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// Copyright 2022 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package foreachref
import (
"encoding/hex"
"fmt"
"io"
"strings"
)
var (
nullChar = []byte("\x00")
dualNullChar = []byte("\x00\x00")
)
// Format supports specifying and parsing an output format for 'git
// for-each-ref'. See See git-for-each-ref(1) for available fields.
type Format struct {
// fieldNames hold %(fieldname)s to be passed to the '--format' flag of
// for-each-ref. See git-for-each-ref(1) for available fields.
fieldNames []string
// fieldDelim is the character sequence that is used to separate fields
// for each reference. fieldDelim and refDelim should be selected to not
// interfere with each other and to not be present in field values.
fieldDelim []byte
// fieldDelimStr is a string representation of fieldDelim. Used to save
// us from repetitive reallocation whenever we need the delimiter as a
// string.
fieldDelimStr string
// refDelim is the character sequence used to separate reference from
// each other in the output. fieldDelim and refDelim should be selected
// to not interfere with each other and to not be present in field
// values.
refDelim []byte
}
// NewFormat creates a forEachRefFormat using the specified fieldNames. See
// git-for-each-ref(1) for available fields.
func NewFormat(fieldNames ...string) Format {
return Format{
fieldNames: fieldNames,
fieldDelim: nullChar,
fieldDelimStr: string(nullChar),
refDelim: dualNullChar,
}
}
// Flag returns a for-each-ref --format flag value that captures the fieldNames.
func (f Format) Flag() string {
var formatFlag strings.Builder
for i, field := range f.fieldNames {
// field key and field value
formatFlag.WriteString(fmt.Sprintf("%s %%(%s)", field, field))
if i < len(f.fieldNames)-1 {
// note: escape delimiters to allow control characters as
// delimiters. For example, '%00' for null character or '%0a'
// for newline.
formatFlag.WriteString(f.hexEscaped(f.fieldDelim))
}
}
formatFlag.WriteString(f.hexEscaped(f.refDelim))
return formatFlag.String()
}
// Parser returns a Parser capable of parsing 'git for-each-ref' output produced
// with this Format.
func (f Format) Parser(r io.Reader) *Parser {
return NewParser(r, f)
}
// hexEscaped produces hex-escpaed characters from a string. For example, "\n\0"
// would turn into "%0a%00".
func (f Format) hexEscaped(delim []byte) string {
escaped := ""
for i := 0; i < len(delim); i++ {
escaped += "%" + hex.EncodeToString([]byte{delim[i]})
}
return escaped
}
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