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https://issues.apache.org/jira/browse/COMPRESS-595?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17439574#comment-17439574
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Peter Lee commented on COMPRESS-595:
------------------------------------
_This is currently not the case, because there is a call to rewind()_
_which results in a buffer whose remaining() is reset to `len` if_
_`readNow` < `len`._
I'm not quite clear about this part. Here is the current implemention of
readRange :
{code:java}
public static byte[] readRange(final ReadableByteChannel input, final int len)
throws IOException {
final ByteArrayOutputStream output = new ByteArrayOutputStream();
final ByteBuffer b = ByteBuffer.allocate(Math.min(len, COPY_BUF_SIZE));
int read = 0;
while (read < len) {
// Make sure we never read more than len bytes
b.limit(Math.min(len - read, b.capacity()));
final int readNow = input.read(b);
if (readNow <= 0) {
break;
}
output.write(b.array(), 0, readNow);
b.rewind();
read += readNow;
}
return output.toByteArray();
}
{code}
As you can see, there's only one call to _rewind()_ of _ByteBuffer b_. The
_ByteBuffer b_ is a locale buffer which is used to copy the bytes from input to
output. The remaining() of b is never called.
Besides that, recently we had a fix in readRange() for partical read in
COMPRESS-584(Github PR
[#214|[https://github.com/apache/commons-compress/pull/214/files])|https://github.com/apache/commons-compress/pull/214/files]).].
Maybe you're testing with Compress 1.21?
> IOUtils.readRange(ReadableByteChannel input, int len) reads more than len
> when input.read() returns < len (ie. there is a partial read)
> ---------------------------------------------------------------------------------------------------------------------------------------
>
> Key: COMPRESS-595
> URL: https://issues.apache.org/jira/browse/COMPRESS-595
> Project: Commons Compress
> Issue Type: Bug
> Affects Versions: 1.21
> Reporter: NP
> Priority: Major
> Attachments: IOUtilsTest.kt
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> When `input.read(b)` returns `readNow` < `len`, then it means
> `input.read(b)` will need to be called again with the same
> buffer, whose `remaining()` is now the old `remaining()` - `readNow`.
> This way the ReadableByteChannel knows how many bytes are to be
> read in subsequent iterations of the `while (read < len)` loop.
> This is currently not the case, because there is a call to rewind()
> which results in a buffer whose remaining() is reset to `len` if
> `readNow` < `len`.
> I suspect the readRange() method has only been used with channels that never
> do partial reads (such In Memory Byte Channels backed by an array), and hence
> the problem has not been experienced until now.
>
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