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-rw-r--r--modules/git/foreachref/parser.go128
1 files changed, 128 insertions, 0 deletions
diff --git a/modules/git/foreachref/parser.go b/modules/git/foreachref/parser.go
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+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package foreachref
+
+import (
+ "bufio"
+ "bytes"
+ "fmt"
+ "io"
+ "strings"
+)
+
+// Parser parses 'git for-each-ref' output according to a given output Format.
+type Parser struct {
+ // tokenizes 'git for-each-ref' output into "reference paragraphs".
+ scanner *bufio.Scanner
+
+ // format represents the '--format' string that describes the expected
+ // 'git for-each-ref' output structure.
+ format Format
+
+ // err holds the last encountered error during parsing.
+ err error
+}
+
+// NewParser creates a 'git for-each-ref' output parser that will parse all
+// references in the provided Reader. The references in the output are assumed
+// to follow the specified Format.
+func NewParser(r io.Reader, format Format) *Parser {
+ scanner := bufio.NewScanner(r)
+
+ // in addition to the reference delimiter we specified in the --format,
+ // `git for-each-ref` will always add a newline after every reference.
+ refDelim := make([]byte, 0, len(format.refDelim)+1)
+ refDelim = append(refDelim, format.refDelim...)
+ refDelim = append(refDelim, '\n')
+
+ // Split input into delimiter-separated "reference blocks".
+ scanner.Split(
+ func(data []byte, atEOF bool) (advance int, token []byte, err error) {
+ // Scan until delimiter, marking end of reference.
+ delimIdx := bytes.Index(data, refDelim)
+ if delimIdx >= 0 {
+ token := data[:delimIdx]
+ advance := delimIdx + len(refDelim)
+ return advance, token, nil
+ }
+ // If we're at EOF, we have a final, non-terminated reference. Return it.
+ if atEOF {
+ return len(data), data, nil
+ }
+ // Not yet a full field. Request more data.
+ return 0, nil, nil
+ })
+
+ return &Parser{
+ scanner: scanner,
+ format: format,
+ err: nil,
+ }
+}
+
+// Next returns the next reference as a collection of key-value pairs. nil
+// denotes EOF but is also returned on errors. The Err method should always be
+// consulted after Next returning nil.
+//
+// It could, for example return something like:
+//
+// { "objecttype": "tag", "refname:short": "v1.16.4", "object": "f460b7543ed500e49c133c2cd85c8c55ee9dbe27" }
+func (p *Parser) Next() map[string]string {
+ if !p.scanner.Scan() {
+ return nil
+ }
+ fields, err := p.parseRef(p.scanner.Text())
+ if err != nil {
+ p.err = err
+ return nil
+ }
+ return fields
+}
+
+// Err returns the latest encountered parsing error.
+func (p *Parser) Err() error {
+ return p.err
+}
+
+// parseRef parses out all key-value pairs from a single reference block, such as
+//
+// "objecttype tag\0refname:short v1.16.4\0object f460b7543ed500e49c133c2cd85c8c55ee9dbe27"
+func (p *Parser) parseRef(refBlock string) (map[string]string, error) {
+ if refBlock == "" {
+ // must be at EOF
+ return nil, nil
+ }
+
+ fieldValues := make(map[string]string)
+
+ fields := strings.Split(refBlock, p.format.fieldDelimStr)
+ if len(fields) != len(p.format.fieldNames) {
+ return nil, fmt.Errorf("unexpected number of reference fields: wanted %d, was %d",
+ len(fields), len(p.format.fieldNames))
+ }
+ for i, field := range fields {
+ field = strings.TrimSpace(field)
+
+ var fieldKey string
+ var fieldVal string
+ firstSpace := strings.Index(field, " ")
+ if firstSpace > 0 {
+ fieldKey = field[:firstSpace]
+ fieldVal = field[firstSpace+1:]
+ } else {
+ // could be the case if the requested field had no value
+ fieldKey = field
+ }
+
+ // enforce the format order of fields
+ if p.format.fieldNames[i] != fieldKey {
+ return nil, fmt.Errorf("unexpected field name at position %d: wanted: '%s', was: '%s'",
+ i, p.format.fieldNames[i], fieldKey)
+ }
+
+ fieldValues[fieldKey] = fieldVal
+ }
+
+ return fieldValues, nil
+}