1 #include <u.h>
2 #include <libc.h>
3 #include <flate.h>
4 #include "zlib.h"
5
6 int
deflatezlibblock(uchar * dst,int dsize,uchar * src,int ssize,int level,int debug)7 deflatezlibblock(uchar *dst, int dsize, uchar *src, int ssize, int level, int debug)
8 {
9 ulong adler;
10 int n;
11
12 if(dsize < 6)
13 return FlateOutputFail;
14
15 n = deflateblock(dst + 2, dsize - 6, src, ssize, level, debug);
16 if(n < 0)
17 return n;
18
19 dst[0] = ZlibDeflate | ZlibWin32k;
20
21 /* bogus zlib encoding of compression level */
22 dst[1] = ((level > 2) + (level > 5) + (level > 8)) << 6;
23
24 /* header check field */
25 dst[1] |= 31 - ((dst[0] << 8) | dst[1]) % 31;
26
27 adler = adler32(1, src, ssize);
28 dst[n + 2] = adler >> 24;
29 dst[n + 3] = adler >> 16;
30 dst[n + 4] = adler >> 8;
31 dst[n + 5] = adler;
32
33 return n + 6;
34 }
35