Package org.bitcoinj.base.internal

Class ByteUtils

java.lang.Object

org.bitcoinj.base.internal.ByteUtils

public class ByteUtils
extends java.lang.Object

Utility methods for bit, byte, and integer manipulation and conversion. Most of these were moved here from org.bitcoinj.core.Utils.

Field Summary

Fields

Modifier and Type	Field	Description
static com.google.common.io.BaseEncoding	HEX	Deprecated. Use hexFormat or parseHex(String) or other available options.
static long	MAX_UNSIGNED_INTEGER	Maximum unsigned value that can be expressed by 32 bits.
static int	MAX_UNSIGNED_SHORT	Maximum unsigned value that can be expressed by 16 bits.

Constructor Summary

Constructors

Constructor	Description
ByteUtils()

Method Summary

Modifier and Type	Method	Description
static java.util.Comparator<byte[]>	arrayUnsignedComparator()	Provides a byte array comparator.
static byte[]	bigIntegerToBytes(java.math.BigInteger b, int numBytes)	The built-in BigInteger.toByteArray() includes the sign bit of the number and may result in an extra byte in cases of unsigned data.
static java.math.BigInteger	bytesToBigInteger(byte[] bytes)	Converts an array of bytes into a positive BigInteger.
static boolean	checkBitLE(byte[] data, int index)	Checks if the given bit is set in data, using little endian (not the same as Java native big endian)
static byte[]	concat(byte[] b1, byte[] b2)	Concatenate two byte arrays
static java.math.BigInteger	decodeCompactBits(long compact)	The "compact" format is a representation of a whole number N using an unsigned 32 bit number similar to a floating point format.
static java.math.BigInteger	decodeMPI(byte[] mpi, boolean hasLength)	MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function.
static long	encodeCompactBits(java.math.BigInteger value)
static byte[]	encodeMPI(java.math.BigInteger value, boolean includeLength)	MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function.
static java.lang.String	formatHex(byte[] bytes)
static byte[]	parseHex(java.lang.String string)
static int	readInt32(java.nio.ByteBuffer buf)	Read 4 bytes from the byte array (starting at the offset) as signed 32-bit integer in little endian format.
static long	readInt64(byte[] bytes, int offset)	Read 8 bytes from the byte array (starting at the offset) as signed 64-bit integer in little endian format.
static long	readInt64(java.nio.ByteBuffer buf)	Read 8 bytes from the buffer as signed 64-bit integer in little endian format.
static int	readUint16(byte[] bytes, int offset)	Read 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in little endian format.
static int	readUint16(java.io.InputStream is)	Read 2 bytes from the stream as unsigned 16-bit integer in little endian format.
static int	readUint16(java.nio.ByteBuffer buf)	Read 2 bytes from the buffer as unsigned 16-bit integer in little endian format.
static int	readUint16BE(byte[] bytes, int offset)	Read 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in big endian format.
static int	readUint16BE(java.nio.ByteBuffer buf)	Read 2 bytes from the buffer as unsigned 16-bit integer in big endian format.
static long	readUint32(byte[] bytes, int offset)	Read 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in little endian format.
static long	readUint32(java.io.InputStream is)	Read 4 bytes from the stream as unsigned 32-bit integer in little endian format.
static long	readUint32(java.nio.ByteBuffer buf)	Read 4 bytes from the buffer as unsigned 32-bit integer in little endian format.
static long	readUint32BE(byte[] bytes, int offset)	Read 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in big endian format.
static long	readUint32BE(java.nio.ByteBuffer buf)	Read 4 bytes from the buffer as unsigned 32-bit integer in big endian format.
static byte[]	reverseBytes(byte[] bytes)	Returns a copy of the given byte array in reverse order.
static void	setBitLE(byte[] data, int index)	Sets the given bit in data to one, using little endian (not the same as Java native big endian)
static void	writeInt16BE(int val, java.io.OutputStream stream)	Write a 16-bit integer to a given output stream in big-endian format.
static java.nio.ByteBuffer	writeInt16BE(int val, java.nio.ByteBuffer buf)	Write a 16-bit integer to a given buffer in big-endian format.
static void	writeInt16LE(int val, java.io.OutputStream stream)	Write a 16-bit integer to a given output stream in little-endian format.
static java.nio.ByteBuffer	writeInt16LE(int val, java.nio.ByteBuffer buf)	Write a 16-bit integer to a given buffer in little-endian format.
static void	writeInt32BE(int val, byte[] out, int offset)	Write a 32-bit integer to a given byte array in big-endian format, starting at a given offset.
static void	writeInt32BE(int val, java.io.OutputStream stream)	Write a 32-bit integer to a given output stream in big-endian format.
static java.nio.ByteBuffer	writeInt32BE(int val, java.nio.ByteBuffer buf)	Write a 32-bit integer to a given buffer in big-endian format.
static void	writeInt32LE(int val, java.io.OutputStream stream)	Write a 32-bit integer to a given output stream in little-endian format.
static java.nio.ByteBuffer	writeInt32LE(int val, java.nio.ByteBuffer buf)	Write a 32-bit integer to a given buffer in little-endian format.
static void	writeInt32LE(long val, byte[] out, int offset)	Write a 32-bit integer to a given byte array in little-endian format, starting at a given offset.
static void	writeInt32LE(long val, java.io.OutputStream stream)	Write a 32-bit integer to a given output stream in little-endian format.
static java.nio.ByteBuffer	writeInt32LE(long val, java.nio.ByteBuffer buf)	Write a 32-bit integer to a given buffer in little-endian format.
static void	writeInt64LE(long val, byte[] out, int offset)	Write a 64-bit integer to a given byte array in little-endian format, starting at a given offset.
static void	writeInt64LE(long val, java.io.OutputStream stream)	Write a 64-bit integer to a given output stream in little-endian format.
static java.nio.ByteBuffer	writeInt64LE(long val, java.nio.ByteBuffer buf)	Write a 64-bit integer to a given buffer in little-endian format.
static void	writeInt64LE(java.math.BigInteger val, java.io.OutputStream stream)	Write a 64-bit integer to a given output stream in little-endian format.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MAX_UNSIGNED_SHORT

public static final int MAX_UNSIGNED_SHORT

Maximum unsigned value that can be expressed by 16 bits.

MAX_UNSIGNED_INTEGER

public static final long MAX_UNSIGNED_INTEGER

Maximum unsigned value that can be expressed by 32 bits.

HEX

@Deprecated
public static final com.google.common.io.BaseEncoding HEX

Deprecated.

Use hexFormat or parseHex(String) or other available options.

Hex encoding used throughout the framework. Use with ByteUtils.formatHex(byte[]) or ByteUtils.parseHex(CharSequence).

Constructor Detail

ByteUtils

public ByteUtils()

Method Detail

formatHex

public static java.lang.String formatHex(byte[] bytes)

parseHex

public static byte[] parseHex(java.lang.String string)

bigIntegerToBytes

public static byte[] bigIntegerToBytes(java.math.BigInteger b,
                                       int numBytes)

The built-in BigInteger.toByteArray() includes the sign bit of the number and may result in an extra byte in cases of unsigned data. This method removes this extra byte.

Assuming only positive numbers, it's possible to tell if an extra byte was added by checking if the first element of the array is 0 (0000_0000). Due to the guarantee of a minimal representation provided by BigInteger, we know that the sign bit will be the least significant bit 0000_0000 of a zero-value first byte. Otherwise the representation would not be minimal.

This is the inverse of bytesToBigInteger(byte[]).

Parameters:

b - the non-negative integer to format into a byte array

numBytes - the maximum allowed size of the resulting byte array

Returns:

byte array of max length numBytes

bytesToBigInteger

public static java.math.BigInteger bytesToBigInteger(byte[] bytes)

Converts an array of bytes into a positive BigInteger. This is the inverse of bigIntegerToBytes(BigInteger, int).

Parameters:

bytes - to convert into a BigInteger

Returns:

the converted BigInteger

writeInt16LE

public static java.nio.ByteBuffer writeInt16LE(int val,
                                               java.nio.ByteBuffer buf)
                                        throws java.nio.BufferOverflowException

Write a 16-bit integer to a given buffer in little-endian format.

The value is expected as an unsigned int as per the Java Unsigned Integer API.

Parameters:

val - value to be written

buf - buffer to be written into

Returns:

the buffer

Throws:

java.nio.BufferOverflowException - if the value doesn't fit the remaining buffer

writeInt16BE

public static java.nio.ByteBuffer writeInt16BE(int val,
                                               java.nio.ByteBuffer buf)
                                        throws java.nio.BufferOverflowException

Write a 16-bit integer to a given buffer in big-endian format.

The value is expected as an unsigned int as per the Java Unsigned Integer API.

Parameters:

val - value to be written

buf - buffer to be written into

Returns:

the buffer

Throws:

java.nio.BufferOverflowException - if the value doesn't fit the remaining buffer

writeInt32LE

public static java.nio.ByteBuffer writeInt32LE(int val,
                                               java.nio.ByteBuffer buf)
                                        throws java.nio.BufferOverflowException

Write a 32-bit integer to a given buffer in little-endian format.

The value is expected as a signed or unsigned int. If you've got an unsigned long as per the Java Unsigned Integer API, use writeInt32LE(long, ByteBuffer).

Parameters:

val - value to be written

buf - buffer to be written into

Returns:

the buffer

Throws:

java.nio.BufferOverflowException - if the value doesn't fit the remaining buffer

writeInt32LE

public static java.nio.ByteBuffer writeInt32LE(long val,
                                               java.nio.ByteBuffer buf)
                                        throws java.nio.BufferOverflowException

Write a 32-bit integer to a given buffer in little-endian format.

The value is expected as an unsigned long as per the Java Unsigned Integer API.

Parameters:

val - value to be written

buf - buffer to be written into

Returns:

the buffer

Throws:

java.nio.BufferOverflowException - if the value doesn't fit the remaining buffer

writeInt32LE

public static void writeInt32LE(long val,
                                byte[] out,
                                int offset)
                         throws java.lang.ArrayIndexOutOfBoundsException

Write a 32-bit integer to a given byte array in little-endian format, starting at a given offset.

The value is expected as an unsigned long as per the Java Unsigned Integer API.

Parameters:

val - value to be written

out - buffer to be written into

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the value doesn't fit the remaining buffer

writeInt32BE

public static java.nio.ByteBuffer writeInt32BE(int val,
                                               java.nio.ByteBuffer buf)
                                        throws java.nio.BufferOverflowException

Write a 32-bit integer to a given buffer in big-endian format.

The value is expected as a signed or unsigned int.

Parameters:

val - value to be written

buf - buffer to be written into

Returns:

the buffer

Throws:

java.nio.BufferOverflowException - if the value doesn't fit the remaining buffer

writeInt32BE

public static void writeInt32BE(int val,
                                byte[] out,
                                int offset)
                         throws java.lang.ArrayIndexOutOfBoundsException

Write a 32-bit integer to a given byte array in big-endian format, starting at a given offset.

The value is expected as a signed or unsigned int.

Parameters:

val - value to be written

out - buffer to be written into

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the value doesn't fit the remaining buffer

writeInt64LE

public static java.nio.ByteBuffer writeInt64LE(long val,
                                               java.nio.ByteBuffer buf)
                                        throws java.nio.BufferOverflowException

Write a 64-bit integer to a given buffer in little-endian format.

The value is expected as a signed or unsigned long.

Parameters:

val - value to be written

buf - buffer to be written into

Returns:

the buffer

Throws:

java.nio.BufferOverflowException - if the value doesn't fit the remaining buffer

writeInt64LE

public static void writeInt64LE(long val,
                                byte[] out,
                                int offset)
                         throws java.lang.ArrayIndexOutOfBoundsException

Write a 64-bit integer to a given byte array in little-endian format, starting at a given offset.

The value is expected as a signed or unsigned long.

Parameters:

val - value to be written

out - buffer to be written into

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the value doesn't fit the remaining buffer

writeInt16LE

public static void writeInt16LE(int val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 16-bit integer to a given output stream in little-endian format.

The value is expected as an unsigned int as per the Java Unsigned Integer API.

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

writeInt16BE

public static void writeInt16BE(int val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 16-bit integer to a given output stream in big-endian format.

The value is expected as an unsigned int as per the Java Unsigned Integer API.

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

writeInt32LE

public static void writeInt32LE(int val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 32-bit integer to a given output stream in little-endian format.

The value is expected as a signed or unsigned int. If you've got an unsigned long as per the Java Unsigned Integer API, use writeInt32LE(long, OutputStream).

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

writeInt32LE

public static void writeInt32LE(long val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 32-bit integer to a given output stream in little-endian format.

The value is expected as an unsigned long as per the Java Unsigned Integer API.

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

writeInt32BE

public static void writeInt32BE(int val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 32-bit integer to a given output stream in big-endian format.

The value is expected as a signed or unsigned int.

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

writeInt64LE

public static void writeInt64LE(long val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 64-bit integer to a given output stream in little-endian format.

The value is expected as a signed or unsigned long.

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

writeInt64LE

public static void writeInt64LE(java.math.BigInteger val,
                                java.io.OutputStream stream)
                         throws java.io.IOException

Write a 64-bit integer to a given output stream in little-endian format.

The value is expected as an unsigned BigInteger.

Parameters:

val - value to be written

stream - stream to be written into

Throws:

java.io.IOException - if an I/O error occurs

readUint16

public static int readUint16(java.nio.ByteBuffer buf)
                      throws java.nio.BufferUnderflowException

Read 2 bytes from the buffer as unsigned 16-bit integer in little endian format.

Parameters:

buf - buffer to be read from

Throws:

java.nio.BufferUnderflowException - if the read value extends beyond the remaining bytes of the buffer

readUint16

public static int readUint16(byte[] bytes,
                             int offset)
                      throws java.lang.ArrayIndexOutOfBoundsException

Read 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in little endian format.

Parameters:

bytes - buffer to be read from

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the read value extends beyond the remaining bytes of the buffer

readUint16BE

public static int readUint16BE(java.nio.ByteBuffer buf)
                        throws java.nio.BufferUnderflowException

Read 2 bytes from the buffer as unsigned 16-bit integer in big endian format.

Parameters:

buf - buffer to be read from

Throws:

java.nio.BufferUnderflowException - if the read value extends beyond the remaining bytes of the buffer

readUint16BE

public static int readUint16BE(byte[] bytes,
                               int offset)
                        throws java.lang.ArrayIndexOutOfBoundsException

Read 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in big endian format.

Parameters:

bytes - buffer to be read from

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the read value extends beyond the remaining bytes of the buffer

readUint32

public static long readUint32(java.nio.ByteBuffer buf)
                       throws java.nio.BufferUnderflowException

Read 4 bytes from the buffer as unsigned 32-bit integer in little endian format.

Parameters:

buf - buffer to be read from

Throws:

java.nio.BufferUnderflowException - if the read value extends beyond the remaining bytes of the buffer

readInt32

public static int readInt32(java.nio.ByteBuffer buf)
                     throws java.nio.BufferUnderflowException

Read 4 bytes from the byte array (starting at the offset) as signed 32-bit integer in little endian format.

Parameters:

buf - buffer to be read from

Returns:

read integer

Throws:

java.nio.BufferUnderflowException - if the read value extends beyond the remaining bytes of the buffer

readUint32

public static long readUint32(byte[] bytes,
                              int offset)
                       throws java.lang.ArrayIndexOutOfBoundsException

Read 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in little endian format.

Parameters:

bytes - buffer to be read from

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the read value extends beyond the remaining bytes of the buffer

readUint32BE

public static long readUint32BE(java.nio.ByteBuffer buf)
                         throws java.nio.BufferUnderflowException

Read 4 bytes from the buffer as unsigned 32-bit integer in big endian format.

Parameters:

buf - buffer to be read from

Throws:

java.nio.BufferUnderflowException - if the read value extends beyond the remaining bytes of the buffer

readUint32BE

public static long readUint32BE(byte[] bytes,
                                int offset)
                         throws java.lang.ArrayIndexOutOfBoundsException

Read 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in big endian format.

Parameters:

bytes - buffer to be read from

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the read value extends beyond the remaining bytes of the buffer

readInt64

public static long readInt64(java.nio.ByteBuffer buf)
                      throws java.nio.BufferUnderflowException

Read 8 bytes from the buffer as signed 64-bit integer in little endian format.

Parameters:

buf - buffer to be read from

Throws:

java.nio.BufferUnderflowException - if the read value extends beyond the remaining bytes of the buffer

readInt64

public static long readInt64(byte[] bytes,
                             int offset)
                      throws java.lang.ArrayIndexOutOfBoundsException

Read 8 bytes from the byte array (starting at the offset) as signed 64-bit integer in little endian format.

Parameters:

bytes - buffer to be read from

offset - offset into the buffer

Throws:

java.lang.ArrayIndexOutOfBoundsException - if offset points outside of the buffer, or if the read value extends beyond the remaining bytes of the buffer

readUint16

public static int readUint16(java.io.InputStream is)

Read 2 bytes from the stream as unsigned 16-bit integer in little endian format.

Parameters:

is - stream to be read from

readUint32

public static long readUint32(java.io.InputStream is)

Read 4 bytes from the stream as unsigned 32-bit integer in little endian format.

Parameters:

is - stream to be read from

reverseBytes

public static byte[] reverseBytes(byte[] bytes)

Returns a copy of the given byte array in reverse order.

decodeMPI

public static java.math.BigInteger decodeMPI(byte[] mpi,
                                             boolean hasLength)

MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function. They consist of a 4 byte big endian length field, followed by the stated number of bytes representing the number in big endian format (with a sign bit).

Parameters:

hasLength - can be set to false if the given array is missing the 4 byte length field

encodeMPI

public static byte[] encodeMPI(java.math.BigInteger value,
                               boolean includeLength)

MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function. They consist of a 4 byte big endian length field, followed by the stated number of bytes representing the number in big endian format (with a sign bit).

Parameters:

includeLength - indicates whether the 4 byte length field should be included

decodeCompactBits

public static java.math.BigInteger decodeCompactBits(long compact)

The "compact" format is a representation of a whole number N using an unsigned 32 bit number similar to a floating point format. The most significant 8 bits are the unsigned exponent of base 256. This exponent can be thought of as "number of bytes of N". The lower 23 bits are the mantissa. Bit number 24 (0x800000) represents the sign of N. Therefore, N = (-1^sign) * mantissa * 256^(exponent-3).

Satoshi's original implementation used BN_bn2mpi() and BN_mpi2bn(). MPI uses the most significant bit of the first byte as sign. Thus 0x1234560000 is compact 0x05123456 and 0xc0de000000 is compact 0x0600c0de. Compact 0x05c0de00 would be -0x40de000000.

Bitcoin only uses this "compact" format for encoding difficulty targets, which are unsigned 256bit quantities. Thus, all the complexities of the sign bit and using base 256 are probably an implementation accident.

encodeCompactBits

public static long encodeCompactBits(java.math.BigInteger value)

See Also:

decodeCompactBits(long)

checkBitLE

public static boolean checkBitLE(byte[] data,
                                 int index)

Checks if the given bit is set in data, using little endian (not the same as Java native big endian)

setBitLE

public static void setBitLE(byte[] data,
                            int index)

Sets the given bit in data to one, using little endian (not the same as Java native big endian)

arrayUnsignedComparator

public static java.util.Comparator<byte[]> arrayUnsignedComparator()

Provides a byte array comparator.

Returns:

A comparator for byte[]

concat

public static byte[] concat(byte[] b1,
                            byte[] b2)

Concatenate two byte arrays

Parameters:

b1 - first byte array

b2 - second byte array

Returns:

new concatenated byte array