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