85 lines
2.4 KiB
Go
85 lines
2.4 KiB
Go
package bytes
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import (
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"errors"
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"fmt"
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"io"
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"regexp"
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"strings"
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"unicode/utf8"
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"git.codemonkeysoftware.net/b/gigaparsec"
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"git.codemonkeysoftware.net/b/gigaparsec/cursor"
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)
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// RuneReader is an io.RuneReader backed by a Cursor, for compatibility
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// with the regexp package.
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type RuneReader struct {
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cursor cursor.Cursor[byte]
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err error
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}
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func NewRuneReader(c cursor.Cursor[byte]) *RuneReader {
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return &RuneReader{cursor: c}
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}
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func (rr *RuneReader) ReadRune() (r rune, size int, err error) {
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defer func() {
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rr.err = err
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}()
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var b [4]byte
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s := b[:]
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n, next, err := rr.cursor.Read(s)
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if err != nil && !errors.Is(err, io.EOF) {
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rr.cursor = next
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return 0, 0, fmt.Errorf("ReadRune: %w", err)
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}
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s = s[:n]
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r, size = utf8.DecodeRune(s)
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rr.cursor = rr.cursor.At(rr.cursor.Pos() + uint64(size))
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return r, size, err
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}
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func (rr *RuneReader) Cursor() cursor.Cursor[byte] {
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return rr.cursor
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}
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func (rr *RuneReader) Error() error {
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return rr.err
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}
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func Regexp(str string) gigaparsec.Parser[byte, string] {
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if !strings.HasPrefix(str, "^") && !strings.HasPrefix(str, `\A`) {
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str = "^" + str
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}
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re := regexp.MustCompile(str)
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expected := fmt.Sprintf("match `%s`", str)
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return func(input gigaparsec.State[byte]) (gigaparsec.Result[byte, string], error) {
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r := NewRuneReader(input.Cursor())
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idx := re.FindReaderIndex(r)
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err := r.Error()
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if err != nil && !errors.Is(err, io.EOF) {
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return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: reader error: %w", err)
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}
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if idx == nil {
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return gigaparsec.Fail[byte, string](false, gigaparsec.Message{
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Pos: input.Pos(),
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Expected: []string{expected},
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// TODO Not having a Got is unsatisfactory, but how do I extract useful information?
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// Maybe just read a fixed number of bytes or to the end, whichever comes first?
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// I could add extra methods to cursor.RuneReader to figure out how much it had read.
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}), nil
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}
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// Alas, this is a little wasteful because a Regexp can only return indices
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// when searching a RuneReader.
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dst := make([]byte, idx[1]-idx[0])
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n, _, err := input.Cursor().Read(dst)
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if err != nil {
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// If we can't access those same bytes again, something is wrong.
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return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: unexpected error: %w", err)
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}
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next := input.At(input.Pos() + n)
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return gigaparsec.Succeed(true, string(dst), next, gigaparsec.MessageOK(input.Pos())), nil
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}
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}
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