[PATCH v3.1 3/9] lib: Introduce macros for bit operations
Austin Clements
aclements at csail.mit.edu
Fri Oct 24 05:49:15 PDT 2014
These macros help clarify basic bit-twiddling code and are written to
be robust against C undefined behavior of shift operators.
---
lib/message.cc | 6 +++---
lib/notmuch-private.h | 11 +++++++++++
2 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/lib/message.cc b/lib/message.cc
index 38bc929..55d2ff6 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -869,7 +869,7 @@ notmuch_bool_t
notmuch_message_get_flag (notmuch_message_t *message,
notmuch_message_flag_t flag)
{
- return message->flags & (1 << flag);
+ return NOTMUCH_TEST_BIT (message->flags, flag);
}
void
@@ -877,9 +877,9 @@ notmuch_message_set_flag (notmuch_message_t *message,
notmuch_message_flag_t flag, notmuch_bool_t enable)
{
if (enable)
- message->flags |= (1 << flag);
+ NOTMUCH_SET_BIT (&message->flags, flag);
else
- message->flags &= ~(1 << flag);
+ NOTMUCH_CLEAR_BIT (&message->flags, flag);
}
time_t
diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index 36cc12b..b86897c 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -63,6 +63,17 @@ NOTMUCH_BEGIN_DECLS
#define STRNCMP_LITERAL(var, literal) \
strncmp ((var), (literal), sizeof (literal) - 1)
+/* Robust bit test/set/reset macros */
+#define NOTMUCH_TEST_BIT(val, bit) \
+ (((bit) < 0 || (bit) >= CHAR_BIT * sizeof (unsigned long long)) ? 0 \
+ : !!((val) & (1ull << (bit))))
+#define NOTMUCH_SET_BIT(valp, bit) \
+ (((bit) < 0 || (bit) >= CHAR_BIT * sizeof (unsigned long long)) ? *(valp) \
+ : (*(valp) |= (1ull << (bit))))
+#define NOTMUCH_CLEAR_BIT(valp, bit) \
+ (((bit) < 0 || (bit) >= CHAR_BIT * sizeof (unsigned long long)) ? *(valp) \
+ : (*(valp) &= ~(1ull << (bit))))
+
#define unused(x) x __attribute__ ((unused))
#ifdef __cplusplus
--
2.1.0
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