Implement most of Regexp parser

This commit is contained in:
Brandon Dyck 2024-09-10 16:46:31 -06:00
parent a7495bde87
commit 96d178efef
3 changed files with 54 additions and 0 deletions

46
bytes/bytes.go Normal file
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@ -0,0 +1,46 @@
package bytes
import (
"fmt"
"regexp"
"strings"
"git.codemonkeysoftware.net/b/gigaparsec"
"git.codemonkeysoftware.net/b/gigaparsec/cursor"
)
func Regexp(str string) gigaparsec.Parser[byte, []byte] {
if !strings.HasPrefix(str, "^") {
str = "^" + str
}
re := regexp.MustCompile(str)
expected := fmt.Sprintf("match `%s`", str)
return func(input gigaparsec.State[byte]) (consumed bool, result gigaparsec.Result[byte, []byte], err error) {
r := cursor.NewRuneReader(input.Cursor())
idx := re.FindReaderIndex(r)
// TODO Check error from r; this requires an Error() method on cursor.RuneReader.
if idx == nil {
return false, gigaparsec.Result[byte, []byte]{}, gigaparsec.ParseError{
Pos: input.Pos(),
Expected: []string{expected},
// TODO Not having a Got is unsatisfactory, but how do I extract useful information?
// Maybe just read a fixed number of bytes or to the end, whichever comes first?
// I could add extra methods to cursor.RuneReader to figure out how much it had read.
}
}
// Alas, this is a little wasteful because a Regexp can only return indices
// when searching a RuneReader.
dst := make([]byte, idx[1]-idx[0])
n, _, err := input.Cursor().Read(dst)
if err != nil {
// If we can't access those same bytes again, something is wrong.
return false, gigaparsec.Result[byte, []byte]{}, fmt.Errorf("Regex: unexpected error: %w", err)
}
result = gigaparsec.Result[byte, []byte]{
State: input.At(input.Pos() + n),
Value: dst,
Message: gigaparsec.MessageOK(input.Pos()),
}
return true, result, nil
}
}

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@ -57,6 +57,10 @@ func (s State[In]) Pos() uint64 {
return s.cursor.Pos()
}
func (s State[In]) At(pos uint64) State[In] {
return State[In]{cursor: s.cursor.At(pos)}
}
type Parser[In, Out any] func(State[In]) (consumed bool, reply Result[In, Out], err error)
func Return[In, Out any](value Out) Parser[In, Out] {

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@ -62,3 +62,7 @@ func TestSlice(t *testing.T) {
test.EqOp(t, uint64(len(s)), result.State.Pos())
}))
}
func TestChoose(t *testing.T) {
Todo(t)
}