org.apache.commons.io.input

Class BOMInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

org.apache.commons.io.input.ProxyInputStream

org.apache.commons.io.input.BOMInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class BOMInputStream
extends ProxyInputStream

This class is used to wrap a stream that includes an encoded ByteOrderMark as its first bytes. This class detects these bytes and, if required, can automatically skip them and return the subsequent byte as the first byte in the stream. The ByteOrderMark implementation has the following pre-defined BOMs:

• UTF-8 - ByteOrderMark.UTF_8
• UTF-16BE - ByteOrderMark.UTF_16LE
• UTF-16LE - ByteOrderMark.UTF_16BE
• UTF-32BE - ByteOrderMark.UTF_32LE
• UTF-32LE - ByteOrderMark.UTF_32BE

Example 1 - Detect and exclude a UTF-8 BOM

 BOMInputStream bomIn = new BOMInputStream(in);
 if (bomIn.hasBOM()) {
     // has a UTF-8 BOM
 }
 

Example 2 - Detect a UTF-8 BOM (but don't exclude it)

 boolean include = true;
 BOMInputStream bomIn = new BOMInputStream(in, include);
 if (bomIn.hasBOM()) {
     // has a UTF-8 BOM
 }
 

Example 3 - Detect Multiple BOMs

 BOMInputStream bomIn = new BOMInputStream(in,
   ByteOrderMark.UTF_16LE, ByteOrderMark.UTF_16BE,
   ByteOrderMark.UTF_32LE, ByteOrderMark.UTF_32BE
   );
 if (bomIn.hasBOM() == false) {
     // No BOM found
 } else if (bomIn.hasBOM(ByteOrderMark.UTF_16LE)) {
     // has a UTF-16LE BOM
 } else if (bomIn.hasBOM(ByteOrderMark.UTF_16BE)) {
     // has a UTF-16BE BOM
 } else if (bomIn.hasBOM(ByteOrderMark.UTF_32LE)) {
     // has a UTF-32LE BOM
 } else if (bomIn.hasBOM(ByteOrderMark.UTF_32BE)) {
     // has a UTF-32BE BOM
 }
 

Since:

2.0

See Also:

ByteOrderMark, Wikipedia - Byte Order Mark

Constructor Summary

Constructors

Constructor and Description
BOMInputStream(InputStream delegate) Constructs a new BOM InputStream that excludes a ByteOrderMark.UTF_8 BOM.
BOMInputStream(InputStream delegate, boolean include) Constructs a new BOM InputStream that detects a a ByteOrderMark.UTF_8 and optionally includes it.
BOMInputStream(InputStream delegate, boolean include, ByteOrderMark... boms) Constructs a new BOM InputStream that detects the specified BOMs and optionally includes them.
BOMInputStream(InputStream delegate, ByteOrderMark... boms) Constructs a new BOM InputStream that excludes the specified BOMs.

Method Summary

Modifier and Type	Method and Description
ByteOrderMark	getBOM() Return the BOM (Byte Order Mark).
String	getBOMCharsetName() Return the BOM charset Name - ByteOrderMark.getCharsetName().
boolean	hasBOM() Indicates whether the stream contains one of the specified BOMs.
boolean	hasBOM(ByteOrderMark bom) Indicates whether the stream contains the specified BOM.
void	mark(int readlimit) Invokes the delegate's mark(int) method.
int	read() Invokes the delegate's read() method, detecting and optionally skipping BOM.
int	read(byte[] buf) Invokes the delegate's read(byte[]) method, detecting and optionally skipping BOM.
int	read(byte[] buf, int off, int len) Invokes the delegate's read(byte[], int, int) method, detecting and optionally skipping BOM.
void	reset() Invokes the delegate's reset() method.
long	skip(long n) Invokes the delegate's skip(long) method, detecting and optionally skipping BOM.

Methods inherited from class org.apache.commons.io.input.ProxyInputStream

available, close, markSupported

Methods inherited from class java.lang.Object

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

Constructor Detail

BOMInputStream

public BOMInputStream(InputStream delegate)

Constructs a new BOM InputStream that excludes a ByteOrderMark.UTF_8 BOM.

Parameters:

delegate - the InputStream to delegate to

BOMInputStream

public BOMInputStream(InputStream delegate,
                      boolean include)

Constructs a new BOM InputStream that detects a a ByteOrderMark.UTF_8 and optionally includes it.

Parameters:

delegate - the InputStream to delegate to

include - true to include the UTF-8 BOM or false to exclude it

BOMInputStream

public BOMInputStream(InputStream delegate,
                      ByteOrderMark... boms)

Constructs a new BOM InputStream that excludes the specified BOMs.

Parameters:

delegate - the InputStream to delegate to

boms - The BOMs to detect and exclude

BOMInputStream

public BOMInputStream(InputStream delegate,
                      boolean include,
                      ByteOrderMark... boms)

Constructs a new BOM InputStream that detects the specified BOMs and optionally includes them.

Parameters:

delegate - the InputStream to delegate to

include - true to include the specified BOMs or false to exclude them

boms - The BOMs to detect and optionally exclude

Method Detail

hasBOM

public boolean hasBOM()
               throws IOException

Indicates whether the stream contains one of the specified BOMs.

Returns:

true if the stream has one of the specified BOMs, otherwise false if it does not

Throws:

IOException - if an error reading the first bytes of the stream occurs

hasBOM

public boolean hasBOM(ByteOrderMark bom)
               throws IOException

Indicates whether the stream contains the specified BOM.

Parameters:

bom - The BOM to check for

Returns:

true if the stream has the specified BOM, otherwise false if it does not

Throws:

IllegalArgumentException - if the BOM is not one the stream is configured to detect

IOException - if an error reading the first bytes of the stream occurs

getBOM

public ByteOrderMark getBOM()
                     throws IOException

Return the BOM (Byte Order Mark).

Returns:

The BOM or null if none

Throws:

IOException - if an error reading the first bytes of the stream occurs

getBOMCharsetName

public String getBOMCharsetName()
                         throws IOException

Return the BOM charset Name - ByteOrderMark.getCharsetName().

Returns:

The BOM charset Name or null if no BOM found

Throws:

IOException - if an error reading the first bytes of the stream occurs

read

public int read()
         throws IOException

Invokes the delegate's read() method, detecting and optionally skipping BOM.

Overrides:

read in class ProxyInputStream

Returns:

the byte read (excluding BOM) or -1 if the end of stream

Throws:

IOException - if an I/O error occurs

read

public int read(byte[] buf,
                int off,
                int len)
         throws IOException

Invokes the delegate's read(byte[], int, int) method, detecting and optionally skipping BOM.

Overrides:

read in class ProxyInputStream

Parameters:

buf - the buffer to read the bytes into

off - The start offset

len - The number of bytes to read (excluding BOM)

Returns:

the number of bytes read or -1 if the end of stream

Throws:

IOException - if an I/O error occurs

read

public int read(byte[] buf)
         throws IOException

Invokes the delegate's read(byte[]) method, detecting and optionally skipping BOM.

Overrides:

read in class ProxyInputStream

Parameters:

buf - the buffer to read the bytes into

Returns:

the number of bytes read (excluding BOM) or -1 if the end of stream

Throws:

IOException - if an I/O error occurs

mark

public void mark(int readlimit)

Invokes the delegate's mark(int) method.

Overrides:

mark in class ProxyInputStream

Parameters:

readlimit - read ahead limit

reset

public void reset()
           throws IOException

Invokes the delegate's reset() method.

Overrides:

reset in class ProxyInputStream

Throws:

IOException - if an I/O error occurs

skip

public long skip(long n)
          throws IOException

Invokes the delegate's skip(long) method, detecting and optionally skipping BOM.

Overrides:

skip in class ProxyInputStream

Parameters:

n - the number of bytes to skip

Returns:

the number of bytes to skipped or -1 if the end of stream

Throws:

IOException - if an I/O error occurs