Binary Read Calling Sequence

The routine package accesses files by file descriptor, an integer variable that is easily passed among multi-language routines.
The routines are stored in the ar library /$LVDLIB/liblvdr.a. All variables are passed to C routines by address. The Fortran caller must define the following variables:

        integer max_size
        parameter (max_size=100000)
        integer buf(max_size),fd,ret
        character file_name*50

with the following meaning:

• buf is the input buffer
• fd is the file descriptor
• ret is the return code (status, byte/word count)
• file_name is the file name with full path

The calling sequences are summarized below.

open:

opens file with name file_name, returns file descriptor value in fd, and operation code in ret

close:

closes file with associated file descriptor fd

read4:

reads integer*4 variables in buf, emulating the Fortran statement:

read(fd) ret,(buf(k),k=1,ret)

read2:

reads integer*2 variables in buf emulating the Fortran statement:

read(fd) buf(1),(buf(k),k=2,buf(1))

n.b. variables fd, ret are interger*4, read address is buf(2), the 2-byte word count must be set with the statement buf(1)=ret

readvms:

reads VMS RMS binary records without interpretation, and returns the user byte count in ret.
In case of integer*4 data the routine emulates the Fortran statement:

read(fd) ret/4,(buf(k),k=1,ret/4)

Return code values and meaning are described below.

Binary Read Return Codes
routine	code	meaning
open	$-1$	no such file
any read	$-2$	record too big
	$-1$	read error
	$0$	EOF in unput
read2_lvd	$>0$	2-byte word count, move to buf(1)
read4_lvd	$>0$	4-byte word count
read_vms	$>0$	byte count

Programs that need our read tool must use the lvdr library to create the executable. A Makefile example follows to compile and link program migr_dist.f that needs routine read4_lvd to read data files imported using ftp.

Linking with make

LIBDIR = /$LVDLIB

migr_dist : migr_dist.o

f77 migr_dist.o -o migr_dist -L$(LIBDIR) -llvdr

migr_dist.o : migr_dist.f

f77 -c migr_dist.f