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/*
* Copyright (C) 2015 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 android.net;
import java.net.URISyntaxException;
import java.nio.ByteBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CodingErrorAction;
/**
* Decodes “application/x-www-form-urlencoded” content.
*
* @hide
*/
public final class UriCodec {
private UriCodec() {}
/**
* Interprets a char as hex digits, returning a number from -1 (invalid char) to 15 ('f').
*/
private static int hexCharToValue(char c) {
if ('0' <= c && c <= '9') {
return c - '0';
}
if ('a' <= c && c <= 'f') {
return 10 + c - 'a';
}
if ('A' <= c && c <= 'F') {
return 10 + c - 'A';
}
return -1;
}
private static URISyntaxException unexpectedCharacterException(
String uri, String name, char unexpected, int index) {
String nameString = (name == null) ? "" : " in [" + name + "]";
return new URISyntaxException(
uri, "Unexpected character" + nameString + ": " + unexpected, index);
}
private static char getNextCharacter(String uri, int index, int end, String name)
throws URISyntaxException {
if (index >= end) {
String nameString = (name == null) ? "" : " in [" + name + "]";
throw new URISyntaxException(
uri, "Unexpected end of string" + nameString, index);
}
return uri.charAt(index);
}
/**
* Decode a string according to the rules of this decoder.
*
* - if {@code convertPlus == true} all ‘+’ chars in the decoded output are converted to ‘ ‘
* (white space)
* - if {@code throwOnFailure == true}, an {@link IllegalArgumentException} is thrown for
* invalid inputs. Else, U+FFFd is emitted to the output in place of invalid input octets.
*/
public static String decode(
String s, boolean convertPlus, Charset charset, boolean throwOnFailure) {
StringBuilder builder = new StringBuilder(s.length());
appendDecoded(builder, s, convertPlus, charset, throwOnFailure);
return builder.toString();
}
/**
* Character to be output when there's an error decoding an input.
*/
private static final char INVALID_INPUT_CHARACTER = '\ufffd';
private static void appendDecoded(
StringBuilder builder,
String s,
boolean convertPlus,
Charset charset,
boolean throwOnFailure) {
CharsetDecoder decoder = charset.newDecoder()
.onMalformedInput(CodingErrorAction.REPLACE)
.replaceWith("\ufffd")
.onUnmappableCharacter(CodingErrorAction.REPORT);
// Holds the bytes corresponding to the escaped chars being read (empty if the last char
// wasn't a escaped char).
ByteBuffer byteBuffer = ByteBuffer.allocate(s.length());
int i = 0;
while (i < s.length()) {
char c = s.charAt(i);
i++;
switch (c) {
case '+':
flushDecodingByteAccumulator(
builder, decoder, byteBuffer, throwOnFailure);
builder.append(convertPlus ? ' ' : '+');
break;
case '%':
// Expect two characters representing a number in hex.
byte hexValue = 0;
for (int j = 0; j < 2; j++) {
try {
c = getNextCharacter(s, i, s.length(), null /* name */);
} catch (URISyntaxException e) {
// Unexpected end of input.
if (throwOnFailure) {
throw new IllegalArgumentException(e);
} else {
flushDecodingByteAccumulator(
builder, decoder, byteBuffer, throwOnFailure);
builder.append(INVALID_INPUT_CHARACTER);
return;
}
}
i++;
int newDigit = hexCharToValue(c);
if (newDigit < 0) {
if (throwOnFailure) {
throw new IllegalArgumentException(
unexpectedCharacterException(s, null /* name */, c, i - 1));
} else {
flushDecodingByteAccumulator(
builder, decoder, byteBuffer, throwOnFailure);
builder.append(INVALID_INPUT_CHARACTER);
break;
}
}
hexValue = (byte) (hexValue * 0x10 + newDigit);
}
byteBuffer.put(hexValue);
break;
default:
flushDecodingByteAccumulator(builder, decoder, byteBuffer, throwOnFailure);
builder.append(c);
}
}
flushDecodingByteAccumulator(builder, decoder, byteBuffer, throwOnFailure);
}
private static void flushDecodingByteAccumulator(
StringBuilder builder,
CharsetDecoder decoder,
ByteBuffer byteBuffer,
boolean throwOnFailure) {
if (byteBuffer.position() == 0) {
return;
}
byteBuffer.flip();
try {
builder.append(decoder.decode(byteBuffer));
} catch (CharacterCodingException e) {
if (throwOnFailure) {
throw new IllegalArgumentException(e);
} else {
builder.append(INVALID_INPUT_CHARACTER);
}
} finally {
// Use the byte buffer to write again.
byteBuffer.flip();
byteBuffer.limit(byteBuffer.capacity());
}
}
}
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