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- #include <u.h>
- #include <libc.h>
- #include <draw.h>
- #include <memdraw.h>
- #define CHUNK 8000
- #define HSHIFT 3 /* HSHIFT==5 runs slightly faster, but hash table is 64x bigger */
- #define NHASH (1<<(HSHIFT*NMATCH))
- #define HMASK (NHASH-1)
- #define hupdate(h, c) ((((h)<<HSHIFT)^(c))&HMASK)
- typedef struct Hlist Hlist;
- struct Hlist{
- uchar *s;
- Hlist *next, *prev;
- };
- int
- writememimage(int fd, Memimage *i)
- {
- uchar *outbuf, *outp, *eout; /* encoded data, pointer, end */
- uchar *loutp; /* start of encoded line */
- Hlist *hash; /* heads of hash chains of past strings */
- Hlist *chain, *hp; /* hash chain members, pointer */
- Hlist *cp; /* next Hlist to fall out of window */
- int h; /* hash value */
- uchar *line, *eline; /* input line, end pointer */
- uchar *data, *edata; /* input buffer, end pointer */
- ulong n; /* length of input buffer */
- ulong nb; /* # of bytes returned by unloadimage */
- int bpl; /* input line length */
- int offs, runlen; /* offset, length of consumed data */
- uchar dumpbuf[NDUMP]; /* dump accumulator */
- int ndump; /* length of dump accumulator */
- int miny, dy; /* y values while unloading input */
- int ncblock; /* size of compressed blocks */
- Rectangle r;
- uchar *p, *q, *s, *es, *t;
- char hdr[11+5*12+1];
- char cbuf[20];
- r = i->r;
- bpl = bytesperline(r, i->depth);
- n = Dy(r)*bpl;
- data = malloc(n);
- ncblock = _compblocksize(r, i->depth);
- outbuf = malloc(ncblock);
- hash = malloc(NHASH*sizeof(Hlist));
- chain = malloc(NMEM*sizeof(Hlist));
- if(data == 0 || outbuf == 0 || hash == 0 || chain == 0){
- ErrOut:
- free(data);
- free(outbuf);
- free(hash);
- free(chain);
- return -1;
- }
- for(miny = r.min.y; miny != r.max.y; miny += dy){
- dy = r.max.y-miny;
- if(dy*bpl > CHUNK)
- dy = CHUNK/bpl;
- nb = unloadmemimage(i, Rect(r.min.x, miny, r.max.x, miny+dy),
- data+(miny-r.min.y)*bpl, dy*bpl);
- if(nb != dy*bpl)
- goto ErrOut;
- }
- sprint(hdr, "compressed\n%11s %11d %11d %11d %11d ",
- chantostr(cbuf, i->chan), r.min.x, r.min.y, r.max.x, r.max.y);
- if(write(fd, hdr, 11+5*12) != 11+5*12)
- goto ErrOut;
- edata = data+n;
- eout = outbuf+ncblock;
- line = data;
- r.max.y = r.min.y;
- while(line != edata){
- memset(hash, 0, NHASH*sizeof(Hlist));
- memset(chain, 0, NMEM*sizeof(Hlist));
- cp = chain;
- h = 0;
- outp = outbuf;
- for(n = 0; n != NMATCH; n++)
- h = hupdate(h, line[n]);
- loutp = outbuf;
- while(line != edata){
- ndump = 0;
- eline = line+bpl;
- for(p = line; p != eline; ){
- if(eline-p < NRUN)
- es = eline;
- else
- es = p+NRUN;
- q = 0;
- runlen = 0;
- for(hp = hash[h].next; hp; hp = hp->next){
- s = p + runlen;
- if(s >= es)
- continue;
- t = hp->s + runlen;
- for(; s >= p; s--)
- if(*s != *t--)
- goto matchloop;
- t += runlen+2;
- s += runlen+2;
- for(; s < es; s++)
- if(*s != *t++)
- break;
- n = s-p;
- if(n > runlen){
- runlen = n;
- q = hp->s;
- if(n == NRUN)
- break;
- }
- matchloop: ;
- }
- if(runlen < NMATCH){
- if(ndump == NDUMP){
- if(eout-outp < ndump+1)
- goto Bfull;
- *outp++ = ndump-1+128;
- memmove(outp, dumpbuf, ndump);
- outp += ndump;
- ndump = 0;
- }
- dumpbuf[ndump++] = *p;
- runlen = 1;
- }
- else{
- if(ndump != 0){
- if(eout-outp < ndump+1)
- goto Bfull;
- *outp++ = ndump-1+128;
- memmove(outp, dumpbuf, ndump);
- outp += ndump;
- ndump = 0;
- }
- offs = p-q-1;
- if(eout-outp < 2)
- goto Bfull;
- *outp++ = ((runlen-NMATCH)<<2) + (offs>>8);
- *outp++ = offs&255;
- }
- for(q = p+runlen; p != q; p++){
- if(cp->prev)
- cp->prev->next = 0;
- cp->next = hash[h].next;
- cp->prev = &hash[h];
- if(cp->next)
- cp->next->prev = cp;
- cp->prev->next = cp;
- cp->s = p;
- if(++cp == &chain[NMEM])
- cp = chain;
- if(edata-p > NMATCH)
- h = hupdate(h, p[NMATCH]);
- }
- }
- if(ndump != 0){
- if(eout-outp < ndump+1)
- goto Bfull;
- *outp++ = ndump-1+128;
- memmove(outp, dumpbuf, ndump);
- outp += ndump;
- }
- line = eline;
- loutp = outp;
- r.max.y++;
- }
- Bfull:
- if(loutp == outbuf)
- goto ErrOut;
- n = loutp-outbuf;
- sprint(hdr, "%11d %11ld ", r.max.y, n);
- write(fd, hdr, 2*12);
- write(fd, outbuf, n);
- r.min.y = r.max.y;
- }
- free(data);
- free(outbuf);
- free(hash);
- free(chain);
- return 0;
- }
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