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54 lines
1.5 KiB
Go
54 lines
1.5 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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//go:build go1.19 && !go1.20
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package slog
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import (
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"reflect"
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"unsafe"
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)
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type (
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stringptr unsafe.Pointer // used in Value.any when the Value is a string
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groupptr unsafe.Pointer // used in Value.any when the Value is a []Attr
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)
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// StringValue returns a new Value for a string.
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func StringValue(value string) Value {
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hdr := (*reflect.StringHeader)(unsafe.Pointer(&value))
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return Value{num: uint64(hdr.Len), any: stringptr(hdr.Data)}
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}
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func (v Value) str() string {
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var s string
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hdr := (*reflect.StringHeader)(unsafe.Pointer(&s))
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hdr.Data = uintptr(v.any.(stringptr))
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hdr.Len = int(v.num)
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return s
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}
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// String returns Value's value as a string, formatted like fmt.Sprint. Unlike
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// the methods Int64, Float64, and so on, which panic if v is of the
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// wrong kind, String never panics.
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func (v Value) String() string {
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if sp, ok := v.any.(stringptr); ok {
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// Inlining this code makes a huge difference.
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var s string
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hdr := (*reflect.StringHeader)(unsafe.Pointer(&s))
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hdr.Data = uintptr(sp)
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hdr.Len = int(v.num)
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return s
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}
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return string(v.append(nil))
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}
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// GroupValue returns a new Value for a list of Attrs.
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// The caller must not subsequently mutate the argument slice.
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func GroupValue(as ...Attr) Value {
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hdr := (*reflect.SliceHeader)(unsafe.Pointer(&as))
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return Value{num: uint64(hdr.Len), any: groupptr(hdr.Data)}
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}
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