org.apache.commons.io.input

Class BOMInputStream

  • All Implemented Interfaces:
    Closeable, AutoCloseable


    public class BOMInputStreamextends 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:

    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
    Version:
    $Id: BOMInputStream.java 1686527 2015-06-20 06:31:39Z krosenvold $
    See Also:
    ByteOrderMark, Wikipedia - Byte Order Mark
    • 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
      • 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
      • skip

        public long skip(long n)          throws IOException
        Invokes the delegate's skip(long) method, detecting and optionallyskipping 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

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