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stream/mts/meta: using order slice so that encoded order reamins consistent with order that we added metadata. And also now using binary.BigEndian.PutUint16() to encode len into metdata rather than doing ugly byte manipulation

This commit is contained in:
saxon 2019-02-05 12:55:32 +10:30
parent ad25785b77
commit 834625a9f7
1 changed files with 16 additions and 12 deletions
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28
stream/mts/meta/meta.go
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@ -45,8 +45,7 @@ const (
// Indices of bytes for uint16 metadata length. // Indices of bytes for uint16 metadata length.
const ( const (
dataLenIdx1 = 2 dataLenIdx = 2
dataLenIdx2 = 3
) )
var ( var (
@ -58,9 +57,10 @@ var (
// Metadata provides functionality for the storage and encoding of metadata // Metadata provides functionality for the storage and encoding of metadata
// using a map. // using a map.
type Metadata struct { type Metadata struct {
mu sync.RWMutex mu sync.RWMutex
data map[string]string data map[string]string
enc []byte order []string
enc []byte
} }
// New returns a pointer to a new Metadata. // New returns a pointer to a new Metadata.
@ -80,6 +80,7 @@ func New() *Metadata {
func (m *Metadata) Add(key, val string) { func (m *Metadata) Add(key, val string) {
m.mu.Lock() m.mu.Lock()
m.data[key] = val m.data[key] = val
m.order = append(m.order, key)
m.mu.Unlock() m.mu.Unlock()
} }
@ -111,6 +112,12 @@ func (m *Metadata) Delete(key string) error {
defer m.mu.Unlock() defer m.mu.Unlock()
if _, ok := m.data[key]; ok { if _, ok := m.data[key]; ok {
delete(m.data, key) delete(m.data, key)
for i, k := range m.order {
if k == key {
m.order = append(m.order[:i], m.order[i+1:]...)
break
}
}
return nil return nil
} }
return errKeyAbsent return errKeyAbsent
@ -123,12 +130,11 @@ func (m *Metadata) Encode() []byte {
// Iterate over map and append entries, only adding tab if we're not on the // Iterate over map and append entries, only adding tab if we're not on the
// last entry. // last entry.
var i int
var entry string var entry string
for k, v := range m.data { for i, k := range m.order {
i++ v := m.data[k]
entry += k + "=" + v entry += k + "=" + v
if i < len(m.data) { if i+1 < len(m.data) {
entry += "\t" entry += "\t"
} }
} }
@ -136,9 +142,7 @@ func (m *Metadata) Encode() []byte {
// Calculate and set data length in encoded meta header. // Calculate and set data length in encoded meta header.
dataLen := len(m.enc[headSize:]) dataLen := len(m.enc[headSize:])
m.enc[dataLenIdx1] = byte(dataLen >> 8) binary.BigEndian.PutUint16(m.enc[dataLenIdx:dataLenIdx+2], uint16(dataLen))
m.enc[dataLenIdx2] = byte(dataLen)
return m.enc return m.enc
} }