268 lines
6.9 KiB
Go
268 lines
6.9 KiB
Go
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// Copyright 2018 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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package text
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import (
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"math"
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"math/bits"
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"strconv"
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"strings"
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"unicode/utf8"
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"google.golang.org/protobuf/internal/detrand"
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"google.golang.org/protobuf/internal/errors"
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)
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// encType represents an encoding type.
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type encType uint8
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const (
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_ encType = (1 << iota) / 2
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name
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scalar
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messageOpen
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messageClose
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)
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// Encoder provides methods to write out textproto constructs and values. The user is
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// responsible for producing valid sequences of constructs and values.
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type Encoder struct {
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encoderState
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indent string
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newline string // set to "\n" if len(indent) > 0
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delims [2]byte
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outputASCII bool
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}
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type encoderState struct {
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lastType encType
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indents []byte
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out []byte
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}
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// NewEncoder returns an Encoder.
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//
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// If indent is a non-empty string, it causes every entry in a List or Message
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// to be preceded by the indent and trailed by a newline.
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//
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// If delims is not the zero value, it controls the delimiter characters used
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// for messages (e.g., "{}" vs "<>").
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//
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// If outputASCII is true, strings will be serialized in such a way that
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// multi-byte UTF-8 sequences are escaped. This property ensures that the
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// overall output is ASCII (as opposed to UTF-8).
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func NewEncoder(indent string, delims [2]byte, outputASCII bool) (*Encoder, error) {
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e := &Encoder{}
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if len(indent) > 0 {
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if strings.Trim(indent, " \t") != "" {
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return nil, errors.New("indent may only be composed of space and tab characters")
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}
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e.indent = indent
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e.newline = "\n"
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}
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switch delims {
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case [2]byte{0, 0}:
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e.delims = [2]byte{'{', '}'}
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case [2]byte{'{', '}'}, [2]byte{'<', '>'}:
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e.delims = delims
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default:
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return nil, errors.New("delimiters may only be \"{}\" or \"<>\"")
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}
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e.outputASCII = outputASCII
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return e, nil
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}
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// Bytes returns the content of the written bytes.
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func (e *Encoder) Bytes() []byte {
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return e.out
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}
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// StartMessage writes out the '{' or '<' symbol.
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func (e *Encoder) StartMessage() {
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e.prepareNext(messageOpen)
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e.out = append(e.out, e.delims[0])
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}
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// EndMessage writes out the '}' or '>' symbol.
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func (e *Encoder) EndMessage() {
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e.prepareNext(messageClose)
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e.out = append(e.out, e.delims[1])
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}
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// WriteName writes out the field name and the separator ':'.
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func (e *Encoder) WriteName(s string) {
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e.prepareNext(name)
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e.out = append(e.out, s...)
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e.out = append(e.out, ':')
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}
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// WriteBool writes out the given boolean value.
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func (e *Encoder) WriteBool(b bool) {
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if b {
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e.WriteLiteral("true")
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} else {
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e.WriteLiteral("false")
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}
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}
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// WriteString writes out the given string value.
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func (e *Encoder) WriteString(s string) {
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e.prepareNext(scalar)
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e.out = appendString(e.out, s, e.outputASCII)
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}
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func appendString(out []byte, in string, outputASCII bool) []byte {
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out = append(out, '"')
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i := indexNeedEscapeInString(in)
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in, out = in[i:], append(out, in[:i]...)
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for len(in) > 0 {
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switch r, n := utf8.DecodeRuneInString(in); {
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case r == utf8.RuneError && n == 1:
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// We do not report invalid UTF-8 because strings in the text format
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// are used to represent both the proto string and bytes type.
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r = rune(in[0])
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fallthrough
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case r < ' ' || r == '"' || r == '\\':
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out = append(out, '\\')
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switch r {
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case '"', '\\':
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out = append(out, byte(r))
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case '\n':
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out = append(out, 'n')
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case '\r':
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out = append(out, 'r')
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case '\t':
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out = append(out, 't')
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default:
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out = append(out, 'x')
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out = append(out, "00"[1+(bits.Len32(uint32(r))-1)/4:]...)
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out = strconv.AppendUint(out, uint64(r), 16)
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}
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in = in[n:]
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case outputASCII && r >= utf8.RuneSelf:
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out = append(out, '\\')
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if r <= math.MaxUint16 {
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out = append(out, 'u')
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out = append(out, "0000"[1+(bits.Len32(uint32(r))-1)/4:]...)
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out = strconv.AppendUint(out, uint64(r), 16)
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} else {
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out = append(out, 'U')
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out = append(out, "00000000"[1+(bits.Len32(uint32(r))-1)/4:]...)
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out = strconv.AppendUint(out, uint64(r), 16)
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}
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in = in[n:]
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default:
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i := indexNeedEscapeInString(in[n:])
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in, out = in[n+i:], append(out, in[:n+i]...)
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}
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}
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out = append(out, '"')
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return out
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}
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// indexNeedEscapeInString returns the index of the character that needs
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// escaping. If no characters need escaping, this returns the input length.
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func indexNeedEscapeInString(s string) int {
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for i := 0; i < len(s); i++ {
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if c := s[i]; c < ' ' || c == '"' || c == '\'' || c == '\\' || c >= utf8.RuneSelf {
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return i
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}
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}
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return len(s)
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}
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// WriteFloat writes out the given float value for given bitSize.
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func (e *Encoder) WriteFloat(n float64, bitSize int) {
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e.prepareNext(scalar)
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e.out = appendFloat(e.out, n, bitSize)
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}
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func appendFloat(out []byte, n float64, bitSize int) []byte {
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switch {
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case math.IsNaN(n):
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return append(out, "nan"...)
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case math.IsInf(n, +1):
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return append(out, "inf"...)
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case math.IsInf(n, -1):
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return append(out, "-inf"...)
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default:
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return strconv.AppendFloat(out, n, 'g', -1, bitSize)
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}
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}
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// WriteInt writes out the given signed integer value.
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func (e *Encoder) WriteInt(n int64) {
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e.prepareNext(scalar)
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e.out = append(e.out, strconv.FormatInt(n, 10)...)
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}
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// WriteUint writes out the given unsigned integer value.
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func (e *Encoder) WriteUint(n uint64) {
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e.prepareNext(scalar)
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e.out = append(e.out, strconv.FormatUint(n, 10)...)
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}
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// WriteLiteral writes out the given string as a literal value without quotes.
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// This is used for writing enum literal strings.
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func (e *Encoder) WriteLiteral(s string) {
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e.prepareNext(scalar)
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e.out = append(e.out, s...)
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}
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// prepareNext adds possible space and indentation for the next value based
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// on last encType and indent option. It also updates e.lastType to next.
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func (e *Encoder) prepareNext(next encType) {
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defer func() {
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e.lastType = next
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}()
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// Single line.
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if len(e.indent) == 0 {
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// Add space after each field before the next one.
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if e.lastType&(scalar|messageClose) != 0 && next == name {
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e.out = append(e.out, ' ')
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// Add a random extra space to make output unstable.
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if detrand.Bool() {
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e.out = append(e.out, ' ')
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}
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}
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return
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}
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// Multi-line.
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switch {
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case e.lastType == name:
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e.out = append(e.out, ' ')
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// Add a random extra space after name: to make output unstable.
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if detrand.Bool() {
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e.out = append(e.out, ' ')
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}
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case e.lastType == messageOpen && next != messageClose:
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e.indents = append(e.indents, e.indent...)
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e.out = append(e.out, '\n')
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e.out = append(e.out, e.indents...)
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case e.lastType&(scalar|messageClose) != 0:
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if next == messageClose {
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e.indents = e.indents[:len(e.indents)-len(e.indent)]
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}
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e.out = append(e.out, '\n')
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e.out = append(e.out, e.indents...)
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}
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}
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// Snapshot returns the current snapshot for use in Reset.
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func (e *Encoder) Snapshot() encoderState {
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return e.encoderState
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}
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// Reset resets the Encoder to the given encoderState from a Snapshot.
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func (e *Encoder) Reset(es encoderState) {
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e.encoderState = es
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}
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