1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 18 package android.filterfw.io; 19 20 import java.util.regex.Matcher; 21 import java.util.regex.Pattern; 22 23 /** 24 * @hide 25 */ 26 public class PatternScanner { 27 28 private String mInput; 29 private Pattern mIgnorePattern; 30 private int mOffset = 0; 31 private int mLineNo = 0; 32 private int mStartOfLine = 0; 33 PatternScanner(String input)34 public PatternScanner(String input) { 35 mInput = input; 36 } 37 PatternScanner(String input, Pattern ignorePattern)38 public PatternScanner(String input, Pattern ignorePattern) { 39 mInput = input; 40 mIgnorePattern = ignorePattern; 41 skip(mIgnorePattern); 42 } 43 tryEat(Pattern pattern)44 public String tryEat(Pattern pattern) { 45 // Skip ignore pattern 46 if (mIgnorePattern != null) { 47 skip(mIgnorePattern); 48 } 49 50 // Create the matcher 51 Matcher matcher = pattern.matcher(mInput); 52 matcher.region(mOffset, mInput.length()); 53 54 // Attempt to match 55 String result = null; 56 if (matcher.lookingAt()) { 57 updateLineCount(mOffset, matcher.end()); 58 mOffset = matcher.end(); 59 result = mInput.substring(matcher.start(), matcher.end()); 60 } 61 62 // Skip ignore pattern 63 if (result != null && mIgnorePattern != null) { 64 skip(mIgnorePattern); 65 } 66 67 return result; 68 } 69 eat(Pattern pattern, String tokenName)70 public String eat(Pattern pattern, String tokenName) { 71 String result = tryEat(pattern); 72 if (result == null) { 73 throw new RuntimeException(unexpectedTokenMessage(tokenName)); 74 } 75 return result; 76 } 77 peek(Pattern pattern)78 public boolean peek(Pattern pattern) { 79 // Skip ignore pattern 80 if (mIgnorePattern != null) { 81 skip(mIgnorePattern); 82 } 83 84 // Create the matcher 85 Matcher matcher = pattern.matcher(mInput); 86 matcher.region(mOffset, mInput.length()); 87 88 // Attempt to match 89 return matcher.lookingAt(); 90 } 91 skip(Pattern pattern)92 public void skip(Pattern pattern) { 93 Matcher matcher = pattern.matcher(mInput); 94 matcher.region(mOffset, mInput.length()); 95 if (matcher.lookingAt()) { 96 updateLineCount(mOffset, matcher.end()); 97 mOffset = matcher.end(); 98 } 99 } 100 atEnd()101 public boolean atEnd() { 102 return mOffset >= mInput.length(); 103 } 104 lineNo()105 public int lineNo() { 106 return mLineNo; 107 } 108 unexpectedTokenMessage(String tokenName)109 public String unexpectedTokenMessage(String tokenName) { 110 String line = mInput.substring(mStartOfLine, mOffset); 111 return "Unexpected token on line " + (mLineNo + 1) + " after '" + line + "' <- Expected " + 112 tokenName + "!"; 113 } 114 updateLineCount(int start, int end)115 public void updateLineCount(int start, int end) { 116 for (int i = start; i < end; ++i) { 117 if (mInput.charAt(i) == '\n') { 118 ++mLineNo; 119 mStartOfLine = i + 1; 120 } 121 } 122 } 123 } 124