What is the most efficient way of writing binary data to disk ?

I want to write a set of structures but even after compressing the resultant
file it takes up too much space.

The structure to write to file is as follows

struct
{
    long
    char[256]
    char[256]
    char[256]
    char[256]
    char[256]
    char[256]
    size_t

    fopen(filename,"wb");

    fwrite(struct, sizeof(struct), 1, stream);

I have thought of using pointers instead of fixed arrays but there would be
the problem of reading the file without knowing the size of each array.  The
size could be written before each array but this seems a bit messy.

Any ideas?

Thanks in advance

--
----------------------------------------------
Eliott R D Mitchelmore

   I have thought of using pointers instead of fixed arrays but there would be
   the problem of reading the file without knowing the size of each array.  The
   size could be written before each array but this seems a bit messy.

That's the typical way it's done, though.  There are other ways, of
course, but most of them are much more complicated.  One exception: if
you know that each char[] element is null-terminated (or terminated
with some other constant value), you can just write them out like
that.

Text files are often a better choice than binary files, BTW, just
because they're easier to read and modify by hand.

Another method is to use Direct Memory Access (DMA) if your platform
has this feature.

struct var_str_t
{
   unsigned int length;
   char *       string;

Here are some questions to ask yourself:
1. Is all this data REALLY necessary?

2. Redundancy:
2.1. Is there any redundant data?
2.2. Can the redundant data not be generated?
2.3. Can the redundant data be compressed (stored once)?

3. Can the data be queued, then written as a big chunk 'o data?

--
Thomas Matthews

On Thu, 28 May 1998 13:09:09 +0100, "Eliott Mitchelmore"

I hope you realize that your requirement is impossible to meet. Being
able to fread() the structure depends on the fact that the exact
memory representation of the structure has been transparently recorded
in the file.

If you want to achieve any compression, however simple, you will have
to write routines to perform encoding and decoding of the data
between the memory representation and the condensed representation.

--
----------------------------------------------
Eliott R D Mitchelmore

--
-----------------------------------------


-----------------------------------------

#>>
#>>Let's see: you want to compress the data, and yet you want to be able
#>>to read it with a simple fread()?
#>>
#>>I hope you realize that your requirement is impossible to meet.
#>
#>Not impossible at all.  The file is simply packed and unpacked using the
#>UNIX system call.

# What Unix system call? Also consider that the C language doesn't support
# any Unix system calls.

signal?

Regards,

        Jens
--
Jens Schweikhardt  http://www.shuttle.de/schweikh
SIGSIG -- signature too long (core dumped)

On Fri, 29 May 1998 09:40:51 +0100, "Eliott Mitchelmore"

In any case, you seem to be hinting at a platform-dependent solution
rather than one which uses standard C.

...

Seriously though, C's support for signal() is much more restrictive than
Unix's (for example in the range of signals supported). These days it is
up to Unix implementations to be compatible with C's definition rather
than the other way around.

--
-----------------------------------------


-----------------------------------------

#># What Unix system call? Also consider that the C language doesn't support
#># any Unix system calls.
#>
#>signal?

# That is of course a standard C library function that Unix supports. :-)
# Seriously though, C's support for signal() is much more restrictive than
# Unix's (for example in the range of signals supported). These days it is
# up to Unix implementations to be compatible with C's definition rather
# than the other way around.

Indeed. I'd *love* to see sigaction in C9X... But signal stuff is a mess
to standardize, I reckon.

Regards,

        Jens
--
Jens Schweikhardt  http://www.shuttle.de/schweikh
SIGSIG -- signature too long (core dumped)