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context.go
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context.go
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// Package metadata is a way of defining message headers
package metadata
import (
"context"
)
type (
mdIncomingKey struct{}
mdOutgoingKey struct{}
mdKey struct{}
)
// FromIncomingContext returns metadata from incoming ctx
// returned metadata shoud not be modified or race condition happens
func FromIncomingContext(ctx context.Context) (Metadata, bool) {
if ctx == nil {
return nil, false
}
md, ok := ctx.Value(mdIncomingKey{}).(*rawMetadata)
if !ok || md.md == nil {
return nil, false
}
return md.md, ok
}
// FromOutgoingContext returns metadata from outgoing ctx
// returned metadata shoud not be modified or race condition happens
func FromOutgoingContext(ctx context.Context) (Metadata, bool) {
if ctx == nil {
return nil, false
}
md, ok := ctx.Value(mdOutgoingKey{}).(*rawMetadata)
if !ok || md.md == nil {
return nil, false
}
return md.md, ok
}
// FromContext returns metadata from the given context
// returned metadata shoud not be modified or race condition happens
//
// Deprecated: use FromIncomingContext or FromOutgoingContext
func FromContext(ctx context.Context) (Metadata, bool) {
if ctx == nil {
return nil, false
}
md, ok := ctx.Value(mdKey{}).(*rawMetadata)
if !ok || md.md == nil {
return nil, false
}
return md.md, ok
}
// NewContext creates a new context with the given metadata
//
// Deprecated: use NewIncomingContext or NewOutgoingContext
func NewContext(ctx context.Context, md Metadata) context.Context {
if ctx == nil {
ctx = context.Background()
}
ctx = context.WithValue(ctx, mdKey{}, &rawMetadata{md})
ctx = context.WithValue(ctx, mdIncomingKey{}, &rawMetadata{})
ctx = context.WithValue(ctx, mdOutgoingKey{}, &rawMetadata{})
return ctx
}
// SetOutgoingContext modify outgoing context with given metadata
func SetOutgoingContext(ctx context.Context, md Metadata) bool {
if ctx == nil {
return false
}
if omd, ok := ctx.Value(mdOutgoingKey{}).(*rawMetadata); ok {
omd.md = md
return true
}
return false
}
// SetIncomingContext modify incoming context with given metadata
func SetIncomingContext(ctx context.Context, md Metadata) bool {
if ctx == nil {
return false
}
if omd, ok := ctx.Value(mdIncomingKey{}).(*rawMetadata); ok {
omd.md = md
return true
}
return false
}
// NewIncomingContext creates a new context with incoming metadata attached
func NewIncomingContext(ctx context.Context, md Metadata) context.Context {
if ctx == nil {
ctx = context.Background()
}
ctx = context.WithValue(ctx, mdIncomingKey{}, &rawMetadata{md})
if v, ok := ctx.Value(mdOutgoingKey{}).(*rawMetadata); !ok || v == nil {
ctx = context.WithValue(ctx, mdOutgoingKey{}, &rawMetadata{})
}
return ctx
}
// NewOutgoingContext creates a new context with outcoming metadata attached
func NewOutgoingContext(ctx context.Context, md Metadata) context.Context {
if ctx == nil {
ctx = context.Background()
}
ctx = context.WithValue(ctx, mdOutgoingKey{}, &rawMetadata{md})
if v, ok := ctx.Value(mdIncomingKey{}).(*rawMetadata); !ok || v == nil {
ctx = context.WithValue(ctx, mdIncomingKey{}, &rawMetadata{})
}
return ctx
}
// AppendOutgoingContext apends new md to context
func AppendOutgoingContext(ctx context.Context, kv ...string) context.Context {
md, ok := Pairs(kv...)
if !ok {
return ctx
}
omd, ok := FromOutgoingContext(ctx)
if !ok {
return NewOutgoingContext(ctx, md)
}
for k, v := range md {
omd.Set(k, v)
}
return NewOutgoingContext(ctx, omd)
}
// AppendIncomingContext apends new md to context
func AppendIncomingContext(ctx context.Context, kv ...string) context.Context {
md, ok := Pairs(kv...)
if !ok {
return ctx
}
omd, ok := FromIncomingContext(ctx)
if !ok {
return NewIncomingContext(ctx, md)
}
for k, v := range md {
omd.Set(k, v)
}
return NewIncomingContext(ctx, omd)
}