Package com.norswap.nanoeth.utils

Class ByteUtils

java.lang.Object
com.norswap.nanoeth.utils.ByteUtils
public final class ByteUtils
extends Object
Utilities dealing with byte values, the byte-array encoding of larger numbers, as well as byte arrays in general.

  • Method Summary

    Modifier and Type Method Description
    static byte addMod​(int a, int b)
    Adds two bytes together with wrap-around behaviour (e.g.
    static byte[] array​(int... bytes)
    Short way to create an array of bytes that also allows 0-255 values.
    static byte[] bytes​(int value)
    Returns a byte array of size byteSize(value) encoding value in big-endian.
    static int byteSize​(int value)
    Returns the minimum number of bytes needed to store the integer.
    static byte[] bytesPadded​(byte[] bytes, int length)
    Pads the given byte array to the given length by adding zeroes at the start.
    static byte[] bytesPadded​(BigInteger value, int length)
    Returns the big-endian encoding of value in bytes padded (at the start) with zeroes so that the length of the output is at least length.
    static byte[] bytesWithoutSign​(BigInteger value)
    Returns the big-endian encoding of value in bytes, excluding any byte that would be included solely to signify the sign of the value.
    static byte[] concat​(byte[]... bytes)
    Returns the concatenation of the byte arrays.
    static byte[] copyOfSizedRange​(byte[] array, int index, int size)
    Just like Arrays.copyOfRange(byte[], int, int), but allows passing a size instead of an end index.
    static byte hexDigitToByte​(char hex)
    Converts a hex digit (in 0-9, a-f or A-F) to its numeric value.
    static byte[] hexStringToBytes​(String hexString)
    Converts a hex-string (e.g.
    static byte[] hexStringToBytes​(String hexString, int minLen)
    Converts a hex-string (e.g.
    static char intToHexDigit​(int b)
    Converts an integer in [0, 15] into an hex digit (0..9 a..f).
    static boolean isByte​(int value)
    True if the value is in the signed byte range [-128, 127] or if it is in [128, 255] (in which case casting it to a byte yield a negative value which can be used to represent an unsigned byte value).
    static byte[] setRangeAt​(byte[] dst, int index, byte[] src)
    Sets dst[index, index + src.length] to src.
    static String toCompressedHexString​(byte[] bytes)
    Converts a byte array into a hex string (e.g.
    static String toFullHexString​(byte[] bytes)
    Converts a byte array into a hex string (e.g.
    static int toInt​(byte... bytes)
    Returns the integer encoded by the big-endian bytes array, whose size should be in [0,4].
    static long toLong​(byte... bytes)
    Returns the integer encoded by the big-endian bytes array, whose size should be in [0,8].
    static byte uadd​(int a, int b)
    Samed as addMod(int, int) but indicates that the numbers are intepreted as unsigned bytes, and that the addition should not overflow under that interpretation.
    static int uint​(byte b)
    Converts the byte to an int by reinterpreting its bit pattern as that of an unsigned number.

    Methods inherited from class java.lang.Object

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

  • Method Details

    • concat

      public static byte[] concat​(byte[]... bytes)
      Returns the concatenation of the byte arrays.

    • isByte

      public static boolean isByte​(int value)
      True if the value is in the signed byte range [-128, 127] or if it is in [128, 255] (in which case casting it to a byte yield a negative value which can be used to represent an unsigned byte value).

    • array

      public static byte[] array​(int... bytes)
      Short way to create an array of bytes that also allows 0-255 values.

    • uint

      public static int uint​(byte b)
      Converts the byte to an int by reinterpreting its bit pattern as that of an unsigned number.

    • addMod

      public static byte addMod​(int a, int b)
      Adds two bytes together with wrap-around behaviour (e.g. 127 + 1 == -128).

      This works whether you want to interpret the byte values as signed or unsigned (where this is equivalent to åddition modulo 255).

      In particular, this behaviour is helpful to implement unsigned byte addition: e.g. 127+127 will overflow to -129 == 256 - 127 which is the signed representation of 127.

      The arguments are supplied as integer, to avoid tiresome casting. Only integer values that can be legaly truncated to a byte value

    • uadd

      public static byte uadd​(int a, int b)
      Samed as addMod(int, int) but indicates that the numbers are intepreted as unsigned bytes, and that the addition should not overflow under that interpretation.

    • byteSize

      public static int byteSize​(int value)
      Returns the minimum number of bytes needed to store the integer. This returns 0 if the value is 0.

    • bytes

      public static byte[] bytes​(int value)
      Returns a byte array of size byteSize(value) encoding value in big-endian.

    • toInt

      public static int toInt​(byte... bytes)
      Returns the integer encoded by the big-endian bytes array, whose size should be in [0,4].

      Returns 0 if the byte array is of length 0, making this compatible with RLP-encoding of byte arrays.

    • toLong

      public static long toLong​(byte... bytes)
      Returns the integer encoded by the big-endian bytes array, whose size should be in [0,8].

      Returns 0 if the byte array is of length 0, making this compatible with RLP-encoding of byte arrays.

    • bytesPadded

      public static byte[] bytesPadded​(byte[] bytes, int length)
      Pads the given byte array to the given length by adding zeroes at the start.

      length should be bigger or equal to the array size.

    • bytesPadded

      public static byte[] bytesPadded​(BigInteger value, int length)
      Returns the big-endian encoding of value in bytes padded (at the start) with zeroes so that the length of the output is at least length.

      length should be bigger or equal than the length unpadded encoding of value, excluding the sign bit.

      This method does not require a sign bit to be included in the result, and should only be called with positive values.

    • bytesWithoutSign

      public static byte[] bytesWithoutSign​(BigInteger value)
      Returns the big-endian encoding of value in bytes, excluding any byte that would be included solely to signify the sign of the value.

      Attention: This means that the 0 big integer encodes as 0-length byte array. This is intended behaviour, as this is how Ethereum encodes such values.

    • setRangeAt

      public static byte[] setRangeAt​(byte[] dst, int index, byte[] src)
      Sets dst[index, index + src.length] to src.

    • copyOfSizedRange

      public static byte[] copyOfSizedRange​(byte[] array, int index, int size)
      Just like Arrays.copyOfRange(byte[], int, int), but allows passing a size instead of an end index.

    • hexDigitToByte

      public static byte hexDigitToByte​(char hex)
      Converts a hex digit (in 0-9, a-f or A-F) to its numeric value.

    • intToHexDigit

      public static char intToHexDigit​(int b)
      Converts an integer in [0, 15] into an hex digit (0..9 a..f).

    • hexStringToBytes

      public static byte[] hexStringToBytes​(String hexString)
      Converts a hex-string (e.g. "0x123") to a byte array, with the first digits occupying the first array slots. If there is odd number of digit, the first byte matches the first digit (its higher-order nibble (4 bits) will be 0).

      This accepts the empty hex string ("0x"), for which an empty array is returned.

    • hexStringToBytes

      public static byte[] hexStringToBytes​(String hexString, int minLen)
      Converts a hex-string (e.g. "0x123") in the same way as hexStringToBytes(String), but ensure the returned array will have at least the given minimum length.

      If the minimum size is larger than the natural size, the low-index bytes are left zeroed.

      This accepts the empty hex string ("0x"), for which an empty array is returned.

    • toFullHexString

      public static String toFullHexString​(byte[] bytes)
      Converts a byte array into a hex string (e.g. "0x123"). This hex string does display all bytes in the byte array, even if it starts with 0s.

      This returns "0x" for empty byte arrays.

      See Also:
      toCompressedHexString(byte[])

    • toCompressedHexString

      public static String toCompressedHexString​(byte[] bytes)
      Converts a byte array into a hex string (e.g. "0x123"). This hex string does not preserve the length of the byte array if it starts with 0s: the returned string never has leading 0s after the "0x" prefix.

      This returns "0x" for empty byte arrays, or arrays comprising only 0s.

      See Also:
      toFullHexString(byte[])