diff options
Diffstat (limited to 'lf_ring_buffer.c')
| -rw-r--r-- | lf_ring_buffer.c | 174 |
1 files changed, 0 insertions, 174 deletions
diff --git a/lf_ring_buffer.c b/lf_ring_buffer.c deleted file mode 100644 index 606e29a..0000000 --- a/lf_ring_buffer.c +++ /dev/null @@ -1,174 +0,0 @@ -/* - * File : lf_ring_buffer.c - * Author : Jérémy Zurcher <jeremy@asynk.ch> - * Date : 05/01/010 - * License : - * - * Permission is hereby granted, free of charge, to any person obtaining - * a copy of this software and associated documentation files (the - * "Software"), to deal in the Software without restriction, including - * without limitation the rights to use, copy, modify, merge, publish, - * distribute, sublicense, and/or sell copies of the Software, and to - * permit persons to whom the Software is furnished to do so, subject to - * the following conditions: - * - * The above copyright notice and this permission notice shall be - * included in all copies or substantial portions of the Software. - * - * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, - * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF - * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND - * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE - * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION - * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION - * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. - * - */ - -#include "lf_ring_buffer.h" -#include "lf_portable_cas.h" -#include <stdlib.h> -#include <string.h> -#include <time.h> - -//#define DEBUG_LFRB_KO 1 -//#define DEBUG_LFRB_CAS 1 -//#define DEBUG_LFRB 1 - -#ifdef DEBUG_LFRB - #include <stdio.h> - #define _LOG_KO_( ... ) fprintf(stdout,__VA_ARGS__) - #define _LOG_CAS_( ... ) fprintf(stdout,__VA_ARGS__) -#elif defined DEBUG_LFRB_CAS - #include <stdio.h> - #define _LOG_KO_( ... ) - #define _LOG_CAS_( ... ) fprintf(stdout,__VA_ARGS__) -#elif defined DEBUG_LFRB_KO - #include <stdio.h> - #define _LOG_KO_( ... ) fprintf(stdout,__VA_ARGS__) - #define _LOG_CAS_( ... ) -#else - #define _LOG_KO_( ... ) - #define _LOG_CAS_( ... ) -#endif - -#define BACKOFF_NANO_SLEEP 100000 - -/* initialize an empty lf_ring_buffer struct */ -lf_ring_buffer_t* lf_ring_buffer_create( size_t n_buf ) { - /* alloc ring_buffer struct */ - lf_ring_buffer_t *r = malloc(sizeof(lf_ring_buffer_t)); - if(r==NULL) return NULL; - /* */ - r->buffer = malloc(LFRB_BUFFER_SIZE*n_buf); - if(r->buffer==NULL) { - free(r); - return NULL; - } - memset(r->buffer,0,LFRB_BUFFER_SIZE*n_buf); - r->n_buf = n_buf; - r->read_from = -1; - r->write_to = 0; - return r; -} - -/* destroy an lf_ring_buffer strcture */ -void lf_ring_buffer_destroy( lf_ring_buffer_t *r ) { - free(r->buffer); - free(r); -} - -/* return 1 if is empty */ -int lf_ring_buffer_empty( lf_ring_buffer_t *r ) { return r->read_from==-1; } - -/* write data into the ring buffer */ -int lf_ring_buffer_write( lf_ring_buffer_t *r, void *data, int flags ) { - int write_to, read_from, next; - struct timespec backoff; - int backoff_time = BACKOFF_NANO_SLEEP; - /* reserve a buffer */ - for(;;){ - write_to = r->write_to; - read_from = r->read_from; - if(LFRB_IS_AVAILABLE( r->buffer[write_to] ) ) { - /* read_from==write_to means that the buffer is full and that a writer thread which at first reserved this buffer - * hasn't had enough CPU cycles to call MARK_AS_FILLED - */ - if( read_from!=write_to ) { - next = write_to+1; - if (next==r->n_buf) next=0; - /* what might have happend between IS_AVAILABLE and now : - * - a writter has reserved this buffer => write_to has moved => CAS fails - * - a reader has consumed a buffer => read_from has moved => we've got more space - */ - _LOG_CAS_( "write: CAS %d %d %d\n", r->write_to, write_to, next ); - if( CompareAndSwapInt( &r->write_to, write_to, next ) ) { - /* !!!!!!!!!!!!!! WARNING !!!!!!!!!!!!!!!!! - * - if the ring is empty before this write operation (r->read_from==-1 or latest idx) - * - and n_buf other threads execute this same function before the next CAS is finished - * then, the last thread will : - * - see this buffer as available - * - and see the ring as empty instead of full !!!!! - * so it will ends with two threads writing on this buffer - */ - if(r->read_from==-1) CompareAndSwapInt( &r->read_from, -1, write_to ); - break; - } - } else { - _LOG_KO_("write: ring full %d %d\n",r->read_from,idx); - if(IS_NOT_BLOCKING(flags)) return -1; - backoff.tv_sec = 0; - backoff.tv_nsec = backoff_time; - nanosleep(&backoff,NULL); - } - } else { - _LOG_KO_("write: buffer not available\n"); - if(IS_NOT_BLOCKING(flags)) return -1; - backoff.tv_sec = 0; - backoff.tv_nsec = backoff_time; - nanosleep(&backoff,NULL); - } - backoff_time += BACKOFF_NANO_SLEEP; - } - /* fill this buffer and mark it as filled */ - memcpy( LFRB_DATA_PTR(r->buffer[write_to]), data, LFRB_DATA_SIZE ); - LFRB_MARK_AS_FILLED( r->buffer[write_to] ); - return 0; -} - -/* read data from the ring buffer */ -int lf_ring_buffer_read( lf_ring_buffer_t *r, void *data, int flags ) { - int write_to, read_from, next; - struct timespec backoff; - int backoff_time = BACKOFF_NANO_SLEEP; - for(;;) { - write_to = r->write_to; - read_from = r->read_from; - if( !(LFRB_IS_AVAILABLE( r->buffer[read_from] )) && read_from!=-1 ) { - next = read_from+1; - if (next==r->n_buf) next=0; - /* will do bad things if data dst buffer is too small !! */ - memcpy( data, LFRB_DATA_PTR(r->buffer[read_from]), LFRB_DATA_SIZE ); - _LOG_CAS_( "read: CAS %d %d %d\n", r->read_from, read_from, next ); - if( CompareAndSwapInt( &r->read_from, read_from, next ) ) { - if(r->read_from==r->write_to) { - /* the buffer is empty but writers will see it as full */ - _LOG_CAS_( "read: empty CAS %d %d %d\n", r->read_from, next, -1 ); - CompareAndSwapInt( &r->read_from, next, -1 ); - } - break; - } - } - - _LOG_KO_("read: ring empty\n"); - if(IS_NOT_BLOCKING(flags)) return -1; - backoff.tv_sec = 0; - backoff.tv_nsec = backoff_time; - nanosleep(&backoff,NULL); - backoff_time += BACKOFF_NANO_SLEEP; - } - /* finish the read process */ - LFRB_MARK_AS_READ( r->buffer[read_from] ); - return 0; -} - |