header.go

// Copyright 2021-2022 Buf Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package connect

import (
	"encoding/base64"
	"net/http"
)

// EncodeBinaryHeader base64-encodes the data. It always emits unpadded values.
//
// In the Connect, gRPC, and gRPC-Web protocols, binary headers must have keys
// ending in "-Bin".
func EncodeBinaryHeader(data []byte) string {
	// gRPC specification says that implementations should emit unpadded values.
	return base64.RawStdEncoding.EncodeToString(data)
}

// DecodeBinaryHeader base64-decodes the data. It can decode padded or unpadded
// values. Following usual HTTP semantics, multiple base64-encoded values may
// be joined with a comma. When receiving such comma-separated values, split
// them with [strings.Split] before calling DecodeBinaryHeader.
//
// Binary headers sent using the Connect, gRPC, and gRPC-Web protocols have
// keys ending in "-Bin".
func DecodeBinaryHeader(data string) ([]byte, error) {
	if len(data)%4 != 0 {
		// Data definitely isn't padded.
		return base64.RawStdEncoding.DecodeString(data)
	}
	// Either the data was padded, or padding wasn't necessary. In both cases,
	// the padding-aware decoder works.
	return base64.StdEncoding.DecodeString(data)
}

func mergeHeaders(into, from http.Header) {
	for k, vals := range from {
		into[k] = append(into[k], vals...)
	}
}