47 lines
1.1 KiB
C
47 lines
1.1 KiB
C
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#ifndef _CIRC_BUF_H
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#define _CIRC_BUF_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct circ_buf {
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char *buf;
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int head;
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int tail;
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};
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/* Return count in buffer. */
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#define CIRC_CNT(head,tail,size) (((head) - (tail)) & ((size)-1))
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/* Return space available, 0..size-1. We always leave one free char
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as a completely full buffer has head == tail, which is the same as
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empty. */
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#define CIRC_SPACE(head,tail,size) CIRC_CNT((tail),((head)+1),(size))
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/* Return count up to the end of the buffer. Carefully avoid
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accessing head and tail more than once, so they can change
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underneath us without returning inconsistent results. */
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static __INLINE int CIRC_CNT_TO_END(uint32_t head, uint32_t tail, uint32_t size)
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{
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int end = (size) - (tail);
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int n = ((head) + end) & ((size)-1);
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return n < end ? n : end;
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}
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/* Return space available up to the end of the buffer. */
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static __INLINE int CIRC_SPACE_TO_END(uint32_t head, uint32_t tail, uint32_t size)
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{
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int end = (size) - 1 - (head);
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int n = (end + (tail)) & ((size) - 1);
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return n <= end ? n : end + 1;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* _LINUX_CIRC_BUF_H */
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