initial import of the C runtime

src/runtime/c/gu/bits.c

@@ -0,0 +1,53 @@
+#include <gu/bits.h>
+
+#include <limits.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <math.h>
+
+unsigned gu_ceil2e(unsigned u)  
+{
+	u--;
+	u |= u >> 1;
+	u |= u >> 2;
+	u |= u >> 4;
+	u |= u >> 8;
+#if UINT_MAX > UINT16_MAX
+	u |= u >> 16;
+#endif
+#if UINT_MAX > UINT32_MAX
+	u |= u >> 32;
+#endif
+	u++;
+	return u;
+}
+
+GU_DEFINE_TYPE(GuIntDecodeExn, abstract, _);
+
+double 
+gu_decode_double(uint64_t u)
+{
+	bool sign = u >> 63;
+	unsigned rawexp = u >> 52 & 0x7ff;
+	uint64_t mantissa = u & 0xfffffffffffff;
+	double ret;
+
+	if (rawexp == 0x7ff) {
+		if (mantissa == 0) {
+			ret = INFINITY;
+		} else {
+			// At least glibc supports specifying the
+			// mantissa like this.
+			int len = snprintf(NULL, 0, "0x%" PRIx64, mantissa);
+			char buf[len + 1];
+			snprintf(buf, len + 1, "0x%" PRIx64, mantissa);
+			ret = nan(buf);
+		}
+	} else {
+		uint64_t m = rawexp ? 1ULL << 52 | mantissa : mantissa << 1;
+		ret = ldexp((double) m, rawexp - 1075);
+	}
+	return sign ? copysign(ret, -1.0) : ret;
+}