github.com/blixtra/rkt@v0.8.1-0.20160204105720-ab0d1add1a43/Godeps/_workspace/src/google.golang.org/grpc/metadata/metadata.go (about)

     1  /*
     2   *
     3   * Copyright 2014, Google Inc.
     4   * All rights reserved.
     5   *
     6   * Redistribution and use in source and binary forms, with or without
     7   * modification, are permitted provided that the following conditions are
     8   * met:
     9   *
    10   *     * Redistributions of source code must retain the above copyright
    11   * notice, this list of conditions and the following disclaimer.
    12   *     * Redistributions in binary form must reproduce the above
    13   * copyright notice, this list of conditions and the following disclaimer
    14   * in the documentation and/or other materials provided with the
    15   * distribution.
    16   *     * Neither the name of Google Inc. nor the names of its
    17   * contributors may be used to endorse or promote products derived from
    18   * this software without specific prior written permission.
    19   *
    20   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    21   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    22   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    23   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    24   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    25   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    26   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    27   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    28   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    29   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    30   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    31   *
    32   */
    33  
    34  // Package metadata define the structure of the metadata supported by gRPC library.
    35  package metadata
    36  
    37  import (
    38  	"encoding/base64"
    39  	"fmt"
    40  	"strings"
    41  
    42  	"golang.org/x/net/context"
    43  )
    44  
    45  const (
    46  	binHdrSuffix = "-bin"
    47  )
    48  
    49  // encodeKeyValue encodes key and value qualified for transmission via gRPC.
    50  // Transmitting binary headers violates HTTP/2 spec.
    51  // TODO(zhaoq): Maybe check if k is ASCII also.
    52  func encodeKeyValue(k, v string) (string, string) {
    53  	k = strings.ToLower(k)
    54  	if strings.HasSuffix(k, binHdrSuffix) {
    55  		val := base64.StdEncoding.EncodeToString([]byte(v))
    56  		v = string(val)
    57  	}
    58  	return k, v
    59  }
    60  
    61  // DecodeKeyValue returns the original key and value corresponding to the
    62  // encoded data in k, v.
    63  func DecodeKeyValue(k, v string) (string, string, error) {
    64  	if !strings.HasSuffix(k, binHdrSuffix) {
    65  		return k, v, nil
    66  	}
    67  	val, err := base64.StdEncoding.DecodeString(v)
    68  	if err != nil {
    69  		return "", "", err
    70  	}
    71  	return k, string(val), nil
    72  }
    73  
    74  // MD is a mapping from metadata keys to values. Users should use the following
    75  // two convenience functions New and Pairs to generate MD.
    76  type MD map[string][]string
    77  
    78  // New creates a MD from given key-value map.
    79  func New(m map[string]string) MD {
    80  	md := MD{}
    81  	for k, v := range m {
    82  		key, val := encodeKeyValue(k, v)
    83  		md[key] = append(md[key], val)
    84  	}
    85  	return md
    86  }
    87  
    88  // Pairs returns an MD formed by the mapping of key, value ...
    89  // Pairs panics if len(kv) is odd.
    90  func Pairs(kv ...string) MD {
    91  	if len(kv)%2 == 1 {
    92  		panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
    93  	}
    94  	md := MD{}
    95  	var k string
    96  	for i, s := range kv {
    97  		if i%2 == 0 {
    98  			k = s
    99  			continue
   100  		}
   101  		key, val := encodeKeyValue(k, s)
   102  		md[key] = append(md[key], val)
   103  	}
   104  	return md
   105  }
   106  
   107  // Len returns the number of items in md.
   108  func (md MD) Len() int {
   109  	return len(md)
   110  }
   111  
   112  // Copy returns a copy of md.
   113  func (md MD) Copy() MD {
   114  	out := MD{}
   115  	for k, v := range md {
   116  		for _, i := range v {
   117  			out[k] = append(out[k], i)
   118  		}
   119  	}
   120  	return out
   121  }
   122  
   123  type mdKey struct{}
   124  
   125  // NewContext creates a new context with md attached.
   126  func NewContext(ctx context.Context, md MD) context.Context {
   127  	return context.WithValue(ctx, mdKey{}, md)
   128  }
   129  
   130  // FromContext returns the MD in ctx if it exists.
   131  func FromContext(ctx context.Context) (md MD, ok bool) {
   132  	md, ok = ctx.Value(mdKey{}).(MD)
   133  	return
   134  }