X-Git-Url: https://git.draconx.ca/gitweb/upkg.git/blobdiff_plain/82568fc97fa528e92f2de5e97717b542b921ccf3..67b795eeb9c9515adb9450562a3e7e15eb63a21d:/src/uobject/primitives.c

diff --git a/src/uobject/primitives.c b/src/uobject/primitives.c
new file mode 100644
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+++ b/src/uobject/primitives.c
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+/*
+ *  upkg: tool for manipulating Unreal Tournament packages.
+ *  Copyright © 2012, 2020 Nick Bowler
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <math.h>
+
+#include <uobject/uobject.h>
+#include "pack.h"
+
+/*
+ * Deserialize an IEEE 754 binary32 value in "little endian" (for whatever
+ * that term is worth in this context).  That is, when interpreted as a little
+ * endian 32-bit unsigned integer: bit 31 is the sign, bits 30-23 are the
+ * (biased) exponent, and bits 22-0 are the encoded part of the significand.
+ *
+ * The implementation is designed to be agnostic of the platform's actual
+ * float type, but the conversion may be lossy if "float" is not itself a
+ * binary32 format.  NaN payloads are not preserved.
+ */
+float u_unpack_binary32_le(const unsigned char *buf)
+{
+	unsigned long raw;
+	long significand;
+	int exponent;
+	float result;
+
+	raw = unpack_32_le(buf);
+	exponent = (raw & 0x7f800000) >> 23;
+	significand = (raw & 0x007fffff) >> 0;
+
+	switch (exponent) {
+	case 255:
+		result = significand ? NAN : INFINITY;
+		break;
+	default:
+		significand |= 0x00800000;
+		/* fall through */
+	case 0:
+		result = ldexpf(significand, exponent-126-24);
+	}
+
+	return copysignf(result, raw & 0x80000000 ? -1 : 1);
+}