testrawdatablock.java

介绍java核心技术的pio编程方法以及基本概念

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   this work for additional information regarding copyright ownership.
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   (the "License"); you may not use this file except in compliance with
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   distributed under the License is distributed on an "AS IS" BASIS,
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   See the License for the specific language governing permissions and
   limitations under the License.
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package org.apache.poi.poifs.storage;

import java.io.*;
import java.util.Random;

import junit.framework.*;

/**
 * Class to test RawDataBlock functionality
 *
 * @author Marc Johnson
 */

public class TestRawDataBlock
    extends TestCase
{

    /**
     * Constructor TestRawDataBlock
     *
     * @param name
     */

    public TestRawDataBlock(String name)
    {
        super(name);
    }

    /**
     * Test creating a normal RawDataBlock
     *
     * @exception IOException
     */

    public void testNormalConstructor()
        throws IOException
    {
        byte[] data = new byte[ 512 ];

        for (int j = 0; j < 512; j++)
        {
            data[ j ] = ( byte ) j;
        }
        RawDataBlock block = new RawDataBlock(new ByteArrayInputStream(data));

        assertTrue("Should not be at EOF", !block.eof());
        byte[] out_data = block.getData();

        assertEquals("Should be same length", data.length, out_data.length);
        for (int j = 0; j < 512; j++)
        {
            assertEquals("Should be same value at offset " + j, data[ j ],
                         out_data[ j ]);
        }
    }

    /**
     * Test creating an empty RawDataBlock
     *
     * @exception IOException
     */

    public void testEmptyConstructor()
        throws IOException
    {
        byte[]       data  = new byte[ 0 ];
        RawDataBlock block = new RawDataBlock(new ByteArrayInputStream(data));

        assertTrue("Should be at EOF", block.eof());
        try
        {
            block.getData();
        }
        catch (IOException ignored)
        {

            // as expected
        }
    }

    /**
     * Test creating a short RawDataBlock
     */

    public void testShortConstructor()
    {
        for (int k = 1; k < 512; k++)
        {
            byte[] data = new byte[ k ];

            for (int j = 0; j < k; j++)
            {
                data[ j ] = ( byte ) j;
            }
            RawDataBlock block = null;

            try
            {
                block = new RawDataBlock(new ByteArrayInputStream(data));
                fail("Should have thrown IOException creating short block");
            }
            catch (IOException ignored)
            {

                // as expected
            }
        }
    }
    
    /**
     * Tests that when using a slow input stream, which
     *  won't return a full block at a time, we don't
     *  incorrectly think that there's not enough data
     */
    public void testSlowInputStream() throws Exception {
        for (int k = 1; k < 512; k++) {
            byte[] data = new byte[ 512 ];
            for (int j = 0; j < data.length; j++) {
                data[j] = (byte) j;
            }
            
            // Shouldn't complain, as there is enough data,
            //  even if it dribbles through
            RawDataBlock block = 
            	new RawDataBlock(new SlowInputStream(data, k));
            assertFalse(block.eof());
        }
        
        // But if there wasn't enough data available, will
        //  complain
        for (int k = 1; k < 512; k++) {
            byte[] data = new byte[ 511 ];
            for (int j = 0; j < data.length; j++) {
                data[j] = (byte) j;
            }
            
            // Shouldn't complain, as there is enough data
            try {
	            RawDataBlock block = 
	            	new RawDataBlock(new SlowInputStream(data, k));
	            fail();
            } catch(IOException e) {
            	// as expected
            }
        }
    }
    
    /**
     * An input stream which will return a maximum of
     *  a given number of bytes to read, and often claims
     *  not to have any data
     */
    public static class SlowInputStream extends InputStream {
    	private Random rnd = new Random();
    	private byte[] data;
    	private int chunkSize;
    	private int pos = 0;
    	
    	public SlowInputStream(byte[] data, int chunkSize) {
    		this.chunkSize = chunkSize;
    		this.data = data;
    	}
    	
    	/**
    	 * 75% of the time, claim there's no data available
    	 */
    	private boolean claimNoData() {
    		if(rnd.nextFloat() < 0.25f) {
    			return false;
    		}
    		return true;
    	}
    	
		public int read() throws IOException {
			if(pos >= data.length) {
				return -1;
			}
			int ret = data[pos];
			pos++;
			
			if(ret < 0) ret += 256;
			return ret;
		}

		/**
		 * Reads the requested number of bytes, or the chunk
		 *  size, whichever is lower.
		 * Quite often will simply claim to have no data
		 */
		public int read(byte[] b, int off, int len) throws IOException {
			// Keep the length within the chunk size
			if(len > chunkSize) {
				len = chunkSize;
			}
			// Don't read off the end of the data
			if(pos + len > data.length) {
				len = data.length - pos;
				
				// Spot when we're out of data
				if(len == 0) {
					return -1;
				}
			}
			
			// 75% of the time, claim there's no data
			if(claimNoData()) {
				return 0;
			}
			
			// Copy, and return what we read
			System.arraycopy(data, pos, b, off, len);
			pos += len;
			return len;
		}

		public int read(byte[] b) throws IOException {
			return read(b, 0, b.length);
		}
		
    }

    /**
     * main method to run the unit tests
     *
     * @param ignored_args
     */

    public static void main(String [] ignored_args)
    {
        System.out
            .println("Testing org.apache.poi.poifs.storage.RawDataBlock");
        junit.textui.TestRunner.run(TestRawDataBlock.class);
    }
}