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 package com.android.dx.util; 18 19 import java.io.UTFDataFormatException; 20 21 /** 22 * Modified UTF-8 as described in the dex file format spec. 23 * 24 * <p>Derived from libcore's MUTF-8 encoder at java.nio.charset.ModifiedUtf8. 25 */ 26 public final class Mutf8 { 27 private Mutf8() {} 28 29 /** 30 * Decodes bytes from {@code in} into {@code out} until a delimiter 0x00 is 31 * encountered. Returns a new string containing the decoded characters. 32 */ 33 public static String decode(ByteInput in, char[] out) throws UTFDataFormatException { 34 int s = 0; 35 while (true) { 36 char a = (char) (in.readByte() & 0xff); 37 if (a == 0) { 38 return new String(out, 0, s); 39 } 40 out[s] = a; 41 if (a < '\u0080') { 42 s++; 43 } else if ((a & 0xe0) == 0xc0) { 44 int b = in.readByte() & 0xff; 45 if ((b & 0xC0) != 0x80) { 46 throw new UTFDataFormatException("bad second byte"); 47 } 48 out[s++] = (char) (((a & 0x1F) << 6) | (b & 0x3F)); 49 } else if ((a & 0xf0) == 0xe0) { 50 int b = in.readByte() & 0xff; 51 int c = in.readByte() & 0xff; 52 if (((b & 0xC0) != 0x80) || ((c & 0xC0) != 0x80)) { 53 throw new UTFDataFormatException("bad second or third byte"); 54 } 55 out[s++] = (char) (((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F)); 56 } else { 57 throw new UTFDataFormatException("bad byte"); 58 } 59 } 60 } 61 62 /** 63 * Returns the number of bytes the modified UTF8 representation of 's' would take. 64 */ 65 private static long countBytes(String s, boolean shortLength) throws UTFDataFormatException { 66 long result = 0; 67 final int length = s.length(); 68 for (int i = 0; i < length; ++i) { 69 char ch = s.charAt(i); 70 if (ch != 0 && ch <= 127) { // U+0000 uses two bytes. 71 ++result; 72 } else if (ch <= 2047) { 73 result += 2; 74 } else { 75 result += 3; 76 } 77 if (shortLength && result > 65535) { 78 throw new UTFDataFormatException("String more than 65535 UTF bytes long"); 79 } 80 } 81 return result; 82 } 83 84 /** 85 * Encodes the modified UTF-8 bytes corresponding to {@code s} into {@code 86 * dst}, starting at {@code offset}. 87 */ 88 public static void encode(byte[] dst, int offset, String s) { 89 final int length = s.length(); 90 for (int i = 0; i < length; i++) { 91 char ch = s.charAt(i); 92 if (ch != 0 && ch <= 127) { // U+0000 uses two bytes. 93 dst[offset++] = (byte) ch; 94 } else if (ch <= 2047) { 95 dst[offset++] = (byte) (0xc0 | (0x1f & (ch >> 6))); 96 dst[offset++] = (byte) (0x80 | (0x3f & ch)); 97 } else { 98 dst[offset++] = (byte) (0xe0 | (0x0f & (ch >> 12))); 99 dst[offset++] = (byte) (0x80 | (0x3f & (ch >> 6))); 100 dst[offset++] = (byte) (0x80 | (0x3f & ch)); 101 } 102 } 103 } 104 105 /** 106 * Returns an array containing the <i>modified UTF-8</i> form of {@code s}. 107 */ 108 public static byte[] encode(String s) throws UTFDataFormatException { 109 int utfCount = (int) countBytes(s, true); 110 byte[] result = new byte[utfCount]; 111 encode(result, 0, s); 112 return result; 113 } 114 } 115
