Class CodecUtil

Utility class for reading and writing versioned headers.

Writing codec headers is useful to ensure that a file is in the format you think it is.

@lucene.experimental

Inheritance
System.Object
CodecUtil
Assembly: DistributedLucene.Net.dll
Syntax
public sealed class CodecUtil : object

Fields

Name Description
CODEC_MAGIC

Constant to identify the start of a codec header.

Constant to identify the start of a codec footer.

Methods

Name Description
CheckEOF(IndexInput)

Checks that the stream is positioned at the end, and throws exception if it is not.

CheckFooter(ChecksumIndexInput)

Validates the codec footer previously written by WriteFooter(IndexOutput).

CheckHeader(DataInput, String, Int32, Int32)

Reads and validates a header previously written with WriteHeader(DataOutput, String, Int32).

When reading a file, supply the expected codec and an expected version range (minVersion to maxVersion).
CheckHeaderNoMagic(DataInput, String, Int32, Int32)

Like CheckHeader(DataInput, String, Int32, Int32) except this version assumes the first has already been read and validated from the input.
ChecksumEntireFile(IndexInput)

Clones the provided input, reads all bytes from the file, and calls CheckFooter(ChecksumIndexInput)

Note that this method may be slow, as it must process the entire file. If you just need to extract the checksum value, call RetrieveChecksum(IndexInput).
FooterLength()

Computes the length of a codec footer.
HeaderLength(String)

Computes the length of a codec header.
RetrieveChecksum(IndexInput)

Returns (but does not validate) the checksum previously written by CheckFooter(ChecksumIndexInput).

WriteFooter(IndexOutput)

Writes a codec footer, which records both a checksum algorithm ID and a checksum. This footer can be parsed and validated with CheckFooter(ChecksumIndexInput).

CodecFooter --> Magic,AlgorithmID,Checksum

  • Magic --> Uint32 (WriteInt32(Int32)). this identifies the start of the footer. It is always FOOTER_MAGIC.
  • AlgorithmID --> Uint32 (WriteInt32(Int32)). this indicates the checksum algorithm used. Currently this is always 0, for zlib-crc32.
  • Checksum --> Uint32 (WriteInt64(Int64)). The actual checksum value for all previous bytes in the stream, including the bytes from Magic and AlgorithmID.
WriteHeader(DataOutput, String, Int32)

Writes a codec header, which records both a string to identify the file and a version number. This header can be parsed and validated with CheckHeader(DataInput, String, Int32, Int32).

CodecHeader --> Magic,CodecName,Version

Note that the length of a codec header depends only upon the name of the codec, so this length can be computed at any time with HeaderLength(String).

Extension Methods