Hi.
The problem is triggered by this line, for any small file,
which seems to me allowed by java specification
srcChannel.transferTo(0, FileUtils.BUF_SIZE,destChannel);
http://java.sun.com/j2se/1.4.2/docs/api/java/nio/channels/FileChannel.html:
An attempt is made to read up to count bytes from the source channel and
write them to this channel's file starting at the given position. An
invocation of this method may or may not transfer all of the requested
bytes; whether or not it does so depends upon the natures and states of
the channels. Fewer than the requested number of bytes will be
transferred
if the source channel has fewer than count bytes remaining, or if the
source channel is non-blocking and has fewer than count bytes
immediately available in its input buffer.
It is implemented in
libjava/gnu/java/nio/channels/FileChannelImpl.java
via smallTransferTo() via map() via mapImpl().
The specification of map() explicitely states:
Many of the details of memory-mapped files are inherently dependent upon
the underlying operating system and are therefore unspecified. The
behavior of this method when the requested region is not completely
contained within this channel's file is unspecified.
The transferTo(0, 8192, ...) is translated into mmap() of 8192
bytes from file of size 1701 on architecture with pagesize 4096.
This system call succeeds, the later acces to 2nd page fails.
Moreover, it looks like transferTo(0, 4096, ...) would write
4096 bytes to destination file from file with size 1701.
IMHO, the implementaion of smallTransferTo() should be fixed.
Petr
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