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Tweak comments, layout and exceptions in IOUtils and RawDataBlock. It should now be clearer exactly what they do, and when they become unhappy. Also include a test that ensures that when reading from a slow inputstream (as per bug #42834), we really are ok with the data dribbling in, and do not require it to all come in in blocksize chunks at one

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git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@610439 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Nick Burch 2008-01-09 16:31:25 +00:00
parent 1558c1472f
commit 400bfacc62
3 changed files with 150 additions and 25 deletions
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46
src/java/org/apache/poi/poifs/storage/RawDataBlock.java
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@ -42,34 +42,44 @@ public class RawDataBlock
* @param stream the InputStream from which the data will be read
*
* @exception IOException on I/O errors, and if an insufficient
* amount of data is read
* amount of data is read (the InputStream must
* be an exact multiple of the block size)
*/
public RawDataBlock(final InputStream stream)
throws IOException
{
_data = new byte[ POIFSConstants.BIG_BLOCK_SIZE ];
throws IOException {
this(stream, POIFSConstants.BIG_BLOCK_SIZE);
}
/**
* Constructor RawDataBlock
*
* @param stream the InputStream from which the data will be read
* @param blockSize the size of the POIFS blocks, normally 512 bytes {@link POIFSConstants#BIG_BLOCK_SIZE}
*
* @exception IOException on I/O errors, and if an insufficient
* amount of data is read (the InputStream must
* be an exact multiple of the block size)
*/
public RawDataBlock(final InputStream stream, int blockSize)
throws IOException {
_data = new byte[ blockSize ];
int count = IOUtils.readFully(stream, _data);
if (count == -1)
{
if (count == -1) {
_eof = true;
}
else if (count != POIFSConstants.BIG_BLOCK_SIZE)
{
if (count == -1)
//Cant have -1 bytes read in the error message!
count = 0;
else if (count != blockSize) {
// IOUtils.readFully will always read the
// requested number of bytes, unless it hits
// an EOF
_eof = true;
String type = " byte" + ((count == 1) ? ("")
: ("s"));
throw new IOException("Unable to read entire block; " + count
+ type + " read; expected "
+ POIFSConstants.BIG_BLOCK_SIZE + " bytes");
+ type + " read before EOF; expected "
+ blockSize + " bytes");
}
else
{
else {
_eof = false;
}
}
@ -82,7 +92,6 @@ public class RawDataBlock
*
* @exception IOException
*/
public boolean eof()
throws IOException
{
@ -98,7 +107,6 @@ public class RawDataBlock
*
* @exception IOException if there is no data
*/
public byte [] getData()
throws IOException
{

14
src/java/org/apache/poi/util/IOUtils.java
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@ -58,11 +58,16 @@ public class IOUtils
}
/**
* Same as the normal <tt>in.read(b, off, len)</tt>, but tries to ensure that
* the entire len number of bytes is read.
* Same as the normal <tt>in.read(b, off, len)</tt>, but
* tries to ensure that the entire len number of bytes
* is read.
* <p>
* If the end of file is reached before any bytes are read, returns -1.
* Otherwise, returns the number of bytes read.
* If the end of file is reached before any bytes
* are read, returns -1.
* If the end of the file is reached after some bytes are
* read, returns the number of bytes read.
* If the end of the file isn't reached before len
* bytes have been read, will return len bytes.
*/
public static int readFully(InputStream in, byte[] b, int off, int len)
throws IOException
@ -80,4 +85,3 @@ public class IOUtils
}
}
}

113
src/testcases/org/apache/poi/poifs/storage/TestRawDataBlock.java
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@ -20,6 +20,7 @@
package org.apache.poi.poifs.storage;
import java.io.*;
import java.util.Random;
import junit.framework.*;
@ -125,6 +126,118 @@ public class TestRawDataBlock
}
}
/**
* 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
*