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io_read() semantics
From: |
Ludovic Courtès |
Subject: |
io_read() semantics |
Date: |
Mon, 10 Jun 2002 14:45:15 +0200 |
User-agent: |
Mutt/1.2.5.1i |
Hi,
I have a question about how io_read() should work, and I couldn't find the
answer in io.def. From what I've seen in libdiskfs/io-read.c , a diskfs server
is supposed to reallocate a new buffer if the provided buffer is smaller than
the requested amount of data:
if (maxread > *datalen)
{
ourbuf = 1;
buf = mmap (0, maxread, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
*data = buf;
}
Therefore, I would not expect io_read() to provide a new buffer with the
following code, since the buffer size if the same as the requested amount of
data (*len == size):
void* d = data;
size = (size > *len)?(*len):size;
*len = size;
err = io_read (mbox, (data_t*)&data, len, start + offset, size);
assert (data == d); // this assertion should not fail!
However, the last assertion does sometimes fail.
Any idea?
Thanks,
Ludovic.