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Combine Cursor with State

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This commit is contained in:
Brandon Dyck
2024-09-27 09:29:27 -06:00
parent 5c779c4a33
commit 82ade62274
8 changed files with 68 additions and 187 deletions
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34
gigaparsec.go
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@ -9,8 +9,6 @@ import (
"io"
"slices"
"strings"
"git.codemonkeysoftware.net/b/gigaparsec/cursor"
)
type Result[In, Out any] struct {
@ -114,29 +112,33 @@ func MessageEnd(pos uint64, expected ...string) Message {
return Message{pos: pos, got: "end of input", expected: expected}
}
func MakeState[In any](c cursor.Cursor[In]) State[In] {
return State[In]{cursor: c}
type ReaderAt[T any] interface {
ReadAt(p []T, off int64) (n int, err error)
}
func MakeState[In any](r ReaderAt[In]) State[In] {
return State[In]{r: r}
}
type State[In any] struct {
cursor cursor.Cursor[In]
}
func (s State[In]) Cursor() cursor.Cursor[In] {
return s.cursor
r ReaderAt[In]
pos uint64
}
func (s State[In]) Read(dst []In) (n uint64, next State[In], err error) {
n, c, err := s.cursor.Read(dst)
return n, State[In]{cursor: c}, err
nread, err := s.r.ReadAt(dst, int64(s.pos))
if n > 0 {
s.pos += uint64(n)
}
return uint64(nread), s, err
}
func (s State[In]) Pos() uint64 {
return s.cursor.Pos()
return s.pos
}
func (s State[In]) At(pos uint64) State[In] {
return State[In]{cursor: s.cursor.At(pos)}
return State[In]{r: s.r, pos: pos}
}
type Parser[In, Out any] func(State[In]) (Result[In, Out], error)
@ -163,8 +165,8 @@ func (pe ParseError) Error() string {
return Message(pe).String()
}
func Run[In, Out any](p Parser[In, Out], c cursor.Cursor[In]) (out Out, err error) {
start := MakeState(c)
func Run[In, Out any](p Parser[In, Out], r ReaderAt[In]) (out Out, err error) {
start := MakeState(r)
result, err := p(start)
if err != nil {
err = fmt.Errorf("Run: %w", err)
@ -315,7 +317,7 @@ func Map[In, Out1, Out2 any](p Parser[In, Out1], f func(Out1) Out2) Parser[In, O
}
func end[In any](s State[In]) (Result[In, struct{}], error) {
_, _, err := s.cursor.Read([]In{})
_, _, err := s.Read([]In{})
if errors.Is(err, io.EOF) {
return Succeed(true, struct{}{}, s, MessageOK(s.Pos())), nil
}