/* Shared-memory interface: The interface functions that the external program should use. * * Author: Georg Martin Reinke * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University * SPDX-License-Identifier: Apache-2.0 */ #pragma once #include #include #include #include #define DEFAULT_SHMEM_QUEUELEN 512u #define DEFAULT_SHMEM_SAMPLELEN 64u namespace villas { namespace node { /* Struct containing all parameters that need to be known when creating a new * shared memory object. */ struct ShmemConfig { int polling; // Whether to use polling instead of POSIX CVs int queuelen; // Size of the queues (in elements) int samplelen; // Maximum number of data entries in a single sample }; // The structure that actually resides in the shared memory. struct ShmemShared { int polling; // Whether to use a pthread_cond_t to signal if new samples are written to incoming queue. struct CQueueSignalled queue; // Queue for samples passed in both directions. struct Pool pool; // Pool for the samples in the queues. }; // Relevant information for one direction of the interface. struct shmem_dir { void *base; // Base address of the region. const char *name; // Name of the shmem object. size_t len; // Total size of the region. struct ShmemShared *shared; // Actually shared datastructure }; // Main structure representing the shared memory interface. struct ShmemInterface { struct shmem_dir read, write; std::atomic readers, writers, closed; }; /* Open the shared memory objects and retrieve / initialize the shared data structures. * Blocks until another process connects by opening the same objects. * * @param[in] wname Name of the POSIX shared memory object containing the output queue. * @param[in] rname Name of the POSIX shared memory object containing the input queue. * @param[inout] shm The shmem_int structure that should be used for following * calls will be written to this pointer. * @param[in] conf Configuration parameters for the output queue. * @retval 0 The objects were opened and initialized successfully. * @retval <0 An error occured; errno is set accordingly. */ int shmem_int_open(const char *wname, const char *rname, struct ShmemInterface *shm, struct ShmemConfig *conf); /* Close and destroy the shared memory interface and related structures. * * @param shm The shared memory interface. * @retval 0 Closing successfull. * @retval <0 An error occurred; errno is set appropiately. */ int shmem_int_close(struct ShmemInterface *shm); /* Read samples from the interface. * * @param shm The shared memory interface. * @param smps An array where the pointers to the samples will be written. The samples * must be freed with sample_decref after use. * @param cnt Number of samples to be read. * @retval >=0 Number of samples that were read. Can be less than cnt (including 0) in case not enough samples were available. * @retval -1 The other process closed the interface; no samples can be read anymore. */ int shmem_int_read(struct ShmemInterface *shm, struct Sample *const smps[], unsigned cnt); /* Write samples to the interface. * * @param shm The shared memory interface. * @param smps The samples to be written. Must be allocated from shm_int_alloc. * @param cnt Number of samples to write. * @retval >=0 Number of samples that were successfully written. Can be less than cnt (including 0) in case of a full queue. * @retval -1 The write failed for some reason; no more samples can be written. */ int shmem_int_write(struct ShmemInterface *shm, const struct Sample *const smps[], unsigned cnt); /* Allocate samples to be written to the interface. * * The writing process must not free the samples; only the receiving process should free them using sample_decref after use. * @param shm The shared memory interface. * @param smps Array where pointers to newly allocated samples will be returned. * @param cnt Number of samples to allocate. * @return Number of samples that were successfully allocated (may be less then cnt). */ int shmem_int_alloc(struct ShmemInterface *shm, struct Sample *smps[], unsigned cnt); /* Returns the total size of the shared memory region with the given size of * the input/output queues (in elements) and the given number of data elements * per struct Sample. */ size_t shmem_total_size(int queuelen, int samplelen); } // namespace node } // namespace villas