C 基本环形缓冲区问题
C Basic ring buffer issue
我在尝试制作基本环形缓冲区时遇到问题。
我似乎无法让它正确环绕。
当我达到元素数量 = buffer_length 时,行为变得不可预测,在调试器中它只会显示第一个 * 元素。
谁能看到我遗漏的明显错误。
提前致谢。
#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#define BUFFER_LENGTH 8
typedef struct circular_buffer
{
float buffer[BUFFER_LENGTH];
float *buffer_end;
float *head;
float *tail;
size_t count;
} circular_buffer;
circular_buffer buffer;
void cb_init(circular_buffer *cb)
{
memset(cb->buffer, 0, BUFFER_LENGTH * sizeof(float));
cb->buffer_end = (float *)cb->buffer + BUFFER_LENGTH * sizeof(float);
cb->count = 0;
cb->head = cb->buffer;
cb->tail = cb->buffer;
}
void cb_push_back(circular_buffer *cb, float item)
{
*cb->head = item;
cb->head = (float *)cb->head++;
if (cb->head == cb->buffer_end)
cb->head = &cb->buffer[0];
cb->count++;
}
float cb_pop_front(circular_buffer *cb)
{
float item = 0;
item = *cb->tail;
cb->tail = (float*)cb->tail++;
if (cb->tail == cb->buffer_end)
cb->tail = &cb->buffer[0];
cb->count--;
return item;
}
float cb_peek_front(circular_buffer *cb, size_t pos)
{
float *arrPos;
size_t i = 0;
do
{
arrPos = (float*)cb->tail + i;
if (arrPos == cb->buffer_end)
arrPos = cb->buffer;
i++;
} while (i <= pos);
return *arrPos;
}
int _tmain(int argc, _TCHAR* argv[])
{
cb_init(&buffer);
cb_push_back(&buffer, 5);
printf("%f\n",cb_pop_front(&buffer));
cb_push_back(&buffer, 6);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 7);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 8);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 9);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 10);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 11);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 12);
printf("%f\n", cb_pop_front(&buffer));
// stops working here
cb_push_back(&buffer, 13);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 14);
printf("%f\n", cb_pop_front(&buffer));
return 0;
}
这个
cb->buffer_end = (float *)cb->buffer + BUFFER_LENGTH * sizeof(float);
不会如您所愿。
改为
cb->buffer_end = cb->buffer + BUFFER_LENGTH;
让它指向缓冲区的最后一个元素。
也只是删除所有那些无用的转换为 (float *)
。
另外你想更换
cb->head = (float *)cb->head++;
通过简单的
cb->head++;
和
cb->tail = (float*)cb->tail++;
来自
cb->tail++;
您在使用指针运算时错误地考虑了元素的大小。例如
bufpointer += 1;
前进到下一个元素,就像使用数组索引一样,您也不需要考虑每个元素的大小。所以
cb->buffer_end = (float *)cb->buffer + BUFFER_LENGTH * sizeof(float);
变成
cb->buffer_end = cb->buffer + BUFFER_LENGTH;
我在尝试制作基本环形缓冲区时遇到问题。 我似乎无法让它正确环绕。 当我达到元素数量 = buffer_length 时,行为变得不可预测,在调试器中它只会显示第一个 * 元素。
谁能看到我遗漏的明显错误。
提前致谢。
#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#define BUFFER_LENGTH 8
typedef struct circular_buffer
{
float buffer[BUFFER_LENGTH];
float *buffer_end;
float *head;
float *tail;
size_t count;
} circular_buffer;
circular_buffer buffer;
void cb_init(circular_buffer *cb)
{
memset(cb->buffer, 0, BUFFER_LENGTH * sizeof(float));
cb->buffer_end = (float *)cb->buffer + BUFFER_LENGTH * sizeof(float);
cb->count = 0;
cb->head = cb->buffer;
cb->tail = cb->buffer;
}
void cb_push_back(circular_buffer *cb, float item)
{
*cb->head = item;
cb->head = (float *)cb->head++;
if (cb->head == cb->buffer_end)
cb->head = &cb->buffer[0];
cb->count++;
}
float cb_pop_front(circular_buffer *cb)
{
float item = 0;
item = *cb->tail;
cb->tail = (float*)cb->tail++;
if (cb->tail == cb->buffer_end)
cb->tail = &cb->buffer[0];
cb->count--;
return item;
}
float cb_peek_front(circular_buffer *cb, size_t pos)
{
float *arrPos;
size_t i = 0;
do
{
arrPos = (float*)cb->tail + i;
if (arrPos == cb->buffer_end)
arrPos = cb->buffer;
i++;
} while (i <= pos);
return *arrPos;
}
int _tmain(int argc, _TCHAR* argv[])
{
cb_init(&buffer);
cb_push_back(&buffer, 5);
printf("%f\n",cb_pop_front(&buffer));
cb_push_back(&buffer, 6);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 7);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 8);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 9);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 10);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 11);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 12);
printf("%f\n", cb_pop_front(&buffer));
// stops working here
cb_push_back(&buffer, 13);
printf("%f\n", cb_pop_front(&buffer));
cb_push_back(&buffer, 14);
printf("%f\n", cb_pop_front(&buffer));
return 0;
}
这个
cb->buffer_end = (float *)cb->buffer + BUFFER_LENGTH * sizeof(float);
不会如您所愿。
改为
cb->buffer_end = cb->buffer + BUFFER_LENGTH;
让它指向缓冲区的最后一个元素。
也只是删除所有那些无用的转换为 (float *)
。
另外你想更换
cb->head = (float *)cb->head++;
通过简单的
cb->head++;
和
cb->tail = (float*)cb->tail++;
来自
cb->tail++;
您在使用指针运算时错误地考虑了元素的大小。例如
bufpointer += 1;
前进到下一个元素,就像使用数组索引一样,您也不需要考虑每个元素的大小。所以
cb->buffer_end = (float *)cb->buffer + BUFFER_LENGTH * sizeof(float);
变成
cb->buffer_end = cb->buffer + BUFFER_LENGTH;