ldopen(3x)                 DG/UX 4.30                  ldopen(3x)



     NAME
          ldopen, ldaopen - open an object file for reading

     SYNOPSIS
          #include <stdio.h>
          #include <filehdr.h>
          #include <ldfcn.h>

          LDFILE *ldopen (filename, ldptr)
          char *filename;
          LDFILE *ldptr;

          LDFILE *ldaopen (filename, oldptr)
          char *filename;
          LDFILE *oldptr;

     DESCRIPTION
          Ldopen and ldclose(3x)  provide uniform access to both
          simple object files and object files that are members of
          archive files.  Thus an archive of object files can be
          processed as if it were a series of simple object files.

          If ldptr has the value NULL, then ldopen will open filename
          and allocate and initialize the LDFILE structure, and return
          a pointer to the structure to the calling program.

          If ldptr is valid and if TYPE(ldptr) is the archive magic
          number, ldopen will re-initialize the LDFILE structure for
          the next archive member of filename.

          Ldopen and ldclose(3x) work in concert.  Ldclose will return
          FAILURE only when TYPE(ldptr) is the archive magic number
          and when another file in the archive is to be processed.
          Only then should ldopen be called with the current value of
          ldptr.  In all other cases, and particularly whenever a new
          filename is opened, ldopen should be called with a NULL
          ldptr argument.

          The following is a model for the use of ldopen and
          ldclose(3x).















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     ldopen(3x)                 DG/UX 4.30                  ldopen(3x)



               /* for each filename to be processed */

               ldptr = NULL;
               do
               {
                    if ( (ldptr = ldopen(filename, ldptr)) != NULL )
                    {
                         /*check magic number*/
                         /* process the file */
                    }
               } while (ldclose(ldptr) == FAILURE );

          If the value of oldptr is not NULL, ldaopen will re-open
          filename and allocate and initialize a new LDFILE structure,
          copying the TYPE, OFFSET, and HEADER fields from oldptr.
          Ldaopen returns a pointer to the new LDFILE structure.  This
          new pointer is independent of the old pointer, oldptr.  The
          two pointers may be used concurrently to read separate parts
          of the object file.

          Both ldopen and ldaopen open filename for reading.  Both
          functions return NULL if:

               a)  filename cannot be opened

               b)  memory for the LDFILE structure cannot be allocated

               c)  filename is too small to be an object file or an
                   archive of object files.  The functions try to read
                   the header of object files, so a file smaller than
                   a header will cause the functions to return NULL.

          Note that a successful open does not ensure that the given
          file is an object file or an archive of object files.

          The program must be loaded with the object file access
          routine library libld.a.

     SEE ALSO
          fopen(3s), ldclose(3x), ldfcn(4).















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