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/*
*
* Copyright 2020 gRPC authors.
*
* 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 metadata contains functions to set and get metadata from addresses.
//
// This package is experimental.
package metadata
import (
"fmt"
"strings"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/resolver"
)
type mdKeyType string
const mdKey = mdKeyType("grpc.internal.address.metadata")
type mdValue metadata.MD
func (m mdValue) Equal(o interface{}) bool {
om, ok := o.(mdValue)
if !ok {
return false
}
if len(m) != len(om) {
return false
}
for k, v := range m {
ov := om[k]
if len(ov) != len(v) {
return false
}
for i, ve := range v {
if ov[i] != ve {
return false
}
}
}
return true
}
// Get returns the metadata of addr.
func Get(addr resolver.Address) metadata.MD {
attrs := addr.Attributes
if attrs == nil {
return nil
}
md, _ := attrs.Value(mdKey).(mdValue)
return metadata.MD(md)
}
// Set sets (overrides) the metadata in addr.
//
// When a SubConn is created with this address, the RPCs sent on it will all
// have this metadata.
func Set(addr resolver.Address, md metadata.MD) resolver.Address {
addr.Attributes = addr.Attributes.WithValue(mdKey, mdValue(md))
return addr
}
// Validate validates every pair in md with ValidatePair.
func Validate(md metadata.MD) error {
for k, vals := range md {
if err := ValidatePair(k, vals...); err != nil {
return err
}
}
return nil
}
// hasNotPrintable return true if msg contains any characters which are not in %x20-%x7E
func hasNotPrintable(msg string) bool {
// for i that saving a conversion if not using for range
for i := 0; i < len(msg); i++ {
if msg[i] < 0x20 || msg[i] > 0x7E {
return true
}
}
return false
}
// ValidatePair validate a key-value pair with the following rules (the pseudo-header will be skipped) :
//
// - key must contain one or more characters.
// - the characters in the key must be contained in [0-9 a-z _ - .].
// - if the key ends with a "-bin" suffix, no validation of the corresponding value is performed.
// - the characters in the every value must be printable (in [%x20-%x7E]).
func ValidatePair(key string, vals ...string) error {
// key should not be empty
if key == "" {
return fmt.Errorf("there is an empty key in the header")
}
// pseudo-header will be ignored
if key[0] == ':' {
return nil
}
// check key, for i that saving a conversion if not using for range
for i := 0; i < len(key); i++ {
r := key[i]
if !(r >= 'a' && r <= 'z') && !(r >= '0' && r <= '9') && r != '.' && r != '-' && r != '_' {
return fmt.Errorf("header key %q contains illegal characters not in [0-9a-z-_.]", key)
}
}
if strings.HasSuffix(key, "-bin") {
return nil
}
// check value
for _, val := range vals {
if hasNotPrintable(val) {
return fmt.Errorf("header key %q contains value with non-printable ASCII characters", key)
}
}
return nil
}
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