GGRUNDY
asked on
Get an IStream given a file on disk
Hi,
I have a file on disk.
I want a COM IStream interface (which will only be used for sequential reading).
It would be real nice if someone could tell me a more sensible way to get from A to B, without having to:
a) GlobalAlloc
b) Load my entire file to memory; and
c) CreateStreamOnHGlobal.
Fingers crossed
I have a file on disk.
I want a COM IStream interface (which will only be used for sequential reading).
It would be real nice if someone could tell me a more sensible way to get from A to B, without having to:
a) GlobalAlloc
b) Load my entire file to memory; and
c) CreateStreamOnHGlobal.
Fingers crossed
jkr
Why not using 'StgOpenStorage()'?
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ASKER
I thought StgOpenStorage opened compound storage files. The file I want to hook up to my input IStream is just a raw data file. Am I missing something?
ASKER
Oh!!! Can I use StgOpenStorage on the directory which contains my file?????
ASKER
>>>Oh!!! Can I use StgOpenStorage on the directory which contains my file?????
NO :-(
But I just found the following on MSDN
Streams on Existing Files
Because streams and files are so close in nature, it seems natural that you should be able to create a stream object that accesses a file through IStream instead of through a file handle. OLE doesn't currently provide a simple API function for this exact purpose, although for small files you can easily load the file into memory and create a stream on that memory.
Structured Storage does, however, define a special access mode that allows a client to open an existing file as if it were a root storage, and the contents of the existing file are exposed through a stream named CONTENTS (big surprise). So while you can't simply open a stream on top of a file, you can open a root storage and then open a stream.
NO :-(
But I just found the following on MSDN
Streams on Existing Files
Because streams and files are so close in nature, it seems natural that you should be able to create a stream object that accesses a file through IStream instead of through a file handle. OLE doesn't currently provide a simple API function for this exact purpose, although for small files you can easily load the file into memory and create a stream on that memory.
Structured Storage does, however, define a special access mode that allows a client to open an existing file as if it were a root storage, and the contents of the existing file are exposed through a stream named CONTENTS (big surprise). So while you can't simply open a stream on top of a file, you can open a root storage and then open a stream.
ASKER
:-( :-( :-( :-(
Before anyone gets too excited about the availabilty of a stream named contents...
Turns out only to be available if you open the storage STGM_CONVERT which (big surprise) trashes your file.
Before anyone gets too excited about the availabilty of a stream named contents...
Turns out only to be available if you open the storage STGM_CONVERT which (big surprise) trashes your file.
ASKER
SHCreateStreamOnFileEx is available but only XP.
So I guess I'm going to have to write my own code.
So I guess I'm going to have to write my own code.
ASKER
Hi JKR, What do you think I should do about finalising this question?
ASKER
I've decided to accept JKRs answer rather than delete the question. Because I know when I go looking for solutions it often saves me heaps of fruitless searching when I find an "It can't be done" answer.