simple implementation and test of packing ints

lib/c/experimental/pack.c

+#include <stdio.h>
+
+
+unsigned char do_pack(unsigned char *buf, unsigned long i) 
+{
+	printf("do_pack %lu == %lx\n", i, i);
+
+	unsigned long tmp = i;
+	unsigned char res = 0;
+
+	while ( tmp >= 0x80 ) {
+		buf[res] = (tmp & 0x7f) | 0x80;
+	        tmp >>= 7;
+		res++;
+	}
+	buf[res] = tmp;
+	return res+1;
+}
+
+unsigned long do_unpack(unsigned char *buf) 
+{
+	unsigned long res=0;
+	unsigned char i=0;
+	unsigned char cont=1;
+	do {
+		res |= (buf[i] & 0x7f) << 7*i; 
+		cont = buf[i++] & 0x80;
+	} while(cont);
+
+	return res;
+}
+
+void print_packed(unsigned char *buf, unsigned char len)
+{
+	int i;
+	
+	for(i=0; i<len;i++) {
+		printf("%2x   ", buf[i]);
+	}
+	printf("\n");
+}
+
+int main()
+{
+	unsigned char buf[10];
+	unsigned char len;
+
+	len = do_pack(buf, 10);
+	print_packed(buf, len);
+	printf("... unpacks to %u\n\n", do_unpack(buf));
+
+	len = do_pack(buf, 100);
+	print_packed(buf, len);
+	printf("... unpacks to %u\n\n", do_unpack(buf));
+
+	len = do_pack(buf, 1000);
+	print_packed(buf, len);
+	printf("... unpacks to %u\n\n", do_unpack(buf));
+
+	len = do_pack(buf, 100000);
+	print_packed(buf, len);
+	printf("... unpacks to %u\n\n", do_unpack(buf));
+
+	len = do_pack(buf, 2345678901);
+	print_packed(buf, len);
+	printf("... unpacks to %u\n\n", do_unpack(buf));
+
+	len = do_pack(buf, 0xffffffffffffffff);
+	print_packed(buf, len);
+	printf("... unpacks to %lx\n", do_unpack(buf));
+
+	return 0;
+}