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npe: add ldexpf

--- a/include/npe/math.h

+++ b/include/npe/math.h

@@ -57,5 +57,6 @@

 double acosh(double x);

 double log1p(double x);

 double fmax(double x, double y);

+float ldexpf(float x, int n);

 #endif

--- /dev/null

+++ b/libnpe/ldexpf.c

@@ -1,0 +1,40 @@

+#include <math.h>

+

+/* taken from musl */

+

+float ldexpf(float x, int n)

+{

+	union {float f; u32int i;} u;

+	float y = x;

+	union {

+		float f;

+		u32int x;

+	}oneP[] = {

+		{.x = 0x7f000000},

+		{.x = 0x800000},

+		{.x = 0x4b800000},

+	};

+

+	if (n > 127) {

+		y *= oneP[0].f;

+		n -= 127;

+		if (n > 127) {

+			y *= oneP[0].f;

+			n -= 127;

+			if (n > 127)

+				n = 127;

+		}

+	} else if (n < -126) {

+		y *= oneP[1].f * oneP[2].f;

+		n += 126 - 24;

+		if (n < -126) {

+			y *= oneP[1].f * oneP[2].f;

+			n += 126 - 24;

+			if (n < -126)

+				n = -126;

+		}

+	}

+	u.i = (u32int)(0x7f+n)<<23;

+	x = y * u.f;

+	return x;

+}

--- a/libnpe/mkfile

+++ b/libnpe/mkfile

@@ -35,6 +35,7 @@

 	isatty.$O\

 	isinf.$O\

 	isnormal.$O\

+	ldexpf.$O\

 	log1p.$O\

 	localtime.$O\

 	log2.$O\