TarUtils (Apache Commons Compress 1.13 API)

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

Methods
Modifier and Type	Method and Description
`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`	`formatLongOctalOrBinaryBytes(long value, byte[] buf, int offset, int length)` Write an long integer into a buffer as an octal string if this will fit, or as a binary number otherwise.
`static int`	`formatNameBytes(String name, byte[] buf, int offset, int length)` Copy a name into a buffer.
`static int`	`formatNameBytes(String name, byte[] buf, int offset, int length, ZipEncoding encoding)` Copy a name 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 boolean`	`parseBoolean(byte[] buffer, int offset)` Parse a boolean byte from a buffer.
`static String`	`parseName(byte[] buffer, int offset, int length)` Parse an entry name from a buffer.
`static String`	`parseName(byte[] buffer, int offset, int length, ZipEncoding encoding)` Parse an entry name from a buffer.
`static long`	`parseOctal(byte[] buffer, int offset, int length)` Parse an octal string from a buffer.
`static long`	`parseOctalOrBinary(byte[] buffer, int offset, int length)` Compute the value contained in a byte buffer.
`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).

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).
    
    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 a invalid byte is detected.
  - parseOctalOrBinary
```
public static long parseOctalOrBinary(byte[] buffer,
                      int offset,
                      int length)
```
    Compute 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
  - parseBoolean
```
public static boolean parseBoolean(byte[] buffer,
                   int offset)
```
    Parse 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.
  - 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.
  - parseName
```
public static String parseName(byte[] buffer,
               int offset,
               int length,
               ZipEncoding encoding)
                        throws IOException
```
    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.
    encoding - name of the encoding to use for file names
    
    Returns:
    The entry name.
    
    Throws:
    
    IOException - on error
    Since:
    
    1.4
  - formatNameBytes
```
public static int formatNameBytes(String name,
                  byte[] buf,
                  int offset,
                  int length)
```
    Copy 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
```
    Copy 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
  - 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
  - formatLongOctalOrBinaryBytes
```
public static int formatLongOctalOrBinaryBytes(long value,
                               byte[] buf,
                               int offset,
                               int length)
```
    Write an 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
  - 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.
  - 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:
    COMPRESS-191

Class TarUtils

Method Summary

Methods inherited from class java.lang.Object

Method Detail

parseOctal

parseOctalOrBinary

parseBoolean

parseName

parseName

formatNameBytes

formatNameBytes

formatUnsignedOctalString

formatOctalBytes

formatLongOctalBytes

formatLongOctalOrBinaryBytes

formatCheckSumOctalBytes

computeCheckSum

verifyCheckSum