Commit 3bcfa431 authored by Tim Bird's avatar Tim Bird Committed by Greg Kroah-Hartman
Browse files

staging: android: logger: simplify and optimize get_entry_len 



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: default avatarTim Bird <tim.bird@am.sony.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c626224d

drivers/staging/android/logger.c

+12 −8
Original line number Diff line number Diff line
@@ -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;

}