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tokenizer.go
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tokenizer.go
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// © 2022-2023 Snyk Limited All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package arm
import (
"errors"
"unicode"
)
func tokenize(input string) ([]token, error) {
var tokens []token
t := &tokenizer{remaining: []rune(input)}
for {
tkn, err := t.next()
if err != nil {
return nil, err
}
if tkn == nil {
return tokens, nil
}
tokens = append(tokens, tkn)
}
}
type tokenizer struct {
remaining []rune
}
func (t *tokenizer) peek() (rune, bool) {
if len(t.remaining) == 0 {
return 0, false
}
return t.remaining[0], true
}
func (t *tokenizer) pop() (rune, bool) {
c, ok := t.peek()
if !ok {
return c, false
}
t.remaining = t.remaining[1:]
return c, ok
}
func (t *tokenizer) next() (token, error) {
// Discard any whitespace
c1, ok := t.pop()
for ok && unicode.IsSpace(c1) {
c1, ok = t.pop()
}
// End of text
if !ok {
return nil, nil
}
switch c1 {
case '(':
return openParen{}, nil
case ')':
return closeParen{}, nil
case ',':
return comma{}, nil
case '.':
return dot{}, nil
case '\'':
// We are inside a string, parse it completely
str := []rune{}
for {
c, ok := t.pop()
if !ok {
return nil, newTokenizerError(errors.New("expected ' to end string"))
}
if c == '\'' {
// Could be end of string or an escaped '\', take a peek.
c2, ok := t.peek()
if ok && c2 == '\'' {
t.pop()
str = append(str, '\'')
} else {
return stringLiteral(string(str)), nil
}
} else {
// A normal character inside a string, just add it.
str = append(str, c)
}
}
default:
// if we reach here, the token is an identifier
if validIdentifierStart(c1) {
id := []rune{c1}
for {
// Keep adding valid characters to id while we can
c, ok := t.peek()
if ok && validIdentifierChar(c) {
t.pop()
id = append(id, c)
} else {
return identifier(string(id)), nil
}
}
}
return nil, newTokenizerError(errors.New("unexpected character"))
}
}
func validIdentifierStart(c rune) bool {
return unicode.IsLetter(c)
}
func validIdentifierChar(c rune) bool {
return unicode.IsLetter(c) || unicode.IsDigit(c) || c == '_'
}
type token interface {
}
type openParen struct{}
type closeParen struct{}
type comma struct{}
type dot struct{}
type identifier string
type stringLiteral string
func newTokenizerError(underlying error) error {
return Error{underlying: underlying, kind: TokenizerError}
}