X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=include%2Fwimlib%2Funaligned.h;h=34240bd0b6e5669b9da266d7b9f9f4099a5bc2a4;hp=5f920e75d30c5a53b39a5bdf099a176bc204b945;hb=aa3a2830cd4154238bc6a342ffea43d9ac69a14c;hpb=226a6dfe2909e054568298196785c944a1b5c4fa

diff --git a/include/wimlib/unaligned.h b/include/wimlib/unaligned.h
index 5f920e75..34240bd0 100644
--- a/include/wimlib/unaligned.h
+++ b/include/wimlib/unaligned.h
@@ -3,6 +3,9 @@
  *
  * Inline functions for unaligned memory accesses.
  *
+ * Author:	Eric Biggers
+ * Year:	2014, 2015
+ *
  * The author dedicates this file to the public domain.
  * You can do whatever you want with this file.
  */
@@ -106,4 +109,38 @@ put_unaligned_u32_le(u32 v, void *p)
 	}
 }
 
+/*
+ * Given a 32-bit value that was loaded with the platform's native endianness,
+ * return a 32-bit value whose high-order 8 bits are 0 and whose low-order 24
+ * bits contain the first 3 bytes, arranged in octets in a platform-dependent
+ * order, at the memory location from which the input 32-bit value was loaded.
+ */
+static inline u32
+loaded_u32_to_u24(u32 v)
+{
+	if (CPU_IS_LITTLE_ENDIAN)
+		return v & 0xFFFFFF;
+	else
+		return v >> 8;
+}
+
+/*
+ * Load the next 3 bytes from the memory location @p into the 24 low-order bits
+ * of a 32-bit value.  The order in which the 3 bytes will be arranged as octets
+ * in the 24 bits is platform-dependent.  At least LOAD_U24_REQUIRED_NBYTES
+ * bytes must be available at @p; note that this may be more than 3.
+ */
+static inline u32
+load_u24_unaligned(const u8 *p)
+{
+#if UNALIGNED_ACCESS_IS_FAST
+#  define LOAD_U24_REQUIRED_NBYTES 4
+	return loaded_u32_to_u24(load_u32_unaligned(p));
+#else
+#  define LOAD_U24_REQUIRED_NBYTES 3
+	return ((u32)p[0] << 0) | ((u32)p[1] << 8) | ((u32)p[2] << 16);
+#endif
+}
+
+
 #endif /* _WIMLIB_UNALIGNED_H */