Mega Code Archive
Translates between byte arrays and strings of 0s and 1s
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/*
* Copyright 2001-2004 The Apache Software Foundation.
*
* 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.
*/
/**
* Translates between byte arrays and strings of "0"s and "1"s.
*
* @todo may want to add more bit vector functions like and/or/xor/nand
* @todo also might be good to generate boolean[] from byte[] et. cetera.
*
* @author Apache Software Foundation
* @since 1.3
* @version $Id $
*/
public class BinaryCodec {
/*
* tried to avoid using ArrayUtils to minimize dependencies while using these
* empty arrays - dep is just not worth it.
*/
/** Empty char array. */
private static final char[] EMPTY_CHAR_ARRAY = new char[0];
/** Empty byte array. */
private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
/** Mask for bit 0 of a byte. */
private static final int BIT_0 = 1;
/** Mask for bit 1 of a byte. */
private static final int BIT_1 = 0x02;
/** Mask for bit 2 of a byte. */
private static final int BIT_2 = 0x04;
/** Mask for bit 3 of a byte. */
private static final int BIT_3 = 0x08;
/** Mask for bit 4 of a byte. */
private static final int BIT_4 = 0x10;
/** Mask for bit 5 of a byte. */
private static final int BIT_5 = 0x20;
/** Mask for bit 6 of a byte. */
private static final int BIT_6 = 0x40;
/** Mask for bit 7 of a byte. */
private static final int BIT_7 = 0x80;
private static final int[] BITS = { BIT_0, BIT_1, BIT_2, BIT_3, BIT_4, BIT_5, BIT_6, BIT_7 };
/**
* Converts an array of raw binary data into an array of ascii 0 and 1
* characters.
*
* @param raw
* the raw binary data to convert
* @return 0 and 1 ascii character bytes one for each bit of the argument
* @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
*/
public byte[] encode(byte[] raw) {
return toAsciiBytes(raw);
}
/**
* Converts an array of raw binary data into an array of ascii 0 and 1 chars.
*
* @param raw
* the raw binary data to convert
* @return 0 and 1 ascii character chars one for each bit of the argument
* @throws EncoderException
* if the argument is not a byte[]
* @see org.apache.commons.codec.Encoder#encode(java.lang.Object)
*/
public Object encode(Object raw) throws RuntimeException {
if (!(raw instanceof byte[])) {
throw new RuntimeException("argument not a byte array");
}
return toAsciiChars((byte[]) raw);
}
/**
* Decodes a byte array where each byte represents an ascii '0' or '1'.
*
* @param ascii
* each byte represents an ascii '0' or '1'
* @return the raw encoded binary where each bit corresponds to a byte in the
* byte array argument
* @throws DecoderException
* if argument is not a byte[], char[] or String
* @see org.apache.commons.codec.Decoder#decode(java.lang.Object)
*/
public Object decode(Object ascii) throws RuntimeException {
if (ascii == null) {
return EMPTY_BYTE_ARRAY;
}
if (ascii instanceof byte[]) {
return fromAscii((byte[]) ascii);
}
if (ascii instanceof char[]) {
return fromAscii((char[]) ascii);
}
if (ascii instanceof String) {
return fromAscii(((String) ascii).toCharArray());
}
throw new RuntimeException("argument not a byte array");
}
/**
* Decodes a byte array where each byte represents an ascii '0' or '1'.
*
* @param ascii
* each byte represents an ascii '0' or '1'
* @return the raw encoded binary where each bit corresponds to a byte in the
* byte array argument
* @see org.apache.commons.codec.Decoder#decode(Object)
*/
public byte[] decode(byte[] ascii) {
return fromAscii(ascii);
}
/**
* Decodes a String where each char of the String represents an ascii '0' or
* '1'.
*
* @param ascii
* String of '0' and '1' characters
* @return the raw encoded binary where each bit corresponds to a byte in the
* byte array argument
* @see org.apache.commons.codec.Decoder#decode(Object)
*/
public byte[] toByteArray(String ascii) {
if (ascii == null) {
return EMPTY_BYTE_ARRAY;
}
return fromAscii(ascii.toCharArray());
}
// ------------------------------------------------------------------------
//
// static codec operations
//
// ------------------------------------------------------------------------
/**
* Decodes a byte array where each char represents an ascii '0' or '1'.
*
* @param ascii
* each char represents an ascii '0' or '1'
* @return the raw encoded binary where each bit corresponds to a char in the
* char array argument
*/
public static byte[] fromAscii(char[] ascii) {
if (ascii == null || ascii.length == 0) {
return EMPTY_BYTE_ARRAY;
}
// get length/8 times bytes with 3 bit shifts to the right of the length
byte[] l_raw = new byte[ascii.length >> 3];
/*
* We decr index jj by 8 as we go along to not recompute indices using
* multiplication every time inside the loop.
*/
for (int ii = 0, jj = ascii.length - 1; ii < l_raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if (ascii[jj - bits] == '1') {
l_raw[ii] |= BITS[bits];
}
}
}
return l_raw;
}
/**
* Decodes a byte array where each byte represents an ascii '0' or '1'.
*
* @param ascii
* each byte represents an ascii '0' or '1'
* @return the raw encoded binary where each bit corresponds to a byte in the
* byte array argument
*/
public static byte[] fromAscii(byte[] ascii) {
if (ascii == null || ascii.length == 0) {
return EMPTY_BYTE_ARRAY;
}
// get length/8 times bytes with 3 bit shifts to the right of the length
byte[] l_raw = new byte[ascii.length >> 3];
/*
* We decr index jj by 8 as we go along to not recompute indices using
* multiplication every time inside the loop.
*/
for (int ii = 0, jj = ascii.length - 1; ii < l_raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if (ascii[jj - bits] == '1') {
l_raw[ii] |= BITS[bits];
}
}
}
return l_raw;
}
/**
* Converts an array of raw binary data into an array of ascii 0 and 1
* character bytes - each byte is a truncated char.
*
* @param raw
* the raw binary data to convert
* @return an array of 0 and 1 character bytes for each bit of the argument
* @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
*/
public static byte[] toAsciiBytes(byte[] raw) {
if (raw == null || raw.length == 0) {
return EMPTY_BYTE_ARRAY;
}
// get 8 times the bytes with 3 bit shifts to the left of the length
byte[] l_ascii = new byte[raw.length << 3];
/*
* We decr index jj by 8 as we go along to not recompute indices using
* multiplication every time inside the loop.
*/
for (int ii = 0, jj = l_ascii.length - 1; ii < raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if ((raw[ii] & BITS[bits]) == 0) {
l_ascii[jj - bits] = '0';
} else {
l_ascii[jj - bits] = '1';
}
}
}
return l_ascii;
}
/**
* Converts an array of raw binary data into an array of ascii 0 and 1
* characters.
*
* @param raw
* the raw binary data to convert
* @return an array of 0 and 1 characters for each bit of the argument
* @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
*/
public static char[] toAsciiChars(byte[] raw) {
if (raw == null || raw.length == 0) {
return EMPTY_CHAR_ARRAY;
}
// get 8 times the bytes with 3 bit shifts to the left of the length
char[] l_ascii = new char[raw.length << 3];
/*
* We decr index jj by 8 as we go along to not recompute indices using
* multiplication every time inside the loop.
*/
for (int ii = 0, jj = l_ascii.length - 1; ii < raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if ((raw[ii] & BITS[bits]) == 0) {
l_ascii[jj - bits] = '0';
} else {
l_ascii[jj - bits] = '1';
}
}
}
return l_ascii;
}
/**
* Converts an array of raw binary data into a String of ascii 0 and 1
* characters.
*
* @param raw
* the raw binary data to convert
* @return a String of 0 and 1 characters representing the binary data
* @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
*/
public static String toAsciiString(byte[] raw) {
return new String(toAsciiChars(raw));
}
}
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