| * See Documentation/circular-buffers.txt for more information. |
| #ifndef _LINUX_CIRC_BUF_H |
| #define _LINUX_CIRC_BUF_H 1 |
| /* Return count in buffer. */ |
| #define CIRC_CNT(head,tail,size) (((head) - (tail)) & ((size)-1)) |
| /* Return space available, 0..size-1. We always leave one free char |
| as a completely full buffer has head == tail, which is the same as |
| #define CIRC_SPACE(head,tail,size) CIRC_CNT((tail),((head)+1),(size)) |
| /* Return count up to the end of the buffer. Carefully avoid |
| accessing head and tail more than once, so they can change |
| underneath us without returning inconsistent results. */ |
| #define CIRC_CNT_TO_END(head,tail,size) \ |
| ({int end = (size) - (tail); \ |
| int n = ((head) + end) & ((size)-1); \ |
| /* Return space available up to the end of the buffer. */ |
| #define CIRC_SPACE_TO_END(head,tail,size) \ |
| ({int end = (size) - 1 - (head); \ |
| int n = (end + (tail)) & ((size)-1); \ |
| #endif /* _LINUX_CIRC_BUF_H */ |