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schoenebeck |
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/*************************************************************************** |
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* * |
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* LinuxSampler - modular, streaming capable sampler * |
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* * |
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schoenebeck |
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* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck * |
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schoenebeck |
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* * |
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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 General Public License as published by * |
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* the Free Software Foundation; either version 2 of the License, or * |
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* (at your option) any later version. * |
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* * |
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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 General Public License for more details. * |
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* * |
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* You should have received a copy of the GNU 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, * |
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* MA 02111-1307 USA * |
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***************************************************************************/ |
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#ifndef RINGBUFFER_H |
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#define RINGBUFFER_H |
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#define DEFAULT_WRAP_ELEMENTS 1024 |
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#include <string.h> |
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#include "atomic.h" |
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template<class T> |
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class RingBuffer |
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{ |
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public: |
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RingBuffer (int sz, int wrap_elements = DEFAULT_WRAP_ELEMENTS) { |
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int power_of_two; |
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this->wrap_elements = wrap_elements; |
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for (power_of_two = 1; |
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1<<power_of_two < sz; |
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power_of_two++); |
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size = 1<<power_of_two; |
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size_mask = size; |
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size_mask -= 1; |
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atomic_set(&write_ptr, 0); |
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atomic_set(&read_ptr, 0); |
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buf = new T[size + wrap_elements]; |
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}; |
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virtual ~RingBuffer() { |
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delete [] buf; |
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} |
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/** |
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* Sets all remaining write space elements to zero. The write pointer |
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* will currently not be incremented after, but that might change in |
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* future. |
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*/ |
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inline void fill_write_space_with_null() { |
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int w = atomic_read(&write_ptr), |
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r = atomic_read(&read_ptr); |
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memset(get_write_ptr(), 0, write_space_to_end()); |
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if (r && w >= r) { |
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memset(get_buffer_begin(), 0, r - 1); |
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} |
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// set the wrap space elements to null |
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if (wrap_elements) memset(&buf[size], 0, wrap_elements); |
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} |
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__inline int read (T *dest, int cnt); |
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__inline int write (T *src, int cnt); |
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inline int push(T* src) { return write(src,1); } |
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inline int pop(T* dst) { return read(dst,1); } |
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__inline T *get_buffer_begin(); |
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__inline T *get_read_ptr(void) { |
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return(&buf[atomic_read(&read_ptr)]); |
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} |
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/** |
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* Returns a pointer to the element from the current read position, |
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* advanced by \a offset elements. |
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*/ |
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/*inline T* get_read_ptr(int offset) { |
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int r = atomic_read(&read_ptr); |
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r += offset; |
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r &= size_mask; |
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return &buf[r]; |
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}*/ |
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__inline T *get_write_ptr(); |
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__inline void increment_read_ptr(int cnt) { |
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atomic_set(&read_ptr , (atomic_read(&read_ptr) + cnt) & size_mask); |
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} |
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__inline void set_read_ptr(int val) { |
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atomic_set(&read_ptr , val); |
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} |
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__inline void increment_write_ptr(int cnt) { |
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atomic_set(&write_ptr, (atomic_read(&write_ptr) + cnt) & size_mask); |
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} |
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/* this function increments the write_ptr by cnt, if the buffer wraps then |
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subtract size from the write_ptr value so that it stays within 0<write_ptr<size |
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use this function to increment the write ptr after you filled the buffer |
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with a number of elements given by write_space_to_end_with_wrap(). |
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This ensures that the data that is written to the buffer fills up all |
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the wrap space that resides past the regular buffer. The wrap_space is needed for |
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interpolation. So that the audio thread sees the ringbuffer like a linear space |
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which allows us to use faster routines. |
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When the buffer wraps the wrap part is memcpy()ied to the beginning of the buffer |
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and the write ptr incremented accordingly. |
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*/ |
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__inline void increment_write_ptr_with_wrap(int cnt) { |
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int w=atomic_read(&write_ptr); |
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w += cnt; |
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if(w >= size) { |
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w -= size; |
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memcpy(&buf[0], &buf[size], w*sizeof(T)); |
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//printf("DEBUG !!!! increment_write_ptr_with_wrap: buffer wrapped, elements wrapped = %d (wrap_elements %d)\n",w,wrap_elements); |
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} |
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atomic_set(&write_ptr, w); |
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} |
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/* this function returns the available write space in the buffer |
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when the read_ptr > write_ptr it returns the space inbetween, otherwise |
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when the read_ptr < write_ptr it returns the space between write_ptr and |
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the buffer end, including the wrap_space. |
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There is an exception to it. When read_ptr <= wrap_elements. In that |
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case we return the write space to buffer end (-1) without the wrap_elements, |
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this is needed because a subsequent increment_write_ptr which copies the |
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data that resides into the wrap space to the beginning of the buffer and increments |
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the write_ptr would cause the write_ptr overstepping the read_ptr which would be an error. |
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So basically the if(r<=wrap_elements) we return the buffer space to end - 1 which |
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ensures that at the next call there will be one element free to write before the buffer wraps |
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and usually (except in EOF situations) the next write_space_to_end_with_wrap() will return |
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1 + wrap_elements which ensures that the wrap part gets fully filled with data |
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*/ |
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__inline int write_space_to_end_with_wrap() { |
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int w, r; |
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w = atomic_read(&write_ptr); |
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r = atomic_read(&read_ptr); |
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//printf("write_space_to_end: w=%d r=%d\n",w,r); |
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if(r > w) { |
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//printf("DEBUG: write_space_to_end_with_wrap: r>w r=%d w=%d val=%d\n",r,w,r - w - 1); |
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return(r - w - 1); |
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} |
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if(r <= wrap_elements) { |
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//printf("DEBUG: write_space_to_end_with_wrap: ATTENTION r <= wrap_elements: r=%d w=%d val=%d\n",r,w,size - w -1); |
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return(size - w -1); |
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} |
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if(r) { |
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//printf("DEBUG: write_space_to_end_with_wrap: r=%d w=%d val=%d\n",r,w,size - w + wrap_elements); |
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return(size - w + wrap_elements); |
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} |
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//printf("DEBUG: write_space_to_end_with_wrap: r=0 w=%d val=%d\n",w,size - w - 1 + wrap_elements); |
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return(size - w - 1 + wrap_elements); |
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} |
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/* this function adjusts the number of elements to write into the ringbuffer |
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in a way that the size boundary is avoided and that the wrap space always gets |
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entirely filled. |
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cnt contains the write_space_to_end_with_wrap() amount while |
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capped_cnt contains a capped amount of samples to read. |
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normally capped_cnt == cnt but in some cases eg when the disk thread needs |
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to refill tracks with smaller blocks because lots of streams require immediate |
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refill because lots of notes were started simultaneously. |
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In that case we set for example capped_cnt to a fixed amount (< cnt, eg 64k), |
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which helps to reduce the buffer refill latencies that occur between streams. |
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the first if() checks if the current write_ptr + capped_cnt resides within |
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the wrap area but is < size+wrap_elements. in that case we cannot return |
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capped_cnt because it would lead to a write_ptr wrapping and only a partial fill |
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of wrap space which would lead to errors. So we simply return cnt which ensures |
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that the the entire wrap space will get filled correctly. |
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In all other cases (which are not problematic because no write_ptr wrapping |
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occurs) we simply return capped_cnt. |
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*/ |
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__inline int adjust_write_space_to_avoid_boundary(int cnt, int capped_cnt) { |
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int w; |
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w = atomic_read(&write_ptr); |
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if((w+capped_cnt) >= size && (w+capped_cnt) < (size+wrap_elements)) { |
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//printf("adjust_write_space_to_avoid_boundary returning cnt = %d\n",cnt); |
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return(cnt); |
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} |
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//printf("adjust_write_space_to_avoid_boundary returning capped_cnt = %d\n",capped_cnt); |
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return(capped_cnt); |
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} |
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__inline int write_space_to_end() { |
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int w, r; |
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w = atomic_read(&write_ptr); |
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r = atomic_read(&read_ptr); |
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//printf("write_space_to_end: w=%d r=%d\n",w,r); |
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if(r > w) return(r - w - 1); |
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if(r) return(size - w); |
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return(size - w - 1); |
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} |
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__inline int read_space_to_end() { |
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int w, r; |
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w = atomic_read(&write_ptr); |
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r = atomic_read(&read_ptr); |
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if(w >= r) return(w - r); |
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return(size - r); |
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} |
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__inline void init() { |
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atomic_set(&write_ptr, 0); |
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atomic_set(&read_ptr, 0); |
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// wrap=0; |
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} |
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int write_space () { |
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int w, r; |
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w = atomic_read(&write_ptr); |
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r = atomic_read(&read_ptr); |
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if (w > r) { |
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return ((r - w + size) & 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 size - 1; |
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} |
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} |
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int read_space () { |
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int w, r; |
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w = atomic_read(&write_ptr); |
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r = atomic_read(&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 + size) & size_mask; |
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} |
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} |
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int size; |
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int wrap_elements; |
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schoenebeck |
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/** |
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* Independent, random access reading from a RingBuffer. This class |
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* allows to read from a RingBuffer without being forced to free read |
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* data while reading / positioning. |
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*/ |
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schoenebeck |
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template<class T1> |
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schoenebeck |
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class _NonVolatileReader { |
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public: |
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int read_space() { |
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int r = read_ptr; |
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int w = atomic_read(&pBuf->write_ptr); |
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return (w >= r) ? w - r : (w - r + pBuf->size) & pBuf->size_mask; |
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} |
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/** |
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schoenebeck |
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* Prefix decrement operator, for reducing NonVolatileReader's |
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* read position by one. |
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*/ |
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inline void operator--() { |
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if (read_ptr == atomic_read(&pBuf->read_ptr)) return; //TODO: or should we react oh this case (e.g. force segfault), as this is a very odd case? |
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--read_ptr & pBuf->size_mask; |
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} |
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/** |
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* Postfix decrement operator, for reducing NonVolatileReader's |
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* read position by one. |
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*/ |
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inline void operator--(int) { |
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--*this; |
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} |
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/** |
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* Returns pointer to the RingBuffer data of current |
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* NonVolatileReader's read position and increments |
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* NonVolatileReader's read position by one. |
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* |
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* @returns pointer to element of current read position |
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*/ |
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T* pop() { |
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if (!read_space()) return NULL; |
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T* pData = &pBuf->buf[read_ptr]; |
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read_ptr++; |
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read_ptr &= pBuf->size_mask; |
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return pData; |
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} |
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/** |
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schoenebeck |
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* Reads one element from the NonVolatileReader's current read |
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* position and copies it to the variable pointed by \a dst and |
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* finally increments the NonVolatileReader's read position by |
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* one. |
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* |
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* @param dst - where the element is copied to |
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* @returns 1 on success, 0 otherwise |
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*/ |
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int pop(T* dst) { return read(dst,1); } |
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/** |
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* Reads \a cnt elements from the NonVolatileReader's current |
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* read position and copies it to the buffer pointed by \a dest |
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* and finally increments the NonVolatileReader's read position |
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* by the number of read elements. |
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* |
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* @param dest - destination buffer |
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* @param cnt - number of elements to read |
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* @returns number of read elements |
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*/ |
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int read(T* dest, int cnt) { |
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int free_cnt; |
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int cnt2; |
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int to_read; |
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int n1, n2; |
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int priv_read_ptr; |
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priv_read_ptr = read_ptr; |
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if ((free_cnt = read_space()) == 0) return 0; |
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to_read = cnt > free_cnt ? free_cnt : cnt; |
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cnt2 = priv_read_ptr + to_read; |
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if (cnt2 > pBuf->size) { |
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n1 = pBuf->size - priv_read_ptr; |
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n2 = cnt2 & pBuf->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, &pBuf->buf[priv_read_ptr], n1 * sizeof(T)); |
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priv_read_ptr = (priv_read_ptr + n1) & pBuf->size_mask; |
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if (n2) { |
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memcpy(dest+n1, pBuf->buf, n2 * sizeof(T)); |
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priv_read_ptr = n2; |
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} |
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this->read_ptr = priv_read_ptr; |
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return to_read; |
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} |
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schoenebeck |
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/** |
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* Finally when the read data is not needed anymore, this method |
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* should be called to free the data in the RingBuffer up to the |
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* current read position of this NonVolatileReader. |
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* |
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* @see RingBuffer::increment_read_ptr() |
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*/ |
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void free() { |
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atomic_set(&pBuf->read_ptr, read_ptr); |
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} |
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schoenebeck |
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protected: |
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schoenebeck |
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_NonVolatileReader(RingBuffer<T1>* pBuf) { |
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schoenebeck |
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this->pBuf = pBuf; |
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this->read_ptr = atomic_read(&pBuf->read_ptr); |
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} |
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schoenebeck |
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RingBuffer<T1>* pBuf; |
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schoenebeck |
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int read_ptr; |
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schoenebeck |
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friend class RingBuffer<T1>; |
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schoenebeck |
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}; |
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typedef _NonVolatileReader<T> NonVolatileReader; |
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NonVolatileReader get_non_volatile_reader() { return NonVolatileReader(this); } |
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schoenebeck |
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protected: |
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T *buf; |
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atomic_t write_ptr; |
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atomic_t read_ptr; |
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int size_mask; |
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schoenebeck |
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friend class _NonVolatileReader<T>; |
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schoenebeck |
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}; |
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template<class T> T * |
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RingBuffer<T>::get_write_ptr (void) { |
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return(&buf[atomic_read(&write_ptr)]); |
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} |
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template<class T> T * |
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RingBuffer<T>::get_buffer_begin (void) { |
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return(buf); |
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} |
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template<class T> int |
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RingBuffer<T>::read (T *dest, int cnt) |
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{ |
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int free_cnt; |
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int cnt2; |
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int to_read; |
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int n1, n2; |
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int priv_read_ptr; |
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priv_read_ptr=atomic_read(&read_ptr); |
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if ((free_cnt = read_space ()) == 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 = priv_read_ptr + to_read; |
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if (cnt2 > size) { |
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n1 = size - priv_read_ptr; |
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n2 = cnt2 & 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, &buf[priv_read_ptr], n1 * sizeof (T)); |
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priv_read_ptr = (priv_read_ptr + n1) & size_mask; |
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if (n2) { |
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memcpy (dest+n1, buf, n2 * sizeof (T)); |
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priv_read_ptr = n2; |
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} |
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atomic_set(&read_ptr, priv_read_ptr); |
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return to_read; |
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} |
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template<class T> int |
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RingBuffer<T>::write (T *src, int cnt) |
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{ |
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int free_cnt; |
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int cnt2; |
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int to_write; |
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int n1, n2; |
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int priv_write_ptr; |
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priv_write_ptr=atomic_read(&write_ptr); |
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if ((free_cnt = write_space ()) == 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 = priv_write_ptr + to_write; |
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if (cnt2 > size) { |
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n1 = size - priv_write_ptr; |
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n2 = cnt2 & 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 (&buf[priv_write_ptr], src, n1 * sizeof (T)); |
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priv_write_ptr = (priv_write_ptr + n1) & size_mask; |
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if (n2) { |
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memcpy (buf, src+n1, n2 * sizeof (T)); |
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priv_write_ptr = n2; |
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} |
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atomic_set(&write_ptr, priv_write_ptr); |
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return to_write; |
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} |
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#endif /* RINGBUFFER_H */ |