131 lines
2.5 KiB
Go
131 lines
2.5 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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"net/textproto"
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"sort"
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)
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var (
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// HeaderPrefix for all headers passed
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HeaderPrefix = "Micro-"
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)
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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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type rawMetadata struct {
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md Metadata
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}
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var (
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// defaultMetadataSize used when need to init new Metadata
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defaultMetadataSize = 2
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)
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// Iterator used to iterate over metadata with order
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type Iterator struct {
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md Metadata
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keys []string
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cur int
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cnt int
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}
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// Next advance iterator to next element
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func (iter *Iterator) Next(k, v *string) bool {
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if iter.cur+1 > iter.cnt {
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return false
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}
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*k = iter.keys[iter.cur]
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*v = iter.md[*k]
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iter.cur++
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return true
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}
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// Iterator returns the itarator for metadata in sorted order
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func (md Metadata) Iterator() *Iterator {
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iter := &Iterator{md: md, cnt: len(md)}
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iter.keys = make([]string, 0, iter.cnt)
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for k := range md {
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iter.keys = append(iter.keys, k)
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}
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sort.Strings(iter.keys)
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return iter
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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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delete(md, key)
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// slow path
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delete(md, textproto.CanonicalMIMEHeaderKey(key))
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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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// 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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// Merge merges metadata to existing metadata, overwriting if specified
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func Merge(omd Metadata, mmd Metadata, overwrite bool) Metadata {
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nmd := Copy(omd)
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for key, val := range mmd {
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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 nmd
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}
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// Pairs from which metadata created
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func Pairs(kv ...string) (Metadata, bool) {
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if len(kv)%2 == 1 {
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return nil, false
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}
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md := New(len(kv) / 2)
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var k string
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for i, v := range kv {
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if i%2 == 0 {
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k = v
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continue
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}
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md.Set(k, v)
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}
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return md, true
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}
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