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/* |
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Modifications for FreeBoB by Pieter Palmers |
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Copied from the jackd sources |
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function names changed in order to avoid naming problems when using this in |
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a jackd backend. |
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Copyright (C) 2000 Paul Davis |
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Copyright (C) 2003 Rohan Drape |
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This program is free software; you can redistribute it and/or modify |
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it under the terms of the GNU Lesser General Public License as published by |
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the Free Software Foundation; either version 2.1 of the License, or |
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(at your option) any later version. |
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This program is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU Lesser General Public License for more details. |
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You should have received a copy of the GNU Lesser General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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ISO/POSIX C version of Paul Davis's lock free ringbuffer C++ code. |
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This is safe for the case of one read thread and one write thread. |
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*/ |
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//#include <config.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#ifdef USE_MLOCK |
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#include <sys/mman.h> |
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#endif /* USE_MLOCK */ |
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#include "ringbuffer.h" |
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/* Create a new ringbuffer to hold at least `sz' bytes of data. The |
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actual buffer size is rounded up to the next power of two. */ |
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freebob_ringbuffer_t * |
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freebob_ringbuffer_create (size_t sz) |
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{ |
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int power_of_two; |
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freebob_ringbuffer_t *rb; |
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rb = malloc (sizeof (freebob_ringbuffer_t)); |
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for (power_of_two = 1; 1 << power_of_two < sz; power_of_two++); |
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rb->size = 1 << power_of_two; |
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rb->size_mask = rb->size; |
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rb->size_mask -= 1; |
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rb->write_ptr = 0; |
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rb->read_ptr = 0; |
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rb->buf = malloc (rb->size); |
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rb->mlocked = 0; |
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return rb; |
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} |
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/* Free all data associated with the ringbuffer `rb'. */ |
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void |
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freebob_ringbuffer_free (freebob_ringbuffer_t * rb) |
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{ |
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#ifdef USE_MLOCK |
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if (rb->mlocked) { |
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munlock (rb->buf, rb->size); |
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} |
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#endif /* USE_MLOCK */ |
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free (rb->buf); |
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} |
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/* Lock the data block of `rb' using the system call 'mlock'. */ |
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int |
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freebob_ringbuffer_mlock (freebob_ringbuffer_t * rb) |
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{ |
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#ifdef USE_MLOCK |
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if (mlock (rb->buf, rb->size)) { |
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return -1; |
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} |
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#endif /* USE_MLOCK */ |
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rb->mlocked = 1; |
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return 0; |
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} |
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/* Reset the read and write pointers to zero. This is not thread |
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safe. */ |
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void |
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freebob_ringbuffer_reset (freebob_ringbuffer_t * rb) |
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{ |
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rb->read_ptr = 0; |
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rb->write_ptr = 0; |
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} |
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/* Return the number of bytes available for reading. This is the |
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number of bytes in front of the read pointer and behind the write |
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pointer. */ |
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size_t |
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freebob_ringbuffer_read_space (const freebob_ringbuffer_t * rb) |
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{ |
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size_t w, r; |
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w = rb->write_ptr; |
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r = rb->read_ptr; |
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if (w > r) { |
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return w - r; |
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} else { |
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return (w - r + rb->size) & rb->size_mask; |
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} |
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} |
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/* Return the number of bytes available for writing. This is the |
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number of bytes in front of the write pointer and behind the read |
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pointer. */ |
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size_t |
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freebob_ringbuffer_write_space (const freebob_ringbuffer_t * rb) |
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{ |
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size_t w, r; |
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w = rb->write_ptr; |
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r = rb->read_ptr; |
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if (w > r) { |
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return ((r - w + rb->size) & rb->size_mask) - 1; |
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} else if (w < r) { |
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return (r - w) - 1; |
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} else { |
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return rb->size - 1; |
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} |
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} |
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/* The copying data reader. Copy at most `cnt' bytes from `rb' to |
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`dest'. Returns the actual number of bytes copied. */ |
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size_t |
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freebob_ringbuffer_read (freebob_ringbuffer_t * rb, char *dest, size_t cnt) |
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{ |
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size_t free_cnt; |
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size_t cnt2; |
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size_t to_read; |
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size_t n1, n2; |
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if ((free_cnt = freebob_ringbuffer_read_space (rb)) == 0) { |
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return 0; |
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} |
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to_read = cnt > free_cnt ? free_cnt : cnt; |
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cnt2 = rb->read_ptr + to_read; |
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if (cnt2 > rb->size) { |
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n1 = rb->size - rb->read_ptr; |
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n2 = cnt2 & rb->size_mask; |
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} else { |
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n1 = to_read; |
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n2 = 0; |
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} |
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memcpy (dest, &(rb->buf[rb->read_ptr]), n1); |
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rb->read_ptr += n1; |
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rb->read_ptr &= rb->size_mask; |
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if (n2) { |
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memcpy (dest + n1, &(rb->buf[rb->read_ptr]), n2); |
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rb->read_ptr += n2; |
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rb->read_ptr &= rb->size_mask; |
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} |
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return to_read; |
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} |
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/* The copying data reader w/o read pointer advance. Copy at most |
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`cnt' bytes from `rb' to `dest'. Returns the actual number of bytes |
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copied. */ |
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size_t |
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freebob_ringbuffer_peek (freebob_ringbuffer_t * rb, char *dest, size_t cnt) |
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{ |
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size_t free_cnt; |
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size_t cnt2; |
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size_t to_read; |
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size_t n1, n2; |
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size_t tmp_read_ptr; |
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tmp_read_ptr = rb->read_ptr; |
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if ((free_cnt = freebob_ringbuffer_read_space (rb)) == 0) { |
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return 0; |
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} |
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to_read = cnt > free_cnt ? free_cnt : cnt; |
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cnt2 = tmp_read_ptr + to_read; |
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if (cnt2 > rb->size) { |
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n1 = rb->size - tmp_read_ptr; |
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n2 = cnt2 & rb->size_mask; |
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} else { |
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n1 = to_read; |
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n2 = 0; |
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} |
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memcpy (dest, &(rb->buf[tmp_read_ptr]), n1); |
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tmp_read_ptr += n1; |
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tmp_read_ptr &= rb->size_mask; |
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if (n2) { |
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memcpy (dest + n1, &(rb->buf[tmp_read_ptr]), n2); |
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tmp_read_ptr += n2; |
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tmp_read_ptr &= rb->size_mask; |
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} |
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return to_read; |
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} |
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/* The copying data writer. Copy at most `cnt' bytes to `rb' from |
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`src'. Returns the actual number of bytes copied. */ |
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size_t |
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freebob_ringbuffer_write (freebob_ringbuffer_t * rb, const char *src, size_t cnt) |
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{ |
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size_t free_cnt; |
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size_t cnt2; |
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size_t to_write; |
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size_t n1, n2; |
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if ((free_cnt = freebob_ringbuffer_write_space (rb)) == 0) { |
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return 0; |
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} |
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to_write = cnt > free_cnt ? free_cnt : cnt; |
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cnt2 = rb->write_ptr + to_write; |
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if (cnt2 > rb->size) { |
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n1 = rb->size - rb->write_ptr; |
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n2 = cnt2 & rb->size_mask; |
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} else { |
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n1 = to_write; |
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n2 = 0; |
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} |
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memcpy (&(rb->buf[rb->write_ptr]), src, n1); |
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rb->write_ptr += n1; |
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rb->write_ptr &= rb->size_mask; |
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if (n2) { |
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memcpy (&(rb->buf[rb->write_ptr]), src + n1, n2); |
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rb->write_ptr += n2; |
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rb->write_ptr &= rb->size_mask; |
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} |
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return to_write; |
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} |
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/* Advance the read pointer `cnt' places. */ |
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void |
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freebob_ringbuffer_read_advance (freebob_ringbuffer_t * rb, size_t cnt) |
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{ |
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rb->read_ptr += cnt; |
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rb->read_ptr &= rb->size_mask; |
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} |
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/* Advance the write pointer `cnt' places. */ |
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void |
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freebob_ringbuffer_write_advance (freebob_ringbuffer_t * rb, size_t cnt) |
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{ |
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rb->write_ptr += cnt; |
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rb->write_ptr &= rb->size_mask; |
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} |
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/* The non-copying data reader. `vec' is an array of two places. Set |
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the values at `vec' to hold the current readable data at `rb'. If |
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the readable data is in one segment the second segment has zero |
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length. */ |
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void |
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freebob_ringbuffer_get_read_vector (const freebob_ringbuffer_t * rb, |
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freebob_ringbuffer_data_t * vec) |
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{ |
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size_t free_cnt; |
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size_t cnt2; |
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size_t w, r; |
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w = rb->write_ptr; |
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r = rb->read_ptr; |
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if (w > r) { |
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free_cnt = w - r; |
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} else { |
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free_cnt = (w - r + rb->size) & rb->size_mask; |
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} |
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cnt2 = r + free_cnt; |
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if (cnt2 > rb->size) { |
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/* Two part vector: the rest of the buffer after the current write |
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ptr, plus some from the start of the buffer. */ |
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vec[0].buf = &(rb->buf[r]); |
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vec[0].len = rb->size - r; |
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vec[1].buf = rb->buf; |
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vec[1].len = cnt2 & rb->size_mask; |
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} else { |
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/* Single part vector: just the rest of the buffer */ |
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vec[0].buf = &(rb->buf[r]); |
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vec[0].len = free_cnt; |
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vec[1].len = 0; |
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} |
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} |
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/* The non-copying data writer. `vec' is an array of two places. Set |
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the values at `vec' to hold the current writeable data at `rb'. If |
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the writeable data is in one segment the second segment has zero |
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length. */ |
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void |
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freebob_ringbuffer_get_write_vector (const freebob_ringbuffer_t * rb, |
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freebob_ringbuffer_data_t * vec) |
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{ |
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size_t free_cnt; |
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size_t cnt2; |
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size_t w, r; |
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w = rb->write_ptr; |
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r = rb->read_ptr; |
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if (w > r) { |
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free_cnt = ((r - w + rb->size) & rb->size_mask) - 1; |
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} else if (w < r) { |
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free_cnt = (r - w) - 1; |
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} else { |
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free_cnt = rb->size - 1; |
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} |
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cnt2 = w + free_cnt; |
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if (cnt2 > rb->size) { |
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/* Two part vector: the rest of the buffer after the current write |
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ptr, plus some from the start of the buffer. */ |
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vec[0].buf = &(rb->buf[w]); |
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vec[0].len = rb->size - w; |
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vec[1].buf = rb->buf; |
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vec[1].len = cnt2 & rb->size_mask; |
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} else { |
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vec[0].buf = &(rb->buf[w]); |
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vec[0].len = free_cnt; |
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vec[1].len = 0; |
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} |
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} |
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