5c7dd7acc3
repo: https://github.com/T-head-Semi/linux commit: b1313fe517ca3703119dcc99ef3bbf75ab42bcfb Change-Id: I6cbb35294024ea3a66140e311f4bb705fd7fd626
38 lines
1.1 KiB
C
38 lines
1.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* See Documentation/core-api/circular-buffers.rst for more information.
|
|
*/
|
|
|
|
#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 */
|