add libflate

src/libflate/deflatezlibblock.c

@@ -0,0 +1,34 @@
+#include <u.h>
+#include <libc.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;
+}