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/*
This file is part of libextractor.
(C) 2002, 2003, 2004, 2009 Vidyut Samanta and Christian Grothoff
libextractor is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 2, or (at your
option) any later version.
libextractor is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with libextractor; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
#include "platform.h"
#include "extractor.h"
#include "extractor_plugins.h"
#include "le_architecture.h"
int
EXTRACTOR_template_extract_method (struct EXTRACTOR_PluginList *plugin,
EXTRACTOR_MetaDataProcessor proc, void *proc_cls)
{
int64_t offset;
unsigned char *data;
/* temporary variables are declared here */
if (plugin == NULL)
return 1;
/* initialize state here */
/* Call pl_seek (plugin, POSITION, WHENCE) to seek (if you know where
* data starts.
*/
/* Call pl_read (plugin, &data, COUNT) to read COUNT bytes (will be stored
* as data[0]..data[COUNT-1], no need to allocate data or free it; but it
* "goes away" when you make another read call, so store interesting values
* somewhere once you find them).
*/
/* If you need to search for a magic id that is not at the beginning of the
* file, do pl_read() calls, reading sizable (1 megabyte or so) chunks,
* then use memchr() on them to find first byte of the magic sequence,
* then compare the rest of the sequence, if found.
* Mind the fact that you need to iterate over COUNT - SEQUENCE_LENGTH chars,
* and seek to POS + COUNT - SEQUENCE_LENGTH once you run out of bytes,
* otherwise you'd have a chance to skip bytes at chunk boundaries.
*/
/* Do try to make a reasonable assumption about the amount of data you're
* going to search through. Iterating over the whole file, byte-by-byte is
* NOT a good idea, if the search itself is slow. Try to make the search as
* efficient as possible.
*/
/* Avoid making long seeks backwards (for performance reasons)
*/
/* pl_get_pos (plugin) will return current offset from the beginning of
* the file (i.e. index of the data[0] in the file, if you call pl_read
* at that point). You might need it do calculate forward-searches, if
* there are offsets stored within the file.
* pl_get_fsize (plugin) will return file size OR -1 if it is not known
* yet (file is not decompressed completely). Don't rely on fsize.
*/
/* Seeking forward is safe
*/
/* If you asked to read X bytes, but got less - it's EOF
*/
/* Seeking backward a bit shouldn't hurt performance (i.e. read 4 bytes,
* then immediately seek 4 bytes back).
*/
/* Don't read too much (you can't read more than MAX_READ from extractor.c,
* which is 32MB at the moment) in one call.
*/
/* Once you find something, call proc(). If it returns non-0 - you're done.
*/
/* Return 1 to indicate that you're done. */
/* Don't forget to free anything you've allocated before returning! */
return 1;
}
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