Re: fopen gives wrong bufsiz
AAW wrote:
--snip--
<<It will never be the same as the filesize other than by pure
> coincidence. >>
Interesting, so at some point the _bufsize should change and count
change to match it?
Why should they be same ? the buffer is internal to the implementation,
it refills buffer when needed and uses other internal variables for
bookkeeping. Changing buffer size is done with setvbuf() but is needed
only for very special cases. The file could also be opened totally
unbuffered (_IONBF flag) and in that case no buffer is used.
Here is more of the code:
if((fp = fopen(strName, "rb")) != NULL)
{
//read in the first part of the data
//if(fread(&m_byDataA, sizeof(BYTE), 1, fp) != EOF)
//if((m_byDataA = getc(fp)) != EOF)
if(fscanf(fp, "%c", &m_byDataA))
{
if(ferror(fp) != 0)
{
//handle error
return FALSE;
}
//read in the second part of the data
//if(fread(&m_byDataB, sizeof(BYTE), 1, fp) != EOF)
//if((m_byDataB = getc(fp)) != EOF)
if(fscanf(fp, "%c", &m_byDataB))
{
if(ferror(fp) != 0)
{
//handle error
return FALSE;
}
}
else
{
//handle error
return FALSE;
}
}
else
{
//handle error
return FALSE;
}
}
As you can see I have tried a few different ways to read the file and
the all ?fail? after reading 0x1000 bytes of data. I say ?fail? but they
never return EOF but they start to return data not in the file.
<<the error must be there. >>
Or perhaps somewhere else? Could some data have been over written in
some other part of the code?
,
You open file, read one character, return from function ? Where is
fclose() ? Are you running out of filedescriptors ?
This cannot be full code of offending function.
Using fscanf with %c will skip whitespace.
What type is m_byDataA ?
Try this :
int count=0;
while( (ch = fgetch(fp) ) != EOF )
++count;
The count be should equal filesize (when reading binary file) after loop
finishes.
Show the whole function or produce minimal example which shows the error.
One more point about the internal buffer :
One can read/write files that are bigger than 4GB (32 bit) and how
could you do that if the file contents would be inside the buffer ( I
guess biggest buffer in normal 32bit executable is less than one GB )
ismo