1c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#ifndef _LINUX_CIRC_BUF_H 2c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#define _LINUX_CIRC_BUF_H 1 3c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru 4c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Querustruct circ_buf { 5c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru char *buf; 6c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru int head; 7c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru int tail; 8c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru}; 9c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru 10c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru/* Return count in buffer. */ 11c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#define CIRC_CNT(head,tail,size) (((head) - (tail)) & ((size)-1)) 12c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru 13c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru/* Return space available, 0..size-1. We always leave one free char 14c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru as a completely full buffer has head == tail, which is the same as 15c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru empty. */ 16c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#define CIRC_SPACE(head,tail,size) CIRC_CNT((tail),((head)+1),(size)) 17c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru 18c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru/* Return count up to the end of the buffer. Carefully avoid 19c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru accessing head and tail more than once, so they can change 20c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru underneath us without returning inconsistent results. */ 21c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#define CIRC_CNT_TO_END(head,tail,size) \ 22c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru ({int end = (size) - (tail); \ 23c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru int n = ((head) + end) & ((size)-1); \ 24c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru n < end ? n : end;}) 25c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru 26c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru/* Return space available up to the end of the buffer. */ 27c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#define CIRC_SPACE_TO_END(head,tail,size) \ 28c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru ({int end = (size) - 1 - (head); \ 29c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru int n = (end + (tail)) & ((size)-1); \ 30c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru n <= end ? n : end+1;}) 31c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru 32c559cd81139f97cecad1ad91a0b2e25a5936d53Jean-Baptiste Queru#endif /* _LINUX_CIRC_BUF_H */ 33