.gzip.Close(); err != nil {
g.reader.Close()
return fmt.Errorf("failed to decompress gzip response, %w", err)
}
return g.reader.Close()
}