gecko-dev/xpcom/io/nsISeekableStream.idl

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/*
 * nsISeekableStream
 *
 * Note that a stream might not implement all methods (e.g., a readonly stream 
 * won't implement setEOF)
 */

#include "nsISupports.idl"

[scriptable, uuid(8429d350-1040-4661-8b71-f2a6ba455980)]
interface nsISeekableStream : nsISupports
{
    /* 
     * Sets the stream pointer to the value of the 'offset' parameter 
     */
    const PRInt32 NS_SEEK_SET = 0;

    /*  
     * Sets the stream pointer to its current location plus the value 
     * of the offset parameter. 
     */
    const PRInt32 NS_SEEK_CUR = 1;

    /* 
     * Sets the stream pointer to the size of the stream plus the value 
     * of the offset parameter. 
     */
    const PRInt32 NS_SEEK_END = 2;

    /**
     *  seek
     *
     *  This method moves the stream offset of the steam implementing this
     *  interface.
     *
     *   @param whence specifies how to interpret the 'offset' parameter in
     *                 setting the stream offset associated with the implementing
     *                 stream.
     *     
     *   @param offset specifies a value, in bytes, that is used in conjunction
     *                 with the 'whence' parameter to set the stream offset of the 
     *                 implementing stream.  A negative value causes seeking in 
     *                 the reverse direction.
     *
     *   @throws NS_BASE_STREAM_CLOSED if called on a closed stream.
     */
    void seek(in long whence, in long long offset);

    /**
     *  tell
     *
     *  This method reports the current offset, in bytes, from the start of the 
     *  stream. 
     *
     *   @throws NS_BASE_STREAM_CLOSED if called on a closed stream.
     */
    long long tell();


    /**
     *  setEOF
     *
     *  This method truncates the stream at the current offset.
     *
     *   @throws NS_BASE_STREAM_CLOSED if called on a closed stream.
     */
    void setEOF();
};