diff --git a/src/scanner/scanFile.go b/src/scanner/scanFile.go
index 04bf2b5..faed4d6 100644
--- a/src/scanner/scanFile.go
+++ b/src/scanner/scanFile.go
@@ -1,8 +1,6 @@
 package scanner
 
 import (
-	"os"
-
 	"git.urbach.dev/cli/q/src/errors"
 	"git.urbach.dev/cli/q/src/fs"
 	"git.urbach.dev/cli/q/src/token"
@@ -10,17 +8,19 @@ import (
 
 // scanFile scans a single file.
 func (s *Scanner) scanFile(path string, pkg string) error {
-	contents, err := os.ReadFile(path)
+	reader := token.Reader{}
+	err := reader.Open(path)
 
 	if err != nil {
 		return err
 	}
 
-	tokens := token.Tokenize(contents)
+	defer reader.File.Close()
+	tokens := token.Tokenize(&reader)
 
 	file := &fs.File{
 		Path:    path,
-		Bytes:   contents,
+		Bytes:   reader.Buffer,
 		Tokens:  tokens,
 		Package: pkg,
 	}
diff --git a/src/token/Reader.go b/src/token/Reader.go
new file mode 100644
index 0000000..401107b
--- /dev/null
+++ b/src/token/Reader.go
@@ -0,0 +1,71 @@
+package token
+
+import (
+	"io"
+	"os"
+)
+
+type Reader struct {
+	File     *os.File
+	Buffer   []byte
+	Size     Position
+	Position Position
+}
+
+func (t *Reader) Advance() {
+	t.Position++
+
+	if t.Position >= Position(len(t.Buffer)) {
+		t.read()
+	}
+}
+
+func (t *Reader) Current() byte {
+	return t.Buffer[t.Position]
+}
+
+func (t *Reader) Next() byte {
+	if t.Position+1 >= Position(len(t.Buffer)) {
+		t.read()
+	}
+
+	return t.Buffer[t.Position+1]
+}
+
+func (t *Reader) read() error {
+	n, err := t.File.Read(t.Buffer[len(t.Buffer):cap(t.Buffer)])
+	t.Buffer = t.Buffer[:len(t.Buffer)+n]
+
+	if err != nil {
+		if err == io.EOF {
+			return nil
+		}
+
+		return err
+	}
+
+	if len(t.Buffer) >= cap(t.Buffer) {
+		d := append(t.Buffer[:cap(t.Buffer)], 0)
+		t.Buffer = d[:len(t.Buffer)]
+	}
+
+	return nil
+}
+
+func (t *Reader) Open(path string) (err error) {
+	t.File, err = os.Open(path)
+
+	if err != nil {
+		return err
+	}
+
+	info, err := t.File.Stat()
+
+	if err != nil {
+		return err
+	}
+
+	t.Size = Position(info.Size())
+	t.Buffer = make([]byte, 0, t.Size+1)
+	return nil
+}
diff --git a/src/token/Tokenize.go b/src/token/Tokenize.go
index 9178314..ee536ec 100644
--- a/src/token/Tokenize.go
+++ b/src/token/Tokenize.go
@@ -1,64 +1,65 @@
 package token
 
 // Tokenize turns the file contents into a list of tokens.
-func Tokenize(buffer []byte) List {
+func Tokenize(reader *Reader) List {
 	var (
-		i      Position
-		tokens = make(List, 0, 8+len(buffer)/2)
+		tokens = make(List, 0, 8+reader.Size/2)
 	)
 
-	for i < Position(len(buffer)) {
-		switch buffer[i] {
+	reader.read()
+
+	for reader.Position < reader.Size {
+		switch reader.Current() {
 		case ' ', '\t':
 		case ',':
-			tokens = append(tokens, Token{Kind: Separator, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: Separator, Position: reader.Position, Length: 1})
 		case '(':
-			tokens = append(tokens, Token{Kind: GroupStart, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: GroupStart, Position: reader.Position, Length: 1})
 		case ')':
-			tokens = append(tokens, Token{Kind: GroupEnd, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: GroupEnd, Position: reader.Position, Length: 1})
 		case '{':
-			tokens = append(tokens, Token{Kind: BlockStart, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: BlockStart, Position: reader.Position, Length: 1})
 		case '}':
-			tokens = append(tokens, Token{Kind: BlockEnd, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: BlockEnd, Position: reader.Position, Length: 1})
 		case '[':
-			tokens = append(tokens, Token{Kind: ArrayStart, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: ArrayStart, Position: reader.Position, Length: 1})
 		case ']':
-			tokens = append(tokens, Token{Kind: ArrayEnd, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: ArrayEnd, Position: reader.Position, Length: 1})
 		case '\n':
-			tokens = append(tokens, Token{Kind: NewLine, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: NewLine, Position: reader.Position, Length: 1})
 		case '-':
-			tokens, i = dash(tokens, buffer, i)
+			tokens = dash(tokens, reader)
 		case '/':
-			tokens, i = slash(tokens, buffer, i)
+			tokens = slash(tokens, reader)
 			continue
 		case '"', '\'':
-			tokens, i = quote(tokens, buffer, i)
+			tokens = quote(tokens, reader)
 			continue
 		case '0':
-			tokens, i = zero(tokens, buffer, i)
+			tokens = zero(tokens, reader)
 			continue
 		default:
-			if isIdentifierStart(buffer[i]) {
-				tokens, i = identifier(tokens, buffer, i)
+			if isIdentifierStart(reader.Current()) {
+				tokens = identifier(tokens, reader)
 				continue
 			}
 
-			if isDigit(buffer[i]) {
-				tokens, i = digit(tokens, buffer, i)
+			if isDigit(reader.Current()) {
+				tokens = digit(tokens, reader)
 				continue
 			}
 
-			if isOperator(buffer[i]) {
-				tokens, i = operator(tokens, buffer, i)
+			if isOperator(reader.Current()) {
+				tokens = operator(tokens, reader)
 				continue
 			}
 
-			tokens = append(tokens, Token{Kind: Invalid, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: Invalid, Position: reader.Position, Length: 1})
 		}
 
-		i++
+		reader.Advance()
 	}
 
-	tokens = append(tokens, Token{Kind: EOF, Position: i, Length: 0})
+	tokens = append(tokens, Token{Kind: EOF, Position: reader.Position, Length: 0})
 	return tokens
 }
diff --git a/src/token/dash.go b/src/token/dash.go
index 63b5453..3671c7b 100644
--- a/src/token/dash.go
+++ b/src/token/dash.go
@@ -1,25 +1,25 @@
 package token
 
 // dash handles all tokens starting with '-'.
-func dash(tokens List, buffer []byte, i Position) (List, Position) {
+func dash(tokens List, reader *Reader) List {
 	if len(tokens) == 0 || tokens[len(tokens)-1].IsOperator() || tokens[len(tokens)-1].IsExpressionStart() || tokens[len(tokens)-1].IsKeyword() {
-		tokens = append(tokens, Token{Kind: Negate, Position: i, Length: 1})
+		tokens = append(tokens, Token{Kind: Negate, Position: reader.Position, Length: 1})
 	} else {
-		if i+1 < Position(len(buffer)) {
-			switch buffer[i+1] {
+		if reader.Position+1 < reader.Size {
+			switch reader.Next() {
 			case '=':
-				tokens = append(tokens, Token{Kind: SubAssign, Position: i, Length: 2})
-				i++
+				tokens = append(tokens, Token{Kind: SubAssign, Position: reader.Position, Length: 2})
+				reader.Advance()
 			case '>':
-				tokens = append(tokens, Token{Kind: ReturnType, Position: i, Length: 2})
-				i++
+				tokens = append(tokens, Token{Kind: ReturnType, Position: reader.Position, Length: 2})
+				reader.Advance()
 			default:
-				tokens = append(tokens, Token{Kind: Sub, Position: i, Length: 1})
+				tokens = append(tokens, Token{Kind: Sub, Position: reader.Position, Length: 1})
 			}
 		} else {
-			tokens = append(tokens, Token{Kind: Sub, Position: i, Length: 1})
+			tokens = append(tokens, Token{Kind: Sub, Position: reader.Position, Length: 1})
 		}
 	}
 
-	return tokens, i
+	return tokens
 }
diff --git a/src/token/digit.go b/src/token/digit.go
index ffdb192..cc2d046 100644
--- a/src/token/digit.go
+++ b/src/token/digit.go
@@ -1,24 +1,24 @@
 package token
 
 // digit handles all tokens that qualify as a digit.
-func digit(tokens List, buffer []byte, i Position) (List, Position) {
-	position := i
-	i++
+func digit(tokens List, reader *Reader) List {
+	position := reader.Position
+	reader.Advance()
 
-	for i < Position(len(buffer)) && isDigit(buffer[i]) {
-		i++
+	for reader.Position < reader.Size && isDigit(reader.Current()) {
+		reader.Advance()
 	}
 
 	last := len(tokens) - 1
 
 	if len(tokens) > 0 && tokens[last].Kind == Negate {
 		tokens[last].Kind = Number
-		tokens[last].Length = Length(i-position) + 1
+		tokens[last].Length = Length(reader.Position-position) + 1
 	} else {
-		tokens = append(tokens, Token{Kind: Number, Position: position, Length: Length(i - position)})
+		tokens = append(tokens, Token{Kind: Number, Position: position, Length: Length(reader.Position - position)})
 	}
 
-	return tokens, i
+	return tokens
 }
 
 func isDigit(c byte) bool {
diff --git a/src/token/identifier.go b/src/token/identifier.go
index 27849ed..65b9c1c 100644
--- a/src/token/identifier.go
+++ b/src/token/identifier.go
@@ -1,15 +1,15 @@
 package token
 
 // identifier handles all tokens that qualify as an identifier.
-func identifier(tokens List, buffer []byte, i Position) (List, Position) {
-	position := i
-	i++
+func identifier(tokens List, reader *Reader) List {
+	position := reader.Position
+	reader.Advance()
 
-	for i < Position(len(buffer)) && isIdentifier(buffer[i]) {
-		i++
+	for reader.Position < reader.Size && isIdentifier(reader.Current()) {
+		reader.Advance()
 	}
 
-	identifier := buffer[position:i]
+	identifier := reader.Buffer[position:reader.Position]
 	kind := Identifier
 
 	switch string(identifier) {
@@ -37,8 +37,7 @@ func identifier(tokens List, buffer []byte, i Position) (List, Position) {
 		kind = Switch
 	}
 
-	tokens = append(tokens, Token{Kind: kind, Position: position, Length: Length(len(identifier))})
-	return tokens, i
+	return append(tokens, Token{Kind: kind, Position: position, Length: Length(len(identifier))})
 }
 
 func isIdentifier(c byte) bool {
diff --git a/src/token/operator.go b/src/token/operator.go
index 3352f9e..18f51ed 100644
--- a/src/token/operator.go
+++ b/src/token/operator.go
@@ -1,17 +1,17 @@
 package token
 
 // operator handles all tokens that qualify as an operator.
-func operator(tokens List, buffer []byte, i Position) (List, Position) {
-	position := i
-	i++
+func operator(tokens List, reader *Reader) List {
+	position := reader.Position
+	reader.Advance()
 
-	for i < Position(len(buffer)) && isOperator(buffer[i]) {
-		i++
+	for reader.Position < reader.Size && isOperator(reader.Current()) {
+		reader.Advance()
 	}
 
 	kind := Invalid
 
-	switch string(buffer[position:i]) {
+	switch string(reader.Buffer[position:reader.Position]) {
 	case "!":
 		kind = Not
 	case "!=":
@@ -72,8 +72,7 @@ func operator(tokens List, buffer []byte, i Position) (List, Position) {
 		kind = LogicalOr
 	}
 
-	tokens = append(tokens, Token{Kind: kind, Position: position, Length: Length(i - position)})
-	return tokens, i
+	return append(tokens, Token{Kind: kind, Position: position, Length: Length(reader.Position - position)})
 }
 
 func isOperator(c byte) bool {
diff --git a/src/token/quote.go b/src/token/quote.go
index e49ca34..bb1627b 100644
--- a/src/token/quote.go
+++ b/src/token/quote.go
@@ -1,20 +1,20 @@
 package token
 
 // quote handles all tokens starting with a single or double quote.
-func quote(tokens List, buffer []byte, i Position) (List, Position) {
-	limiter := buffer[i]
-	start := i
-	end := Position(len(buffer))
-	i++
+func quote(tokens List, reader *Reader) List {
+	limiter := reader.Current()
+	start := reader.Position
+	end := reader.Size
+	reader.Advance()
 
-	for i < Position(len(buffer)) {
-		if buffer[i] == limiter && (buffer[i-1] != '\\' || buffer[i-2] == '\\') {
-			end = i + 1
-			i++
+	for reader.Position < reader.Size {
+		if reader.Current() == limiter && (reader.Buffer[reader.Position-1] != '\\' || reader.Buffer[reader.Position-2] == '\\') {
+			end = reader.Position + 1
+			reader.Advance()
 			break
 		}
 
-		i++
+		reader.Advance()
 	}
 
 	kind := String
@@ -23,6 +23,5 @@ func quote(tokens List, buffer []byte, i Position) (List, Position) {
 		kind = Rune
 	}
 
-	tokens = append(tokens, Token{Kind: kind, Position: start, Length: Length(end - start)})
-	return tokens, i
+	return append(tokens, Token{Kind: kind, Position: start, Length: Length(end - start)})
 }
diff --git a/src/token/slash.go b/src/token/slash.go
index c8196a3..5f8a756 100644
--- a/src/token/slash.go
+++ b/src/token/slash.go
@@ -1,34 +1,34 @@
 package token
 
 // slash handles all tokens starting with '/'.
-func slash(tokens List, buffer []byte, i Position) (List, Position) {
-	if i+1 < Position(len(buffer)) && buffer[i+1] == '/' {
-		position := i
+func slash(tokens List, reader *Reader) List {
+	if reader.Next() == '/' {
+		position := reader.Position
 
-		for i < Position(len(buffer)) && buffer[i] != '\n' {
-			i++
+		for reader.Position < reader.Size && reader.Current() != '\n' {
+			reader.Advance()
 		}
 
-		tokens = append(tokens, Token{Kind: Comment, Position: position, Length: Length(i - position)})
+		tokens = append(tokens, Token{Kind: Comment, Position: position, Length: Length(reader.Position - position)})
 	} else {
-		position := i
-		i++
+		position := reader.Position
+		reader.Advance()
 
-		for i < Position(len(buffer)) && isOperator(buffer[i]) {
-			i++
+		for reader.Position < reader.Size && isOperator(reader.Current()) {
+			reader.Advance()
 		}
 
 		kind := Invalid
 
-		switch string(buffer[position:i]) {
+		switch string(reader.Buffer[position:reader.Position]) {
 		case "/":
 			kind = Div
 		case "/=":
 			kind = DivAssign
 		}
 
-		tokens = append(tokens, Token{Kind: kind, Position: position, Length: Length(i - position)})
+		tokens = append(tokens, Token{Kind: kind, Position: position, Length: Length(reader.Position - position)})
 	}
 
-	return tokens, i
+	return tokens
 }
diff --git a/src/token/zero.go b/src/token/zero.go
index df414c4..d8ee49e 100644
--- a/src/token/zero.go
+++ b/src/token/zero.go
@@ -1,35 +1,33 @@
 package token
 
 // zero handles all tokens starting with a '0'.
-func zero(tokens List, buffer []byte, i Position) (List, Position) {
-	position := i
-	i++
+func zero(tokens List, reader *Reader) List {
+	position := reader.Position
+	reader.Advance()
 
-	if i >= Position(len(buffer)) {
-		tokens = append(tokens, Token{Kind: Number, Position: position, Length: 1})
-		return tokens, i
+	if reader.Position >= reader.Size {
+		return append(tokens, Token{Kind: Number, Position: position, Length: 1})
 	}
 
 	filter := isDigit
 
-	switch buffer[i] {
+	switch reader.Current() {
 	case 'x':
-		i++
+		reader.Advance()
 		filter = isHexDigit
 
 	case 'b':
-		i++
+		reader.Advance()
 		filter = isBinaryDigit
 
 	case 'o':
-		i++
+		reader.Advance()
 		filter = isOctalDigit
 	}
 
-	for i < Position(len(buffer)) && filter(buffer[i]) {
-		i++
+	for reader.Position < reader.Size && filter(reader.Current()) {
+		reader.Advance()
 	}
 
-	tokens = append(tokens, Token{Kind: Number, Position: position, Length: Length(i - position)})
-	return tokens, i
+	return append(tokens, Token{Kind: Number, Position: position, Length: Length(reader.Position - position)})
 }