com.elopteryx.paint.upload.impl.Base64Decoder Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* 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 com.elopteryx.paint.upload.impl;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
/**
* An efficient and flexible MIME Base64 implementation.
*
* @author Jason T. Greene
*/
class Base64Decoder {
private static final byte[] ENCODING_TABLE;
private static final byte[] DECODING_TABLE = new byte[80];
static {
ENCODING_TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".getBytes(StandardCharsets.US_ASCII);
for (int i = 0; i < ENCODING_TABLE.length; i++) {
int v = (ENCODING_TABLE[i] & 0xFF) - 43;
DECODING_TABLE[v] = (byte)(i + 1); // zero = illegal
}
}
private int state;
private int last;
private static final int SKIP = 0x0FD00;
private static final int MARK = 0x0FE00;
private static final int DONE = 0x0FF00;
private static final int ERROR = 0xF0000;
private static int nextByte(ByteBuffer buffer, int state, int last, boolean ignoreErrors) throws IOException {
return nextByte(buffer.get() & 0xFF, state, last, ignoreErrors);
}
private static int nextByte(int c, int state, int last, boolean ignoreErrors) throws IOException {
if (last == MARK) {
if (c != '=') {
throw new IOException("Expected padding character");
}
return DONE;
}
if (c == '=') {
if (state == 2) {
return MARK;
} else if (state == 3) {
return DONE;
} else {
throw new IOException("Unexpected padding character");
}
}
if (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
return SKIP;
}
if (c < 43 || c > 122) {
if (ignoreErrors) {
return ERROR;
}
throw new IOException("Invalid base64 character encountered: " + c);
}
int b = (DECODING_TABLE[c - 43] & 0xFF) - 1;
if (b < 0) {
if (ignoreErrors) {
return ERROR;
}
throw new IOException("Invalid base64 character encountered: " + c);
}
return b;
}
/**
* Decodes one Base64 byte buffer into another. This method will return and save state
* if the target does not have the required capacity. Subsequent calls with a new target will
* resume reading where it last left off (the source buffer's position). Similarly not all of the
* source data need be available, this method can be repetitively called as data is made available.
*
* The decoder will skip white space, but will error if it detects corruption.
*
* @param source the byte buffer to read encoded data from
* @param target the byte buffer to write decoded data to
* @throws java.io.IOException if the encoded data is corrupted
*/
public void decode(ByteBuffer source, ByteBuffer target) throws IOException {
if (target == null)
throw new IllegalStateException();
int last = this.last;
int state = this.state;
int remaining = source.remaining();
int targetRemaining = target.remaining();
int b = 0;
while (remaining-- > 0 && targetRemaining > 0) {
b = nextByte(source, state, last, false);
if (b == MARK) {
last = MARK;
if (--remaining <= 0) {
break;
}
b = nextByte(source, state, last, false);
}
if (b == DONE) {
last = state = 0;
break;
}
if (b == SKIP) {
continue;
}
// ( 6 | 2) (4 | 4) (2 | 6)
if (state == 0) {
last = b << 2;
state++;
if (remaining-- <= 0) {
break;
}
b = nextByte(source, state, last, false);
if ((b & 0xF000) != 0) {
source.position(source.position() - 1);
continue;
}
}
if (state == 1) {
target.put((byte)(last | (b >>> 4)));
last = (b & 0x0F) << 4;
state++;
if (remaining-- <= 0 || --targetRemaining <= 0) {
break;
}
b = nextByte(source, state, last, false);
if ((b & 0xF000) != 0) {
source.position(source.position() - 1);
continue;
}
}
if (state == 2) {
target.put((byte) (last | (b >>> 2)));
last = (b & 0x3) << 6;
state++;
if (remaining-- <= 0 || --targetRemaining <= 0) {
break;
}
b = nextByte(source, state, last, false);
if ((b & 0xF000) != 0) {
source.position(source.position() - 1);
continue;
}
}
if (state == 3) {
target.put((byte)(last | b));
last = state = 0;
targetRemaining--;
}
}
if (remaining > 0) {
drain(source, b, state, last);
}
this.last = last;
this.state = state;
}
private static void drain(ByteBuffer source, int b, int state, int last) {
while (b != DONE && source.remaining() > 0) {
try {
b = nextByte(source, state, last, true);
} catch (IOException e) {
b = 0;
}
if (b == MARK) {
last = MARK;
continue;
}
// Not WS/pad
if ((b & 0xF000) == 0) {
source.position(source.position() - 1);
break;
}
}
if (b == DONE) {
// SKIP one line of trailing whitespace
while (source.remaining() > 0) {
b = source.get();
if (b == '\n') {
break;
} else if (b != ' ' && b != '\t' && b != '\r') {
source.position(source.position() - 1);
break;
}
}
}
}
}
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