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author | Steffen Trumtrar <s.trumtrar@pengutronix.de> | 2016-02-12 14:12:36 +0100 |
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committer | Sascha Hauer <s.hauer@pengutronix.de> | 2016-02-12 15:55:55 +0100 |
commit | acf6849208ea18fce88b6271af34134730342de4 (patch) | |
tree | 37a4c67fbbb620e2d6925d7d13b81c768edf11ca /include/linux | |
parent | 0f1c0c4d3070b5d67395b7ab60f7d9f1791399e6 (diff) | |
download | barebox-acf6849208ea18fce88b6271af34134730342de4.tar.gz barebox-acf6849208ea18fce88b6271af34134730342de4.tar.xz |
include: linux: add circular buffers
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/circ_buf.h | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/include/linux/circ_buf.h b/include/linux/circ_buf.h new file mode 100644 index 0000000000..90f2471dc6 --- /dev/null +++ b/include/linux/circ_buf.h @@ -0,0 +1,36 @@ +/* + * See Documentation/circular-buffers.txt 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 */ |