com.google.common.hash

## Interface Hasher

- All Superinterfaces:
    PrimitiveSink

      @Beta
      public interface Hasher
      extends PrimitiveSink

  A `PrimitiveSink` that can compute a hash code after reading the input. Each hasher should translate all multibyte values (`putInt(int)`, `putLong(long)`, etc) to bytes in little-endian order.

  Warning: The result of calling any methods after calling `hash()` is undefined.

  Warning: Using a specific character encoding when hashing a `CharSequence` with `putString(CharSequence, Charset)` is generally only useful for cross-language compatibility (otherwise prefer `putUnencodedChars(java.lang.CharSequence)`). However, the character encodings must be identical across languages. Also beware that `Charset` definitions may occasionally change between Java releases.

  Warning: Chunks of data that are put into the `Hasher` are not delimited. The resulting `HashCode` is dependent only on the bytes inserted, and the order in which they were inserted, not how those bytes were chunked into discrete put() operations. For example, the following three expressions all generate colliding hash codes:

         newHasher().putByte(b1).putByte(b2).putByte(b3).hash()
         newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash()
         newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()

  If you wish to avoid this, you should either prepend or append the size of each chunk. Keep in mind that when dealing with char sequences, the encoded form of two concatenated char sequences is not equivalent to the concatenation of their encoded form. Therefore, `putString(CharSequence, Charset)` should only be used consistently with complete sequences and not broken into chunks.

  Since:
    11.0

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `HashCode` | `hash()` Computes a hash code based on the data that have been provided to this hasher.
    `int` | `hashCode()` Deprecated. This returns `Object.hashCode()`; you almost certainly mean to call `hash().asInt()`.
    `Hasher` | `putBoolean(boolean b)` Equivalent to `putByte(b ? (byte) 1 : (byte) 0)`.
    `Hasher` | `putByte(byte b)` Puts a byte into this sink.
    `Hasher` | `putBytes(byte[] bytes)` Puts an array of bytes into this sink.
    `Hasher` | `putBytes(byte[] bytes, int off, int len)` Puts a chunk of an array of bytes into this sink.
    `Hasher` | `putChar(char c)` Puts a character into this sink.
    `Hasher` | `putDouble(double d)` Equivalent to `putLong(Double.doubleToRawLongBits(d))`.
    `Hasher` | `putFloat(float f)` Equivalent to `putInt(Float.floatToRawIntBits(f))`.
    `Hasher` | `putInt(int i)` Puts an int into this sink.
    `Hasher` | `putLong(long l)` Puts a long into this sink.
    `<T> Hasher` | `putObject(T instance, Funnel<? super T> funnel)` A simple convenience for `funnel.funnel(object, this)`.
    `Hasher` | `putShort(short s)` Puts a short into this sink.
    `Hasher` | `putString(java.lang.CharSequence charSequence, java.nio.charset.Charset charset)` Equivalent to `putBytes(charSequence.toString().getBytes(charset))`.
    `Hasher` | `putUnencodedChars(java.lang.CharSequence charSequence)` Equivalent to processing each `char` value in the `CharSequence`, in order.

- - ### Method Detail

    - #### putByte

          Hasher putByte(byte b)

      Description copied from interface: `PrimitiveSink`
      Puts a byte into this sink.
      Specified by:
        `putByte` in interface `PrimitiveSink`
      Parameters:
        `b` - a byte
      Returns:
        this instance

    - #### putBytes

          Hasher putBytes(byte[] bytes)

      Description copied from interface: `PrimitiveSink`
      Puts an array of bytes into this sink.
      Specified by:
        `putBytes` in interface `PrimitiveSink`
      Parameters:
        `bytes` - a byte array
      Returns:
        this instance

    - #### putBytes

          Hasher putBytes(byte[] bytes,
                        int off,
                        int len)

      Description copied from interface: `PrimitiveSink`
      Puts a chunk of an array of bytes into this sink. `bytes[off]` is the first byte written, `bytes[off + len - 1]` is the last.
      Specified by:
        `putBytes` in interface `PrimitiveSink`
      Parameters:
        `bytes` - a byte array
        `off` - the start offset in the array
        `len` - the number of bytes to write
      Returns:
        this instance

    - #### putShort

          Hasher putShort(short s)

      Description copied from interface: `PrimitiveSink`
      Puts a short into this sink.
      Specified by:
        `putShort` in interface `PrimitiveSink`

    - #### putInt

          Hasher putInt(int i)

      Description copied from interface: `PrimitiveSink`
      Puts an int into this sink.
      Specified by:
        `putInt` in interface `PrimitiveSink`

    - #### putLong

          Hasher putLong(long l)

      Description copied from interface: `PrimitiveSink`
      Puts a long into this sink.
      Specified by:
        `putLong` in interface `PrimitiveSink`

    - #### putFloat

          Hasher putFloat(float f)

      Equivalent to `putInt(Float.floatToRawIntBits(f))`.
      Specified by:
        `putFloat` in interface `PrimitiveSink`

    - #### putDouble

          Hasher putDouble(double d)

      Equivalent to `putLong(Double.doubleToRawLongBits(d))`.
      Specified by:
        `putDouble` in interface `PrimitiveSink`

    - #### putBoolean

          Hasher putBoolean(boolean b)

      Equivalent to `putByte(b ? (byte) 1 : (byte) 0)`.
      Specified by:
        `putBoolean` in interface `PrimitiveSink`

    - #### putChar

          Hasher putChar(char c)

      Description copied from interface: `PrimitiveSink`
      Puts a character into this sink.
      Specified by:
        `putChar` in interface `PrimitiveSink`

    - #### putUnencodedChars

          Hasher putUnencodedChars(java.lang.CharSequence charSequence)

      Equivalent to processing each `char` value in the `CharSequence`, in order. The input must not be updated while this method is in progress.
      Specified by:
        `putUnencodedChars` in interface `PrimitiveSink`
      Since:
        15.0 (since 11.0 as putString(CharSequence)).

    - #### putString

          Hasher putString(java.lang.CharSequence charSequence,
                         java.nio.charset.Charset charset)

      Equivalent to `putBytes(charSequence.toString().getBytes(charset))`.
      Specified by:
        `putString` in interface `PrimitiveSink`

    - #### putObject

          <T> Hasher putObject(T instance,
                             Funnel<? super T> funnel)

      A simple convenience for `funnel.funnel(object, this)`.

    - #### hash

          @CheckReturnValue
          HashCode hash()

      Computes a hash code based on the data that have been provided to this hasher. The result is unspecified if this method is called more than once on the same instance.

    - #### hashCode

          @Deprecated
          int hashCode()

      Deprecated. This returns `Object.hashCode()`; you almost certainly mean to call `hash().asInt()`.
      Overrides:
        `hashCode` in class `java.lang.Object`