129 lines
2.8 KiB
Go
129 lines
2.8 KiB
Go
// Package metadata is a way of defining message headers
|
|
package metadata
|
|
|
|
import (
|
|
"context"
|
|
"net/textproto"
|
|
)
|
|
|
|
type metadataKey struct{}
|
|
|
|
// Metadata is our way of representing request headers internally.
|
|
// They're used at the RPC level and translate back and forth
|
|
// from Transport headers.
|
|
type Metadata map[string]string
|
|
|
|
var (
|
|
// DefaultMetadataSize used when need to init new Metadata
|
|
DefaultMetadataSize = 6
|
|
)
|
|
|
|
// Get returns value from metadata by key
|
|
func (md Metadata) Get(key string) (string, bool) {
|
|
// fast path
|
|
val, ok := md[key]
|
|
if !ok {
|
|
// slow path
|
|
val, ok = md[textproto.CanonicalMIMEHeaderKey(key)]
|
|
}
|
|
return val, ok
|
|
}
|
|
|
|
// Set is used to store value in metadata
|
|
func (md Metadata) Set(key, val string) {
|
|
md[textproto.CanonicalMIMEHeaderKey(key)] = val
|
|
}
|
|
|
|
// Del is used to remove value from metadata
|
|
func (md Metadata) Del(key string) {
|
|
// fast path
|
|
if _, ok := md[key]; ok {
|
|
delete(md, key)
|
|
} else {
|
|
// slow path
|
|
delete(md, textproto.CanonicalMIMEHeaderKey(key))
|
|
}
|
|
}
|
|
|
|
// Copy makes a copy of the metadata
|
|
func Copy(md Metadata) Metadata {
|
|
nmd := New(len(md))
|
|
for key, val := range md {
|
|
nmd.Set(key, val)
|
|
}
|
|
return nmd
|
|
}
|
|
|
|
func Del(ctx context.Context, key string) context.Context {
|
|
md, ok := FromContext(ctx)
|
|
if !ok {
|
|
md = New(0)
|
|
}
|
|
md.Del(key)
|
|
return context.WithValue(ctx, metadataKey{}, md)
|
|
}
|
|
|
|
// Set add key with val to metadata
|
|
func Set(ctx context.Context, key, val string) context.Context {
|
|
md, ok := FromContext(ctx)
|
|
if !ok {
|
|
md = New(0)
|
|
}
|
|
md.Set(key, val)
|
|
return context.WithValue(ctx, metadataKey{}, md)
|
|
}
|
|
|
|
// Get returns a single value from metadata in the context
|
|
func Get(ctx context.Context, key string) (string, bool) {
|
|
md, ok := FromContext(ctx)
|
|
if !ok {
|
|
return "", ok
|
|
}
|
|
return md.Get(key)
|
|
}
|
|
|
|
// FromContext returns metadata from the given context
|
|
func FromContext(ctx context.Context) (Metadata, bool) {
|
|
md, ok := ctx.Value(metadataKey{}).(Metadata)
|
|
if !ok {
|
|
return nil, ok
|
|
}
|
|
nmd := Copy(md)
|
|
return nmd, ok
|
|
}
|
|
|
|
// New return new sized metadata
|
|
func New(size int) Metadata {
|
|
if size == 0 {
|
|
size = DefaultMetadataSize
|
|
}
|
|
return make(Metadata, size)
|
|
}
|
|
|
|
// NewContext creates a new context with the given metadata
|
|
func NewContext(ctx context.Context, md Metadata) context.Context {
|
|
return context.WithValue(ctx, metadataKey{}, Copy(md))
|
|
}
|
|
|
|
// MergeContext merges metadata to existing metadata, overwriting if specified
|
|
func MergeContext(ctx context.Context, pmd Metadata, overwrite bool) context.Context {
|
|
if ctx == nil {
|
|
ctx = context.Background()
|
|
}
|
|
md, ok := FromContext(ctx)
|
|
if !ok {
|
|
return context.WithValue(ctx, metadataKey{}, Copy(pmd))
|
|
}
|
|
nmd := Copy(md)
|
|
for key, val := range pmd {
|
|
if _, ok := nmd[key]; ok && !overwrite {
|
|
// skip
|
|
} else if val != "" {
|
|
nmd.Set(key, val)
|
|
} else {
|
|
nmd.Del(key)
|
|
}
|
|
}
|
|
return context.WithValue(ctx, metadataKey{}, nmd)
|
|
}
|