| // Copyright (C) 2014 The Android Open Source Project |
| // |
| // 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 parse |
| |
| import "unicode/utf8" |
| |
| type SkipMode int |
| |
| const ( |
| // SkipPrefix is the skip mode that skips tokens that are associated with |
| // the following lexically relevant token. This is mostly important for |
| // comment association. |
| SkipPrefix SkipMode = iota |
| // SkipSuffix is the skip mode that skips tokens that are associated with |
| // the preceding lexically relevant token. This is mostly important for |
| // comment association. |
| SkipSuffix |
| ) |
| |
| // Skip is the function used to skip separating tokens. |
| // A separating token is one where, as far as the parser is concerned, the |
| // tokens do not exist, even though the tokens may have been necessary to |
| // separate the lexical tokens (whitespace), or carry useful information |
| // (comments). |
| type Skip func(parser *Parser, mode SkipMode) Separator |
| |
| // NewSkip builds a Skip function for the common case of a parser that has one |
| // type of line comment, one type of block comment, and want to treat all |
| // unicode space characters as skippable. |
| func NewSkip(line, blockstart, blockend string) Skip { |
| return func(p *Parser, mode SkipMode) Separator { |
| var sep Separator |
| for { |
| switch { |
| case p.Space(): |
| n := &fragment{} |
| n.SetToken(p.Consume()) |
| sep = append(sep, n) |
| case mode == SkipPrefix && p.Rune(RuneEOL): |
| n := &fragment{} |
| n.SetToken(p.Consume()) |
| sep = append(sep, n) |
| case p.String(line): |
| if !p.SeekRune(RuneEOL) { |
| for !p.IsEOF() { |
| p.Advance() |
| } |
| } |
| n := &fragment{} |
| n.SetToken(p.Consume()) |
| sep = append(sep, n) |
| case p.String(blockstart): |
| first, _ := utf8.DecodeRuneInString(blockend) |
| for { |
| if !p.SeekRune(first) { |
| p.Error("Unterminated block comment") |
| break |
| } |
| if p.String(blockend) { |
| break |
| } |
| p.Advance() |
| } |
| n := &fragment{} |
| n.SetToken(p.Consume()) |
| sep = append(sep, n) |
| default: |
| return sep |
| } |
| } |
| } |
| } |