ref: 7a29422cfefaf76315eafa82ca606f9ded9517b3
dir: /os/boot/libflate/deflatezlibblock.c/
#include "lib9.h"
#include <flate.h>
#include "zlib.h"
int
deflatezlibblock(uchar *dst, int dsize, uchar *src, int ssize, int level, int debug)
{
ulong adler;
int n;
if(dsize < 6)
return FlateOutputFail;
n = deflateblock(dst + 2, dsize - 6, src, ssize, level, debug);
if(n < 0)
return n;
dst[0] = ZlibDeflate | ZlibWin32k;
/* bogus zlib encoding of compression level */
dst[1] = ((level > 2) + (level > 5) + (level > 8)) << 6;
/* header check field */
dst[1] |= 31 - ((dst[0] << 8) | dst[1]) % 31;
adler = adler32(1, src, ssize);
dst[n + 2] = adler >> 24;
dst[n + 3] = adler >> 16;
dst[n + 4] = adler >> 8;
dst[n + 5] = adler;
return n + 6;
}