mirror of
https://github.com/reactos/reactos.git
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263 lines
4.2 KiB
C
263 lines
4.2 KiB
C
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#include "fitz-base.h"
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#include "fitz-stream.h"
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#define noDEBUG 1
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enum
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{
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MINBITS = 9,
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MAXBITS = 12,
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MAXBYTES = 2,
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NUMCODES = (1 << MAXBITS),
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LZW_CLEAR = 256,
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LZW_EOD = 257,
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LZW_FIRST = 258,
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HSIZE = 9001, /* 91% occupancy (???) */
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HSHIFT = (13 - 8)
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};
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typedef struct lzw_hash_s lzw_hash;
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struct lzw_hash_s
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{
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int hash;
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int code;
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};
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typedef struct fz_lzwe_s fz_lzwe;
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struct fz_lzwe_s
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{
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fz_filter super;
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int earlychange;
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int bidx; /* partial bits used in out->wp */
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unsigned char bsave; /* partial byte saved between process() calls */
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int resume;
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int code;
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int fcode;
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int hcode;
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int codebits;
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int oldcode;
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int nextcode;
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lzw_hash table[HSIZE];
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};
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static void
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clearhash(fz_lzwe *lzw)
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{
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int i;
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for (i = 0; i < HSIZE; i++)
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lzw->table[i].hash = -1;
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}
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fz_error *
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fz_newlzwe(fz_filter **fp, fz_obj *params)
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{
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FZ_NEWFILTER(fz_lzwe, lzw, lzwe);
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lzw->earlychange = 0;
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if (params)
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{
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fz_obj *obj;
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obj = fz_dictgets(params, "EarlyChange");
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if (obj) lzw->earlychange = fz_toint(obj) != 0;
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}
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lzw->bidx = 0;
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lzw->bsave = 0;
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lzw->resume = 0;
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lzw->code = -1;
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lzw->hcode = -1;
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lzw->fcode = -1;
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lzw->codebits = MINBITS;
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lzw->nextcode = LZW_FIRST;
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lzw->oldcode = -1; /* generates LZW_CLEAR */
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clearhash(lzw);
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return nil;
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}
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void
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fz_droplzwe(fz_filter *filter)
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{
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}
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static void
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putcode(fz_lzwe *lzw, fz_buffer *out, int code)
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{
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int nbits = lzw->codebits;
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while (nbits > 0)
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{
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if (lzw->bidx == 0)
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{
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*out->wp = 0;
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}
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/* code does not fit: shift right */
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if (nbits > (8 - lzw->bidx))
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{
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*out->wp |= code >> (nbits - (8 - lzw->bidx));
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nbits = nbits - (8 - lzw->bidx);
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lzw->bidx = 0;
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out->wp ++;
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}
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/* shift left */
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else
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{
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*out->wp |= code << ((8 - lzw->bidx) - nbits);
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lzw->bidx += nbits;
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if (lzw->bidx == 8)
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{
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lzw->bidx = 0;
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out->wp ++;
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}
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nbits = 0;
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}
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}
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}
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static fz_error *
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compress(fz_lzwe *lzw, fz_buffer *in, fz_buffer *out)
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{
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if (lzw->resume)
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{
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lzw->resume = 0;
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goto resume;
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}
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/* at start of data, output a clear code */
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if (lzw->oldcode == -1)
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{
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if (out->wp + 3 > out->ep)
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return fz_ioneedout;
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if (in->rp + 1 > in->wp)
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{
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if (in->eof)
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goto eof;
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return fz_ioneedin;
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}
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putcode(lzw, out, LZW_CLEAR);
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lzw->oldcode = *in->rp++;
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}
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begin:
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while (1)
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{
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if (in->rp + 1 > in->wp)
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{
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if (in->eof)
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goto eof;
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return fz_ioneedin;
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}
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/* read character */
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lzw->code = *in->rp++;
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/* hash string + character */
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lzw->fcode = (lzw->code << MAXBITS) + lzw->oldcode;
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lzw->hcode = (lzw->code << HSHIFT) ^ lzw->oldcode;
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/* primary hash */
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if (lzw->table[lzw->hcode].hash == lzw->fcode)
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{
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lzw->oldcode = lzw->table[lzw->hcode].code;
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continue;
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}
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/* secondary hash */
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if (lzw->table[lzw->hcode].hash != -1)
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{
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int disp = HSIZE - lzw->hcode;
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if (lzw->hcode == 0)
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disp = 1;
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do
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{
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lzw->hcode = lzw->hcode - disp;
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if (lzw->hcode < 0)
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lzw->hcode += HSIZE;
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if (lzw->table[lzw->hcode].hash == lzw->fcode)
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{
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lzw->oldcode = lzw->table[lzw->hcode].code;
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goto begin;
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}
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} while (lzw->table[lzw->hcode].hash != -1);
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}
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resume:
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/* new entry: emit code and add to table */
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/* reserve space for this code and an eventual CLEAR code */
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if (out->wp + 5 > out->ep)
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{
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lzw->resume = 1;
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return fz_ioneedout;
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}
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putcode(lzw, out, lzw->oldcode);
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lzw->oldcode = lzw->code;
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lzw->table[lzw->hcode].code = lzw->nextcode;
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lzw->table[lzw->hcode].hash = lzw->fcode;
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lzw->nextcode ++;
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/* table is full: emit clear code and reset */
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if (lzw->nextcode == NUMCODES - 1)
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{
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putcode(lzw, out, LZW_CLEAR);
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clearhash(lzw);
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lzw->nextcode = LZW_FIRST;
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lzw->codebits = MINBITS;
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}
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/* check if next entry will be too big for the code size */
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else if (lzw->nextcode >= (1 << lzw->codebits) - lzw->earlychange)
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{
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lzw->codebits ++;
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}
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}
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eof:
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if (out->wp + 5 > out->ep)
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return fz_ioneedout;
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putcode(lzw, out, lzw->oldcode);
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putcode(lzw, out, LZW_EOD);
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out->eof = 1;
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return fz_iodone;
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}
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fz_error *
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fz_processlzwe(fz_filter *filter, fz_buffer *in, fz_buffer *out)
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{
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fz_lzwe *lzw = (fz_lzwe*)filter;
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fz_error *error;
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/* restore partial bits */
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*out->wp = lzw->bsave;
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error = compress(lzw, in, out);
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/* save partial bits */
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lzw->bsave = *out->wp;
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return error;
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}
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