Commit | Line | Data |
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1da177e4 LT |
1 | #ifndef _LINUX_CIRC_BUF_H |
2 | #define _LINUX_CIRC_BUF_H 1 | |
3 | ||
4 | struct circ_buf { | |
5 | char *buf; | |
6 | int head; | |
7 | int tail; | |
8 | }; | |
9 | ||
10 | /* Return count in buffer. */ | |
11 | #define CIRC_CNT(head,tail,size) (((head) - (tail)) & ((size)-1)) | |
12 | ||
13 | /* Return space available, 0..size-1. We always leave one free char | |
14 | as a completely full buffer has head == tail, which is the same as | |
15 | empty. */ | |
16 | #define CIRC_SPACE(head,tail,size) CIRC_CNT((tail),((head)+1),(size)) | |
17 | ||
18 | /* Return count up to the end of the buffer. Carefully avoid | |
19 | accessing head and tail more than once, so they can change | |
20 | underneath us without returning inconsistent results. */ | |
21 | #define CIRC_CNT_TO_END(head,tail,size) \ | |
22 | ({int end = (size) - (tail); \ | |
23 | int n = ((head) + end) & ((size)-1); \ | |
24 | n < end ? n : end;}) | |
25 | ||
26 | /* Return space available up to the end of the buffer. */ | |
27 | #define CIRC_SPACE_TO_END(head,tail,size) \ | |
28 | ({int end = (size) - 1 - (head); \ | |
29 | int n = (end + (tail)) & ((size)-1); \ | |
30 | n <= end ? n : end+1;}) | |
31 | ||
32 | #endif /* _LINUX_CIRC_BUF_H */ |