#include <sys/types.h>
Go to the source code of this file.
Data Structures |
struct | jack_ringbuffer_data_t |
struct | jack_ringbuffer_t |
Functions |
jack_ringbuffer_t * | jack_ringbuffer_create (size_t sz) |
void | jack_ringbuffer_free (jack_ringbuffer_t *rb) |
void | jack_ringbuffer_get_read_vector (const jack_ringbuffer_t *rb, jack_ringbuffer_data_t *vec) |
void | jack_ringbuffer_get_write_vector (const jack_ringbuffer_t *rb, jack_ringbuffer_data_t *vec) |
size_t | jack_ringbuffer_read (jack_ringbuffer_t *rb, char *dest, size_t cnt) |
size_t | jack_ringbuffer_peek (jack_ringbuffer_t *rb, char *dest, size_t cnt) |
void | jack_ringbuffer_read_advance (jack_ringbuffer_t *rb, size_t cnt) |
size_t | jack_ringbuffer_read_space (const jack_ringbuffer_t *rb) |
int | jack_ringbuffer_mlock (jack_ringbuffer_t *rb) |
void | jack_ringbuffer_reset (jack_ringbuffer_t *rb) |
size_t | jack_ringbuffer_write (jack_ringbuffer_t *rb, const char *src, size_t cnt) |
void | jack_ringbuffer_write_advance (jack_ringbuffer_t *rb, size_t cnt) |
size_t | jack_ringbuffer_write_space (const jack_ringbuffer_t *rb) |
Detailed Description
A set of library functions to make lock-free ringbuffers available to JACK clients. The `capture_client.c' (in the example_clients directory) is a fully functioning user of this API.
The key attribute of a ringbuffer is that it can be safely accessed by two threads simultaneously -- one reading from the buffer and the other writing to it -- without using any synchronization or mutual exclusion primitives. For this to work correctly, there can only be a single reader and a single writer thread. Their identities cannot be interchanged.
Function Documentation
Allocates a ringbuffer data structure of a specified size. The caller must arrange for a call to jack_ringbuffer_free() to release the memory associated with the ringbuffer.
- Parameters:
-
sz | the ringbuffer size in bytes. |
- Returns:
- a pointer to a new jack_ringbuffer_t, if successful; NULL otherwise.
Frees the ringbuffer data structure allocated by an earlier call to jack_ringbuffer_create().
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
Fill a data structure with a description of the current readable data held in the ringbuffer. This description is returned in a two element array of jack_ringbuffer_data_t. Two elements are needed because the data to be read may be split across the end of the ringbuffer.
The first element will always contain a valid len field, which may be zero or greater. If the len field is non-zero, then data can be read in a contiguous fashion using the address given in the corresponding buf field.
If the second element has a non-zero len field, then a second contiguous stretch of data can be read from the address given in its corresponding buf field.
- Parameters:
-
Fill a data structure with a description of the current writable space in the ringbuffer. The description is returned in a two element array of jack_ringbuffer_data_t. Two elements are needed because the space available for writing may be split across the end of the ringbuffer.
The first element will always contain a valid len field, which may be zero or greater. If the len field is non-zero, then data can be written in a contiguous fashion using the address given in the corresponding buf field.
If the second element has a non-zero len field, then a second contiguous stretch of data can be written to the address given in the corresponding buf field.
- Parameters:
-
Lock a ringbuffer data block into memory.
Uses the mlock() system call. This is not a realtime operation.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
Read data from the ringbuffer. Opposed to jack_ringbuffer_read() this function does not move the read pointer. Thus it's a convenient way to inspect data in the ringbuffer in a continous fashion. The price is that the data is copied into a user provided buffer. For "raw" non-copy inspection of the data in the ringbuffer use jack_ringbuffer_get_read_vector().
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
dest | a pointer to a buffer where data read from the ringbuffer will go. |
cnt | the number of bytes to read. |
- Returns:
- the number of bytes read, which may range from 0 to cnt.
Read data from the ringbuffer.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
dest | a pointer to a buffer where data read from the ringbuffer will go. |
cnt | the number of bytes to read. |
- Returns:
- the number of bytes read, which may range from 0 to cnt.
Advance the read pointer.
After data have been read from the ringbuffer using the pointers returned by jack_ringbuffer_get_read_vector(), use this function to advance the buffer pointers, making that space available for future write operations.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
cnt | the number of bytes read. |
Return the number of bytes available for reading.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
- Returns:
- the number of bytes available to read.
Reset the read and write pointers, making an empty buffer.
This is not thread safe.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
size_t jack_ringbuffer_write |
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jack_ringbuffer_t * |
rb, |
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const char * |
src, |
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size_t |
cnt |
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) |
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Write data into the ringbuffer.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
src | a pointer to the data to be written to the ringbuffer. |
cnt | the number of bytes to write. |
- Returns:
- the number of bytes write, which may range from 0 to cnt
Advance the write pointer.
After data have been written the ringbuffer using the pointers returned by jack_ringbuffer_get_write_vector(), use this function to advance the buffer pointer, making the data available for future read operations.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
cnt | the number of bytes written. |
Return the number of bytes available for writing.
- Parameters:
-
rb | a pointer to the ringbuffer structure. |
- Returns:
- the amount of free space (in bytes) available for writing.