buffer.c File Reference

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <mwalib.h>
#include "vcsbeam.h"
#include "gpu_macros.h"

Include dependency graph for buffer.c:

Functions
host_buffer *	vmInitReadBuffer (size_t read_size, size_t copy_size)
	Initialise a buffer for reading in voltage data. More...
void	vmFreeReadBuffer (host_buffer *rb)
	Frees the memory allocated in vmInitReadBuffer() More...
vm_error	vmReadBufferCopyMargin (host_buffer *rb)
	Copy the data from the end of the read buffer to the beginning. More...

Function Documentation

vmFreeReadBuffer()

void vmFreeReadBuffer

(

host_buffer *

rb

)

Frees the memory allocated in vmInitReadBuffer()

Parameters

rb	The read buffer to be freed

See also

vmInitReadBuffer()

vmInitReadBuffer()

host_buffer* vmInitReadBuffer	(	size_t	read_size,
		size_t	copy_size
	)

Initialise a buffer for reading in voltage data.

Parameters

read_size	The size of the "read" portion of the buffer into which the data are read
copy_size	The size of the "copy" portion of the buffer

Returns

A pointer to a newly allocated read buffer

The read buffer is designed for situations where the data must be read in a section at a time, but where operations on the data require it to be treated list a continuous stream. In this regard, it is similar to a ring buffer. Here, however, the problem is solved by copying a portion of data at the end of the buffer to the beginning of the buffer at each successive read. For this to be efficient, the size of the needed overlap between consecutive sections must be small enough that copying the data around in this way does not carry a significant amount of overhead.

The relationship between the total buffer, the read buffer, and the copy buffer are illustrated in the following diagram.

 <----------------------- buffer_size ------------------------->
               <---------------- read_size -------------------->
 <-copy_size->                                     <-copy_size->
 
|-------------|-----------------------------------|-------------|
^             ^                                   ^
buffer        read_ptr                            copy_from_ptr
copy_to_ptr

See also

vmFreeReadBuffer()

vmReadBufferCopyMargin()

vmReadNextSecond()

vmReadBufferCopyMargin()

vm_error vmReadBufferCopyMargin

(

host_buffer *

rb

)

Copy the data from the end of the read buffer to the beginning.

Parameters

rb	The read buffer to be operated on

Returns

VM_READ_BUFFER_NOT_SET if either rb or rb→buffer is NULL, or VM_SUCCESS if the memory is copied successfully.

This copies copy_size bytes from copy_from_ptr to copy_to_ptr. See vmInitReadBuffer() for a relevant diagram.

See also

vmInitReadBuffer()

vmReadNextSecond()