3f82a553bd
Reading a ringbuffer backwards in order to process the most recent data first, is a very common operation. Nearly every dive computer backend has its own implementation. Thus with a common implementation, the amount of code duplication and complexity in the dive computer backends can be greatly reduced. The common algorithm is implemented as a simple ringbuffer stream, which takes care of all the technical details like the ringbuffer boundaries, alignment to the page size, using the optimal packet size and caching the remaining data.
79 lines
2.5 KiB
C
79 lines
2.5 KiB
C
/*
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* libdivecomputer
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*
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* Copyright (C) 2016 Jef Driesen
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301 USA
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*/
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#ifndef DC_RBSTREAM_H
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#define DC_RBSTREAM_H
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#include <libdivecomputer/device.h>
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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/**
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* Opaque object representing a ringbuffer stream.
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*/
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typedef struct dc_rbstream_t dc_rbstream_t;
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/**
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* Create a new ringbuffer stream.
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*
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* @param[out] rbstream A location to store the ringbuffer stream.
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* @param[in] device A valid device object.
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* @param[in] pagesize The page size in bytes.
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* @param[in] packetsize The packet size in bytes.
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* @param[in] begin The ringbuffer begin address.
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* @param[in] end The ringbuffer end address.
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* @param[in] address The stream start address.
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* @returns #DC_STATUS_SUCCESS on success, or another #dc_status_t code
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* on failure.
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*/
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dc_status_t
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dc_rbstream_new (dc_rbstream_t **rbstream, dc_device_t *device, unsigned int pagesize, unsigned int packetsize, unsigned int begin, unsigned int end, unsigned int address);
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/**
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* Read data from the ringbuffer stream.
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*
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* @param[in] rbstream A valid ringbuffer stream.
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* @param[in] progress An (optional) progress event structure.
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* @param[out] data The memory buffer to read the data into.
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* @param[in] size The number of bytes to read.
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* @returns #DC_STATUS_SUCCESS on success, or another #dc_status_t code
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* on failure.
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*/
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dc_status_t
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dc_rbstream_read (dc_rbstream_t *rbstream, dc_event_progress_t *progress, unsigned char data[], unsigned int size);
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/**
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* Destroy the ringbuffer stream.
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*
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* @param[in] rbstream A valid ringbuffer stream.
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* @returns #DC_STATUS_SUCCESS on success, or another #dc_status_t code
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* on failure.
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*/
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dc_status_t
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dc_rbstream_free (dc_rbstream_t *rbstream);
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#ifdef __cplusplus
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}
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#endif /* __cplusplus */
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#endif /* DC_RBSTREAM_H */
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