include/ringbuffer/iterator.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * ringbuffer/iterator.h
   4  *
   5  * Ring buffer and channel iterators.
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #ifndef _LIB_RING_BUFFER_ITERATOR_H
  11 #define _LIB_RING_BUFFER_ITERATOR_H
  12
  13 #include <ringbuffer/backend.h>
  14 #include <ringbuffer/frontend.h>
  15 #include <ringbuffer/vfs.h>
  16
  17 /*
  18  * lib_ring_buffer_get_next_record advances the buffer read position to the next
  19  * record. It returns either the size of the next record, -EAGAIN if there is
  20  * currently no data available, or -ENODATA if no data is available and buffer
  21  * is finalized.
  22  */
  23 extern ssize_t lib_ring_buffer_get_next_record(struct lttng_kernel_ring_buffer_channel *chan,
  24                                                struct lib_ring_buffer *buf);
  25
  26 /*
  27  * Ensure that the current subbuffer is put after client code has read the
  28  * payload of the current record. Has an effect when the end of subbuffer is
  29  * reached. It is not required if get_next_record is called successively.
  30  * However, it should be invoked before returning data to user-space to ensure
  31  * that the get/put subbuffer state is quiescent.
  32  */
  33 extern void lib_ring_buffer_put_current_record(struct lib_ring_buffer *buf);
  34
  35 /*
  36  * channel_get_next_record advances the buffer read position to the next record.
  37  * It returns either the size of the next record, -EAGAIN if there is currently
  38  * no data available, or -ENODATA if no data is available and buffer is
  39  * finalized.
  40  * Returns the current buffer in ret_buf.
  41  */
  42 extern ssize_t channel_get_next_record(struct lttng_kernel_ring_buffer_channel *chan,
  43                                        struct lib_ring_buffer **ret_buf);
  44
  45 /**
  46  * read_current_record - copy the buffer current record into dest.
  47  * @buf: ring buffer
  48  * @dest: destination where the record should be copied
  49  *
  50  * dest should be large enough to contain the record. Returns the number of
  51  * bytes copied.
  52  */
  53 static inline size_t read_current_record(struct lib_ring_buffer *buf, void *dest)
  54 {
  55         return lib_ring_buffer_read(&buf->backend, buf->iter.read_offset,
  56                                     dest, buf->iter.payload_len);
  57 }
  58
  59 extern int lib_ring_buffer_iterator_open(struct lib_ring_buffer *buf);
  60 extern void lib_ring_buffer_iterator_release(struct lib_ring_buffer *buf);
  61 extern int channel_iterator_open(struct lttng_kernel_ring_buffer_channel *chan);
  62 extern void channel_iterator_release(struct lttng_kernel_ring_buffer_channel *chan);
  63
  64 extern const struct file_operations channel_payload_file_operations;
  65 extern const struct file_operations lib_ring_buffer_payload_file_operations;
  66
  67 /*
  68  * Used internally.
  69  */
  70 int channel_iterator_init(struct lttng_kernel_ring_buffer_channel *chan);
  71 void channel_iterator_unregister_notifiers(struct lttng_kernel_ring_buffer_channel *chan);
  72 void channel_iterator_free(struct lttng_kernel_ring_buffer_channel *chan);
  73 void channel_iterator_reset(struct lttng_kernel_ring_buffer_channel *chan);
  74 void lib_ring_buffer_iterator_reset(struct lib_ring_buffer *buf);
  75
  76 #endif /* _LIB_RING_BUFFER_ITERATOR_H */