NAME
        elf_zscn_compress

SYNOPSIS
        cc [ flag ... ] file ... -lelf [ library ... ]
        #include <libelf.h>

        int elf_zscn_compress(Elf_Scn *scn, Elf_ZScn_Type ztype,
            const char *scn_name);

DESCRIPTION
        elf_zscn_compress is used to compress a section using a
        specified compression type.

        The ztype argument specifies the desired compression type, and
        can  be one of the following.

            ELF_ZSCN_T_ZLIB       ZLIB compression, ELF ABI format.

            ELF_ZSCN_T_ZLIB_GNU   ZLIB compression, in the original GNU
                                  format. See NOTES.

        scn_name is the name of the section. It can be set to NULL
        under some circumstances. See elf_zscn_compressible(3ELF).

RETURN VALUE
        Upon failure, elf_zscn_compress returns -1 and sets elf_errno.
        Otherwise, 0 is returned.

        On success, elf_zscn_compress updates the section header,
        and the original data is replaced with the compressed data. Any
        information previously returned for the section by elf32_getshdr,
        elf64_shdr, or elf_getdata, is invalidated, and should no longer be
        referenced by the caller. The caller should defer calling those
        functions until after calling elf_zscn_compress, or should call
        them again afterwards in order to obtain the new information.

EXAMPLES
        Example 1 Display compressible sections

        The following code fragment iterates over all the sections
        of an ELF object, and compresses all possible sections using
        the ELF_ZSCN_T_ZLIB compression type. The section index and
        name for each section is printed. The details of obtaining the
        section name, and error handling, are omitted in the interest
        of brevity.

        modified = 0;
        ndx = 1;
        for (scn = NULL; scn = elf_nextscn(elf, scn); ndx++) {
                scn_name = get_scn_name(...);
                status = elf_zscn_compressible(scn, ELF_ZSCN_T_ZLIB, scn_name);
                if (status == -1)
                        error(...);
                if (status == 0)
                        continue;
                ztype = elf_zscn_identify(scn, scn_name);
                if (ztype == -1)
                        error(...);
                if (ztype != ELF_ZSCN_T_NONE)
                        continue;

                (void) printf("[%d] %s\n", ndx, scn_name);
                if(elf_zscn_compress(scn, ELF_ZSCN_T_ZLIB, scn_name) == -1)
                        error(...);
                modified = 1;
        }
        if (modified)
                elf_update(elf, ELF_C_WRITE);

NOTES
        elf_zscn_compress will reject any compression attempt that
        would be rejected by elf_zscn_compressible. The use of
        elf_zscn_compressible to identify sections suitable for
        compression before calling elf_zscn_compress is recommended.
        Unlike elf_zscn_compressible, elf_zscn_compress will also reject
        a compression attempt for a section that is already compressed.
        The caller must first decompress the section, and then compress
        it into the desired format. In such situations, the use of
        elf_zscn_identify is recommended in conjunction with
        elf_zscn_compressible.

        The ELF_ZSCN_T_ZLIB_GNU compression type is deprecated, and is
        provided in order to support existing objects. The ELF_ZSCN_T_ZLIB
        type, which is not dependent on section name, is preferred.

        The ELF_ZSCN_T_ZLIB_GNU compression type can only be applied
        to sections with names that start with .debug. On compression,
        that type requires the name to be altered to start with .zdebug.
        elf_zscn_compress does not provide the replacement name. The caller
        is responsible for for providing the replacement name. See
        elf_zscn_compressible(3ELF).

SEE ALSO
       elf32_getshdr(3ELF), elf64_getshdr(3ELF), elf_errno(3ELF),
       elf_getdata(3ELF), elf_zscn_compressible(3ELF),
       elf_zscn_decompress(3ELF), elf_zscn_identify(3ELF), libelf(3LIB)