mirror of
https://github.com/autc04/Retro68.git
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697 lines
20 KiB
Go
697 lines
20 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:generate go run encgen.go -output enc_helpers.go
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package gob
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import (
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"encoding"
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"math"
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"reflect"
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)
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const uint64Size = 8
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type encHelper func(state *encoderState, v reflect.Value) bool
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// encoderState is the global execution state of an instance of the encoder.
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// Field numbers are delta encoded and always increase. The field
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// number is initialized to -1 so 0 comes out as delta(1). A delta of
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// 0 terminates the structure.
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type encoderState struct {
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enc *Encoder
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b *encBuffer
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sendZero bool // encoding an array element or map key/value pair; send zero values
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fieldnum int // the last field number written.
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buf [1 + uint64Size]byte // buffer used by the encoder; here to avoid allocation.
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next *encoderState // for free list
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}
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// encBuffer is an extremely simple, fast implementation of a write-only byte buffer.
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// It never returns a non-nil error, but Write returns an error value so it matches io.Writer.
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type encBuffer struct {
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data []byte
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scratch [64]byte
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}
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func (e *encBuffer) WriteByte(c byte) {
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e.data = append(e.data, c)
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}
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func (e *encBuffer) Write(p []byte) (int, error) {
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e.data = append(e.data, p...)
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return len(p), nil
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}
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func (e *encBuffer) WriteString(s string) {
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e.data = append(e.data, s...)
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}
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func (e *encBuffer) Len() int {
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return len(e.data)
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}
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func (e *encBuffer) Bytes() []byte {
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return e.data
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}
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func (e *encBuffer) Reset() {
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e.data = e.data[0:0]
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}
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func (enc *Encoder) newEncoderState(b *encBuffer) *encoderState {
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e := enc.freeList
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if e == nil {
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e = new(encoderState)
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e.enc = enc
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} else {
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enc.freeList = e.next
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}
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e.sendZero = false
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e.fieldnum = 0
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e.b = b
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if len(b.data) == 0 {
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b.data = b.scratch[0:0]
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}
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return e
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}
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func (enc *Encoder) freeEncoderState(e *encoderState) {
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e.next = enc.freeList
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enc.freeList = e
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}
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// Unsigned integers have a two-state encoding. If the number is less
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// than 128 (0 through 0x7F), its value is written directly.
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// Otherwise the value is written in big-endian byte order preceded
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// by the byte length, negated.
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// encodeUint writes an encoded unsigned integer to state.b.
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func (state *encoderState) encodeUint(x uint64) {
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if x <= 0x7F {
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state.b.WriteByte(uint8(x))
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return
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}
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i := uint64Size
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for x > 0 {
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state.buf[i] = uint8(x)
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x >>= 8
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i--
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}
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state.buf[i] = uint8(i - uint64Size) // = loop count, negated
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state.b.Write(state.buf[i : uint64Size+1])
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}
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// encodeInt writes an encoded signed integer to state.w.
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// The low bit of the encoding says whether to bit complement the (other bits of the)
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// uint to recover the int.
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func (state *encoderState) encodeInt(i int64) {
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var x uint64
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if i < 0 {
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x = uint64(^i<<1) | 1
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} else {
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x = uint64(i << 1)
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}
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state.encodeUint(uint64(x))
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}
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// encOp is the signature of an encoding operator for a given type.
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type encOp func(i *encInstr, state *encoderState, v reflect.Value)
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// The 'instructions' of the encoding machine
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type encInstr struct {
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op encOp
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field int // field number in input
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index []int // struct index
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indir int // how many pointer indirections to reach the value in the struct
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}
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// update emits a field number and updates the state to record its value for delta encoding.
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// If the instruction pointer is nil, it does nothing
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func (state *encoderState) update(instr *encInstr) {
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if instr != nil {
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state.encodeUint(uint64(instr.field - state.fieldnum))
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state.fieldnum = instr.field
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}
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}
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// Each encoder for a composite is responsible for handling any
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// indirections associated with the elements of the data structure.
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// If any pointer so reached is nil, no bytes are written. If the
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// data item is zero, no bytes are written. Single values - ints,
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// strings etc. - are indirected before calling their encoders.
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// Otherwise, the output (for a scalar) is the field number, as an
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// encoded integer, followed by the field data in its appropriate
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// format.
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// encIndirect dereferences pv indir times and returns the result.
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func encIndirect(pv reflect.Value, indir int) reflect.Value {
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for ; indir > 0; indir-- {
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if pv.IsNil() {
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break
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}
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pv = pv.Elem()
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}
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return pv
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}
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// encBool encodes the bool referenced by v as an unsigned 0 or 1.
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func encBool(i *encInstr, state *encoderState, v reflect.Value) {
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b := v.Bool()
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if b || state.sendZero {
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state.update(i)
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if b {
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state.encodeUint(1)
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} else {
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state.encodeUint(0)
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}
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}
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}
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// encInt encodes the signed integer (int int8 int16 int32 int64) referenced by v.
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func encInt(i *encInstr, state *encoderState, v reflect.Value) {
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value := v.Int()
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if value != 0 || state.sendZero {
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state.update(i)
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state.encodeInt(value)
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}
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}
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// encUint encodes the unsigned integer (uint uint8 uint16 uint32 uint64 uintptr) referenced by v.
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func encUint(i *encInstr, state *encoderState, v reflect.Value) {
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value := v.Uint()
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if value != 0 || state.sendZero {
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state.update(i)
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state.encodeUint(value)
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}
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}
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// floatBits returns a uint64 holding the bits of a floating-point number.
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// Floating-point numbers are transmitted as uint64s holding the bits
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// of the underlying representation. They are sent byte-reversed, with
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// the exponent end coming out first, so integer floating point numbers
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// (for example) transmit more compactly. This routine does the
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// swizzling.
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func floatBits(f float64) uint64 {
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u := math.Float64bits(f)
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var v uint64
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for i := 0; i < 8; i++ {
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v <<= 8
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v |= u & 0xFF
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u >>= 8
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}
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return v
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}
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// encFloat encodes the floating point value (float32 float64) referenced by v.
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func encFloat(i *encInstr, state *encoderState, v reflect.Value) {
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f := v.Float()
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if f != 0 || state.sendZero {
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bits := floatBits(f)
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state.update(i)
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state.encodeUint(bits)
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}
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}
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// encComplex encodes the complex value (complex64 complex128) referenced by v.
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// Complex numbers are just a pair of floating-point numbers, real part first.
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func encComplex(i *encInstr, state *encoderState, v reflect.Value) {
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c := v.Complex()
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if c != 0+0i || state.sendZero {
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rpart := floatBits(real(c))
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ipart := floatBits(imag(c))
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state.update(i)
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state.encodeUint(rpart)
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state.encodeUint(ipart)
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}
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}
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// encUint8Array encodes the byte array referenced by v.
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// Byte arrays are encoded as an unsigned count followed by the raw bytes.
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func encUint8Array(i *encInstr, state *encoderState, v reflect.Value) {
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b := v.Bytes()
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if len(b) > 0 || state.sendZero {
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state.update(i)
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state.encodeUint(uint64(len(b)))
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state.b.Write(b)
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}
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}
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// encString encodes the string referenced by v.
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// Strings are encoded as an unsigned count followed by the raw bytes.
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func encString(i *encInstr, state *encoderState, v reflect.Value) {
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s := v.String()
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if len(s) > 0 || state.sendZero {
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state.update(i)
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state.encodeUint(uint64(len(s)))
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state.b.WriteString(s)
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}
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}
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// encStructTerminator encodes the end of an encoded struct
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// as delta field number of 0.
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func encStructTerminator(i *encInstr, state *encoderState, v reflect.Value) {
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state.encodeUint(0)
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}
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// Execution engine
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// encEngine an array of instructions indexed by field number of the encoding
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// data, typically a struct. It is executed top to bottom, walking the struct.
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type encEngine struct {
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instr []encInstr
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}
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const singletonField = 0
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// valid reports whether the value is valid and a non-nil pointer.
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// (Slices, maps, and chans take care of themselves.)
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func valid(v reflect.Value) bool {
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switch v.Kind() {
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case reflect.Invalid:
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return false
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case reflect.Ptr:
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return !v.IsNil()
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}
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return true
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}
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// encodeSingle encodes a single top-level non-struct value.
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func (enc *Encoder) encodeSingle(b *encBuffer, engine *encEngine, value reflect.Value) {
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state := enc.newEncoderState(b)
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defer enc.freeEncoderState(state)
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state.fieldnum = singletonField
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// There is no surrounding struct to frame the transmission, so we must
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// generate data even if the item is zero. To do this, set sendZero.
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state.sendZero = true
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instr := &engine.instr[singletonField]
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if instr.indir > 0 {
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value = encIndirect(value, instr.indir)
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}
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if valid(value) {
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instr.op(instr, state, value)
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}
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}
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// encodeStruct encodes a single struct value.
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func (enc *Encoder) encodeStruct(b *encBuffer, engine *encEngine, value reflect.Value) {
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if !valid(value) {
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return
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}
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state := enc.newEncoderState(b)
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defer enc.freeEncoderState(state)
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state.fieldnum = -1
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for i := 0; i < len(engine.instr); i++ {
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instr := &engine.instr[i]
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if i >= value.NumField() {
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// encStructTerminator
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instr.op(instr, state, reflect.Value{})
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break
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}
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field := value.FieldByIndex(instr.index)
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if instr.indir > 0 {
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field = encIndirect(field, instr.indir)
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// TODO: Is field guaranteed valid? If so we could avoid this check.
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if !valid(field) {
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continue
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}
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}
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instr.op(instr, state, field)
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}
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}
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// encodeArray encodes an array.
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func (enc *Encoder) encodeArray(b *encBuffer, value reflect.Value, op encOp, elemIndir int, length int, helper encHelper) {
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state := enc.newEncoderState(b)
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defer enc.freeEncoderState(state)
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state.fieldnum = -1
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state.sendZero = true
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state.encodeUint(uint64(length))
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if helper != nil && helper(state, value) {
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return
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}
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for i := 0; i < length; i++ {
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elem := value.Index(i)
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if elemIndir > 0 {
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elem = encIndirect(elem, elemIndir)
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// TODO: Is elem guaranteed valid? If so we could avoid this check.
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if !valid(elem) {
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errorf("encodeArray: nil element")
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}
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}
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op(nil, state, elem)
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}
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}
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// encodeReflectValue is a helper for maps. It encodes the value v.
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func encodeReflectValue(state *encoderState, v reflect.Value, op encOp, indir int) {
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for i := 0; i < indir && v.IsValid(); i++ {
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v = reflect.Indirect(v)
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}
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if !v.IsValid() {
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errorf("encodeReflectValue: nil element")
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}
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op(nil, state, v)
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}
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// encodeMap encodes a map as unsigned count followed by key:value pairs.
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func (enc *Encoder) encodeMap(b *encBuffer, mv reflect.Value, keyOp, elemOp encOp, keyIndir, elemIndir int) {
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state := enc.newEncoderState(b)
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state.fieldnum = -1
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state.sendZero = true
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keys := mv.MapKeys()
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state.encodeUint(uint64(len(keys)))
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for _, key := range keys {
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encodeReflectValue(state, key, keyOp, keyIndir)
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encodeReflectValue(state, mv.MapIndex(key), elemOp, elemIndir)
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}
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enc.freeEncoderState(state)
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}
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// encodeInterface encodes the interface value iv.
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// To send an interface, we send a string identifying the concrete type, followed
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// by the type identifier (which might require defining that type right now), followed
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// by the concrete value. A nil value gets sent as the empty string for the name,
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// followed by no value.
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func (enc *Encoder) encodeInterface(b *encBuffer, iv reflect.Value) {
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// Gobs can encode nil interface values but not typed interface
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// values holding nil pointers, since nil pointers point to no value.
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elem := iv.Elem()
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if elem.Kind() == reflect.Ptr && elem.IsNil() {
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errorf("gob: cannot encode nil pointer of type %s inside interface", iv.Elem().Type())
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}
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state := enc.newEncoderState(b)
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state.fieldnum = -1
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state.sendZero = true
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if iv.IsNil() {
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state.encodeUint(0)
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return
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}
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ut := userType(iv.Elem().Type())
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registerLock.RLock()
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name, ok := concreteTypeToName[ut.base]
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registerLock.RUnlock()
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if !ok {
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errorf("type not registered for interface: %s", ut.base)
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}
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// Send the name.
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state.encodeUint(uint64(len(name)))
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state.b.WriteString(name)
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// Define the type id if necessary.
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enc.sendTypeDescriptor(enc.writer(), state, ut)
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// Send the type id.
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enc.sendTypeId(state, ut)
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// Encode the value into a new buffer. Any nested type definitions
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// should be written to b, before the encoded value.
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enc.pushWriter(b)
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data := new(encBuffer)
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data.Write(spaceForLength)
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enc.encode(data, elem, ut)
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if enc.err != nil {
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error_(enc.err)
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}
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enc.popWriter()
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enc.writeMessage(b, data)
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if enc.err != nil {
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error_(enc.err)
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}
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enc.freeEncoderState(state)
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}
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// isZero reports whether the value is the zero of its type.
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func isZero(val reflect.Value) bool {
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switch val.Kind() {
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case reflect.Array:
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for i := 0; i < val.Len(); i++ {
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if !isZero(val.Index(i)) {
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return false
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}
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}
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return true
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case reflect.Map, reflect.Slice, reflect.String:
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return val.Len() == 0
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case reflect.Bool:
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return !val.Bool()
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case reflect.Complex64, reflect.Complex128:
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return val.Complex() == 0
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case reflect.Chan, reflect.Func, reflect.Interface, reflect.Ptr:
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return val.IsNil()
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return val.Int() == 0
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case reflect.Float32, reflect.Float64:
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return val.Float() == 0
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return val.Uint() == 0
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case reflect.Struct:
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for i := 0; i < val.NumField(); i++ {
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if !isZero(val.Field(i)) {
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return false
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}
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}
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return true
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}
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panic("unknown type in isZero " + val.Type().String())
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}
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// encGobEncoder encodes a value that implements the GobEncoder interface.
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// The data is sent as a byte array.
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func (enc *Encoder) encodeGobEncoder(b *encBuffer, ut *userTypeInfo, v reflect.Value) {
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// TODO: should we catch panics from the called method?
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var data []byte
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var err error
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// We know it's one of these.
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switch ut.externalEnc {
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case xGob:
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data, err = v.Interface().(GobEncoder).GobEncode()
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case xBinary:
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data, err = v.Interface().(encoding.BinaryMarshaler).MarshalBinary()
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case xText:
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data, err = v.Interface().(encoding.TextMarshaler).MarshalText()
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}
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if err != nil {
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error_(err)
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}
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state := enc.newEncoderState(b)
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state.fieldnum = -1
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state.encodeUint(uint64(len(data)))
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state.b.Write(data)
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enc.freeEncoderState(state)
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}
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var encOpTable = [...]encOp{
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reflect.Bool: encBool,
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reflect.Int: encInt,
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reflect.Int8: encInt,
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reflect.Int16: encInt,
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reflect.Int32: encInt,
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reflect.Int64: encInt,
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reflect.Uint: encUint,
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reflect.Uint8: encUint,
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reflect.Uint16: encUint,
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reflect.Uint32: encUint,
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reflect.Uint64: encUint,
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reflect.Uintptr: encUint,
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reflect.Float32: encFloat,
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reflect.Float64: encFloat,
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reflect.Complex64: encComplex,
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reflect.Complex128: encComplex,
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reflect.String: encString,
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}
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// encOpFor returns (a pointer to) the encoding op for the base type under rt and
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// the indirection count to reach it.
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func encOpFor(rt reflect.Type, inProgress map[reflect.Type]*encOp, building map[*typeInfo]bool) (*encOp, int) {
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ut := userType(rt)
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// If the type implements GobEncoder, we handle it without further processing.
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if ut.externalEnc != 0 {
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return gobEncodeOpFor(ut)
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}
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// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
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// Return the pointer to the op we're already building.
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if opPtr := inProgress[rt]; opPtr != nil {
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return opPtr, ut.indir
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}
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typ := ut.base
|
|
indir := ut.indir
|
|
k := typ.Kind()
|
|
var op encOp
|
|
if int(k) < len(encOpTable) {
|
|
op = encOpTable[k]
|
|
}
|
|
if op == nil {
|
|
inProgress[rt] = &op
|
|
// Special cases
|
|
switch t := typ; t.Kind() {
|
|
case reflect.Slice:
|
|
if t.Elem().Kind() == reflect.Uint8 {
|
|
op = encUint8Array
|
|
break
|
|
}
|
|
// Slices have a header; we decode it to find the underlying array.
|
|
elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
|
|
helper := encSliceHelper[t.Elem().Kind()]
|
|
op = func(i *encInstr, state *encoderState, slice reflect.Value) {
|
|
if !state.sendZero && slice.Len() == 0 {
|
|
return
|
|
}
|
|
state.update(i)
|
|
state.enc.encodeArray(state.b, slice, *elemOp, elemIndir, slice.Len(), helper)
|
|
}
|
|
case reflect.Array:
|
|
// True arrays have size in the type.
|
|
elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
|
|
helper := encArrayHelper[t.Elem().Kind()]
|
|
op = func(i *encInstr, state *encoderState, array reflect.Value) {
|
|
state.update(i)
|
|
state.enc.encodeArray(state.b, array, *elemOp, elemIndir, array.Len(), helper)
|
|
}
|
|
case reflect.Map:
|
|
keyOp, keyIndir := encOpFor(t.Key(), inProgress, building)
|
|
elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
|
|
op = func(i *encInstr, state *encoderState, mv reflect.Value) {
|
|
// We send zero-length (but non-nil) maps because the
|
|
// receiver might want to use the map. (Maps don't use append.)
|
|
if !state.sendZero && mv.IsNil() {
|
|
return
|
|
}
|
|
state.update(i)
|
|
state.enc.encodeMap(state.b, mv, *keyOp, *elemOp, keyIndir, elemIndir)
|
|
}
|
|
case reflect.Struct:
|
|
// Generate a closure that calls out to the engine for the nested type.
|
|
getEncEngine(userType(typ), building)
|
|
info := mustGetTypeInfo(typ)
|
|
op = func(i *encInstr, state *encoderState, sv reflect.Value) {
|
|
state.update(i)
|
|
// indirect through info to delay evaluation for recursive structs
|
|
enc := info.encoder.Load().(*encEngine)
|
|
state.enc.encodeStruct(state.b, enc, sv)
|
|
}
|
|
case reflect.Interface:
|
|
op = func(i *encInstr, state *encoderState, iv reflect.Value) {
|
|
if !state.sendZero && (!iv.IsValid() || iv.IsNil()) {
|
|
return
|
|
}
|
|
state.update(i)
|
|
state.enc.encodeInterface(state.b, iv)
|
|
}
|
|
}
|
|
}
|
|
if op == nil {
|
|
errorf("can't happen: encode type %s", rt)
|
|
}
|
|
return &op, indir
|
|
}
|
|
|
|
// gobEncodeOpFor returns the op for a type that is known to implement GobEncoder.
|
|
func gobEncodeOpFor(ut *userTypeInfo) (*encOp, int) {
|
|
rt := ut.user
|
|
if ut.encIndir == -1 {
|
|
rt = reflect.PtrTo(rt)
|
|
} else if ut.encIndir > 0 {
|
|
for i := int8(0); i < ut.encIndir; i++ {
|
|
rt = rt.Elem()
|
|
}
|
|
}
|
|
var op encOp
|
|
op = func(i *encInstr, state *encoderState, v reflect.Value) {
|
|
if ut.encIndir == -1 {
|
|
// Need to climb up one level to turn value into pointer.
|
|
if !v.CanAddr() {
|
|
errorf("unaddressable value of type %s", rt)
|
|
}
|
|
v = v.Addr()
|
|
}
|
|
if !state.sendZero && isZero(v) {
|
|
return
|
|
}
|
|
state.update(i)
|
|
state.enc.encodeGobEncoder(state.b, ut, v)
|
|
}
|
|
return &op, int(ut.encIndir) // encIndir: op will get called with p == address of receiver.
|
|
}
|
|
|
|
// compileEnc returns the engine to compile the type.
|
|
func compileEnc(ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
|
|
srt := ut.base
|
|
engine := new(encEngine)
|
|
seen := make(map[reflect.Type]*encOp)
|
|
rt := ut.base
|
|
if ut.externalEnc != 0 {
|
|
rt = ut.user
|
|
}
|
|
if ut.externalEnc == 0 && srt.Kind() == reflect.Struct {
|
|
for fieldNum, wireFieldNum := 0, 0; fieldNum < srt.NumField(); fieldNum++ {
|
|
f := srt.Field(fieldNum)
|
|
if !isSent(&f) {
|
|
continue
|
|
}
|
|
op, indir := encOpFor(f.Type, seen, building)
|
|
engine.instr = append(engine.instr, encInstr{*op, wireFieldNum, f.Index, indir})
|
|
wireFieldNum++
|
|
}
|
|
if srt.NumField() > 0 && len(engine.instr) == 0 {
|
|
errorf("type %s has no exported fields", rt)
|
|
}
|
|
engine.instr = append(engine.instr, encInstr{encStructTerminator, 0, nil, 0})
|
|
} else {
|
|
engine.instr = make([]encInstr, 1)
|
|
op, indir := encOpFor(rt, seen, building)
|
|
engine.instr[0] = encInstr{*op, singletonField, nil, indir}
|
|
}
|
|
return engine
|
|
}
|
|
|
|
// getEncEngine returns the engine to compile the type.
|
|
func getEncEngine(ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
|
|
info, err := getTypeInfo(ut)
|
|
if err != nil {
|
|
error_(err)
|
|
}
|
|
enc, ok := info.encoder.Load().(*encEngine)
|
|
if !ok {
|
|
enc = buildEncEngine(info, ut, building)
|
|
}
|
|
return enc
|
|
}
|
|
|
|
func buildEncEngine(info *typeInfo, ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
|
|
// Check for recursive types.
|
|
if building != nil && building[info] {
|
|
return nil
|
|
}
|
|
info.encInit.Lock()
|
|
defer info.encInit.Unlock()
|
|
enc, ok := info.encoder.Load().(*encEngine)
|
|
if !ok {
|
|
if building == nil {
|
|
building = make(map[*typeInfo]bool)
|
|
}
|
|
building[info] = true
|
|
enc = compileEnc(ut, building)
|
|
info.encoder.Store(enc)
|
|
}
|
|
return enc
|
|
}
|
|
|
|
func (enc *Encoder) encode(b *encBuffer, value reflect.Value, ut *userTypeInfo) {
|
|
defer catchError(&enc.err)
|
|
engine := getEncEngine(ut, nil)
|
|
indir := ut.indir
|
|
if ut.externalEnc != 0 {
|
|
indir = int(ut.encIndir)
|
|
}
|
|
for i := 0; i < indir; i++ {
|
|
value = reflect.Indirect(value)
|
|
}
|
|
if ut.externalEnc == 0 && value.Type().Kind() == reflect.Struct {
|
|
enc.encodeStruct(b, engine, value)
|
|
} else {
|
|
enc.encodeSingle(b, engine, value)
|
|
}
|
|
}
|