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org.apache.poi.util
Class LittleEndian

java.lang.Object
  extended by org.apache.poi.util.LittleEndian
All Implemented Interfaces:
LittleEndianConsts
public class LittleEndian
extends java.lang.Object
implements LittleEndianConsts

a utility class for handling little-endian numbers, which the 80x86 world is replete with. The methods are all static, and input/output is from/to byte arrays, or from InputStreams.

Author:
Marc Johnson (mjohnson at apache dot org), Andrew Oliver (acoliver at apache dot org)

Nested Class Summary
static class LittleEndian.BufferUnderrunException
          Exception to handle buffer underruns
 
Field Summary
 
Fields inherited from interface org.apache.poi.util.LittleEndianConsts
BYTE_SIZE, DOUBLE_SIZE, INT_SIZE, LONG_SIZE, SHORT_SIZE
 
Method Summary
static byte[] getByteArray(byte[] data, int offset, int size)
          Copy a portion of a byte array
static double getDouble(byte[] data)
          get a double value from the beginning of a byte array
static double getDouble(byte[] data, int offset)
          get a double value from a byte array, reads it in little endian format then converts the resulting revolting IEEE 754 (curse them) floating point number to a happy java double
static int getInt(byte[] data)
          get an int value from the beginning of a byte array
static int getInt(byte[] data, int offset)
          get an int value from a byte array
static long getLong(byte[] data)
          get a long value from the beginning of a byte array
static long getLong(byte[] data, int offset)
          get a long value from a byte array
static short getShort(byte[] data)
          get a short value from the beginning of a byte array
static short getShort(byte[] data, int offset)
          get a short value from a byte array
static short[] getShortArray(byte[] data, int offset)
          get a short array from a byte array.
static short[] getSimpleShortArray(byte[] data, int offset, int size)
          get a short array from a byte array.
static long getUInt(byte[] data)
          get an unsigned int value from a byte array
static long getUInt(byte[] data, int offset)
          get an unsigned int value from a byte array
static long getULong(byte[] data, int offset)
          Gets an unsigned int value (8 bytes) from a byte array.
static int getUnsignedByte(byte[] data)
          get the unsigned value of a byte.
static int getUnsignedByte(byte[] data, int offset)
          get the unsigned value of a byte.
static int getUShort(byte[] data)
          get an unsigned short value from the beginning of a byte array
static int getUShort(byte[] data, int offset)
          get an unsigned short value from a byte array
static void putByte(byte[] data, int offset, int value)
          executes:

data[offset] = (byte)value;

static void putDouble(byte[] data, double value)
          put a double value into beginning of a byte array
static void putDouble(byte[] data, int offset, double value)
          put a double value into a byte array
static void putInt(byte[] data, int value)
          put an int value into beginning of a byte array
static void putInt(byte[] data, int offset, int value)
          put an int value into a byte array
static void putLong(byte[] data, int offset, long value)
          put a long value into a byte array
static void putLong(byte[] data, long value)
          put a long value into beginning of a byte array
static void putShort(byte[] data, int offset, short value)
          put a short value into a byte array
static void putShort(byte[] data, short value)
          put a short value into beginning of a byte array
static void putShortArray(byte[] data, int offset, short[] value)
          put a array of shorts into a byte array
static void putUShort(byte[] data, int offset, int value)
          put an unsigned short value into a byte array
static byte[] readFromStream(java.io.InputStream stream, int size)
          Read the appropriate number of bytes from the stream and return them to the caller.
static int readInt(java.io.InputStream stream)
          get an int value from an InputStream
static long readLong(java.io.InputStream stream)
          get a long value from an InputStream
static short readShort(java.io.InputStream stream)
          get a short value from an InputStream
static int ubyteToInt(byte b)
          Convert an 'unsigned' byte to an integer.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

getShort

public static short getShort(byte[] data,
                             int offset)
get a short value from a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the short (16-bit) value

getUShort

public static int getUShort(byte[] data,
                            int offset)
get an unsigned short value from a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the unsigned short (16-bit) value in an integer

getSimpleShortArray

public static short[] getSimpleShortArray(byte[] data,
                                          int offset,
                                          int size)
get a short array from a byte array.

Parameters:
data - Description of the Parameter
offset - Description of the Parameter
size - Description of the Parameter
Returns:
The simpleShortArray value

getShortArray

public static short[] getShortArray(byte[] data,
                                    int offset)
get a short array from a byte array. The short array is assumed to start with a word describing the length of the array.

Parameters:
data - Description of the Parameter
offset - Description of the Parameter
Returns:
The shortArray value

getShort

public static short getShort(byte[] data)
get a short value from the beginning of a byte array

Parameters:
data - the byte array
Returns:
the short (16-bit) value

getUShort

public static int getUShort(byte[] data)
get an unsigned short value from the beginning of a byte array

Parameters:
data - the byte array
Returns:
the unsigned short (16-bit) value in an int

getInt

public static int getInt(byte[] data,
                         int offset)
get an int value from a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the int (32-bit) value

getInt

public static int getInt(byte[] data)
get an int value from the beginning of a byte array

Parameters:
data - the byte array
Returns:
the int (32-bit) value

getUInt

public static long getUInt(byte[] data,
                           int offset)
get an unsigned int value from a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the unsigned int (32-bit) value in a long

getUInt

public static long getUInt(byte[] data)
get an unsigned int value from a byte array

Parameters:
data - the byte array
Returns:
the unsigned int (32-bit) value in a long

getLong

public static long getLong(byte[] data,
                           int offset)
get a long value from a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the long (64-bit) value

getLong

public static long getLong(byte[] data)
get a long value from the beginning of a byte array

Parameters:
data - the byte array
Returns:
the long (64-bit) value

getDouble

public static double getDouble(byte[] data,
                               int offset)
get a double value from a byte array, reads it in little endian format then converts the resulting revolting IEEE 754 (curse them) floating point number to a happy java double

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the double (64-bit) value

getDouble

public static double getDouble(byte[] data)
get a double value from the beginning of a byte array

Parameters:
data - the byte array
Returns:
the double (64-bit) value

putShort

public static void putShort(byte[] data,
                            int offset,
                            short value)
put a short value into a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
value - the short (16-bit) value

putByte

public static void putByte(byte[] data,
                           int offset,
                           int value)
executes:

data[offset] = (byte)value;

Added for consistency with other put~() methods

putShortArray

public static void putShortArray(byte[] data,
                                 int offset,
                                 short[] value)
put a array of shorts into a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
value - the short array

putUShort

public static void putUShort(byte[] data,
                             int offset,
                             int value)
put an unsigned short value into a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
value - the short (16-bit) value
Throws:
java.lang.ArrayIndexOutOfBoundsException - may be thrown

putShort

public static void putShort(byte[] data,
                            short value)
put a short value into beginning of a byte array

Parameters:
data - the byte array
value - the short (16-bit) value

putInt

public static void putInt(byte[] data,
                          int offset,
                          int value)
put an int value into a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
value - the int (32-bit) value

putInt

public static void putInt(byte[] data,
                          int value)
put an int value into beginning of a byte array

Parameters:
data - the byte array
value - the int (32-bit) value

putLong

public static void putLong(byte[] data,
                           int offset,
                           long value)
put a long value into a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
value - the long (64-bit) value

putLong

public static void putLong(byte[] data,
                           long value)
put a long value into beginning of a byte array

Parameters:
data - the byte array
value - the long (64-bit) value

putDouble

public static void putDouble(byte[] data,
                             int offset,
                             double value)
put a double value into a byte array

Parameters:
data - the byte array
offset - a starting offset into the byte array
value - the double (64-bit) value

putDouble

public static void putDouble(byte[] data,
                             double value)
put a double value into beginning of a byte array

Parameters:
data - the byte array
value - the double (64-bit) value

readShort

public static short readShort(java.io.InputStream stream)
                       throws java.io.IOException,
                              LittleEndian.BufferUnderrunException
get a short value from an InputStream

Parameters:
stream - the InputStream from which the short is to be read
Returns:
the short (16-bit) value
Throws:
java.io.IOException - will be propagated back to the caller
LittleEndian.BufferUnderrunException - if the stream cannot provide enough bytes

readInt

public static int readInt(java.io.InputStream stream)
                   throws java.io.IOException,
                          LittleEndian.BufferUnderrunException
get an int value from an InputStream

Parameters:
stream - the InputStream from which the int is to be read
Returns:
the int (32-bit) value
Throws:
java.io.IOException - will be propagated back to the caller
LittleEndian.BufferUnderrunException - if the stream cannot provide enough bytes

readLong

public static long readLong(java.io.InputStream stream)
                     throws java.io.IOException,
                            LittleEndian.BufferUnderrunException
get a long value from an InputStream

Parameters:
stream - the InputStream from which the long is to be read
Returns:
the long (64-bit) value
Throws:
java.io.IOException - will be propagated back to the caller
LittleEndian.BufferUnderrunException - if the stream cannot provide enough bytes

readFromStream

public static byte[] readFromStream(java.io.InputStream stream,
                                    int size)
                             throws java.io.IOException,
                                    LittleEndian.BufferUnderrunException
Read the appropriate number of bytes from the stream and return them to the caller.

However, for the purposes of the POI project, this risk is deemed negligible. It is, however, so noted.

Parameters:
stream - the InputStream we're reading from
size - the number of bytes to read; in 99.99% of cases, this will be SHORT_SIZE, INT_SIZE, or LONG_SIZE -- but it doesn't have to be.
Returns:
the byte array containing the required number of bytes. The array will contain all zero's on end of stream
Throws:
java.io.IOException - will be propagated back to the caller
LittleEndian.BufferUnderrunException - if the stream cannot provide enough bytes

ubyteToInt

public static int ubyteToInt(byte b)
Convert an 'unsigned' byte to an integer. ie, don't carry across the sign.

Parameters:
b - Description of the Parameter
Returns:
Description of the Return Value

getUnsignedByte

public static int getUnsignedByte(byte[] data,
                                  int offset)
get the unsigned value of a byte.

Parameters:
data - the byte array.
offset - a starting offset into the byte array.
Returns:
the unsigned value of the byte as a 32 bit integer

getUnsignedByte

public static int getUnsignedByte(byte[] data)
get the unsigned value of a byte.

Parameters:
data - the byte array
Returns:
the unsigned value of the byte as a 32 bit integer

getByteArray

public static byte[] getByteArray(byte[] data,
                                  int offset,
                                  int size)
Copy a portion of a byte array

Parameters:
data - the original byte array
offset - Where to start copying from.
size - Number of bytes to copy.
Returns:
The byteArray value
Throws:
java.lang.IndexOutOfBoundsException - - if copying would cause access of data outside array bounds.

getULong

public static long getULong(byte[] data,
                            int offset)

Gets an unsigned int value (8 bytes) from a byte array.

Parameters:
data - the byte array
offset - a starting offset into the byte array
Returns:
the unsigned int (32-bit) value in a long
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