build-sys: import build system from darvaza.org/core

Signed-off-by: Alejandro Mery <amery@jpi.io>

lexer/lexer.go

@@ -1,2 +1,17 @@
 // Package lexer provides basic helpers to implement parsers
 package lexer
+
+// StateFn is a State Function of the parser
+type StateFn func() (StateFn, error)
+
+// Run runs a state machine until the state function either
+// returns nil or an error
+func Run(fn StateFn) error {
+	var err error
+
+	for fn != nil && err == nil {
+		fn, err = fn()
+	}
+
+	return err
+}

lexer/position.go

@@ -1,66 +0,0 @@
-package lexer
-
-import "fmt"
-
-// Position indicates a line and column pair on a file.
-// Counting starts at 1.
-type Position struct {
-	Line   int
-	Column int
-}
-
-// String generates a pretty "(Line, Column)"" representation of the Position
-func (p Position) String() string {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	return fmt.Sprintf("(%v, %v)", p.Line, p.Column)
-}
-
-// GoString generates a string representation of the Position for %#v usage
-func (p Position) GoString() string {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	return fmt.Sprintf("lexer.Position{%v, %v}", p.Line, p.Column)
-}
-
-// Reset places a position at (1,1)
-func (p *Position) Reset() {
-	p.Line, p.Column = 1, 1
-}
-
-// Step moves the column one place
-func (p *Position) Step() {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	p.Column++
-}
-
-// StepN moves the column N places forward
-func (p *Position) StepN(n int) {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	switch {
-	case n > 0:
-		p.Column += n
-	default:
-		panic(fmt.Errorf("invalid %v increment", n))
-	}
-}
-
-// StepLine moves position to the start of the next line
-func (p *Position) StepLine() {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	p.Line++
-	p.Column = 1
-}

lexer/reader.go

@@ -198,6 +198,41 @@ func (b *Reader) PeekRune() (rune, int, error) {
 	return r, l, err
 }
 
+// Accept consumes a rune from the source if it meets the condition.
+// it returns true if the condition was met and false if it wasn't.
+func (b *Reader) Accept(cond func(r rune) bool) bool {
+	r, _, err := b.ReadRune()
+	switch {
+	case err != nil:
+		return false
+	case cond(r):
+		return true
+	default:
+		_ = b.UnreadRune()
+		return false
+	}
+}
+
+// AcceptAll consumes runes from the source as long as they meet the
+// condition. it returns true if the condition was met for at least one rune,
+// and false if it wasn't.
+func (b *Reader) AcceptAll(cond func(r rune) bool) bool {
+	var accepted bool
+
+	for {
+		r, _, err := b.ReadRune()
+		switch {
+		case err != nil:
+			return accepted
+		case cond(r):
+			accepted = true
+		default:
+			_ = b.UnreadRune()
+			return accepted
+		}
+	}
+}
+
 // NewReader creates a new runes [Reader] using the given [io.Reader]
 func NewReader(r io.Reader) *Reader {
 	if r == nil {