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WebSVN – planix.SVN – Blame – /os/branches/feature_unix/sys/src/libdraw/writeimage.c – Rev 2

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#include <u.h>
2 
#include <libc.h>
3 
#include <draw.h>
4 
 
5 
#define	HSHIFT	3	/* HSHIFT==5 runs slightly faster, but hash table is 64x bigger */
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#define	NHASH	(1<<(HSHIFT*NMATCH))
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#define	HMASK	(NHASH-1)
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#define	hupdate(h, c)	((((h)<<HSHIFT)^(c))&HMASK)
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typedef struct Hlist Hlist;
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struct Hlist{
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	uchar *s;
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	Hlist *next, *prev;
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};
14 
 
15 
int
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writeimage(int fd, Image *i, int dolock)
17 
{
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	uchar *outbuf, *outp, *eout;		/* encoded data, pointer, end */
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	uchar *loutp;				/* start of encoded line */
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	Hlist *hash;				/* heads of hash chains of past strings */
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	Hlist *chain, *hp;			/* hash chain members, pointer */
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	Hlist *cp;				/* next Hlist to fall out of window */
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	int h;					/* hash value */
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	uchar *line, *eline;			/* input line, end pointer */
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	uchar *data, *edata;			/* input buffer, end pointer */
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	ulong n;				/* length of input buffer */
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	ulong nb;				/* # of bytes returned by unloadimage */
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	int bpl;				/* input line length */
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	int offs, runlen;			/* offset, length of consumed data */
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	uchar dumpbuf[NDUMP];			/* dump accumulator */
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	int ndump;				/* length of dump accumulator */
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	int miny, dy;				/* y values while unloading input */
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	int chunk, ncblock;
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	Rectangle r;
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	uchar *p, *q, *s, *es, *t;
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	char hdr[11+5*12+1];
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	char cbuf[20];
38 
 
39 
	chunk = i->display->bufsize - 32;	/* a little room for header */
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	r = i->r;
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	bpl = bytesperline(r, i->depth);
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	n = Dy(r)*bpl;
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	data = malloc(n);
44 
	ncblock = _compblocksize(r, i->depth);
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	outbuf = malloc(ncblock);
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	hash = malloc(NHASH*sizeof(Hlist));
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	chain = malloc(NMEM*sizeof(Hlist));
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	if(data == 0 || outbuf == 0 || hash == 0 || chain == 0){
49 
	ErrOut:
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		free(data);
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		free(outbuf);
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		free(hash);
53 
		free(chain);
54 
		return -1;
55 
	}
56 
	for(miny = r.min.y; miny != r.max.y; miny += dy){
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		dy = r.max.y-miny;
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		if(dy*bpl > chunk)
59 
			dy = chunk/bpl;
60 
		if(dolock)
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			lockdisplay(i->display);
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		nb = unloadimage(i, Rect(r.min.x, miny, r.max.x, miny+dy),
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			data+(miny-r.min.y)*bpl, dy*bpl);
64 
		if(dolock)
65 
			unlockdisplay(i->display);
66 
		if(nb != dy*bpl)
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			goto ErrOut;
68 
	}
69 
	sprint(hdr, "compressed\n%11s %11d %11d %11d %11d ",
70 
		chantostr(cbuf, i->chan), r.min.x, r.min.y, r.max.x, r.max.y);
71 
	if(write(fd, hdr, 11+5*12) != 11+5*12)
72 
		goto ErrOut;
73 
	edata = data+n;
74 
	eout = outbuf+ncblock;
75 
	line = data;
76 
	r.max.y = r.min.y;
77 
	while(line != edata){
78 
		memset(hash, 0, NHASH*sizeof(Hlist));
79 
		memset(chain, 0, NMEM*sizeof(Hlist));
80 
		cp = chain;
81 
		h = 0;
82 
		outp = outbuf;
83 
		for(n = 0; n != NMATCH; n++)
84 
			h = hupdate(h, line[n]);
85 
		loutp = outbuf;
86 
		while(line != edata){
87 
			ndump = 0;
88 
			eline = line+bpl;
89 
			for(p = line; p != eline; ){
90 
				if(eline-p < NRUN)
91 
					es = eline;
92 
				else
93 
					es = p+NRUN;
94 
				q = 0;
95 
				runlen = 0;
96 
				for(hp = hash[h].next; hp; hp = hp->next){
97 
					s = p + runlen;
98 
					if(s >= es)
99 
						continue;
100 
					t = hp->s + runlen;
101 
					for(; s >= p; s--)
102 
						if(*s != *t--)
103 
							goto matchloop;
104 
					t += runlen+2;
105 
					s += runlen+2;
106 
					for(; s < es; s++)
107 
						if(*s != *t++)
108 
							break;
109 
					n = s-p;
110 
					if(n > runlen){
111 
						runlen = n;
112 
						q = hp->s;
113 
						if(n == NRUN)
114 
							break;
115 
					}
116 
			matchloop: ;
117 
				}
118 
				if(runlen < NMATCH){
119 
					if(ndump == NDUMP){
120 
						if(eout-outp < ndump+1)
121 
							goto Bfull;
122 
						*outp++ = ndump-1+128;
123 
						memmove(outp, dumpbuf, ndump);
124 
						outp += ndump;
125 
						ndump = 0;
126 
					}
127 
					dumpbuf[ndump++] = *p;
128 
					runlen = 1;
129 
				}
130 
				else{
131 
					if(ndump != 0){
132 
						if(eout-outp < ndump+1)
133 
							goto Bfull;
134 
						*outp++ = ndump-1+128;
135 
						memmove(outp, dumpbuf, ndump);
136 
						outp += ndump;
137 
						ndump = 0;
138 
					}
139 
					offs = p-q-1;
140 
					if(eout-outp < 2)
141 
						goto Bfull;
142 
					*outp++ = ((runlen-NMATCH)<<2) + (offs>>8);
143 
					*outp++ = offs&255;
144 
				}
145 
				for(q = p+runlen; p != q; p++){
146 
					if(cp->prev)
147 
						cp->prev->next = 0;
148 
					cp->next = hash[h].next;
149 
					cp->prev = &hash[h];
150 
					if(cp->next)
151 
						cp->next->prev = cp;
152 
					cp->prev->next = cp;
153 
					cp->s = p;
154 
					if(++cp == &chain[NMEM])
155 
						cp = chain;
156 
					if(edata-p > NMATCH)
157 
						h = hupdate(h, p[NMATCH]);
158 
				}
159 
			}
160 
			if(ndump != 0){
161 
				if(eout-outp < ndump+1)
162 
					goto Bfull;
163 
				*outp++ = ndump-1+128;
164 
				memmove(outp, dumpbuf, ndump);
165 
				outp += ndump;
166 
			}
167 
			line = eline;
168 
			loutp = outp;
169 
			r.max.y++;
170 
		}
171 
	Bfull:
172 
		if(loutp == outbuf)
173 
			goto ErrOut;
174 
		n = loutp-outbuf;
175 
		sprint(hdr, "%11d %11ld ", r.max.y, n);
176 
		write(fd, hdr, 2*12);
177 
		write(fd, outbuf, n);
178 
		r.min.y = r.max.y;
179 
	}
180 
	free(data);
181 
	free(outbuf);
182 
	free(hash);
183 
	free(chain);
184 
	return 0;
185 
}