Neil Fuller | 0f6f3bd | 2018-07-13 20:02:58 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2015 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 android.net; |
| 18 | |
| 19 | import java.net.URISyntaxException; |
| 20 | import java.nio.ByteBuffer; |
| 21 | import java.nio.charset.CharacterCodingException; |
| 22 | import java.nio.charset.Charset; |
| 23 | import java.nio.charset.CharsetDecoder; |
| 24 | import java.nio.charset.CodingErrorAction; |
| 25 | |
| 26 | /** |
| 27 | * Decodes “application/x-www-form-urlencoded” content. |
| 28 | * |
| 29 | * @hide |
| 30 | */ |
| 31 | public final class UriCodec { |
| 32 | |
| 33 | private UriCodec() {} |
| 34 | |
| 35 | /** |
| 36 | * Interprets a char as hex digits, returning a number from -1 (invalid char) to 15 ('f'). |
| 37 | */ |
| 38 | private static int hexCharToValue(char c) { |
| 39 | if ('0' <= c && c <= '9') { |
| 40 | return c - '0'; |
| 41 | } |
| 42 | if ('a' <= c && c <= 'f') { |
| 43 | return 10 + c - 'a'; |
| 44 | } |
| 45 | if ('A' <= c && c <= 'F') { |
| 46 | return 10 + c - 'A'; |
| 47 | } |
| 48 | return -1; |
| 49 | } |
| 50 | |
| 51 | private static URISyntaxException unexpectedCharacterException( |
| 52 | String uri, String name, char unexpected, int index) { |
| 53 | String nameString = (name == null) ? "" : " in [" + name + "]"; |
| 54 | return new URISyntaxException( |
| 55 | uri, "Unexpected character" + nameString + ": " + unexpected, index); |
| 56 | } |
| 57 | |
| 58 | private static char getNextCharacter(String uri, int index, int end, String name) |
| 59 | throws URISyntaxException { |
| 60 | if (index >= end) { |
| 61 | String nameString = (name == null) ? "" : " in [" + name + "]"; |
| 62 | throw new URISyntaxException( |
| 63 | uri, "Unexpected end of string" + nameString, index); |
| 64 | } |
| 65 | return uri.charAt(index); |
| 66 | } |
| 67 | |
| 68 | /** |
| 69 | * Decode a string according to the rules of this decoder. |
| 70 | * |
| 71 | * - if {@code convertPlus == true} all ‘+’ chars in the decoded output are converted to ‘ ‘ |
| 72 | * (white space) |
| 73 | * - if {@code throwOnFailure == true}, an {@link IllegalArgumentException} is thrown for |
| 74 | * invalid inputs. Else, U+FFFd is emitted to the output in place of invalid input octets. |
| 75 | */ |
| 76 | public static String decode( |
| 77 | String s, boolean convertPlus, Charset charset, boolean throwOnFailure) { |
| 78 | StringBuilder builder = new StringBuilder(s.length()); |
| 79 | appendDecoded(builder, s, convertPlus, charset, throwOnFailure); |
| 80 | return builder.toString(); |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Character to be output when there's an error decoding an input. |
| 85 | */ |
| 86 | private static final char INVALID_INPUT_CHARACTER = '\ufffd'; |
| 87 | |
| 88 | private static void appendDecoded( |
| 89 | StringBuilder builder, |
| 90 | String s, |
| 91 | boolean convertPlus, |
| 92 | Charset charset, |
| 93 | boolean throwOnFailure) { |
| 94 | CharsetDecoder decoder = charset.newDecoder() |
| 95 | .onMalformedInput(CodingErrorAction.REPLACE) |
| 96 | .replaceWith("\ufffd") |
| 97 | .onUnmappableCharacter(CodingErrorAction.REPORT); |
| 98 | // Holds the bytes corresponding to the escaped chars being read (empty if the last char |
| 99 | // wasn't a escaped char). |
| 100 | ByteBuffer byteBuffer = ByteBuffer.allocate(s.length()); |
| 101 | int i = 0; |
| 102 | while (i < s.length()) { |
| 103 | char c = s.charAt(i); |
| 104 | i++; |
| 105 | switch (c) { |
| 106 | case '+': |
| 107 | flushDecodingByteAccumulator( |
| 108 | builder, decoder, byteBuffer, throwOnFailure); |
| 109 | builder.append(convertPlus ? ' ' : '+'); |
| 110 | break; |
| 111 | case '%': |
| 112 | // Expect two characters representing a number in hex. |
| 113 | byte hexValue = 0; |
| 114 | for (int j = 0; j < 2; j++) { |
| 115 | try { |
| 116 | c = getNextCharacter(s, i, s.length(), null /* name */); |
| 117 | } catch (URISyntaxException e) { |
| 118 | // Unexpected end of input. |
| 119 | if (throwOnFailure) { |
| 120 | throw new IllegalArgumentException(e); |
| 121 | } else { |
| 122 | flushDecodingByteAccumulator( |
| 123 | builder, decoder, byteBuffer, throwOnFailure); |
| 124 | builder.append(INVALID_INPUT_CHARACTER); |
| 125 | return; |
| 126 | } |
| 127 | } |
| 128 | i++; |
| 129 | int newDigit = hexCharToValue(c); |
| 130 | if (newDigit < 0) { |
| 131 | if (throwOnFailure) { |
| 132 | throw new IllegalArgumentException( |
| 133 | unexpectedCharacterException(s, null /* name */, c, i - 1)); |
| 134 | } else { |
| 135 | flushDecodingByteAccumulator( |
| 136 | builder, decoder, byteBuffer, throwOnFailure); |
| 137 | builder.append(INVALID_INPUT_CHARACTER); |
| 138 | break; |
| 139 | } |
| 140 | } |
| 141 | hexValue = (byte) (hexValue * 0x10 + newDigit); |
| 142 | } |
| 143 | byteBuffer.put(hexValue); |
| 144 | break; |
| 145 | default: |
| 146 | flushDecodingByteAccumulator(builder, decoder, byteBuffer, throwOnFailure); |
| 147 | builder.append(c); |
| 148 | } |
| 149 | } |
| 150 | flushDecodingByteAccumulator(builder, decoder, byteBuffer, throwOnFailure); |
| 151 | } |
| 152 | |
| 153 | private static void flushDecodingByteAccumulator( |
| 154 | StringBuilder builder, |
| 155 | CharsetDecoder decoder, |
| 156 | ByteBuffer byteBuffer, |
| 157 | boolean throwOnFailure) { |
| 158 | if (byteBuffer.position() == 0) { |
| 159 | return; |
| 160 | } |
| 161 | byteBuffer.flip(); |
| 162 | try { |
| 163 | builder.append(decoder.decode(byteBuffer)); |
| 164 | } catch (CharacterCodingException e) { |
| 165 | if (throwOnFailure) { |
| 166 | throw new IllegalArgumentException(e); |
| 167 | } else { |
| 168 | builder.append(INVALID_INPUT_CHARACTER); |
| 169 | } |
| 170 | } finally { |
| 171 | // Use the byte buffer to write again. |
| 172 | byteBuffer.flip(); |
| 173 | byteBuffer.limit(byteBuffer.capacity()); |
| 174 | } |
| 175 | } |
| 176 | } |