62 lines
1.7 KiB
C
62 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* See Documentation/core-api/circular-buffers.rst for more information.
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
|
|
#define CIRC_BUF(name, type, bits) \
|
|
struct s##name { \
|
|
type buf[1 << (bits)]; \
|
|
int head; \
|
|
int tail; \
|
|
} name = { \
|
|
{ 0 }, \
|
|
0, \
|
|
0 };
|
|
|
|
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;})
|
|
|
|
|
|
int main(int ac, char **av)
|
|
{
|
|
int size = 5;
|
|
|
|
if (ac > 8) {
|
|
size = atoi(*(av + 1));
|
|
}
|
|
printf("size-%d\n", size);
|
|
|
|
CIRC_BUF(foo, int, 5);
|
|
printf("sizeof(elt)=%lu\n", sizeof(foo.buf[0]));
|
|
printf("sizeof(buf)=%lu\n", sizeof(foo.buf));
|
|
|
|
}
|