c/openssl: bignum, rsa

c/openssl/_demo/cbigintdemo/fib.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/c/openssl"
+)
+
+func newInt(n openssl.BN_ULONG) *openssl.BIGNUM {
+	ret := openssl.BNNew()
+	ret.SetWord(n)
+	return ret
+}
+
+func main() {
+	ctx := openssl.BN_CTXNew()
+	defer ctx.Free()
+
+	// Initialize two big ints with the first two numbers in the sequence.
+	a := newInt(0)
+	b := newInt(1)
+	defer a.Free()
+	defer b.Free()
+
+	// Initialize limit as 10^99, the smallest integer with 100 digits.
+	v10, v99 := newInt(10), newInt(99)
+	defer v10.Free()
+	defer v99.Free()
+
+	limit := openssl.BNNew()
+	defer limit.Free()
+
+	limit.Exp(v10, v99, ctx)
+
+	// Loop while a is smaller than 1e100.
+	for a.Cmp(limit) < 0 {
+		// Compute the next Fibonacci number, storing it in a.
+		a.Add(a, b)
+		// Swap a and b so that b is the next number in the sequence.
+		a, b = b, a
+	}
+	c.Printf(c.Str("%s\n"), a.CStr()) // 100-digit Fibonacci number
+}