[CRT:MATH] Import scalbn/scalbnf from musl

Author: tkreuzer

dll/win32/ucrtbase/ucrtbase.spec

@@ -2553,8 +2553,8 @@
 @ cdecl scalbln(double long) scalbn # double scalbln(double x, long exp);
 @ cdecl scalblnf(float long) scalbnf # float scalblnf(float x, long exp);
 @ cdecl scalblnl(double long) scalbn # long double scalblnl(long double x, long exp);
-@ cdecl -stub scalbn(double long) # double scalbn(double x, int exp);
-@ cdecl -stub scalbnf(float long) # float scalbnf(float x, int exp);
+@ cdecl scalbn(double long) # double scalbn(double x, int exp);
+@ cdecl scalbnf(float long) # float scalbnf(float x, int exp);
 @ cdecl scalbnl(double long) scalbn # long double scalbnl(long double x, int exp);
 @ cdecl set_terminate(ptr)
 @ cdecl set_unexpected(ptr)

sdk/lib/crt/math/math.cmake

@@ -16,6 +16,8 @@ list(APPEND LIBCNTPR_MATH_SOURCE
     math/labs.c
     math/round.c
     math/roundf.c
+    math/scalbn.c
+    math/scalbnf.c
     math/sincos.c
 )
 

sdk/lib/crt/math/scalbn.c

@@ -0,0 +1,43 @@
+/*
+ * PROJECT:     ReactOS CRT
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of scalbn.
+ * COPYRIGHT:   Imported from musl libc
+ *              https://git.musl-libc.org/cgit/musl/tree/src/math/scalbn.c
+ *              blob: 182f561068fda7bc8321dfc7991df8b6d58e1b56
+ *              See https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
+ */
+
+#include <math.h>
+#include <stdint.h>
+
+double scalbn(double x, int n)
+{
+	union {double f; uint64_t i;} u;
+	double_t y = x;
+
+	if (n > 1023) {
+		y *= 0x1p1023;
+		n -= 1023;
+		if (n > 1023) {
+			y *= 0x1p1023;
+			n -= 1023;
+			if (n > 1023)
+				n = 1023;
+		}
+	} else if (n < -1022) {
+		/* make sure final n < -53 to avoid double
+		   rounding in the subnormal range */
+		y *= 0x1p-1022 * 0x1p53;
+		n += 1022 - 53;
+		if (n < -1022) {
+			y *= 0x1p-1022 * 0x1p53;
+			n += 1022 - 53;
+			if (n < -1022)
+				n = -1022;
+		}
+	}
+	u.i = (uint64_t)(0x3ff+n)<<52;
+	x = y * u.f;
+	return x;
+}

sdk/lib/crt/math/scalbnf.c

@@ -0,0 +1,41 @@
+/*
+ * PROJECT:     ReactOS CRT
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of scalbnf.
+ * COPYRIGHT:   Imported from musl libc
+ *              https://git.musl-libc.org/cgit/musl/tree/src/math/scalbnf.c
+ *              blob: a5ad208b69929f24336fae40e6af37101c99a72f
+ *              See https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
+ */
+
+#include <math.h>
+#include <stdint.h>
+
+float scalbnf(float x, int n)
+{
+	union {float f; uint32_t i;} u;
+	float_t y = x;
+
+	if (n > 127) {
+		y *= 0x1p127f;
+		n -= 127;
+		if (n > 127) {
+			y *= 0x1p127f;
+			n -= 127;
+			if (n > 127)
+				n = 127;
+		}
+	} else if (n < -126) {
+		y *= 0x1p-126f * 0x1p24f;
+		n += 126 - 24;
+		if (n < -126) {
+			y *= 0x1p-126f * 0x1p24f;
+			n += 126 - 24;
+			if (n < -126)
+				n = -126;
+		}
+	}
+	u.i = (uint32_t)(0x7f+n)<<23;
+	x = y * u.f;
+	return x;
+}