HP-UX Reference (11i v3 07/02) - 3 Library Functions A-M (vol 6)

e
elf_begin(3E) elf_begin(3E)
descriptor. If, however, a program must process many files simultaneously and the underlying operating
system limits the number of open files, the program can use
elf_cntl() to let it reuse file descriptors.
After calling
elf_cntl() with appropriate arguments, the program may close the file descriptor without
interfering with the library.
All data associated with an ELF descriptor remain allocated until
elf_end() terminates the descriptor’s
last activation. After the descriptors have been terminated, the storage is released; attempting to reference
such data gives undefined behavior. Consequently, a program that deals with multiple input (or output)
files must keep the ELF descriptors active until it finishes with them.
Note
When a program calls
elf_begin() on a COFF file, the library translates COFF structures to their ELF
equivalents, allowing programs to read (but not to write) a COFF file as if it were ELF. This conversion
happens only to the memory image and not to the file itself.
EXAMPLES
A prototype for reading a file appears below. If the file is a simple object file, the program executes the loop
one time, receiving a null descriptor in the second iteration. In this case, both
elf and arf will have the
same value, the activation count will be two, and the program calls
elf_end() twice to terminate the
descriptor. If the file is an archive, the loop processes each archive member in turn, ignoring those that are
not object files.
if (elf_version(EV_CURRENT) == EV_NONE)
{
/* library out of date */
/* recover from error */
}
cmd = ELF_C_READ;
arf = elf_begin(fildes, cmd, (Elf *)0);
while ((elf = elf_begin(fildes, cmd, arf)) != 0)
{
if ((ehdr = elf32_getehdr(elf)) != 0)
{
/* process the file...*/
}
cmd = elf_next(elf);
elf_end(elf);
}
elf_end(arf);
Alternatively, the next example illustrates random archive processing. After identifying the file as an
archive, the program repeatedly processes archive members of interest. For clarity, this example omits
error checking and ignores simple object files. Additionally, this fragment preserves the ELF descriptors
for all archive members, because it does not call elf_end() to terminate them.
elf_version(EV_CURRENT);
arf = elf_begin(fildes, ELF_C_READ, (Elf *)0);
if (elf_kind(arf) != ELF_K_AR)
{
/* not an archive */
}
/* initial processing */
/* set offset=...fordesired member header */
while (elf_rand(arf, offset) == offset)
{
if ((elf = elf_begin(fildes, ELF_C_READ, arf)) == 0)
break;
if ((ehdr = elf32_getehdr(elf)) != 0)
{
/* process archive member...*/
}
/* set offset=...fordesired member header */
}
HP-UX 11i Version 3: February 2007 − 2 − Hewlett-Packard Company 335