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-rw-r--r--src/log/slog/json_handler.go336
1 files changed, 336 insertions, 0 deletions
diff --git a/src/log/slog/json_handler.go b/src/log/slog/json_handler.go
new file mode 100644
index 0000000..1c51ab0
--- /dev/null
+++ b/src/log/slog/json_handler.go
@@ -0,0 +1,336 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package slog
+
+import (
+ "bytes"
+ "context"
+ "encoding/json"
+ "errors"
+ "fmt"
+ "io"
+ "log/slog/internal/buffer"
+ "strconv"
+ "sync"
+ "time"
+ "unicode/utf8"
+)
+
+// JSONHandler is a Handler that writes Records to an io.Writer as
+// line-delimited JSON objects.
+type JSONHandler struct {
+ *commonHandler
+}
+
+// NewJSONHandler creates a JSONHandler that writes to w,
+// using the given options.
+// If opts is nil, the default options are used.
+func NewJSONHandler(w io.Writer, opts *HandlerOptions) *JSONHandler {
+ if opts == nil {
+ opts = &HandlerOptions{}
+ }
+ return &JSONHandler{
+ &commonHandler{
+ json: true,
+ w: w,
+ opts: *opts,
+ mu: &sync.Mutex{},
+ },
+ }
+}
+
+// Enabled reports whether the handler handles records at the given level.
+// The handler ignores records whose level is lower.
+func (h *JSONHandler) Enabled(_ context.Context, level Level) bool {
+ return h.commonHandler.enabled(level)
+}
+
+// WithAttrs returns a new JSONHandler whose attributes consists
+// of h's attributes followed by attrs.
+func (h *JSONHandler) WithAttrs(attrs []Attr) Handler {
+ return &JSONHandler{commonHandler: h.commonHandler.withAttrs(attrs)}
+}
+
+func (h *JSONHandler) WithGroup(name string) Handler {
+ return &JSONHandler{commonHandler: h.commonHandler.withGroup(name)}
+}
+
+// Handle formats its argument Record as a JSON object on a single line.
+//
+// If the Record's time is zero, the time is omitted.
+// Otherwise, the key is "time"
+// and the value is output as with json.Marshal.
+//
+// If the Record's level is zero, the level is omitted.
+// Otherwise, the key is "level"
+// and the value of [Level.String] is output.
+//
+// If the AddSource option is set and source information is available,
+// the key is "source", and the value is a record of type [Source].
+//
+// The message's key is "msg".
+//
+// To modify these or other attributes, or remove them from the output, use
+// [HandlerOptions.ReplaceAttr].
+//
+// Values are formatted as with an [encoding/json.Encoder] with SetEscapeHTML(false),
+// with two exceptions.
+//
+// First, an Attr whose Value is of type error is formatted as a string, by
+// calling its Error method. Only errors in Attrs receive this special treatment,
+// not errors embedded in structs, slices, maps or other data structures that
+// are processed by the encoding/json package.
+//
+// Second, an encoding failure does not cause Handle to return an error.
+// Instead, the error message is formatted as a string.
+//
+// Each call to Handle results in a single serialized call to io.Writer.Write.
+func (h *JSONHandler) Handle(_ context.Context, r Record) error {
+ return h.commonHandler.handle(r)
+}
+
+// Adapted from time.Time.MarshalJSON to avoid allocation.
+func appendJSONTime(s *handleState, t time.Time) {
+ if y := t.Year(); y < 0 || y >= 10000 {
+ // RFC 3339 is clear that years are 4 digits exactly.
+ // See golang.org/issue/4556#c15 for more discussion.
+ s.appendError(errors.New("time.Time year outside of range [0,9999]"))
+ }
+ s.buf.WriteByte('"')
+ *s.buf = t.AppendFormat(*s.buf, time.RFC3339Nano)
+ s.buf.WriteByte('"')
+}
+
+func appendJSONValue(s *handleState, v Value) error {
+ switch v.Kind() {
+ case KindString:
+ s.appendString(v.str())
+ case KindInt64:
+ *s.buf = strconv.AppendInt(*s.buf, v.Int64(), 10)
+ case KindUint64:
+ *s.buf = strconv.AppendUint(*s.buf, v.Uint64(), 10)
+ case KindFloat64:
+ // json.Marshal is funny about floats; it doesn't
+ // always match strconv.AppendFloat. So just call it.
+ // That's expensive, but floats are rare.
+ if err := appendJSONMarshal(s.buf, v.Float64()); err != nil {
+ return err
+ }
+ case KindBool:
+ *s.buf = strconv.AppendBool(*s.buf, v.Bool())
+ case KindDuration:
+ // Do what json.Marshal does.
+ *s.buf = strconv.AppendInt(*s.buf, int64(v.Duration()), 10)
+ case KindTime:
+ s.appendTime(v.Time())
+ case KindAny:
+ a := v.Any()
+ _, jm := a.(json.Marshaler)
+ if err, ok := a.(error); ok && !jm {
+ s.appendString(err.Error())
+ } else {
+ return appendJSONMarshal(s.buf, a)
+ }
+ default:
+ panic(fmt.Sprintf("bad kind: %s", v.Kind()))
+ }
+ return nil
+}
+
+func appendJSONMarshal(buf *buffer.Buffer, v any) error {
+ // Use a json.Encoder to avoid escaping HTML.
+ var bb bytes.Buffer
+ enc := json.NewEncoder(&bb)
+ enc.SetEscapeHTML(false)
+ if err := enc.Encode(v); err != nil {
+ return err
+ }
+ bs := bb.Bytes()
+ buf.Write(bs[:len(bs)-1]) // remove final newline
+ return nil
+}
+
+// appendEscapedJSONString escapes s for JSON and appends it to buf.
+// It does not surround the string in quotation marks.
+//
+// Modified from encoding/json/encode.go:encodeState.string,
+// with escapeHTML set to false.
+func appendEscapedJSONString(buf []byte, s string) []byte {
+ char := func(b byte) { buf = append(buf, b) }
+ str := func(s string) { buf = append(buf, s...) }
+
+ start := 0
+ for i := 0; i < len(s); {
+ if b := s[i]; b < utf8.RuneSelf {
+ if safeSet[b] {
+ i++
+ continue
+ }
+ if start < i {
+ str(s[start:i])
+ }
+ char('\\')
+ switch b {
+ case '\\', '"':
+ char(b)
+ case '\n':
+ char('n')
+ case '\r':
+ char('r')
+ case '\t':
+ char('t')
+ default:
+ // This encodes bytes < 0x20 except for \t, \n and \r.
+ str(`u00`)
+ char(hex[b>>4])
+ char(hex[b&0xF])
+ }
+ i++
+ start = i
+ continue
+ }
+ c, size := utf8.DecodeRuneInString(s[i:])
+ if c == utf8.RuneError && size == 1 {
+ if start < i {
+ str(s[start:i])
+ }
+ str(`\ufffd`)
+ i += size
+ start = i
+ continue
+ }
+ // U+2028 is LINE SEPARATOR.
+ // U+2029 is PARAGRAPH SEPARATOR.
+ // They are both technically valid characters in JSON strings,
+ // but don't work in JSONP, which has to be evaluated as JavaScript,
+ // and can lead to security holes there. It is valid JSON to
+ // escape them, so we do so unconditionally.
+ // See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+ if c == '\u2028' || c == '\u2029' {
+ if start < i {
+ str(s[start:i])
+ }
+ str(`\u202`)
+ char(hex[c&0xF])
+ i += size
+ start = i
+ continue
+ }
+ i += size
+ }
+ if start < len(s) {
+ str(s[start:])
+ }
+ return buf
+}
+
+var hex = "0123456789abcdef"
+
+// Copied from encoding/json/tables.go.
+//
+// safeSet holds the value true if the ASCII character with the given array
+// position can be represented inside a JSON string without any further
+// escaping.
+//
+// All values are true except for the ASCII control characters (0-31), the
+// double quote ("), and the backslash character ("\").
+var safeSet = [utf8.RuneSelf]bool{
+ ' ': true,
+ '!': true,
+ '"': false,
+ '#': true,
+ '$': true,
+ '%': true,
+ '&': true,
+ '\'': true,
+ '(': true,
+ ')': true,
+ '*': true,
+ '+': true,
+ ',': true,
+ '-': true,
+ '.': true,
+ '/': true,
+ '0': true,
+ '1': true,
+ '2': true,
+ '3': true,
+ '4': true,
+ '5': true,
+ '6': true,
+ '7': true,
+ '8': true,
+ '9': true,
+ ':': true,
+ ';': true,
+ '<': true,
+ '=': true,
+ '>': true,
+ '?': true,
+ '@': true,
+ 'A': true,
+ 'B': true,
+ 'C': true,
+ 'D': true,
+ 'E': true,
+ 'F': true,
+ 'G': true,
+ 'H': true,
+ 'I': true,
+ 'J': true,
+ 'K': true,
+ 'L': true,
+ 'M': true,
+ 'N': true,
+ 'O': true,
+ 'P': true,
+ 'Q': true,
+ 'R': true,
+ 'S': true,
+ 'T': true,
+ 'U': true,
+ 'V': true,
+ 'W': true,
+ 'X': true,
+ 'Y': true,
+ 'Z': true,
+ '[': true,
+ '\\': false,
+ ']': true,
+ '^': true,
+ '_': true,
+ '`': true,
+ 'a': true,
+ 'b': true,
+ 'c': true,
+ 'd': true,
+ 'e': true,
+ 'f': true,
+ 'g': true,
+ 'h': true,
+ 'i': true,
+ 'j': true,
+ 'k': true,
+ 'l': true,
+ 'm': true,
+ 'n': true,
+ 'o': true,
+ 'p': true,
+ 'q': true,
+ 'r': true,
+ 's': true,
+ 't': true,
+ 'u': true,
+ 'v': true,
+ 'w': true,
+ 'x': true,
+ 'y': true,
+ 'z': true,
+ '{': true,
+ '|': true,
+ '}': true,
+ '~': true,
+ '\u007f': true,
+}
generated by cgit v1.2.3 (git 2.39.1) at 2025-02-19 09:45:05 +0000