On Tue, 30 Mar 2010, Levente Uzonyi wrote:
On Mon, 29 Mar 2010, Andreas Raab wrote:
Hi Levente -
Could you check the failure of FileStreamTest>>testNextChunkOutOfBounds? This looks like it might be a problem with caching file stream behavior. If it's not (i.e., the infinite recursion is the 'expected' behavior) can we add something that addresses the issue?
Seems like #primAtEnd: doesn't answer true if position is out of bounds and there are no more bytes to read:
I realized that even if I push the changes for #basicUpTo: and friends there may be arbitrary code that assumes that #atEnd will return true if there's nothing more to read. How should this issue be fixed?
One solution is to change StandardFileStream >> #atEnd to something like this:
atEnd "Answer whether the receiver is at its end. "
collection ifNotNil: [ position < readLimit ifTrue: [ ^false ] ]. ^(self primSizeNoError: fileID) ifNil: [ true ] ifNotNil: [ :size | size <= self position ]
But this means that #primAtEnd: is not used at all, so it's just a workaroud.
The other option is to change the VM code. This means changing == to >= like this:
For unix and mac (cross):
sqInt sqFileAtEnd(SQFile *f) { /* Return true if the file's read/write head is at the end of the file. */
if (!sqFileValid(f)) return interpreterProxy->success(false); return ftell(getFile(f)) >= getSize(f); }
For windows:
sqInt sqFileAtEnd(SQFile *f) { win32FileOffset ofs; /* Return true if the file's read/write head is at the end of the file. */ if (!sqFileValid(f)) FAIL(); ofs.offset = 0; ofs.dwLow = SetFilePointer(FILE_HANDLE(f), 0, &ofs.dwHigh, FILE_CURRENT); return ofs.offset >= sqFileSize(f); }
What do you think?
Levente
FileStream forceNewFileNamed: 'testFileStreamAtEnd' do: [ :file | file position: 1000. self assert: file next isNil. self assert: file atEnd ].
Read buffering doesn't affect this behavior:
FileStream forceNewFileNamed: 'testFileStreamAtEnd' do: [ :file | file disableReadBuffering. file position: 1000. self assert: file next isNil. self assert: file atEnd ].
Really:
FileStream forceNewFileNamed: 'testFileStreamAtEnd' do: [ :file | | fileID buffer1 count | file disableReadBuffering. file position: 1000. fileID := file instVarNamed: #fileID. buffer1 := String new: 1. count := file primRead: fileID into: buffer1 startingAt: 1 count: 1. self assert: count = 0. self assert: (file primAtEnd: fileID) ].
We can work around this issue with StandardFileStream >> #upTo: and friends (by replacing the old code which uses recursion and is pretty inefficient btw), but I think #atEnd should answer true in this case.
Levente
Thanks,
- Andreas