Make this code slightly easier to read, and eliminate calls
to sub-routines. Some of these were previously optimized away
by the compiler, but one memcpy was not.
In my testing, this makes the code about 20% smaller, and
has no sub-routine calls and no branches (on ARM).
v2 of this patch is, IMHO, easier to read than v1. Compared to
that patch it uses __u8 instead of unsigned char, for
consistency with the __u16 val data type, simplifies the
conditional expression, adds a another comment, and
moves a common statement out of the if.
Signed-off-by: Tim Bird <tim.bird@xxxxxxxxxxx>
---
drivers/staging/android/logger.c | 20 ++++++++++++--------
1 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c
index 92456d7..3475cb7 100644
--- a/drivers/staging/android/logger.c
+++ b/drivers/staging/android/logger.c
@@ -93,20 +93,24 @@ static inline struct logger_log *file_get_log(struct file *file)
* get_entry_len - Grabs the length of the payload of the next entry starting
* from 'off'.
*
+ * An entry length is 2 bytes (16 bits) in host endian order.
+ * In the log, the length does not include the size of the log entry structure.
+ * This function returns the size including the log entry structure.
+ *
* Caller needs to hold log->mutex.
*/
static __u32 get_entry_len(struct logger_log *log, size_t off)
{
__u16 val;
- switch (log->size - off) {
- case 1:
- memcpy(&val, log->buffer + off, 1);
- memcpy(((char *) &val) + 1, log->buffer, 1);
- break;
- default:
- memcpy(&val, log->buffer + off, 2);
- }
+ /* copy 2 bytes from buffer, in memcpy order, */
+ /* handling possible wrap at end of buffer */
+
+ ((__u8 *)&val)[0] = log->buffer[off];
+ if (likely(off+1 < log->size))
+ ((__u8 *)&val)[1] = log->buffer[off+1];
+ else
+ ((__u8 *)&val)[1] = log->buffer[0];
return sizeof(struct logger_entry) + val;
}
--
1.7.2.3
--
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