Package org.apache.commons.codec.digest

Class GitIdentifiers

  • public class GitIdentifiers
extends java.lang.Object
    Computes Git object identifiers and their generalizations described by the SWHID specification.

    When the hash algorithm is SHA-1, the identifiers produced by this class are identical to those used by Git. Other hash algorithms produce generalized identifiers as described by the SWHID specification.

    This class is immutable and thread-safe. However, the MessageDigest instances passed to it generally won't be.

    Since:
    1.22.0
    See Also:
    Git Internals – Git Objects, SWHID Specification

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      (package private) static class  GitIdentifiers.DirectoryEntry
      Represents a single entry in a Git tree object.
      static class  GitIdentifiers.FileMode
      The type of a Git tree entry, which maps to a Unix file-mode string.
      static class  GitIdentifiers.TreeIdBuilder
      Builds a Git tree identifier for a virtual directory structure, such as the contents of an archive.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private GitIdentifiers()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static byte[] blobId​(java.security.MessageDigest messageDigest, byte[] data)
      Reads through a byte array and returns a generalized Git blob identifier.
      static byte[] blobId​(java.security.MessageDigest messageDigest, long dataSize, java.io.InputStream data)
      Reads through a stream of known size and returns a generalized Git blob identifier, without buffering.
      static byte[] blobId​(java.security.MessageDigest messageDigest, java.nio.file.Path data)
      Reads through a file and returns a generalized Git blob identifier.
      private static byte[] getGitBlobPrefix​(long dataSize)  
      private static byte[] getGitPrefix​(java.lang.String type, long dataSize)  
      private static byte[] getGitTreePrefix​(long dataSize)  
      static byte[] treeId​(java.security.MessageDigest messageDigest, java.nio.file.Path data)
      Reads through a directory and returns a generalized Git tree identifier.
      static GitIdentifiers.TreeIdBuilder treeIdBuilder​(java.security.MessageDigest messageDigest)
      Returns a new GitIdentifiers.TreeIdBuilder for constructing a generalized Git tree identifier from a virtual directory structure, such as the contents of an archive.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • GitIdentifiers

        private GitIdentifiers()

    • Method Detail

      • blobId

        public static byte[] blobId​(java.security.MessageDigest messageDigest,
                            byte[] data)
        Reads through a byte array and returns a generalized Git blob identifier.

        The identifier is computed in the way described by the SWHID contents identifier, but it can use any hash algorithm.

        When the hash algorithm is SHA-1, the identifier is identical to Git blob identifier and SWHID contents identifier.

        Parameters:
        messageDigest - The MessageDigest to use (for example SHA-1).
        data - Data to digest.
        Returns:
        A generalized Git blob identifier.

      • blobId

        public static byte[] blobId​(java.security.MessageDigest messageDigest,
                            long dataSize,
                            java.io.InputStream data)
                     throws java.io.IOException
        Reads through a stream of known size and returns a generalized Git blob identifier, without buffering.

        When the size of the content is known in advance, this overload streams data directly through the digest without buffering the full content in memory.

        When the hash algorithm is SHA-1, the identifier is identical to Git blob identifier and SWHID contents identifier.

        Parameters:
        messageDigest - The MessageDigest to use (for example SHA-1).
        dataSize - The exact number of bytes in data.
        data - Stream to digest.
        Returns:
        A generalized Git blob identifier.
        Throws:
        java.io.IOException - On error reading the stream.

      • blobId

        public static byte[] blobId​(java.security.MessageDigest messageDigest,
                            java.nio.file.Path data)
                     throws java.io.IOException
        Reads through a file and returns a generalized Git blob identifier.

        The identifier is computed in the way described by the SWHID contents identifier, but it can use any hash algorithm.

        When the hash algorithm is SHA-1, the identifier is identical to Git blob identifier and SWHID contents identifier.

        Parameters:
        messageDigest - The MessageDigest to use (for example SHA-1).
        data - Path to the file to digest.
        Returns:
        A generalized Git blob identifier.
        Throws:
        java.io.IOException - On error accessing the file.

      • getGitBlobPrefix

        private static byte[] getGitBlobPrefix​(long dataSize)

      • getGitPrefix

        private static byte[] getGitPrefix​(java.lang.String type,
                                   long dataSize)

      • getGitTreePrefix

        private static byte[] getGitTreePrefix​(long dataSize)

      • treeId

        public static byte[] treeId​(java.security.MessageDigest messageDigest,
                            java.nio.file.Path data)
                     throws java.io.IOException
        Reads through a directory and returns a generalized Git tree identifier.

        The identifier is computed in the way described by the SWHID directory identifier, but it can use any hash algorithm.

        When the hash algorithm is SHA-1, the identifier is identical to Git tree identifier and SWHID directory identifier.

        Parameters:
        messageDigest - The MessageDigest to use (for example SHA-1).
        data - Path to the directory to digest.
        Returns:
        A generalized Git tree identifier.
        Throws:
        java.io.IOException - On error accessing the directory or its contents.

      • treeIdBuilder

        public static GitIdentifiers.TreeIdBuilder treeIdBuilder​(java.security.MessageDigest messageDigest)
        Returns a new GitIdentifiers.TreeIdBuilder for constructing a generalized Git tree identifier from a virtual directory structure, such as the contents of an archive.

        The identifier is computed in the way described by the SWHID directory identifier, but it can use any hash algorithm.

        When the hash algorithm is SHA-1, the identifier is identical to Git tree identifier and SWHID directory identifier.

        Parameters:
        messageDigest - The MessageDigest to use (for example SHA-1).
        Returns:
        A new GitIdentifiers.TreeIdBuilder.