diff options
author | Richard Braun <rbraun@sceen.net> | 2017-05-28 17:05:16 +0200 |
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committer | Richard Braun <rbraun@sceen.net> | 2017-05-28 17:11:49 +0200 |
commit | df6e8f87ad6800ecb348f11b01a42db48237b371 (patch) | |
tree | 50432b64e6b28aca10cef8263b0455325986e4d2 /kern/cbuf.h | |
parent | a72801f115413cd3eab46857545ab527f31abb2b (diff) |
kern/cbuf: new module
Diffstat (limited to 'kern/cbuf.h')
-rw-r--r-- | kern/cbuf.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/kern/cbuf.h b/kern/cbuf.h new file mode 100644 index 0000000..3ea3841 --- /dev/null +++ b/kern/cbuf.h @@ -0,0 +1,101 @@ +/* + * Copyright (c) 2015 Richard Braun. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * + * Circular character buffer. + */ + +#ifndef _KERN_CBUF_H +#define _KERN_CBUF_H + +/* + * Circular buffer descriptor. + * + * The buffer capacity must be a power-of-two. Indexes are absolute values + * which can overflow. Their difference cannot exceed the capacity. + */ +struct cbuf { + char *buf; + unsigned long capacity; + unsigned long start; + unsigned long end; +}; + +static inline unsigned long +cbuf_capacity(const struct cbuf *cbuf) +{ + return cbuf->capacity; +} + +static inline unsigned long +cbuf_start(const struct cbuf *cbuf) +{ + return cbuf->start; +} + +static inline unsigned long +cbuf_end(const struct cbuf *cbuf) +{ + return cbuf->end; +} + +static inline unsigned long +cbuf_size(const struct cbuf *cbuf) +{ + return cbuf->end - cbuf->start; +} + +static inline void +cbuf_clear(struct cbuf *cbuf) +{ + cbuf->start = cbuf->end; +} + +/* + * Initialize a circular buffer. + * + * The descriptor is set to use the given buffer for storage. Capacity + * must be a power-of-two. + */ +void cbuf_init(struct cbuf *cbuf, char *buf, unsigned long capacity); + +/* + * Append a byte to a circular buffer. + * + * The end index is incremented. If the buffer is full, the oldest byte + * is overwritten and the start index is updated accordingly. + */ +void cbuf_push(struct cbuf *cbuf, char byte); + +/* + * Read a byte from a circular buffer. + * + * If the buffer is empty, ERROR_AGAIN is returned. Otherwise, the oldest + * byte is stored at the bytep address, the start index is incremented, + * and 0 is returned. + */ +int cbuf_pop(struct cbuf *cbuf, char *bytep); + +/* + * Read a byte at a specific location. + * + * If the given index is outside buffer boundaries, ERROR_INVAL is returned. + * Otherwise the byte is stored at the bytep address and 0 is returned. + * The buffer isn't changed by this operation. + */ +int cbuf_read(const struct cbuf *cbuf, unsigned long index, char *bytep); + +#endif /* _KERN_CBUF_H */ |