forked from toolshed/abra
337 lines
8.0 KiB
Go
337 lines
8.0 KiB
Go
// Copyright 2022 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 slog
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import (
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"bytes"
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"strconv"
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"time"
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"unicode/utf8"
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"golang.org/x/exp/slog/internal/buffer"
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)
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// JSONHandler is a Handler that writes Records to an io.Writer as
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// line-delimited JSON objects.
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type JSONHandler struct {
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*commonHandler
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}
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// NewJSONHandler creates a JSONHandler that writes to w,
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// using the given options.
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// If opts is nil, the default options are used.
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func NewJSONHandler(w io.Writer, opts *HandlerOptions) *JSONHandler {
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if opts == nil {
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opts = &HandlerOptions{}
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}
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return &JSONHandler{
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&commonHandler{
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json: true,
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w: w,
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opts: *opts,
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},
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}
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}
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// Enabled reports whether the handler handles records at the given level.
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// The handler ignores records whose level is lower.
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func (h *JSONHandler) Enabled(_ context.Context, level Level) bool {
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return h.commonHandler.enabled(level)
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}
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// WithAttrs returns a new JSONHandler whose attributes consists
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// of h's attributes followed by attrs.
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func (h *JSONHandler) WithAttrs(attrs []Attr) Handler {
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return &JSONHandler{commonHandler: h.commonHandler.withAttrs(attrs)}
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}
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func (h *JSONHandler) WithGroup(name string) Handler {
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return &JSONHandler{commonHandler: h.commonHandler.withGroup(name)}
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}
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// Handle formats its argument Record as a JSON object on a single line.
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//
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// If the Record's time is zero, the time is omitted.
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// Otherwise, the key is "time"
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// and the value is output as with json.Marshal.
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//
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// If the Record's level is zero, the level is omitted.
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// Otherwise, the key is "level"
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// and the value of [Level.String] is output.
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//
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// If the AddSource option is set and source information is available,
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// the key is "source"
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// and the value is output as "FILE:LINE".
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//
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// The message's key is "msg".
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//
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// To modify these or other attributes, or remove them from the output, use
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// [HandlerOptions.ReplaceAttr].
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//
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// Values are formatted as with an [encoding/json.Encoder] with SetEscapeHTML(false),
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// with two exceptions.
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//
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// First, an Attr whose Value is of type error is formatted as a string, by
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// calling its Error method. Only errors in Attrs receive this special treatment,
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// not errors embedded in structs, slices, maps or other data structures that
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// are processed by the encoding/json package.
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//
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// Second, an encoding failure does not cause Handle to return an error.
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// Instead, the error message is formatted as a string.
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//
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// Each call to Handle results in a single serialized call to io.Writer.Write.
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func (h *JSONHandler) Handle(_ context.Context, r Record) error {
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return h.commonHandler.handle(r)
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}
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// Adapted from time.Time.MarshalJSON to avoid allocation.
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func appendJSONTime(s *handleState, t time.Time) {
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if y := t.Year(); y < 0 || y >= 10000 {
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// RFC 3339 is clear that years are 4 digits exactly.
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// See golang.org/issue/4556#c15 for more discussion.
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s.appendError(errors.New("time.Time year outside of range [0,9999]"))
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}
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s.buf.WriteByte('"')
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*s.buf = t.AppendFormat(*s.buf, time.RFC3339Nano)
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s.buf.WriteByte('"')
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}
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func appendJSONValue(s *handleState, v Value) error {
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switch v.Kind() {
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case KindString:
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s.appendString(v.str())
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case KindInt64:
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*s.buf = strconv.AppendInt(*s.buf, v.Int64(), 10)
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case KindUint64:
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*s.buf = strconv.AppendUint(*s.buf, v.Uint64(), 10)
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case KindFloat64:
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// json.Marshal is funny about floats; it doesn't
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// always match strconv.AppendFloat. So just call it.
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// That's expensive, but floats are rare.
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if err := appendJSONMarshal(s.buf, v.Float64()); err != nil {
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return err
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}
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case KindBool:
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*s.buf = strconv.AppendBool(*s.buf, v.Bool())
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case KindDuration:
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// Do what json.Marshal does.
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*s.buf = strconv.AppendInt(*s.buf, int64(v.Duration()), 10)
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case KindTime:
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s.appendTime(v.Time())
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case KindAny:
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a := v.Any()
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_, jm := a.(json.Marshaler)
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if err, ok := a.(error); ok && !jm {
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s.appendString(err.Error())
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} else {
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return appendJSONMarshal(s.buf, a)
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}
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default:
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panic(fmt.Sprintf("bad kind: %s", v.Kind()))
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}
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return nil
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}
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func appendJSONMarshal(buf *buffer.Buffer, v any) error {
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// Use a json.Encoder to avoid escaping HTML.
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var bb bytes.Buffer
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enc := json.NewEncoder(&bb)
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enc.SetEscapeHTML(false)
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if err := enc.Encode(v); err != nil {
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return err
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}
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bs := bb.Bytes()
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buf.Write(bs[:len(bs)-1]) // remove final newline
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return nil
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}
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// appendEscapedJSONString escapes s for JSON and appends it to buf.
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// It does not surround the string in quotation marks.
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//
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// Modified from encoding/json/encode.go:encodeState.string,
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// with escapeHTML set to false.
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func appendEscapedJSONString(buf []byte, s string) []byte {
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char := func(b byte) { buf = append(buf, b) }
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str := func(s string) { buf = append(buf, s...) }
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start := 0
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for i := 0; i < len(s); {
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if b := s[i]; b < utf8.RuneSelf {
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if safeSet[b] {
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i++
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continue
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}
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if start < i {
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str(s[start:i])
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}
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char('\\')
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switch b {
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case '\\', '"':
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char(b)
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case '\n':
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char('n')
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case '\r':
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char('r')
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case '\t':
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char('t')
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default:
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// This encodes bytes < 0x20 except for \t, \n and \r.
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str(`u00`)
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char(hex[b>>4])
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char(hex[b&0xF])
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}
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i++
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start = i
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continue
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}
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c, size := utf8.DecodeRuneInString(s[i:])
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if c == utf8.RuneError && size == 1 {
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if start < i {
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str(s[start:i])
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}
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str(`\ufffd`)
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i += size
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start = i
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continue
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}
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// U+2028 is LINE SEPARATOR.
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// U+2029 is PARAGRAPH SEPARATOR.
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// They are both technically valid characters in JSON strings,
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// but don't work in JSONP, which has to be evaluated as JavaScript,
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// and can lead to security holes there. It is valid JSON to
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// escape them, so we do so unconditionally.
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// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
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if c == '\u2028' || c == '\u2029' {
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if start < i {
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str(s[start:i])
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}
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str(`\u202`)
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char(hex[c&0xF])
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i += size
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start = i
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continue
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}
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i += size
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}
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if start < len(s) {
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str(s[start:])
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}
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return buf
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}
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var hex = "0123456789abcdef"
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// Copied from encoding/json/tables.go.
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//
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// safeSet holds the value true if the ASCII character with the given array
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// position can be represented inside a JSON string without any further
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// escaping.
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//
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// All values are true except for the ASCII control characters (0-31), the
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// double quote ("), and the backslash character ("\").
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var safeSet = [utf8.RuneSelf]bool{
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' ': true,
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'!': true,
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'"': false,
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'#': true,
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'$': true,
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'%': true,
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'&': true,
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'\'': true,
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'(': true,
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')': true,
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'*': true,
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'+': true,
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',': true,
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'-': true,
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'.': true,
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'/': true,
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'0': true,
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'1': true,
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'2': true,
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'3': true,
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'4': true,
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'5': true,
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'6': true,
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'7': true,
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'8': true,
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'9': true,
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':': true,
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';': true,
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'<': true,
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'=': true,
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'>': true,
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'?': true,
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'@': true,
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'A': true,
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'B': true,
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'C': true,
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'D': true,
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'E': true,
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'F': true,
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'G': true,
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'H': true,
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'I': true,
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'J': true,
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'K': true,
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'L': true,
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'M': true,
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'N': true,
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'O': true,
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'P': true,
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'Q': true,
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'R': true,
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'S': true,
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'T': true,
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'U': true,
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'V': true,
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'W': true,
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'X': true,
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'Y': true,
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'Z': true,
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'[': true,
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'\\': false,
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']': true,
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'^': true,
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'_': true,
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'`': true,
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'a': true,
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'b': true,
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'c': true,
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'd': true,
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'e': true,
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'f': true,
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'g': true,
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'h': true,
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'i': true,
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'j': true,
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'k': true,
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'l': true,
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'm': true,
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'n': true,
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'o': true,
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'p': true,
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'q': true,
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'r': true,
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's': true,
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't': true,
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'u': true,
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'v': true,
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'w': true,
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'x': true,
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'y': true,
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'z': true,
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'{': true,
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'|': true,
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'}': true,
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'~': true,
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'\u007f': true,
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}
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