Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

gob: keep free lists of encoder and decoder states.

Browse source 
Avoids 3 mallocs in a round trip encoding/decoding a struct.

R=rsc, rsc1
CC=golang-dev
https://golang.org/cl/4278052
This commit is contained in:
Rob Pike 2011-03-15 21:30:07 -07:00
parent bcd747204d
commit eb864e92db
5 changed files with 86 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files

29
src/pkg/gob/decode.go
View file

@ -31,18 +31,29 @@ type decoderState struct {
b *bytes.Buffer
fieldnum int // the last field number read.
buf []byte
next *decoderState // for free list
}
// We pass the bytes.Buffer separately for easier testing of the infrastructure
// without requiring a full Decoder.
func newDecodeState(dec *Decoder, buf *bytes.Buffer) *decoderState {
d := new(decoderState)
d.dec = dec
func (dec *Decoder) newDecoderState(buf *bytes.Buffer) *decoderState {
d := dec.freeList
if d == nil {
d = new(decoderState)
d.dec = dec
} else {
dec.freeList = d.next
}
d.b = buf
d.buf = make([]byte, uint64Size)
return d
}
func (dec *Decoder) freeDecoderState(d *decoderState) {
d.next = dec.freeList
dec.freeList = d
}
func overflow(name string) os.ErrorString {
return os.ErrorString(`value for "` + name + `" out of range`)
}
@ -445,7 +456,7 @@ func (dec *Decoder) decodeSingle(engine *decEngine, ut *userTypeInfo, p uintptr)
indir = int(ut.decIndir)
}
p = allocate(ut.base, p, indir)
state := newDecodeState(dec, &dec.buf)
state := dec.newDecoderState(&dec.buf)
state.fieldnum = singletonField
basep := p
delta := int(state.decodeUint())
@ -458,6 +469,7 @@ func (dec *Decoder) decodeSingle(engine *decEngine, ut *userTypeInfo, p uintptr)
ptr = decIndirect(ptr, instr.indir)
}
instr.op(instr, state, ptr)
dec.freeDecoderState(state)
return nil
}
@ -468,7 +480,7 @@ func (dec *Decoder) decodeSingle(engine *decEngine, ut *userTypeInfo, p uintptr)
// from the user's value, not from the innards of an engine.
func (dec *Decoder) decodeStruct(engine *decEngine, ut *userTypeInfo, p uintptr, indir int) (err os.Error) {
p = allocate(ut.base.(*reflect.StructType), p, indir)
state := newDecodeState(dec, &dec.buf)
state := dec.newDecoderState(&dec.buf)
state.fieldnum = -1
basep := p
for state.b.Len() > 0 {
@ -492,12 +504,13 @@ func (dec *Decoder) decodeStruct(engine *decEngine, ut *userTypeInfo, p uintptr,
instr.op(instr, state, p)
state.fieldnum = fieldnum
}
dec.freeDecoderState(state)
return nil
}
// ignoreStruct discards the data for a struct with no destination.
func (dec *Decoder) ignoreStruct(engine *decEngine) (err os.Error) {
state := newDecodeState(dec, &dec.buf)
state := dec.newDecoderState(&dec.buf)
state.fieldnum = -1
for state.b.Len() > 0 {
delta := int(state.decodeUint())
@ -515,13 +528,14 @@ func (dec *Decoder) ignoreStruct(engine *decEngine) (err os.Error) {
instr.op(instr, state, unsafe.Pointer(nil))
state.fieldnum = fieldnum
}
dec.freeDecoderState(state)
return nil
}
// ignoreSingle discards the data for a top-level non-struct value with no
// destination. It's used when calling Decode with a nil value.
func (dec *Decoder) ignoreSingle(engine *decEngine) (err os.Error) {
state := newDecodeState(dec, &dec.buf)
state := dec.newDecoderState(&dec.buf)
state.fieldnum = singletonField
delta := int(state.decodeUint())
if delta != 0 {
@ -529,6 +543,7 @@ func (dec *Decoder) ignoreSingle(engine *decEngine) (err os.Error) {
}
instr := &engine.instr[singletonField]
instr.op(instr, state, unsafe.Pointer(nil))
dec.freeDecoderState(state)
return nil
}