/*
* Copyright 2013-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.amazonaws.util;
import static com.amazonaws.util.CodecUtils.sanityCheckLastPos;
/**
* Common base class for Base 32 like codec implementation.
*
* @author Hanson Char
*/
abstract class AbstractBase32Codec implements Codec {
private static final int MASK_2BITS = (1 << 2) - 1;
private static final int MASK_3BITS = (1 << 3) - 1;
private static final int MASK_4BITS = (1 << 4) - 1;
private static final int MASK_5BITS = (1 << 5) - 1;
// Base 32 alphabet as defined at http://www.ietf.org/rfc/rfc4648.txt
private static final byte PAD = '=';
private final byte[] ALPAHBETS;
protected AbstractBase32Codec(byte[] alphabets) {
ALPAHBETS = alphabets;
}
@Override
public final byte[] encode(byte[] src) {
final int num5bytes = src.length / 5;
final int remainder = src.length % 5;
if (remainder == 0)
{
byte[] dest = new byte[num5bytes * 8];
for (int s = 0, d = 0; s < src.length; s += 5, d += 8)
encode5bytes(src, s, dest, d);
return dest;
}
byte[] dest = new byte[(num5bytes + 1) * 8];
int s = 0, d = 0;
for (; s < src.length - remainder; s += 5, d += 8)
encode5bytes(src, s, dest, d);
switch (remainder) {
case 1:
encode1byte(src, s, dest, d);
break;
case 2:
encode2bytes(src, s, dest, d);
break;
case 3:
encode3bytes(src, s, dest, d);
break;
case 4:
encode4bytes(src, s, dest, d);
break;
}
return dest;
}
private final void encode5bytes(byte[] src, int s, byte[] dest, int d) {
// operator precedence in descending order: >>> or <<, &, |
byte p;
dest[d++] = ALPAHBETS[(p = src[s++]) >>> 3 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_3BITS) << 2 | (p = src[s++]) >>> 6 & MASK_2BITS]; // 3
// 2
dest[d++] = ALPAHBETS[p >>> 1 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & 1) << 4 | (p = src[s++]) >>> 4 & MASK_4BITS]; // 1
// 4
dest[d++] = ALPAHBETS[(p & MASK_4BITS) << 1 | (p = src[s++]) >>> 7 & 1]; // 4
// 1
dest[d++] = ALPAHBETS[p >>> 2 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_2BITS) << 3 | (p = src[s]) >>> 5 & MASK_3BITS]; // 2
// 3
dest[d] = ALPAHBETS[p & MASK_5BITS]; // 5
return;
}
private final void encode4bytes(byte[] src, int s, byte[] dest, int d) {
// operator precedence in descending order: >>> or <<, &, |
byte p;
dest[d++] = ALPAHBETS[(p = src[s++]) >>> 3 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_3BITS) << 2 | (p = src[s++]) >>> 6 & MASK_2BITS]; // 3
// 2
dest[d++] = ALPAHBETS[p >>> 1 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & 1) << 4 | (p = src[s++]) >>> 4 & MASK_4BITS]; // 1
// 4
dest[d++] = ALPAHBETS[(p & MASK_4BITS) << 1 | (p = src[s]) >>> 7 & 1]; // 4
// 1
dest[d++] = ALPAHBETS[p >>> 2 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_2BITS) << 3]; // 2
dest[d] = PAD;
return;
}
private final void encode3bytes(byte[] src, int s, byte[] dest, int d) {
// operator precedence in descending order: >>> or <<, &, |
byte p;
dest[d++] = ALPAHBETS[(p = src[s++]) >>> 3 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_3BITS) << 2 | (p = src[s++]) >>> 6 & MASK_2BITS]; // 3
// 2
dest[d++] = ALPAHBETS[p >>> 1 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & 1) << 4 | (p = src[s]) >>> 4 & MASK_4BITS]; // 1
// 4
dest[d++] = ALPAHBETS[(p & MASK_4BITS) << 1]; // 4
for (int i = 0; i < 3; i++)
dest[d++] = PAD;
return;
}
private final void encode2bytes(byte[] src, int s, byte[] dest, int d) {
// operator precedence in descending order: >>> or <<, &, |
byte p;
dest[d++] = ALPAHBETS[(p = src[s++]) >>> 3 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_3BITS) << 2 | (p = src[s]) >>> 6 & MASK_2BITS]; // 3
// 2
dest[d++] = ALPAHBETS[p >>> 1 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & 1) << 4]; // 1
for (int i = 0; i < 4; i++)
dest[d++] = PAD;
return;
}
private final void encode1byte(byte[] src, int s, byte[] dest, int d) {
// operator precedence in descending order: >>> or <<, &, |
byte p;
dest[d++] = ALPAHBETS[(p = src[s]) >>> 3 & MASK_5BITS]; // 5
dest[d++] = ALPAHBETS[(p & MASK_3BITS) << 2]; // 3
for (int i = 0; i < 6; i++)
dest[d++] = PAD;
return;
}
private final void decode5bytes(byte[] src, int s, byte[] dest, int d) {
int p = 0;
// operator precedence in descending order: >>> or <<, &, |
dest[d++] = (byte)
(
pos(src[s++]) << 3
| (p = pos(src[s++])) >>> 2 & MASK_3BITS
); // 5 3
dest[d++] = (byte)
(
(p & MASK_2BITS) << 6
| pos(src[s++]) << 1
| (p = pos(src[s++])) >>> 4 & 1
); // 2 5 1
dest[d++] = (byte)
(
(p & MASK_4BITS) << 4
| (p = pos(src[s++])) >>> 1 & MASK_4BITS
); // 4 4
dest[d++] = (byte)
(
(p & 1) << 7
| pos(src[s++]) << 2
| (p = pos(src[s++])) >>> 3 & MASK_2BITS
); // 1 5 2
dest[d] = (byte)
(
(p & MASK_3BITS) << 5
| pos(src[s])
); // 3 5
return;
}
/**
* @param n the number of final quantum in bytes to decode into. Ranges from
* 1 to 4, inclusive.
*/
private final void decode1to4bytes(int n, byte[] src, int s, byte[] dest, int d) {
int p = 0;
// operator precedence in descending order: >>> or <<, &, |
dest[d++] = (byte)
(
pos(src[s++]) << 3
| (p = pos(src[s++])) >>> 2 & MASK_3BITS
); // 5 3
if (n == 1) {
sanityCheckLastPos(p, MASK_2BITS);
return;
}
dest[d++] = (byte)
(
(p & MASK_2BITS) << 6
| (pos(src[s++])) << 1
| (p = pos(src[s++])) >>> 4 & 1
); // 2 5 1
if (n == 2) {
sanityCheckLastPos(p, MASK_4BITS);
return;
}
dest[d++] = (byte)
(
(p & MASK_4BITS) << 4
| (p = pos(src[s++])) >>> 1 & MASK_4BITS
); // 4 4
if (n == 3) {
sanityCheckLastPos(p, 1);
return;
}
dest[d] = (byte)
(
(p & 1) << 7
| pos(src[s++]) << 2
| (p = pos(src[s])) >>> 3 & MASK_2BITS
); // 1 5 2
sanityCheckLastPos(p, MASK_3BITS);
return;
}
@Override
public final byte[] decode(byte[] src, final int length)
{
if (length % 8 != 0)
throw new IllegalArgumentException(
"Input is expected to be encoded in multiple of 8 bytes but found: " + length);
int pads = 0;
int last = length - 1;
// max possible padding in b32 encoding is 6
for (; pads < 6 && last > -1; last--, pads++) {
if (src[last] != PAD)
break;
}
final int fq; // final quantum in unit of bytes
switch (pads) {
case 0:
fq = 5;
break; // final quantum of encoding input is an integral
// multiple of 40 bits
case 1:
fq = 4;
break; // final quantum of encoding input is exactly 32 bits
case 3:
fq = 3;
break; // final quantum of encoding input is exactly 24 bits
case 4:
fq = 2;
break; // final quantum of encoding input is exactly 16 bits
case 6:
fq = 1;
break; // final quantum of encoding input is exactly 8 bits
default:
throw new IllegalArgumentException("Invalid number of paddings " + pads);
}
final byte[] dest = new byte[length / 8 * 5 - (5 - fq)];
int s = 0, d = 0;
// % has a higher precedence than - than <
for (; d < dest.length - fq % 5; s += 8, d += 5)
decode5bytes(src, s, dest, d);
if (fq < 5)
decode1to4bytes(fq, src, s, dest, d);
return dest;
}
protected abstract int pos(byte in);
}