function zlib_decompress( p_src in blob )
return blob
is
t_out blob;
t_tmp blob;
t_buf raw(8132);
t_buffer raw(1);
t_hdl binary_integer;
t_max_loops pls_integer;
t_s1 pls_integer; — s1 part of adler32 checksum
t_last_chr pls_integer;
begin
dbms_lob.createtemporary( t_out, true );
dbms_lob.createtemporary( t_tmp, true );
t_tmp := hextoraw( ‘1F8B0800000000000003′ ); — gzip header
dbms_lob.copy( t_tmp, p_src, dbms_lob.getlength( p_src ) – 2 – 4, 11, 3 );
dbms_lob.append( t_tmp, hextoraw( ‘0000000000000000′ ) ); — add a fake trailer
t_hdl := utl_compress.lz_uncompress_open( t_tmp );
t_s1 := 1;
t_max_loops := 0;
loop
begin
utl_compress.lz_uncompress_extract( t_hdl, t_buf );
dbms_lob.append( t_out, t_buf );
for i in 1 .. 8132
loop
t_s1 := mod( t_s1 + utl_raw.cast_to_binary_integer( utl_raw.substr( t_buf, i, 1 ) ), 65521 );
end loop;
t_max_loops := t_max_loops + 1;
exception
when others
then
if utl_compress.isopen( t_hdl )
then
utl_compress.lz_uncompress_close( t_hdl );
end if;
t_hdl := utl_compress.lz_uncompress_open( t_tmp );
exit;
end;
end loop;
for i in 1 .. t_max_loops
loop
utl_compress.lz_uncompress_extract( t_hdl, t_buf );
end loop;
loop
begin
utl_compress.lz_uncompress_extract( t_hdl, t_buffer );
exception
when others
then
exit;
end;
dbms_lob.append( t_out, t_buffer );
t_s1 := mod( t_s1 + to_number( rawtohex( t_buffer ), ‘xx’ ), 65521 );
end loop;
t_last_chr := to_number( dbms_lob.substr( p_src, 2, dbms_lob.getlength( p_src ) – 1 ), ‘0XXX’) – t_s1;
if t_last_chr < 0
then
t_last_chr := t_last_chr + 65521;
end if;
dbms_output.put_line( t_s1 || 'x' || t_last_chr );
dbms_lob.append( t_out, hextoraw( to_char( t_last_chr, 'fm0X' ) ) );
if utl_compress.isopen( t_hdl )
then
utl_compress.lz_uncompress_close( t_hdl );
end if;
dbms_lob.freetemporary( t_tmp );
return t_out;
end;