Package org.apache.commons.compress.archivers.tar

Class TarUtils

java.lang.Object
org.apache.commons.compress.archivers.tar.TarUtils
public class TarUtils extends Object
This class provides static utility methods to work with byte streams.
This class is immutable

  • Method Details

    • computeCheckSum

      public static long computeCheckSum(byte[] buf)
      Computes the checksum of a tar entry header.
      Parameters:
      buf - The tar entry's header buffer.
      Returns:
      The computed checksum.

    • formatCheckSumOctalBytes

      public static int formatCheckSumOctalBytes(long value, byte[] buf, int offset, int length)
      Writes an octal value into a buffer. Uses formatUnsignedOctalString(long, byte[], int, int) to format the value as an octal string with leading zeros. The converted number is followed by NUL and then space.
      Parameters:
      value - The value to convert
      buf - The destination buffer
      offset - The starting offset into the buffer.
      length - The size of the buffer.
      Returns:
      The updated value of offset, i.e. offset+length
      Throws:
      IllegalArgumentException - if the value (and trailer) will not fit in the buffer

    • formatLongOctalBytes

      public static int formatLongOctalBytes(long value, byte[] buf, int offset, int length)
      Writes an octal long integer into a buffer. Uses formatUnsignedOctalString(long, byte[], int, int) to format the value as an octal string with leading zeros. The converted number is followed by a space.
      Parameters:
      value - The value to write as octal
      buf - The destinationbuffer.
      offset - The starting offset into the buffer.
      length - The length of the buffer
      Returns:
      The updated offset
      Throws:
      IllegalArgumentException - if the value (and trailer) will not fit in the buffer

    • formatLongOctalOrBinaryBytes

      public static int formatLongOctalOrBinaryBytes(long value, byte[] buf, int offset, int length)
      Writes a long integer into a buffer as an octal string if this will fit, or as a binary number otherwise. Uses formatUnsignedOctalString(long, byte[], int, int) to format the value as an octal string with leading zeros. The converted number is followed by a space.
      Parameters:
      value - The value to write into the buffer.
      buf - The destination buffer.
      offset - The starting offset into the buffer.
      length - The length of the buffer.
      Returns:
      The updated offset.
      Throws:
      IllegalArgumentException - if the value (and trailer) will not fit in the buffer.
      Since:
      1.4

    • formatNameBytes

      public static int formatNameBytes(String name, byte[] buf, int offset, int length)
      Copies a name into a buffer. Copies characters from the name into the buffer starting at the specified offset. If the buffer is longer than the name, the buffer is filled with trailing NULs. If the name is longer than the buffer, the output is truncated.
      Parameters:
      name - The header name from which to copy the characters.
      buf - The buffer where the name is to be stored.
      offset - The starting offset into the buffer
      length - The maximum number of header bytes to copy.
      Returns:
      The updated offset, i.e. offset + length

    • formatNameBytes

      public static int formatNameBytes(String name, byte[] buf, int offset, int length, ZipEncoding encoding) throws IOException
      Copies a name into a buffer. Copies characters from the name into the buffer starting at the specified offset. If the buffer is longer than the name, the buffer is filled with trailing NULs. If the name is longer than the buffer, the output is truncated.
      Parameters:
      name - The header name from which to copy the characters.
      buf - The buffer where the name is to be stored.
      offset - The starting offset into the buffer
      length - The maximum number of header bytes to copy.
      encoding - name of the encoding to use for file names
      Returns:
      The updated offset, i.e. offset + length
      Throws:
      IOException - on error
      Since:
      1.4

    • formatOctalBytes

      public static int formatOctalBytes(long value, byte[] buf, int offset, int length)
      Writes an octal integer into a buffer. Uses formatUnsignedOctalString(long, byte[], int, int) to format the value as an octal string with leading zeros. The converted number is followed by space and NUL
      Parameters:
      value - The value to write
      buf - The buffer to receive the output
      offset - The starting offset into the buffer
      length - The size of the output buffer
      Returns:
      The updated offset, i.e. offset+length
      Throws:
      IllegalArgumentException - if the value (and trailer) will not fit in the buffer

    • formatUnsignedOctalString

      public static void formatUnsignedOctalString(long value, byte[] buffer, int offset, int length)
      Fills a buffer with unsigned octal number, padded with leading zeroes.
      Parameters:
      value - number to convert to octal - treated as unsigned
      buffer - destination buffer
      offset - starting offset in buffer
      length - length of buffer to fill
      Throws:
      IllegalArgumentException - if the value will not fit in the buffer

    • parseBoolean

      public static boolean parseBoolean(byte[] buffer, int offset)
      Parses a boolean byte from a buffer. Leading spaces and NUL are ignored. The buffer may contain trailing spaces or NULs.
      Parameters:
      buffer - The buffer from which to parse.
      offset - The offset into the buffer from which to parse.
      Returns:
      The boolean value of the bytes.
      Throws:
      IllegalArgumentException - if an invalid byte is detected.

    • parseFromPAX01SparseHeaders

      protected static List<TarArchiveStructSparse> parseFromPAX01SparseHeaders(String sparseMap) throws IOException
      For PAX Format 0.1, the sparse headers are stored in a single variable : GNU.sparse.map GNU.sparse.map Map of non-null data chunks. It is a string consisting of comma-separated values "offset,size[,offset-1,size-1...]"
      Parameters:
      sparseMap - the sparse map string consisting of comma-separated values "offset,size[,offset-1,size-1...]"
      Returns:
      unmodifiable list of sparse headers parsed from sparse map
      Throws:
      IOException - Corrupted TAR archive.
      Since:
      1.21

    • parseName

      public static String parseName(byte[] buffer, int offset, int length)
      Parses an entry name from a buffer. Parsing stops when a NUL is found or the buffer length is reached.
      Parameters:
      buffer - The buffer from which to parse.
      offset - The offset into the buffer from which to parse.
      length - The maximum number of bytes to parse.
      Returns:
      The entry name.

    • parseName

      public static String parseName(byte[] buffer, int offset, int length, ZipEncoding encoding) throws IOException
      Parses an entry name from a buffer. Parsing stops when a NUL is found or the buffer length is reached.
      Parameters:
      buffer - The buffer from which to parse.
      offset - The offset into the buffer from which to parse.
      length - The maximum number of bytes to parse.
      encoding - name of the encoding to use for file names
      Returns:
      The entry name.
      Throws:
      IOException - on error
      Since:
      1.4

    • parseOctal

      public static long parseOctal(byte[] buffer, int offset, int length)
      Parses an octal string from a buffer.

      Leading spaces are ignored. The buffer must contain a trailing space or NUL, and may contain an additional trailing space or NUL.

      The input buffer is allowed to contain all NULs, in which case the method returns 0L (this allows for missing fields).

      To work-around some tar implementations that insert a leading NUL this method returns 0 if it detects a leading NUL since Commons Compress 1.4.

      Parameters:
      buffer - The buffer from which to parse.
      offset - The offset into the buffer from which to parse.
      length - The maximum number of bytes to parse - must be at least 2 bytes.
      Returns:
      The long value of the octal string.
      Throws:
      IllegalArgumentException - if the trailing space/NUL is missing or if an invalid byte is detected.

    • parseOctalOrBinary

      public static long parseOctalOrBinary(byte[] buffer, int offset, int length)
      Computes the value contained in a byte buffer. If the most significant bit of the first byte in the buffer is set, this bit is ignored and the rest of the buffer is interpreted as a binary number. Otherwise, the buffer is interpreted as an octal number as per the parseOctal function above.
      Parameters:
      buffer - The buffer from which to parse.
      offset - The offset into the buffer from which to parse.
      length - The maximum number of bytes to parse.
      Returns:
      The long value of the octal or binary string.
      Throws:
      IllegalArgumentException - if the trailing space/NUL is missing or an invalid byte is detected in an octal number, or if a binary number would exceed the size of a signed long 64-bit integer.
      Since:
      1.4

    • parsePAX01SparseHeaders

      @Deprecated protected static List<TarArchiveStructSparse> parsePAX01SparseHeaders(String sparseMap)
      Deprecated.
      use #parseFromPAX01SparseHeaders instead
      For PAX Format 0.1, the sparse headers are stored in a single variable : GNU.sparse.map

      GNU.sparse.map: Map of non-null data chunks. It is a string consisting of comma-separated values "offset,size[,offset-1,size-1...]"

      Will internally invoke parseFromPAX01SparseHeaders(java.lang.String) and map IOExceptions to a RzuntimeException, You should use parseFromPAX01SparseHeaders(java.lang.String) directly instead.

      Parameters:
      sparseMap - the sparse map string consisting of comma-separated values "offset,size[,offset-1,size-1...]"
      Returns:
      sparse headers parsed from sparse map

    • parsePAX1XSparseHeaders

      protected static List<TarArchiveStructSparse> parsePAX1XSparseHeaders(InputStream inputStream, int recordSize) throws IOException
      For PAX Format 1.X: The sparse map itself is stored in the file data block, preceding the actual file data. It consists of a series of decimal numbers delimited by newlines. The map is padded with nulls to the nearest block boundary. The first number gives the number of entries in the map. Following are map entries, each one consisting of two numbers giving the offset and size of the data block it describes.
      Parameters:
      inputStream - parsing source.
      recordSize - The size the TAR header
      Returns:
      sparse headers
      Throws:
      IOException - if an I/O error occurs.

    • parsePaxHeaders

      @Deprecated protected static Map<String,String> parsePaxHeaders(InputStream inputStream, List<TarArchiveStructSparse> sparseHeaders, Map<String,String> globalPaxHeaders) throws IOException
      Deprecated.
      use the four-arg version instead
      For PAX Format 0.0, the sparse headers(GNU.sparse.offset and GNU.sparse.numbytes) may appear multi times, and they look like: 
       GNU.sparse.size=size
 GNU.sparse.numblocks=numblocks
 repeat numblocks times
   GNU.sparse.offset=offset
   GNU.sparse.numbytes=numbytes
 end repeat

      For PAX Format 0.1, the sparse headers are stored in a single variable: GNU.sparse.map

      GNU.sparse.map: Map of non-null data chunks. It is a string consisting of comma-separated values "offset,size[,offset-1,size-1...]"

      Parameters:
      inputStream - input stream to read keys and values
      sparseHeaders - used in PAX Format 0.0 & 0.1, as it may appear multiple times, the sparse headers need to be stored in an array, not a map
      globalPaxHeaders - global PAX headers of the tar archive
      Returns:
      map of PAX headers values found inside the current (local or global) PAX headers tar entry.
      Throws:
      IOException - if an I/O error occurs.

    • parsePaxHeaders

      protected static Map<String,String> parsePaxHeaders(InputStream inputStream, List<TarArchiveStructSparse> sparseHeaders, Map<String,String> globalPaxHeaders, long headerSize) throws IOException
      For PAX Format 0.0, the sparse headers(GNU.sparse.offset and GNU.sparse.numbytes) may appear multi times, and they look like: 
       GNU.sparse.size=size
 GNU.sparse.numblocks=numblocks
 repeat numblocks times
   GNU.sparse.offset=offset
   GNU.sparse.numbytes=numbytes
 end repeat

      For PAX Format 0.1, the sparse headers are stored in a single variable : GNU.sparse.map

      GNU.sparse.map: Map of non-null data chunks. It is a string consisting of comma-separated values "offset,size[,offset-1,size-1...]"

      Parameters:
      inputStream - input stream to read keys and values
      sparseHeaders - used in PAX Format 0.0 & 0.1, as it may appear multiple times, the sparse headers need to be stored in an array, not a map
      globalPaxHeaders - global PAX headers of the tar archive
      headerSize - total size of the PAX header, will be ignored if negative
      Returns:
      map of PAX headers values found inside the current (local or global) PAX headers tar entry.
      Throws:
      IOException - if an I/O error occurs.
      Since:
      1.21

    • parseSparse

      public static TarArchiveStructSparse parseSparse(byte[] buffer, int offset)
      Parses the content of a PAX 1.0 sparse block.
      Parameters:
      buffer - The buffer from which to parse.
      offset - The offset into the buffer from which to parse.
      Returns:
      a parsed sparse struct
      Since:
      1.20

    • verifyCheckSum

      public static boolean verifyCheckSum(byte[] header)
      Wikipedia says:
      The checksum is calculated by taking the sum of the unsigned byte values of the header block with the eight checksum bytes taken to be ASCII spaces (decimal value 32). It is stored as a six digit octal number with leading zeroes followed by a NUL and then a space. Various implementations do not adhere to this format. For better compatibility, ignore leading and trailing whitespace, and get the first six digits. In addition, some historic tar implementations treated bytes as signed. Implementations typically calculate the checksum both ways, and treat it as good if either the signed or unsigned sum matches the included checksum.

      The return value of this method should be treated as a best-effort heuristic rather than an absolute and final truth. The checksum verification logic may well evolve over time as more special cases are encountered.

      Parameters:
      header - tar header
      Returns:
      whether the checksum is reasonably good
      Since:
      1.5
      See Also: