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From 3937db18a203f9936387286b95328f27013a5ffe Mon Sep 17 00:00:00 2001
From: Peter Hutterer <peter.hutterer@who-t.net>
Date: Mon, 29 Jun 2009 13:09:57 +1000
Subject: [PATCH 2/4] include: introduce byte counting functions.
This patch adds the following three functions:
bits_to_bytes(bits) - the number of bytes needed to hold 'bits'
bytes_to_int32(bytes) - the number of 4-byte units to hold 'bytes'
pad_to_int32(bytes) - the closest multiple of 4 equal to or larger than
'bytes'.
All three operations are common in protocol processing and currently the
server has ((foo + 7)/8 + 3)/4 operations all over the place. A common set
of functions reduce the error rate of these (albeit simple) calculations and
improve readability of the code.
The functions do not check for overflow.
v2: backport to nx-libs 3.6.x as a prereq for
the CVE-2015-0255 fix (Mike DePaulo)
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
---
nx-X11/programs/Xserver/include/misc.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/nx-X11/programs/Xserver/include/misc.h b/nx-X11/programs/Xserver/include/misc.h
index 5944a42..849f1b5 100644
--- a/nx-X11/programs/Xserver/include/misc.h
+++ b/nx-X11/programs/Xserver/include/misc.h
@@ -193,6 +193,36 @@ typedef struct _xReq *xReqPtr;
#endif
+/**
+ * Calculate the number of bytes needed to hold bits.
+ * @param bits The minimum number of bits needed.
+ * @return The number of bytes needed to hold bits.
+ */
+static __inline__ int
+bits_to_bytes(const int bits) {
+ return ((bits + 7) >> 3);
+}
+/**
+ * Calculate the number of 4-byte units needed to hold the given number of
+ * bytes.
+ * @param bytes The minimum number of bytes needed.
+ * @return The number of 4-byte units needed to hold bytes.
+ */
+static __inline__ int
+bytes_to_int32(const int bytes) {
+ return (((bytes) + 3) >> 2);
+}
+
+/**
+ * Calculate the number of bytes (in multiples of 4) needed to hold bytes.
+ * @param bytes The minimum number of bytes needed.
+ * @return The closest multiple of 4 that is equal or higher than bytes.
+ */
+static __inline__ int
+pad_to_int32(const int bytes) {
+ return (((bytes) + 3) & ~3);
+}
+
/* some macros to help swap requests, replies, and events */
#define LengthRestB(stuff) \
--
1.9.1
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