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/include/linux/circ_buf.h

https://bitbucket.org/thekraven/iscream_thunderc-2.6.35
C++ Header | 36 lines | 18 code | 7 blank | 11 comment | 0 complexity | a6b42537db1bc2f2516bb8b5e2ceab93 MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
 1/*
 2 * See Documentation/circular-buffers.txt for more information.
 3 */
 4
 5#ifndef _LINUX_CIRC_BUF_H
 6#define _LINUX_CIRC_BUF_H 1
 7
 8struct circ_buf {
 9	char *buf;
10	int head;
11	int tail;
12};
13
14/* Return count in buffer.  */
15#define CIRC_CNT(head,tail,size) (((head) - (tail)) & ((size)-1))
16
17/* Return space available, 0..size-1.  We always leave one free char
18   as a completely full buffer has head == tail, which is the same as
19   empty.  */
20#define CIRC_SPACE(head,tail,size) CIRC_CNT((tail),((head)+1),(size))
21
22/* Return count up to the end of the buffer.  Carefully avoid
23   accessing head and tail more than once, so they can change
24   underneath us without returning inconsistent results.  */
25#define CIRC_CNT_TO_END(head,tail,size) \
26	({int end = (size) - (tail); \
27	  int n = ((head) + end) & ((size)-1); \
28	  n < end ? n : end;})
29
30/* Return space available up to the end of the buffer.  */
31#define CIRC_SPACE_TO_END(head,tail,size) \
32	({int end = (size) - 1 - (head); \
33	  int n = (end + (tail)) & ((size)-1); \
34	  n <= end ? n : end+1;})
35
36#endif /* _LINUX_CIRC_BUF_H  */