Package org.bitcoinj.core

Class Utils

java.lang.Object
org.bitcoinj.core.Utils
public class Utils extends Object
A collection of various utility methods that are helpful for working with the Bitcoin protocol. To enable debug logging from the library, run with -Dbitcoinj.logging=true on your command line.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final com.google.common.io.BaseEncoding
    HEX
    Hex encoding used throughout the framework.
    static final int
    MAX_INITIAL_ARRAY_LENGTH
    Max initial size of variable length arrays and ArrayLists that could be attacked.
    static final com.google.common.base.Joiner
    SPACE_JOINER
    Joiner for concatenating words with a space inbetween.
    static final com.google.common.base.Splitter
    WHITESPACE_SPLITTER
    Splitter for splitting words on whitespaces.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Utils()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static byte[]
    bigIntegerToBytes(BigInteger b, int numBytes)
    The regular BigInteger.toByteArray() includes the sign bit of the number and might result in an extra byte addition.
    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 long
    currentTimeMillis()
    Returns the current time in milliseconds since the epoch, or a mocked out equivalent.
    static long
    currentTimeSeconds()
    Returns the current time in seconds since the epoch, or a mocked out equivalent.
    static String
    dateTimeFormat(long dateTime)
    Formats a given date+time value to an ISO 8601 string.
    static String
    dateTimeFormat(Date dateTime)
    Formats a given date+time value to an ISO 8601 string.
    static 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 BigInteger
    decodeMPI(byte[] mpi, boolean hasLength)
    MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function.
    static long
    encodeCompactBits(BigInteger value)
     
    static byte[]
    encodeMPI(BigInteger value, boolean includeLength)
    MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function.
    static void
    int64ToByteArrayLE(long val, byte[] out, int offset)
    Write 8 bytes to the byte array (starting at the offset) as signed 64-bit integer in little endian format.
    static void
    int64ToByteStreamLE(long val, OutputStream stream)
    Write 8 bytes to the output stream as signed 64-bit integer in little endian format.
    static boolean
    isAndroidRuntime()
     
    static boolean
    isLinux()
     
    static boolean
    isMac()
     
    static boolean
    isOpenJDKRuntime()
     
    static boolean
    isOracleJavaRuntime()
     
    static boolean
    isWindows()
     
    static Date
    now()
    Returns the current time, or a mocked out equivalent.
    static long
    readInt64(byte[] bytes, int offset)
    Parse 8 bytes from the byte array (starting at the offset) as signed 64-bit integer in little endian format.
    static int
    readUint16(byte[] bytes, int offset)
    Parse 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in little endian format.
    static int
    readUint16BE(byte[] bytes, int offset)
    Parse 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in big endian format.
    static int
    readUint16FromStream(InputStream is)
    Parse 2 bytes from the stream as unsigned 16-bit integer in little endian format.
    static long
    readUint32(byte[] bytes, int offset)
    Parse 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in little endian format.
    static long
    readUint32BE(byte[] bytes, int offset)
    Parse 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in big endian format.
    static long
    readUint32FromStream(InputStream is)
    Parse 4 bytes from the stream as unsigned 32-bit integer in little endian format.
    static void
    resetMocking()
    Clears the mock clock and sleep
    static byte[]
    reverseBytes(byte[] bytes)
    Returns a copy of the given byte array in reverse order.
    static Date
    rollMockClock(int seconds)
    Advances (or rewinds) the mock clock by the given number of seconds.
    static Date
    rollMockClockMillis(long millis)
    Advances (or rewinds) the mock clock by the given number of milliseconds.
    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
    setMockClock()
    Sets the mock clock to the current time.
    static void
    setMockClock(long mockClockSeconds)
    Sets the mock clock to the given time (in seconds).
    static byte[]
    sha256hash160(byte[] input)
    Calculates RIPEMD160(SHA256(input)).
    static String
    toString(List<byte[]> stack)
     
    static void
    uint16ToByteArrayLE(int val, byte[] out, int offset)
    Write 2 bytes to the byte array (starting at the offset) as unsigned 16-bit integer in little endian format.
    static void
    uint16ToByteStreamBE(int val, OutputStream stream)
    Write 2 bytes to the output stream as unsigned 16-bit integer in big endian format.
    static void
    uint16ToByteStreamLE(int val, OutputStream stream)
    Write 2 bytes to the output stream as unsigned 16-bit integer in little endian format.
    static void
    uint32ToByteArrayBE(long val, byte[] out, int offset)
    Write 4 bytes to the byte array (starting at the offset) as unsigned 32-bit integer in big endian format.
    static void
    uint32ToByteArrayLE(long val, byte[] out, int offset)
    Write 4 bytes to the byte array (starting at the offset) as unsigned 32-bit integer in little endian format.
    static void
    uint32ToByteStreamBE(long val, OutputStream stream)
    Write 4 bytes to the output stream as unsigned 32-bit integer in big endian format.
    static void
    uint32ToByteStreamLE(long val, OutputStream stream)
    Write 4 bytes to the output stream as unsigned 32-bit integer in little endian format.
    static void
    uint64ToByteStreamLE(BigInteger val, OutputStream stream)
    Write 8 bytes to the output stream as unsigned 64-bit integer in little endian format.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • SPACE_JOINER

      public static final com.google.common.base.Joiner SPACE_JOINER
      Joiner for concatenating words with a space inbetween.

    • WHITESPACE_SPLITTER

      public static final com.google.common.base.Splitter WHITESPACE_SPLITTER
      Splitter for splitting words on whitespaces.

    • HEX

      public static final com.google.common.io.BaseEncoding HEX
      Hex encoding used throughout the framework. Use with HEX.encode(byte[]) or HEX.decode(CharSequence).

    • MAX_INITIAL_ARRAY_LENGTH

      public static final int MAX_INITIAL_ARRAY_LENGTH
      Max initial size of variable length arrays and ArrayLists that could be attacked. Avoids this attack: Attacker sends a msg indicating it will contain a huge number (eg 2 billion) elements (eg transaction inputs) and forces bitcoinj to try to allocate a huge piece of the memory resulting in OutOfMemoryError.
      See Also:

  • Constructor Details

    • Utils

      public Utils()

  • Method Details

    • bigIntegerToBytes

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

      The regular BigInteger.toByteArray() includes the sign bit of the number and might result in an extra byte addition. This method removes this extra byte.

      Assuming only positive numbers, it's possible to discriminate if an extra byte is added by checking if the first element of the array is 0 (0000_0000). Due to the minimal representation provided by BigInteger, it means that the bit sign is the least significant bit 0000_0000 . Otherwise the representation is not minimal. For example, if the sign bit is 0000_0000, then the representation is not minimal due to the rightmost zero.

      Parameters:
      b - the integer to format into a byte array
      numBytes - the desired size of the resulting byte array
      Returns:
      numBytes byte long array.

    • uint16ToByteArrayLE

      public static void uint16ToByteArrayLE(int val, byte[] out, int offset)
      Write 2 bytes to the byte array (starting at the offset) as unsigned 16-bit integer in little endian format.

    • uint32ToByteArrayLE

      public static void uint32ToByteArrayLE(long val, byte[] out, int offset)
      Write 4 bytes to the byte array (starting at the offset) as unsigned 32-bit integer in little endian format.

    • uint32ToByteArrayBE

      public static void uint32ToByteArrayBE(long val, byte[] out, int offset)
      Write 4 bytes to the byte array (starting at the offset) as unsigned 32-bit integer in big endian format.

    • int64ToByteArrayLE

      public static void int64ToByteArrayLE(long val, byte[] out, int offset)
      Write 8 bytes to the byte array (starting at the offset) as signed 64-bit integer in little endian format.

    • uint16ToByteStreamLE

      public static void uint16ToByteStreamLE(int val, OutputStream stream) throws IOException
      Write 2 bytes to the output stream as unsigned 16-bit integer in little endian format.
      Throws:
      IOException

    • uint16ToByteStreamBE

      public static void uint16ToByteStreamBE(int val, OutputStream stream) throws IOException
      Write 2 bytes to the output stream as unsigned 16-bit integer in big endian format.
      Throws:
      IOException

    • uint32ToByteStreamLE

      public static void uint32ToByteStreamLE(long val, OutputStream stream) throws IOException
      Write 4 bytes to the output stream as unsigned 32-bit integer in little endian format.
      Throws:
      IOException

    • uint32ToByteStreamBE

      public static void uint32ToByteStreamBE(long val, OutputStream stream) throws IOException
      Write 4 bytes to the output stream as unsigned 32-bit integer in big endian format.
      Throws:
      IOException

    • int64ToByteStreamLE

      public static void int64ToByteStreamLE(long val, OutputStream stream) throws IOException
      Write 8 bytes to the output stream as signed 64-bit integer in little endian format.
      Throws:
      IOException

    • uint64ToByteStreamLE

      public static void uint64ToByteStreamLE(BigInteger val, OutputStream stream) throws IOException
      Write 8 bytes to the output stream as unsigned 64-bit integer in little endian format.
      Throws:
      IOException

    • readUint16

      public static int readUint16(byte[] bytes, int offset)
      Parse 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in little endian format.

    • readUint32

      public static long readUint32(byte[] bytes, int offset)
      Parse 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in little endian format.

    • readInt64

      public static long readInt64(byte[] bytes, int offset)
      Parse 8 bytes from the byte array (starting at the offset) as signed 64-bit integer in little endian format.

    • readUint32BE

      public static long readUint32BE(byte[] bytes, int offset)
      Parse 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in big endian format.

    • readUint16BE

      public static int readUint16BE(byte[] bytes, int offset)
      Parse 2 bytes from the byte array (starting at the offset) as unsigned 16-bit integer in big endian format.

    • readUint16FromStream

      public static int readUint16FromStream(InputStream is)
      Parse 2 bytes from the stream as unsigned 16-bit integer in little endian format.

    • readUint32FromStream

      public static long readUint32FromStream(InputStream is)
      Parse 4 bytes from the stream as unsigned 32-bit integer in little endian format.

    • reverseBytes

      public static byte[] reverseBytes(byte[] bytes)
      Returns a copy of the given byte array in reverse order.

    • sha256hash160

      public static byte[] sha256hash160(byte[] input)
      Calculates RIPEMD160(SHA256(input)). This is used in Address calculations.

    • decodeMPI

      public static 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(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 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(BigInteger value)
      See Also:

    • rollMockClock

      public static Date rollMockClock(int seconds)
      Advances (or rewinds) the mock clock by the given number of seconds.

    • rollMockClockMillis

      public static Date rollMockClockMillis(long millis)
      Advances (or rewinds) the mock clock by the given number of milliseconds.

    • setMockClock

      public static void setMockClock()
      Sets the mock clock to the current time.

    • setMockClock

      public static void setMockClock(long mockClockSeconds)
      Sets the mock clock to the given time (in seconds).

    • resetMocking

      public static void resetMocking()
      Clears the mock clock and sleep

    • now

      public static Date now()
      Returns the current time, or a mocked out equivalent.

    • currentTimeMillis

      public static long currentTimeMillis()
      Returns the current time in milliseconds since the epoch, or a mocked out equivalent.

    • currentTimeSeconds

      public static long currentTimeSeconds()
      Returns the current time in seconds since the epoch, or a mocked out equivalent.

    • dateTimeFormat

      public static String dateTimeFormat(Date dateTime)
      Formats a given date+time value to an ISO 8601 string.
      Parameters:
      dateTime - value to format, as a Date

    • dateTimeFormat

      public static String dateTimeFormat(long dateTime)
      Formats a given date+time value to an ISO 8601 string.
      Parameters:
      dateTime - value to format, unix time (ms)

    • 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)

    • isAndroidRuntime

      public static boolean isAndroidRuntime()

    • isOpenJDKRuntime

      public static boolean isOpenJDKRuntime()

    • isOracleJavaRuntime

      public static boolean isOracleJavaRuntime()

    • isLinux

      public static boolean isLinux()

    • isWindows

      public static boolean isWindows()

    • isMac

      public static boolean isMac()

    • toString

      public static String toString(List<byte[]> stack)