initial bigint48 implementation, will be used for the 5200 port

1 files changed, 119 insertions, 0 deletions

diff --git a/div.c b/div.c
new file mode 100644
index 0000000..9ee232d
--- /dev/null
+++ b/div.c
@@ -0,0 +1,119 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+example: 10 / 3
+
+num   denom   quotient    result
+10    3       1           0
+10    6       2           2
+4     3       1           3
+*/
+
+/*
+	// working, let's simplify it.
+int divide(int num, int denom) {
+	int result = 0, quotient = 1, newdenom;
+	fprintf(stderr, "\tdivide(%d, %d)\n", num, denom);
+	do {
+		fprintf(stderr, "outer loop\n");
+		newdenom = denom;
+		quotient = 1;
+		if(newdenom > num) {
+			fprintf(stderr, "%d > %d: quotient = 0;\n", newdenom, num);
+			quotient = 0;
+			num = 0;
+			// return result;
+		} else if(newdenom == num) {
+			fprintf(stderr, "%d == %d: quotient = 1;\n", newdenom, num);
+			quotient = 1;
+			num = 0;
+			// return ++result;
+		} else {
+			while(newdenom <= num) {
+				fprintf(stderr, "inner loop %d %d %d\n", num, newdenom, quotient);
+				newdenom <<= 1;
+				quotient <<= 1;
+			}
+			newdenom >>= 1;
+			num -= newdenom;
+			quotient >>= 1;
+		}
+		result += quotient;
+		fprintf(stderr, "num==%d, newdenom==%d, quotient==%d, result==%d\n", num, newdenom, quotient, result);
+	} while(num);
+	return result;
+}
+*/
+
+int divide(int num, int denom) {
+	int result, quotient, newdenom, halfnum;
+
+	result = 0;
+outerloop:
+	newdenom = denom;
+	quotient = 1;
+
+	if(newdenom < num)
+		goto innerprep;
+	if(newdenom == num)
+		goto innerprep;
+
+	quotient = 0;
+	num = 0;
+	goto addquot;
+
+innerprep:
+	halfnum = num >> 1;
+
+innerloop:
+	if(newdenom > halfnum)
+		goto innerdone;
+	newdenom <<= 1;
+	quotient <<= 1;
+	goto innerloop;
+
+innerdone:
+	num -= newdenom;
+
+addquot:
+	result += quotient;
+	if(num) goto outerloop;
+
+	return result;
+}
+
+/*
+	// working, but recursive, doesn't lend itself well to
+	// rewriting in asm.
+int divide(int num, int denom) {
+	int quotient = 1, olddenom = denom;
+	fprintf(stderr, "\tdivide(%d, %d)\n", num, denom);
+	if(denom > num) return 0;
+	if(denom == num) return 1;
+	while(denom <= num) {
+		denom <<= 1;
+		quotient <<= 1;
+		fprintf(stderr, "num==%d, denom==%d, quotient==%d\n", num, denom, quotient);
+	}
+	num -= (denom >> 1);
+	return ((quotient >> 1) + divide(num, olddenom));
+}
+*/
+
+int main(int argc, char **argv) {
+	int num = 100, denom = 10, result1, result2;
+
+	if(argc > 1) num = atoi(argv[1]);
+	if(argc > 2) denom = atoi(argv[2]);
+	result1 = num / denom;
+	result2 = divide(num, denom);
+	printf("%d / %d == %d\n", num, denom, result1);
+	printf("divide(%d, %d) == %d\n", num, denom, result2);
+	if(result1 == result2) {
+		puts("OK");
+		return 0;
+	}
+	puts("FAIL");
+	return 1;
+}