Java Byte Array Create toBytesFromBin(String binSymbols)

Description

Given a string of binary symbols, convert it to an array of bytes

License

Open Source License

Parameter

Parameter	Description
binSymbols	The binary string to convert

Return

The byte array corresponding to the input string

Declaration

public static byte[] toBytesFromBin(String binSymbols) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    public static final String BINARY_STRING_PREFIX1 = "0b";
    public static final String BINARY_STRING_PREFIX2 = "0B";
    /** The regular expression for a binary string */
    public static final String BINARY_REGEXP = "((" + BINARY_STRING_PREFIX1 + ")|(" + BINARY_STRING_PREFIX2
            + ")){0,1}[0-1]{0,}";

    /**//from w ww . j  ava2 s .c  o  m
     * Given a string of binary symbols, convert it to an array of bytes
     *
     * @param binSymbols
     *            The binary string to convert
     * @return The byte array corresponding to the input string
     */
    public static byte[] toBytesFromBin(String binSymbols) {
        if (binSymbols == null || binSymbols.trim().length() == 0) {
            return (new byte[0]);
        } else if (isValidBin(binSymbols) == false) {
            throw new IllegalArgumentException("Invalid bin string specified");
        }

        binSymbols = stripBinaryPrefix(binSymbols);
        while ((binSymbols.length() % 8) != 0) {
            binSymbols = "0" + binSymbols;
        }

        // 8 bits in a byte
        int numBytes = binSymbols.length() / 8;
        byte[] bytes = new byte[numBytes];

        // loop through all the input symbols
        for (int i = 0; i < bytes.length; i++) {
            bytes[i] = toByteFromBin(binSymbols.substring(i * 8, (i * 8) + 8));
        }

        return (bytes);
    }

    public static boolean isValidBin(final String binSymbols) {
        return (binSymbols.matches(BINARY_REGEXP));
    }

    public static String stripBinaryPrefix(String binSymbols) {
        if (binSymbols.startsWith(BINARY_STRING_PREFIX1)) {
            binSymbols = binSymbols.substring(BINARY_STRING_PREFIX1.length());
        } else if (binSymbols.startsWith(BINARY_STRING_PREFIX2)) {
            binSymbols = binSymbols.substring(BINARY_STRING_PREFIX2.length());
        }

        return (binSymbols);
    }

    /**
     * Transform a string of 8 bits into a byte
     *
     * @param binSymbols
     *            A string of binary symbols of length 8
     * @return The byte representing the input bit string
     */
    public static byte toByteFromBin(String binSymbols) {
        if (isValidBin(binSymbols) == false) {
            throw new IllegalArgumentException("Illegal characters in bin string");
        }

        binSymbols = stripBinaryPrefix(binSymbols);

        if (binSymbols.length() > 8) {
            throw new IllegalArgumentException(
                    "More than 8 bits in input bit string, cannot convert to a single byte");
        }

        while (binSymbols.length() != 8) {
            binSymbols = "0" + binSymbols;
        }

        // make a corresponding bit out of each symbol in the input string
        //
        // we make a single bit by reading in the symbol, shifting it to the correct place
        // in the byte and zeroing the rest of the byte. If we add all 8 of these bytes together
        // we'll get the correct final byte value
        //
        // bit 0 is MSB, bit 7 is LSB
        byte bit0 = (byte) (((Integer.parseInt(binSymbols.substring(0, 1))) & 0x01) << 7);
        byte bit1 = (byte) (((Integer.parseInt(binSymbols.substring(1, 2))) & 0x01) << 6);
        byte bit2 = (byte) (((Integer.parseInt(binSymbols.substring(2, 3))) & 0x01) << 5);
        byte bit3 = (byte) (((Integer.parseInt(binSymbols.substring(3, 4))) & 0x01) << 4);
        byte bit4 = (byte) (((Integer.parseInt(binSymbols.substring(4, 5))) & 0x01) << 3);
        byte bit5 = (byte) (((Integer.parseInt(binSymbols.substring(5, 6))) & 0x01) << 2);
        byte bit6 = (byte) (((Integer.parseInt(binSymbols.substring(6, 7))) & 0x01) << 1);
        byte bit7 = (byte) ((Integer.parseInt(binSymbols.substring(7, 8))) & 0x01);

        return ((byte) (bit0 + bit1 + bit2 + bit3 + bit4 + bit5 + bit6 + bit7));
    }
}

Related

1. toBytesBigEndian(long value, int sizeInByte)
2. toBytesBinary(String in)
3. toBytesDirect(final String singleOctets)
4. toBytesFromASCII(final char[] chars)
5. toBytesFromBase64(String inBase64String)
6. toBytesFromHexStr(String hexStr)
7. toBytesFromHexString(String digits)
8. toBytesFromOct(String octSymbols)
9. toBytesFromString(String s)