recordstorefile.jpp

来自「This is a resource based on j2me embedde」· JPP 代码 · 共 459 行 · 第 1/2 页

     *        pointer to.
     *
     * @exception IOException if there is a problem with the seek.
     */
    public void seek(int pos) throws IOException {
        setPosition(handle, pos);
    }

    /**
     * Sets the position within <code>recordStream</code> to
     * <code>pos</code>.  This will implicitly grow
     * the underlying stream if <code>pos</code> is made greater
     * than the current length of the storage stream.
     *
     * @param handle handle to a record store file
     * @param pos position within the file to move the current_pos
     *        pointer to.
     *
     * @exception IOException if there is a problem with the seek.
     */
    private static native void setPosition(int handle, int pos)
        throws IOException;

    /**
     * Write all of <code>buf</code> to <code>recordStream</code>.
     *
     * @param buf buffer to read out of.
     *
     * @exception IOException if a write error occurs.
     */
    public void write(byte[] buf) throws IOException {
        write(buf, 0, buf.length);
    }

    /**
     * Write <code>buf</code> to <code>recordStream</code>, starting
     * at <code>offset</code> and continuing for <code>numBytes</code>
     * bytes.
     *
     * @param buf buffer to read out of.
     * @param offset starting point write offset, from beginning of buffer.
     * @param numBytes the number of bytes to write.
     *
     * @exception IOException if a write error occurs.
     */
    public void write(byte[] buf, int offset, int numBytes)
            throws IOException {
        if (numBytes == 0) {
            return;
        }

        // Test before we goto the native code
        // This expression will cause a ArrayOutOfBoundsException if the values
        // passed for offset and numBytes is not valid and is much faster then
        // explicitly checking the values with if statements.
        int test = buf[offset] + buf[numBytes - 1] +
            buf[offset + numBytes - 1];

        writeBytes(handle, buf, offset, numBytes);
    }

    /**
     * Write <code>buf</code> to <code>recordStream</code>, starting
     * at <code>offset</code> and continuing for <code>numBytes</code>
     * bytes.
     *
     * @param handle handle to a record store file
     * @param buf buffer to read out of.
     * @param offset starting point write offset, from beginning of buffer.
     * @param numBytes the number of bytes to write.
     *
     * @exception IOException if a write error occurs.
     */
    private static native void writeBytes(int handle, byte[] buf, int offset,
                                   int numBytes) throws IOException;

    /**
     * Commit pending writes
     *
     * @exception IOException if an error occurs while flushing
     *            <code>recordStream</code>.
     */
    public void commitWrite() throws IOException {

        commitWrite(handle);
    }

    /**
     * Commit pending writes
     *
     * @param handle handle to a record store file
     *
     * @exception IOException if an error occurs while flushing
     *            <code>recordStream</code>.
     */
    private native static void commitWrite(int handle) throws IOException;

    /**
     * Read up to <code>buf.length</code> into <code>buf</code>.
     *
     * @param buf buffer to read in to.
     *
     * @return the number of bytes read.
     *
     * @exception IOException if a read error occurs.
     */
    public int read(byte[] buf) throws IOException {
        return read(buf, 0, buf.length);
    }

    /**
     * Read up to <code>buf.length</code> into <code>buf</code>
     * starting at offset <code>offset</code> in <code>recordStream
     * </code> and continuing for up to <code>numBytes</code> bytes.
     *
     * @param buf buffer to read in to.
     * @param offset starting point read offset, from beginning of buffer.
     * @param numBytes the number of bytes to read.
     *
     * @return the number of bytes read.
     *
     * @exception IOException if a read error occurs.
     */
    public int read(byte[] buf, int offset, int numBytes) throws IOException {
        if (numBytes == 0) {
            return 0;
        }

        // Test before we goto the native code
        // This expression will cause a ArrayOutOfBoundsException if the values
        // passed for offset and numBytes is not valid and is much faster then
        // explicitly checking the values with if statements.
        int test = buf[offset] + buf[numBytes - 1] +
            buf[offset + numBytes - 1];

        return readBytes(handle, buf, offset, numBytes);
    }

    /**
     * Read up to <code>buf.length</code> into <code>buf</code>
     * starting at offset <code>offset</code> in <code>recordStream
     * </code> and continuing for up to <code>numBytes</code> bytes.
     *
     * @param handle handle to a record store file
     * @param buf buffer to read in to.
     * @param offset starting point read offset, from beginning of buffer.
     * @param numBytes the number of bytes to read.
     *
     * @return the number of bytes read.
     *
     * @exception IOException if a read error occurs.
     */
    private static native int readBytes(int handle, byte[] buf, int offset,
                                        int numBytes) throws IOException;

    /**
     * Disconnect from <code>recordStream</code> if it is
     * non null.  May be called more than once without error.
     *
     * @exception IOException if an error occurs closing
     *            <code>recordStream</code>.
     */
    public void close() throws IOException {
        int temp;

        if (handle == -1) {
            return;
        }

        temp = handle;
        handle = -1;
        closeFile(temp);
    }

    /**
     * Disconnect from <code>recordStream</code> if it is
     * non null.  May be called more than once without error.
     *
     * @param handle handle to a record store file
     *
     * @exception IOException if an error occurs closing
     *            <code>recordStream</code>.
     */
    private native static void closeFile(int handle) throws IOException;

    /**
     * Sets the length of this <code>RecordStoreFile</code>
     * <code>size</code> bytes.  If this file was previously
     * larger than <code>size</code> the extra data is lost.
     *
     * <code>size</code> must be <= the current length of
     * <code>recordStream</code>
     *
     * @param size new size for this file.
     *
     * @exception IOException if an error occurs, or if
     * <code>size</code> is less than zero.
     */
    public void truncate(int size) throws IOException {
        truncateFile(handle, size);
    }

    /**
     * Sets the length of this <code>RecordStoreFile</code>
     * <code>size</code> bytes.  If this file was previously
     * larger than <code>size</code> the extra data is lost.
     *
     * <code>size</code> must be <= the current length of
     * <code>recordStream</code>
     *
     * @param handle handle to a record store file
     * @param size new size for this file.
     *
     * @exception IOException if an error occurs, or if
     * <code>size</code> is less than zero.
     */
    private static native void truncateFile(int handle,
                                            int size) throws IOException;

    /**
     * Ensures native resources are freed when Object is collected.
     */
// #ifdef ENABLE_CDC
    protected native void finalize();
// #else
    private native void finalize();
// #endif
}