Initial Engine.Mesh implementation.

[upkg.git] / src / uobject / primitives.c

diff --git a/src/uobject/primitives.c b/src/uobject/primitives.c
new file mode 100644 (file)
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--- /dev/null
+++ b/src/uobject/primitives.c
@@ -0,0 +1,58 @@
+/*
+ *  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);
+}