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Added fs-utils libs

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.\"     @(#)fread.3	8.2 (Berkeley) 3/8/94
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.Dd March 15, 2009
.Dt FSU_FREAD 3
.Os
.Sh NAME
.Nm fsu_fread ,
.Nm fsu_fwrite
.Nd binary stream input/output
.Sh LIBRARY
fsu_utils Library (libfsu_utils, \-lfsu_utils)
.Sh SYNOPSIS
.In stdio.h
.Ft size_t
.Fn fsu_fread "void * ptr" "size_t size" "size_t nmemb" "FILE * stream"
.Ft size_t
.Fn fsu_fwrite "const void * ptr" "size_t size" "size_t nmemb" "FILE * stream"
.Sh DESCRIPTION
The function
.Fn fsu_fread
reads
.Fa nmemb
objects, each
.Fa size
bytes long, from the stream pointed to by
.Fa stream ,
storing them at the location given by
.Fa ptr .
.Pp
The function
.Fn fsu_fwrite
writes
.Fa nmemb
objects, each
.Fa size
bytes long, to the stream pointed to by
.Fa stream ,
obtaining them from the location given by
.Fa ptr .
.Pp
Mixing
.Fn fsu_fread
and
.Fn fsu_fwrite
calls without setting the file position explicitly using
.Fn fsu_fseek
between read and write or write and read operations will lead to unexpected
results because of buffering the file pointer not being set to the
expected position after each operation completes.
This behavior is allowed by ANSI C for efficiency and it will not be changed.
.Sh RETURN VALUES
The functions
.Fn fsu_fread
and
.Fn fsu_fwrite
advance the file position indicator for the stream
by the number of bytes read or written.
They return the number of objects read or written.
If
.Fa size
or
.Fa nmemb
is 0, the functions return 0 and the state of
.Fa stream
remains unchanged.
If an error occurs, or the end-of-file is reached,
the return value is a short object count (or zero).
.Pp
The function
.Fn fsu_fread
does not distinguish between end-of-file and error, and callers
must use
.Xr fsu_feof 3
and
.Xr fsu_ferror 3
to determine which occurred.
The function
.Fn fsu_fwrite
returns a value less than
.Fa nmemb
only if a write error has occurred.
.Sh SEE ALSO
.Xr ukfs 3 ,
.Xr fsu_utils 3