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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package fmtutil
import (
"fmt"
"strings"
)
// FmtStateString returns the fmt.Printf string that produced a given
// fmt.State and verb.
func FmtStateString(st fmt.State, verb rune) string {
var ret strings.Builder
ret.WriteByte('%')
for _, flag := range []int{'-', '+', '#', ' ', '0'} {
if st.Flag(flag) {
ret.WriteByte(byte(flag))
}
}
if width, ok := st.Width(); ok {
fmt.Fprintf(&ret, "%v", width)
}
if prec, ok := st.Precision(); ok {
if prec == 0 {
ret.WriteByte('.')
} else {
fmt.Fprintf(&ret, ".%v", prec)
}
}
ret.WriteRune(verb)
return ret.String()
}
// FormatByteArrayStringer is function for helping to implement
// fmt.Formatter for []byte or [n]byte types that have a custom string
// representation. Use it like:
//
// type MyType [16]byte
//
// func (val MyType) String() string {
// …
// }
//
// func (val MyType) Format(f fmt.State, verb rune) {
// util.FormatByteArrayStringer(val, val[:], f, verb)
// }
func FormatByteArrayStringer(
obj interface {
fmt.Stringer
fmt.Formatter
},
objBytes []byte,
f fmt.State, verb rune,
) {
switch verb {
case 'v':
if !f.Flag('#') {
FormatByteArrayStringer(obj, objBytes, f, 's') // as a string
} else {
byteStr := fmt.Sprintf("%#v", objBytes)
objType := fmt.Sprintf("%T", obj)
objStr := objType + strings.TrimPrefix(byteStr, "[]byte")
fmt.Fprintf(f, FmtStateString(f, 's'), objStr)
}
case 's', 'q': // string
fmt.Fprintf(f, FmtStateString(f, verb), obj.String())
default:
fmt.Fprintf(f, FmtStateString(f, verb), objBytes)
}
}
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