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 Summary

static long	computeCheckSum(byte[] buf) Compute the checksum of a tar entry header.
static int	formatCheckSumOctalBytes(long value, byte[] buf, int offset, int length) Writes an octal value into a buffer.
static int	formatLongOctalBytes(long value, byte[] buf, int offset, int length) Write an octal long integer into a buffer.
static int	formatNameBytes(String name, byte[] buf, int offset, int length) Copy a name (StringBuffer) into a buffer.
static int	formatOctalBytes(long value, byte[] buf, int offset, int length) Write an octal integer into a buffer.
static void	formatUnsignedOctalString(long value, byte[] buffer, int offset, int length) Fill buffer with unsigned octal number, padded with leading zeroes.
static String	parseName(byte[] buffer, int offset, int length) Parse an entry name from a buffer.
static long	parseOctal(byte[] buffer, int offset, int length) Parse an octal string from a buffer.

Methods inherited from class java.lang.Object

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

Method Detail

parseOctal

public static long parseOctal(byte[] buffer,
                              int offset,
                              int length)

Parse 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).

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 a invalid byte is detected.

parseName

public static String parseName(byte[] buffer,
                               int offset,
                               int length)

Parse 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.

formatNameBytes

public static int formatNameBytes(String name,
                                  byte[] buf,
                                  int offset,
                                  int length)

Copy a name (StringBuffer) 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

formatUnsignedOctalString

public static void formatUnsignedOctalString(long value,
                                             byte[] buffer,
                                             int offset,
                                             int length)

Fill 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

formatOctalBytes

public static int formatOctalBytes(long value,
                                   byte[] buf,
                                   int offset,
                                   int length)

Write 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

formatLongOctalBytes

public static int formatLongOctalBytes(long value,
                                       byte[] buf,
                                       int offset,
                                       int length)

Write 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

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

computeCheckSum

public static long computeCheckSum(byte[] buf)

Compute the checksum of a tar entry header.

Parameters:

buf - The tar entry's header buffer.

Returns:

The computed checksum.