mirror of
https://git.code.sf.net/p/quake/quakeforge
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212 lines
7.4 KiB
C
212 lines
7.4 KiB
C
/*
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ringbuffer.h
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ring buffer
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Copyright (C) 2020 Bill Currie <bill@taniwha.org>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (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.
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See the GNU General Public License for more details.
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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:
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Free Software Foundation, Inc.
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59 Temple Place - Suite 330
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Boston, MA 02111-1307, USA
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*/
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#ifndef __QF_ringbuffer_h
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#define __QF_ringbuffer_h
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/** Type declaration for a type-safe ring buffer.
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*
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* While not in itself thread-safe, the buffer is designed (and tested) to be
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* used in a threaded environment using suitable locking mechanisms.
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*
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* \param type The type of data element stored in the ring buffer.
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* \param size The number of objects in the ring buffer. Note that the
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* actual capacity of the buffer is `size - 1` due to the
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* way ring buffers work.
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*/
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#define RING_BUFFER(type, size) \
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struct { \
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type buffer[size]; \
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unsigned head; \
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unsigned tail; \
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}
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#define RB_buffer_size(ring_buffer) \
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({ __auto_type rb = (ring_buffer); \
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sizeof (rb->buffer) / sizeof (rb->buffer[0]); \
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})
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/** Return the amount of space available for writing in the ring buffer.
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*
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* Use this to know how much data can be written (RB_WRITE_DATA()) or acquired
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* (RB_ACQUIRE()), or just to see if any space is available.
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*
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* \note Does NOT affect buffer state.
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*
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* \param ring_buffer The ring buffer to check for available space.
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*/
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#define RB_SPACE_AVAILABLE(ring_buffer) \
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({ __auto_type rb = &(ring_buffer); \
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(rb->tail + RB_buffer_size(rb) - rb->head - 1) % RB_buffer_size(rb);\
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})
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/** Return the number of objects available in the ring buffer.
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*
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* Use this to know how much data can be read (RB_READ_DATA()) or discarded
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* (RB_RELEASE()), or just to see if any data is available.
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*
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* \note Does NOT affect buffer state.
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*
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* \param ring_buffer The ring buffer to check for available data.
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*/
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#define RB_DATA_AVAILABLE(ring_buffer) \
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({ __auto_type rb = &(ring_buffer); \
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(rb->head + RB_buffer_size (rb) - rb->tail) % RB_buffer_size (rb); \
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})
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/** Write \a count objects from \a data to the buffer, wrapping if necessary.
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*
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* \note Affects buffer state (advances the head).
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*
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* \note Does NOT check that the space is available. It is the caller's
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* responsitiblity to do so using RB_SPACE_AVAILABLE().
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*
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* \param ring_buffer The ring buffer to which the data will be written.
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* \param data Pointer to the data to be copied into the ring buffer.
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* \param count unsigned int. The number of objects to copy from
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* \a data
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*/
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#define RB_WRITE_DATA(ring_buffer, data, count) \
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({ __auto_type rb = &(ring_buffer); \
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const typeof (rb->buffer[0]) *d = (data); \
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unsigned c = (count); \
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unsigned h = rb->head; \
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rb->head = (h + c) % RB_buffer_size (rb); \
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if (c > RB_buffer_size (rb) - h) { \
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memcpy (rb->buffer + h, d, \
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(RB_buffer_size (rb) - h) * sizeof (rb->buffer[0])); \
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c -= RB_buffer_size (rb) - h; \
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d += RB_buffer_size (rb) - h; \
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h = 0; \
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} \
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memcpy (rb->buffer + h, d, c * sizeof (rb->buffer[0])); \
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})
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/** Acquire \a count objects from the buffer, wrapping if necessary.
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*
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* \note Affects buffer state (advances the head).
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*
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* \note Does NOT check that the space is available. It is the caller's
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* responsitiblity to do so using RB_SPACE_AVAILABLE().
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*
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* \param ring_buffer The ring buffer to which the data will be written.
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* \param count unsigned int. The number of objects to copy from
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* \a data.
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* \return Address of the first object acquired.
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*/
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#define RB_ACQUIRE(ring_buffer, count) \
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({ __auto_type rb = &(ring_buffer); \
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unsigned c = (count); \
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unsigned h = rb->head; \
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rb->head = (h + c) % RB_buffer_size (rb); \
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&rb->buffer[h]; \
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})
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/** Read \a count objects from the buffer to \a data, wrapping if necessary.
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*
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* \note Affects buffer state (advances the tail).
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*
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* \note Does NOT check that the data is available. It is the caller's
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* responsitiblity to do so using RB_DATA_AVAILABLE().
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*
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* \param ring_buffer The ring buffer from which the data will be read.
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* \param data Pointer to the location into which data will be copied
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* from the ring buffer.
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* \param count unsigned int. The number of objects to copy from
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* the buffer into \a data
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*/
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#define RB_READ_DATA(ring_buffer, data, count) \
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({ __auto_type rb = &(ring_buffer); \
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typeof (&rb->buffer[0]) d = (data); \
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unsigned c = (count); \
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unsigned oc = c; \
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unsigned t = rb->tail; \
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if (c > RB_buffer_size (rb) - t) { \
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memcpy (d, rb->buffer + t, \
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(RB_buffer_size (rb) - t) * sizeof (rb->buffer[0])); \
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c -= RB_buffer_size (rb) - t; \
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d += RB_buffer_size (rb) - t; \
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t = 0; \
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} \
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memcpy (d, rb->buffer + t, c * sizeof (rb->buffer[0])); \
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rb->tail = (t + oc) % RB_buffer_size (rb); \
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})
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/** Discard \a count objects from the ring buffer.
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*
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* \note Affects buffer state (advances the tail).
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*
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* \note Does NOT check that the data is available. It is the caller's
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* responsitiblity to do so using RB_DATA_AVAILABLE().
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*
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* \param ring_buffer The ring buffer from which the objects will be
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* discarded.
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* \param count The number of objects to discard.
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*/
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#define RB_RELEASE(ring_buffer, count) \
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({ __auto_type rb = &(ring_buffer); \
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unsigned c = (count); \
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unsigned t = rb->tail; \
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rb->tail = (t + c) % RB_buffer_size (rb); \
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})
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/** Access a single item from the buffer without affecting buffer state.
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*
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* \note Does NOT affect buffer state.
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*
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* \note Does NOT check that the data is available. It is the caller's
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* responsitiblity to do so using RB_DATA_AVAILABLE().
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*
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* \param ring_buffer The ring buffer from which to access the object.
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* \param ahead The tail-relative index of the object to access from
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* the buffer. Valid range is 0 to
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* `RB_DATA_AVAILABLE() - 1`
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* \return Address of the accessed element
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*/
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#define RB_PEEK_DATA(ring_buffer, ahead) \
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({ __auto_type rb = &(ring_buffer); \
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&rb->buffer[(rb->tail + ahead) % RB_buffer_size (rb)]; \
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})
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/** WRite a single item to the buffer without affecting buffer state.
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*
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* \note Does NOT affect buffer state.
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*
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* \note Does NOT check that the data is available. It is the caller's
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* responsitiblity to do so using RB_DATA_AVAILABLE().
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*
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* \param ring_buffer The ring buffer from which to read the object.
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* \param ahead The tail-relative index of the buffer object to write.
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* Valid range is 0 to `RB_DATA_AVAILABLE() - 1`
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* \param data The data to write to the buffer.
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*/
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#define RB_POKE_DATA(ring_buffer, ahead, data) \
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({ __auto_type rb = &(ring_buffer); \
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rb->buffer[(rb->tail + ahead) % RB_buffer_size (rb)] = (data); \
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})
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#endif//__QF_ringbuffer_h
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