deflatezlibblock.c (686B)
1 #include <u.h> 2 #include <libc.h> 3 #include <flate.h> 4 #include "zlib.h" 5 6 int 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 }