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ldfcn(4)
NAME
  ldfcn - Common object file access routines

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

DESCRIPTION
  The common object file access routines are a collection of functions for
  reading an object file that is in common object file form (COFF).  Although
  the calling program must know the detailed structure of the parts of the
  object file that it processes, the routines effectively insulate the
  calling program from knowledge of the overall structure of the object file.

  The interface between the calling program and the object file access
  routines is based on the defined type LDFILE (defined as struct ldfile),
  which is declared in the header file ldfcn.h.	 Primarily, this structure
  provides uniform access to simple object files and object files that are
  members of an archive file.

  The function ldopen allocates and initializes the LDFILE structure, reads
  in the symbol table header, if present, and returns a pointer to the
  structure to the calling program.  The fields of the LDFILE structure can
  be accessed individually through macros defined in ldfcn.h.  The fields
  contain the following information:

  LDFILE *ldptr;

  TYPE(ldptr)	 The file magic number, used to distinguish between archive
		 members and simple object files.

  IOPTR(ldptr)	 Not used because files are memory mapped.

  OFFSET(ldptr)	 The file address of the beginning of the object file or
		 archive entry; if the object file is a member of an archive
		 file, the offset is nonzero.

  HEADER(ldptr)	 The file header structure of the object file.

  SYMHEADER(ldptr)
		 The symbolic header structure for the symbol table
		 associated with the object file.

  PFD(ldptr)	 The file table associated with the symbol table.

  SYMTAB(ldptr)	 A pointer to a copy of the symbol table in memory.  It is
		 accessed through the pCHDR structure (see
		 /usr/include/cmplrs/stsupport.h).  If no symbol table is
		 present, this field is NULL.  (Note: This macro causes the
		 whole symbol table to be read.)

  LDSWAP(ldptr)	 If the header and symbol table structures are swapped within
		 the object file and all access requires using libsex, this
		 field is set to true.	(Note: If you use libmld routines,
		 all structures except the optional header and auxiliaries
		 are swapped.)

  The object file access functions can be divided into four categories:

   1.  Functions that open or close an object file:

       - ldopen and ldaopen open an object file.

       - ldclose and ldaclose close an object file.

   2.  Functions that return header or symbol table information:

       - ldahread reads the archive header of a member of an archive file.

       - ldfhread reads the file header of an object file.

       - ldshread and ldnshread read a section header of an object file.

       - ldtbread reads a symbol table entry of an object file.

       - ldgetname retrieves a symbol name from a symbol table entry or from
	 the string table.

       - ldgetaux retrieves a pointer into the aux table for the specified
	 ldptr.

       - ldgetpd retrieves a procedure descriptor.

   3.  Functions that seek to specified portions of an object file:

       - ldohseek seeks to the optional file header of an object file.
	 ldsseek and ldnsseek seek to a section of an object file.

       - ldrseek and ldnrseek seek to the relocation information for a
	 section of an object file.

       - ldlseek and ldnlseek seek to the line number information for an
	 object file.  ldlseek and ldnlseek ignore section number and name
	 arguments, respectively.

       - ldtbseek seeks to the symbol table of an object file.

   4.  Miscellaneous functions

       - ranhashinit (see ranhash(3)) initializes the tables and constants so
	 that the archive hash and lookup routines can work.

       - Given a string, ranhash returns the hash index for it.

       - ranlookup returns an archive hash bucket that is empty or matches
	 the string argument.

       - disassembler prints assembly instructions.

  These functions are described in detail in their own reference pages.

  The ldopen and ldaopen functions both return pointers to a LDFILE
  structure.

MACROS
  Additional access to an object file is provided through a set of macros
  defined in ldfcn.h.  These macros parallel the standard input/output file
  reading and manipulating functions.  They translate a reference of the
  LDFILE structure into a reference to its file descriptor field.

  The following macros are provided:

    GETC(ldptr)
    FGETC(ldptr)
    GETW(ldptr)
    UNGETC(c, ldptr)
    FGETS(s, n, ldptr)
    FREADM((char *) ptr, sizeof (*ptr), nitems, ldptr)
    FSEEK(ldptr, offset, ptrname)
    FTELL(ldptr)
    REWIND(ldptr)
    FEOF(ldptr)
    FERROR(ldptr)
    FILENO(ldptr)
    SETBUF(ldptr, buf)
    STROFFSET(ldptr)

  The STROFFSET macro calculates the address of the local symbol's string
  table in an object file.  See the reference pages for the corresponding
  standard input/output library functions for details on the use of these
  macros.

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

WARNINGS
  The FSEEK macro defined in the header file ldfcn.h translates into a call
  to the standard input/output function fseek.	FSEEK should not be used to
  seek from the end of an archive file because the end of an archive file
  cannot be the same as the end of one of its object file members.

RELATED INFORMATION
  Commands: ar(1)

  Functions: fopen(3), fseek(3), ldahread(3), ldclose(3), ldfhread(3),
  ldgetname(3), ldlseek(3), ldohseek(3), ldopen(3), ldrseek(3), ldshread(3),
  ldtbread(3), ldtbseek(3).

Index for Section 4

Alphabetical listing for L

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