33 lines
1000 B
C
33 lines
1000 B
C
|
#ifndef _LINUX_CIRC_BUF_H
|
||
|
|
#define _LINUX_CIRC_BUF_H 1
|
||
|
|
|
||
|
|
struct circ_buf {
|
||
|
|
char *buf;
|
||
|
|
int head;
|
||
|
|
int tail;
|
||
|
|
};
|
||
|
|
|
||
|
|
/* 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
|
||
|
|
empty. */
|
||
|
|
#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); \
|
||
|
|
n < end ? n : end;})
|
||
|
|
|
||
|
|
/* 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); \
|
||
|
|
n <= end ? n : end+1;})
|
||
|
|
|
||
|
|
#endif /* _LINUX_CIRC_BUF_H */
|