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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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1234567891011121314151617181920212223242526272829303132333435363738/* 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 */