X-Git-Url: https://git.draconx.ca/gitweb/upkg.git/blobdiff_plain/e404a2b5e81aa989c541023f08702e254236f98a..96f81be8f602195ab40e2e1b33129e050dfe5c6a:/src/uobject/uobject.c

diff --git a/src/uobject/uobject.c b/src/uobject/uobject.c
index a082690..627abe6 100644
--- a/src/uobject/uobject.c
+++ b/src/uobject/uobject.c
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <math.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <inttypes.h>
@@ -299,6 +300,41 @@ static int decode_object_property(UObject *uo, GValue *val, unsigned long len)
 	return 0;
 }
 
+/*
+ * 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.
+ */
+static float 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);
+}
+
 static unsigned long deserialize_property(UObject *uo, struct prop_head *head)
 {
 	struct u_object_priv *priv = U_OBJECT_GET_PRIV(uo);
@@ -340,6 +376,13 @@ static unsigned long deserialize_property(UObject *uo, struct prop_head *head)
 			return 0;
 		g_object_set_property(G_OBJECT(uo), head->prop_name, &val);
 		break;
+	case PROPERTY_FLOAT:
+		if (head->size != 4 || priv->nbuf-len < head->size)
+			return 0;
+		g_value_init(&val, G_TYPE_FLOAT);
+		g_value_set_float(&val, unpack_binary32_le(priv->buf+len));
+		g_object_set_property(G_OBJECT(uo), head->prop_name, &val);
+		break;
 	default:
 		u_warn(uo, "%s: unsupported property type %u",
 		           head->prop_name, (unsigned)head->type);