egs_prs: C module implementing PRS compression from fuzziqer.
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Loïc Hoguin
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c_src/.gitignore
vendored
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c_src/.gitignore
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*.o
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74
c_src/egs_prs_drv.c
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c_src/egs_prs_drv.c
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/*
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@author Loïc Hoguin <essen@dev-extend.eu>
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@copyright 2010 Loïc Hoguin.
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@doc PRS Erlang driver for EGS.
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This file is part of EGS.
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EGS is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as
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published by the Free Software Foundation, either version 3 of the
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License, or (at your option) any later version.
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EGS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with EGS. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "/opt/erlang/lib/erlang/usr/include/erl_nif.h"
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extern unsigned long prs_compress(unsigned char* source, unsigned char* dest, unsigned long size);
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static ERL_NIF_TERM compress_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
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{
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ErlNifBinary srcbin;
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ErlNifBinary destbin;
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unsigned int size;
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if (argc != 1)
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return enif_make_badarg(env);
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if (!enif_is_binary(env, argv[0]))
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return enif_make_badarg(env);
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if (!enif_inspect_binary(env, argv[0], &srcbin))
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return enif_make_badarg(env);
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if (!enif_alloc_binary((9 * srcbin.size) / 8 + 2, &destbin))
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return enif_make_badarg(env);
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size = prs_compress(srcbin.data, destbin.data, srcbin.size);
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enif_realloc_binary(&destbin, size);
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return enif_make_binary(env, &destbin);
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}
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static int load(ErlNifEnv* env, void** priv, ERL_NIF_TERM load_info)
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{
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return 0;
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}
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static int reload(ErlNifEnv* env, void** priv, ERL_NIF_TERM load_info)
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{
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return 0;
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}
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static int upgrade(ErlNifEnv* env, void** priv, void** old_priv, ERL_NIF_TERM load_info)
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{
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return 0;
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}
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static void unload(ErlNifEnv* env, void* priv)
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{
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return;
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}
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static ErlNifFunc nif_funcs[] = {
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{"compress", 1, compress_nif}
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};
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ERL_NIF_INIT(egs_prs, nif_funcs, load, reload, upgrade, unload)
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173
c_src/prs.c
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c_src/prs.c
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/*
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Original code from the PRSutil project.
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http://www.fuzziqersoftware.com/projects.php
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*/
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#include <string.h>
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typedef struct {
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unsigned char bitpos;
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unsigned char* controlbyteptr;
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unsigned char* srcptr_orig;
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unsigned char* dstptr_orig;
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unsigned char* srcptr;
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unsigned char* dstptr; } PRS_COMPRESSOR;
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void prs_put_control_bit(PRS_COMPRESSOR* pc,unsigned char bit)
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{
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*pc->controlbyteptr = *pc->controlbyteptr >> 1;
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*pc->controlbyteptr |= ((!!bit) << 7);
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pc->bitpos++;
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if (pc->bitpos >= 8)
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{
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pc->bitpos = 0;
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pc->controlbyteptr = pc->dstptr;
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pc->dstptr++;
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}
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}
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void prs_put_control_bit_nosave(PRS_COMPRESSOR* pc,unsigned char bit)
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{
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*pc->controlbyteptr = *pc->controlbyteptr >> 1;
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*pc->controlbyteptr |= ((!!bit) << 7);
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pc->bitpos++;
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}
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void prs_put_control_save(PRS_COMPRESSOR* pc)
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{
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if (pc->bitpos >= 8)
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{
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pc->bitpos = 0;
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pc->controlbyteptr = pc->dstptr;
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pc->dstptr++;
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}
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}
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void prs_put_static_data(PRS_COMPRESSOR* pc,unsigned char data)
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{
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*pc->dstptr = data;
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pc->dstptr++;
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}
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unsigned char prs_get_static_data(PRS_COMPRESSOR* pc)
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{
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unsigned char data = *pc->srcptr;
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pc->srcptr++;
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return data;
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}
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/* **************************************************** */
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void prs_init(PRS_COMPRESSOR* pc,void* src,void* dst)
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{
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pc->bitpos = 0;
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pc->srcptr = (unsigned char*)src;
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pc->srcptr_orig = (unsigned char*)src;
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pc->dstptr = (unsigned char*)dst;
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pc->dstptr_orig = (unsigned char*)dst;
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pc->controlbyteptr = pc->dstptr;
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pc->dstptr++;
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}
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void prs_finish(PRS_COMPRESSOR* pc)
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{
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prs_put_control_bit(pc,0);
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prs_put_control_bit(pc,1);
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if (pc->bitpos != 0)
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{
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*pc->controlbyteptr = ((*pc->controlbyteptr << pc->bitpos) >> 8);
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}
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prs_put_static_data(pc,0);
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prs_put_static_data(pc,0);
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}
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void prs_rawbyte(PRS_COMPRESSOR* pc)
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{
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prs_put_control_bit_nosave(pc,1);
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prs_put_static_data(pc,prs_get_static_data(pc));
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prs_put_control_save(pc);
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}
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void prs_shortcopy(PRS_COMPRESSOR* pc,int offset,unsigned char size)
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{
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size -= 2;
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prs_put_control_bit(pc,0);
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prs_put_control_bit(pc,0);
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prs_put_control_bit(pc,(size >> 1) & 1);
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prs_put_control_bit_nosave(pc,size & 1);
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prs_put_static_data(pc,offset & 0xFF);
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prs_put_control_save(pc);
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}
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void prs_longcopy(PRS_COMPRESSOR* pc,int offset,unsigned char size)
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{
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if (size <= 9)
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{
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prs_put_control_bit(pc,0);
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prs_put_control_bit_nosave(pc,1);
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prs_put_static_data(pc,((offset << 3) & 0xF8) | ((size - 2) & 0x07));
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prs_put_static_data(pc,(offset >> 5) & 0xFF);
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prs_put_control_save(pc);
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} else {
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prs_put_control_bit(pc,0);
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prs_put_control_bit_nosave(pc,1);
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prs_put_static_data(pc,(offset << 3) & 0xF8);
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prs_put_static_data(pc,(offset >> 5) & 0xFF);
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prs_put_static_data(pc,size - 1);
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prs_put_control_save(pc);
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}
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}
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void prs_copy(PRS_COMPRESSOR* pc,int offset,unsigned char size)
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{
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if ((offset > -0x100) && (size <= 5))
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prs_shortcopy(pc,offset,size);
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else
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prs_longcopy(pc,offset,size);
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pc->srcptr += size;
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}
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/* **************************************************** */
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unsigned long prs_compress(void* source,void* dest,unsigned long size)
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{
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PRS_COMPRESSOR pc;
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int x,y;
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unsigned long xsize;
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int lsoffset,lssize;
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prs_init(&pc,source,dest);
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for (x = 0; x < size; x++)
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{
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lsoffset = lssize = xsize = 0;
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for (y = x - 3; (y > 0) && (y > (x - 0x1FF0)) && (xsize < 255); y--)
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{
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xsize = 3;
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if (!memcmp((void*)((unsigned long)source + y),(void*)((unsigned long)source + x),xsize))
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{
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do xsize++;
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while (!memcmp((void*)((unsigned long)source + y),
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(void*)((unsigned long)source + x),
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xsize) &&
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(xsize < 256) &&
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((y + xsize) < x) &&
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((x + xsize) <= size)
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);
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xsize--;
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if (xsize > lssize)
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{
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lsoffset = -(x - y);
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lssize = xsize;
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}
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}
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}
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if (lssize == 0)
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{
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prs_rawbyte(&pc);
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} else {
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prs_copy(&pc,lsoffset,lssize);
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x += (lssize - 1);
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}
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}
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prs_finish(&pc);
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return pc.dstptr - pc.dstptr_orig;
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}
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1
priv/.gitignore
vendored
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1
priv/.gitignore
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@ -0,0 +1 @@
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egs_drv.so
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28
src/egs_prs.erl
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28
src/egs_prs.erl
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@ -0,0 +1,28 @@
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%% @author Loïc Hoguin <essen@dev-extend.eu>
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%% @copyright 2010 Loïc Hoguin.
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%% @doc EGS file creation functions.
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%%
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%% This file is part of EGS.
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%%
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%% EGS is free software: you can redistribute it and/or modify
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%% it under the terms of the GNU Affero General Public License as
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%% published by the Free Software Foundation, either version 3 of the
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%% License, or (at your option) any later version.
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%%
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%% EGS is distributed in the hope that it will be useful,
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%% but WITHOUT ANY WARRANTY; without even the implied warranty of
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%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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%% GNU Affero General Public License for more details.
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%%
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%% You should have received a copy of the GNU Affero General Public License
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%% along with EGS. If not, see <http://www.gnu.org/licenses/>.
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-module(egs_prs).
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-export([init/0, compress/1]).
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-on_load(init/0).
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init() ->
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erlang:load_nif("priv/egs_drv", 0).
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compress(_SrcBin) ->
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exit(nif_library_not_loaded).
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