Package org.xerial.snappy

Class SnappyFramed

  • final class SnappyFramed
extends java.lang.Object
    Constants and utilities for implementing x-snappy-framed.
    Since:
    1.1.0

    • Constructor Summary

      Constructors 
      Constructor Description
      SnappyFramed()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static java.util.zip.Checksum getCRC32C()  
      static int mask​(int crc)
      Checksums are not stored directly, but masked, as checksumming data and then its own checksum can be problematic.
      static int maskedCrc32c​(java.util.zip.Checksum crc32c, byte[] data, int offset, int length)  
      (package private) static int readBytes​(java.nio.channels.ReadableByteChannel source, java.nio.ByteBuffer dest)  
      (package private) static int skip​(java.nio.channels.ReadableByteChannel source, int skip, java.nio.ByteBuffer buffer)  

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • CHECKSUM_SUPPLIER

        private static final java.util.function.Supplier<java.util.zip.Checksum> CHECKSUM_SUPPLIER

      • HEADER_BYTES

        public static final byte[] HEADER_BYTES
        The header consists of the stream identifier flag, 3 bytes indicating a length of 6, and "sNaPpY" in ASCII.

    • Constructor Detail

      • SnappyFramed

        SnappyFramed()

    • Method Detail

      • getCRC32C

        public static java.util.zip.Checksum getCRC32C()

      • maskedCrc32c

        public static int maskedCrc32c​(java.util.zip.Checksum crc32c,
                               byte[] data,
                               int offset,
                               int length)

      • mask

        public static int mask​(int crc)
        Checksums are not stored directly, but masked, as checksumming data and then its own checksum can be problematic. The masking is the same as used in Apache Hadoop: Rotate the checksum by 15 bits, then add the constant 0xa282ead8 (using wraparound as normal for unsigned integers). This is equivalent to the following C code: 

         uint32_t mask_checksum(uint32_t x) {
     return ((x >> 15) | (x << 17)) + 0xa282ead8;
 }

      • readBytes

        static final int readBytes​(java.nio.channels.ReadableByteChannel source,
                           java.nio.ByteBuffer dest)
                    throws java.io.IOException
        Throws:
        java.io.IOException

      • skip

        static int skip​(java.nio.channels.ReadableByteChannel source,
                int skip,
                java.nio.ByteBuffer buffer)
         throws java.io.IOException
        Throws:
        java.io.IOException