我正在尝试完成一个循环缓冲程序，该程序只包含一系列股票报价。但是，当缩小循环缓冲区时，我似乎无法使输出正确。
缩小缓冲区的条件是缓冲区中3/4的空间是空闲的，将缓冲区收缩1/2。缩小/放大的代码如下：
void cbuf_update(cbuf *cb_ptr, unsigned int time, double rate){
int threeFourths;
threeFourths = (cb_ptr->maxSize/4)*3;
if((cb_ptr->maxSize != startSize) && cb_ptr->freeSlots >= threeFourths){
printf("Shrinking!\n");
int newSize;
newSize = (cb_ptr->maxSize/2)-1;
cbuf *newBuffer = malloc(sizeof(cbuf) + newSize * sizeof(quote));
newBuffer ->maxSize = (cb_ptr->maxSize/2);
newBuffer ->freeSlots = newBuffer->maxSize - (cb_ptr->maxSize - cb_ptr->freeSlots);
int x;
int counter;
int y;
counter = 0;
if(cb_ptr->end > cb_ptr->start){
for(x = cb_ptr->end; x < cb_ptr->maxSize; x ++){
if(cb_ptr->quoteBuffer[x].time != -1){
newBuffer->quoteBuffer[counter].time = cb_ptr->quoteBuffer[x].time;
newBuffer->quoteBuffer[counter].rate = cb_ptr->quoteBuffer[x].rate;
counter ++;
}
}
for(y = 0; y < cb_ptr->start; y++){
if(cb_ptr->quoteBuffer[y].time != -1){
newBuffer->quoteBuffer[counter].time = cb_ptr->quoteBuffer[y].time;
newBuffer->quoteBuffer[counter].rate = cb_ptr->quoteBuffer[y].rate;
counter++;
}
}
}
if(cb_ptr->end < cb_ptr->start){
//printf("second condition\n");
for(x = cb_ptr->end; x < cb_ptr->start; x ++){
if(cb_ptr->quoteBuffer[x].time != -1){
newBuffer->quoteBuffer[counter].time = cb_ptr->quoteBuffer[x].time;
newBuffer->quoteBuffer[counter].rate = cb_ptr->quoteBuffer[x].rate;
counter ++;
}
}
}
newBuffer->start = counter;
newBuffer->end = 0;
cbuf_dump(newBuffer);
*cb_ptr = *newBuffer;
}
if(cb_ptr->freeSlots == 0){
printf("EXPANDING CIRCULAR BUFFER!\n");
int newSize;
newSize = (cb_ptr->maxSize * 2) - 1;
cbuf *newBuffer = malloc(sizeof(cbuf) + newSize * sizeof(quote));
newBuffer->maxSize = cb_ptr->maxSize * 2;
newBuffer->start = cb_ptr->start;
newBuffer->end = cb_ptr->end;
newBuffer->freeSlots = newBuffer->maxSize - cb_ptr->maxSize;
int x;
int counter;
counter = 0;
for(x = cb_ptr->end; x < cb_ptr->maxSize; x ++){
newBuffer->quoteBuffer[counter].time = cb_ptr->quoteBuffer[x].time;
newBuffer->quoteBuffer[counter].rate = cb_ptr->quoteBuffer[x].rate;
counter ++;
}
int y;
for(y = 0; y < cb_ptr->start; y ++){
newBuffer->quoteBuffer[counter].time = cb_ptr->quoteBuffer[y].time;
newBuffer->quoteBuffer[counter].rate = cb_ptr->quoteBuffer[y].rate;
counter++;
}
newBuffer->start = cb_ptr->maxSize;
newBuffer->end = 0;
*cb_ptr = *newBuffer;
}
//If the start pointer has reached the end of the array and there are still free slots back at the beginning of the array, loop back.
if(cb_ptr->start == cb_ptr->maxSize && cb_ptr->freeSlots > 0){
//printf("Cannot insert time: %d\n", time);
cb_ptr->start = 0;
};
cb_ptr->quoteBuffer[cb_ptr->start].time = time;
cb_ptr->quoteBuffer[cb_ptr->start].rate = rate;
cb_ptr->start = cb_ptr->start +1;
cb_ptr->freeSlots = cb_ptr->freeSlots -1;
//If any quote in the array is older than 5 minutes when compared to the current quote, flag it as null and move the end pointer up one.
//Also, clear up a freeSlot.
int x;
for(x = cb_ptr->end; x < (cb_ptr->start); x ++){
if((time) - (cb_ptr->quoteBuffer[x].time) >= fiveMin){
cb_ptr->end = cb_ptr->end + 1;
cb_ptr->quoteBuffer[x].time = -1;
cb_ptr->quoteBuffer[x].rate = -1.00;
cb_ptr->freeSlots = cb_ptr->freeSlots +1;
}
}
}
转储缓冲区（打印）的代码如下：
void cbuf_dump(cbuf *cb_ptr){
printf("*****\t DUMPING \t*****\n");
if(cb_ptr->start > cb_ptr->end){
//printf("first dump cond.\n");
printf("start: %d\t end:%d\n", cb_ptr->start, cb_ptr->end);
int x;
for(x = cb_ptr->end; x<(cb_ptr->start); x++){
printf("%d.) time = %d, \t rate = %f\n",x,(cb_ptr->quoteBuffer[x].time),(cb_ptr->quoteBuffer[x].rate));
}
}
/*
If the start pointer has been wrapped back around to the beginning of the circular buffer, then the end pointer must be at an index that is greater than the start index. For this, we need to print out the data ranging from the end pointer to the end of the array, and then the data from the start pointer to the end pointer provided the data isn't flagged as null (having -1 for both entries in the quote struct).
*/
if(cb_ptr->end >= cb_ptr->start){
//printf("Secondary condition\n");
int x;
for(x=cb_ptr->end; x < cb_ptr->maxSize; x ++){
printf("%d.) time = %d, \t rate = %f\n",x,(cb_ptr->quoteBuffer[x].time),(cb_ptr->quoteBuffer[x].rate));
}
int y;
for(y = 0; y < cb_ptr->start; y ++){
if(cb_ptr->quoteBuffer[y].time != -1){
printf("%d.) time = %d, \t rate = %f\n",y,(cb_ptr->quoteBuffer[y].time),(cb_ptr->quoteBuffer[y].rate));
}
}
}
//printf("freeslots = %d\n", cb_ptr->freeSlots);
}
最后，我的主要是：
int main(){
cbuf *cb1 ;
cb1 = cbuf_init() ;
cbuf_update(cb1, 60, 1.291) ;
cbuf_update(cb1, 63, 1.287) ;
cbuf_update(cb1, 63, 1.231) ;
cbuf_update(cb1, 69, 1.229) ;
cbuf_update(cb1, 72, 1.247) ;
cbuf_update(cb1,361,1.291);
cbuf_update(cb1, 411, 1.291) ;
cbuf_update(cb1, 412, 1.281) ;
cbuf_update(cb1, 413, 1.292) ;
cbuf_update(cb1, 414, 1.284) ;
cbuf_update(cb1, 414, 1.290) ;
cbuf_update(cb1, 511, 1.241) ;
cbuf_update(cb1, 512, 1.251) ;
cbuf_update(cb1, 513, 1.232) ;
cbuf_update(cb1, 514, 1.202) ;
cbuf_update(cb1, 517, 1.119) ;
cbuf_update(cb1, 551, 1.080) ;
cbuf_update(cb1, 552, 1.081) ;
cbuf_update(cb1, 553, 1.079) ;
cbuf_update(cb1, 554, 1.088) ;
cbuf_update(cb1, 561, 1.072) ;
cbuf_update(cb1, 562, 1.113) ;
cbuf_update(cb1, 563, 1.091) ;
cbuf_update(cb1, 564, 1.092) ;
cbuf_update(cb1, 571, 1.089) ;
cbuf_update(cb1, 572, 1.073) ;
cbuf_update(cb1, 573, 1.061) ;
cbuf_update(cb1, 574, 1.111) ;
cbuf_update(cb1, 581, 1.119) ;
cbuf_update(cb1, 582, 1.123) ;
cbuf_update(cb1, 583, 1.151) ;
cbuf_update(cb1, 584, 1.153) ;
cbuf_dump(cb1);
cbuf_update(cb1, 750, 1.200) ;
cbuf_dump(cb1) ;
cbuf_update(cb1, 818, 1.210) ;
cbuf_dump(cb1) ;
cbuf_update(cb1, 868, 1.230) ;
cbuf_dump(cb1) ;
cbuf_update(cb1, 878, 1.230) ;
cbuf_dump(cb1) ;
cbuf_update(cb1, 900, 1.240) ;
cbuf_dump(cb1) ;
cbuf_update(cb1, 2000, 1.240) ;
cbuf_dump(cb1) ;
return 0;
}
到最后的输出应该是：
*** Circular Buffer Dump ***
size = 11, max = 40
start = 19, end = 29
19: time = 571, rate = 1.089000
20: time = 572, rate = 1.073000
21: time = 573, rate = 1.061000
22: time = 574, rate = 1.111000
23: time = 581, rate = 1.119000
24: time = 582, rate = 1.123000
25: time = 583, rate = 1.151000
26: time = 584, rate = 1.153000
27: time = 750, rate = 1.200000
28: time = 818, rate = 1.210000
29: time = 868, rate = 1.230000
****************************
Shrinking circular buffer: old max = 40, new max = 20
*** Circular Buffer Dump ***
size = 8, max = 20
start = 3, end = 10
3: time = 581, rate = 1.119000
4: time = 582, rate = 1.123000
5: time = 583, rate = 1.151000
6: time = 584, rate = 1.153000
7: time = 750, rate = 1.200000
8: time = 818, rate = 1.210000
9: time = 868, rate = 1.230000
10: time = 878, rate = 1.230000
****************************
Shrinking circular buffer: old max = 20, new max = 10
*** Circular Buffer Dump ***
size = 5, max = 10
start = 1, end = 5
1: time = 750, rate = 1.200000
2: time = 818, rate = 1.210000
3: time = 868, rate = 1.230000
4: time = 878, rate = 1.230000
5: time = 900, rate = 1.240000
****************************
*** Circular Buffer Dump ***
size = 1, max = 10
start = 6, end = 6
6: time = 2000, rate = 1.240000
****************************
然而，我的输出仍然像这样完成：
***** DUMPING *****
start: 30 end:19
19.) time = 571, rate = 1.089000
20.) time = 572, rate = 1.073000
21.) time = 573, rate = 1.061000
22.) time = 574, rate = 1.111000
23.) time = 581, rate = 1.119000
24.) time = 582, rate = 1.123000
25.) time = 583, rate = 1.151000
26.) time = 584, rate = 1.153000
27.) time = 750, rate = 1.200000
28.) time = 818, rate = 1.210000
29.) time = 868, rate = 1.230000
***** DUMPING *****
start: 31 end:23
23.) time = 581, rate = 1.119000
24.) time = 582, rate = 1.123000
25.) time = 583, rate = 1.151000
26.) time = 584, rate = 1.153000
27.) time = 750, rate = 1.200000
28.) time = 818, rate = 1.210000
29.) time = 868, rate = 1.230000
30.) time = 878, rate = 1.230000
Shrinking!
***** DUMPING *****
start: 9 end:8
8.) time = 900, rate = 1.240000
Shrinking!
***** DUMPING *****
start: 2 end:1
1.) time = 2000, rate = 1.240000
显然格式不同，但数字应匹配。我无法弄清楚为什么只要900的时间被添加到我的缓冲区，它似乎认为时间码581-878都距离900大于5分钟（打印标准只打印最新的报价在5分钟的时间内）。我意识到581-600显然会被丢弃，但其余部分仍应保留在缓冲区中。
答案 0 :(得分：2)
试试这个：
#include <stdio.h>
#include <stdlib.h>
enum { startSize = 0 };
enum { fiveMin = 5 * 60 };
typedef struct quote { int time; double rate; } quote;
typedef struct cbuf { int maxSize; int freeSlots; int start; int end; quote quoteBuffer[]; } cbuf;
static void cbuf_dump(cbuf *cb_ptr);
static void cbuf_update(cbuf **cb_dblptr, unsigned int time, double rate)
{
cbuf *cb_ptr = *cb_dblptr;
int threeFourths = (cb_ptr->maxSize/4)*3;
if (cb_ptr->maxSize != startSize && cb_ptr->freeSlots >= threeFourths)
{
printf("Shrinking!\n");
int newSize;
newSize = (cb_ptr->maxSize/2)-1;
cbuf *newBuffer = malloc(sizeof(cbuf) + newSize * sizeof(quote));
newBuffer->maxSize = (cb_ptr->maxSize/2);
newBuffer->freeSlots = newBuffer->maxSize - (cb_ptr->maxSize - cb_ptr->freeSlots);
int counter = 0;
if (cb_ptr->end > cb_ptr->start)
{
for (int x = cb_ptr->end; x < cb_ptr->maxSize; x++)
{
if (cb_ptr->quoteBuffer[x].time != -1)
newBuffer->quoteBuffer[counter++] = cb_ptr->quoteBuffer[x];
}
for (int y = 0; y < cb_ptr->start; y++)
{
if (cb_ptr->quoteBuffer[y].time != -1)
newBuffer->quoteBuffer[counter++] = cb_ptr->quoteBuffer[y];
}
}
if (cb_ptr->end < cb_ptr->start)
{
for (int x = cb_ptr->end; x < cb_ptr->start; x++)
{
if (cb_ptr->quoteBuffer[x].time != -1)
newBuffer->quoteBuffer[counter++] = cb_ptr->quoteBuffer[x];
}
}
newBuffer->start = counter;
newBuffer->end = 0;
cbuf_dump(newBuffer);
*cb_dblptr = cb_ptr = newBuffer;
}
if (cb_ptr->freeSlots == 0)
{
printf("EXPANDING CIRCULAR BUFFER!\n");
int newSize;
newSize = (cb_ptr->maxSize * 2) - 1;
cbuf *newBuffer = malloc(sizeof(cbuf) + newSize * sizeof(quote));
newBuffer->maxSize = cb_ptr->maxSize * 2;
newBuffer->start = cb_ptr->start;
newBuffer->end = cb_ptr->end;
newBuffer->freeSlots = newBuffer->maxSize - cb_ptr->maxSize;
int counter = 0;
for (int x = cb_ptr->end; x < cb_ptr->maxSize; x++)
newBuffer->quoteBuffer[counter++] = cb_ptr->quoteBuffer[x];
for (int y = 0; y < cb_ptr->start; y++)
newBuffer->quoteBuffer[counter++] = cb_ptr->quoteBuffer[y];
newBuffer->start = cb_ptr->maxSize;
newBuffer->end = 0;
*cb_dblptr = cb_ptr = newBuffer;
}
if (cb_ptr->start == cb_ptr->maxSize && cb_ptr->freeSlots > 0)
cb_ptr->start = 0;
cb_ptr->quoteBuffer[cb_ptr->start].time = time;
cb_ptr->quoteBuffer[cb_ptr->start].rate = rate;
cb_ptr->start = cb_ptr->start +1;
cb_ptr->freeSlots = cb_ptr->freeSlots -1;
for (int x = cb_ptr->end; x < (cb_ptr->start); x++)
{
if ((time) - (cb_ptr->quoteBuffer[x].time) >= fiveMin)
{
cb_ptr->end = cb_ptr->end + 1;
cb_ptr->quoteBuffer[x].time = -1;
cb_ptr->quoteBuffer[x].rate = -1.00;
cb_ptr->freeSlots = cb_ptr->freeSlots +1;
}
}
}
static void cbuf_dump(cbuf *cb_ptr)
{
printf("*****\t DUMPING \t*****\n");
if (cb_ptr->start > cb_ptr->end)
{
printf("start: %d\t end:%d\n", cb_ptr->start, cb_ptr->end);
for (int x = cb_ptr->end; x < cb_ptr->start; x++)
{
printf("%d.) time = %d, \t rate = %f\n",x,(cb_ptr->quoteBuffer[x].time),(cb_ptr->quoteBuffer[x].rate));
}
}
if (cb_ptr->end >= cb_ptr->start)
{
for (int x = cb_ptr->end; x < cb_ptr->maxSize; x++)
{
printf("%d.) time = %d, \t rate = %f\n",x,(cb_ptr->quoteBuffer[x].time),(cb_ptr->quoteBuffer[x].rate));
}
for (int y = 0; y < cb_ptr->start; y++)
{
if (cb_ptr->quoteBuffer[y].time != -1)
{
printf("%d.) time = %d, \t rate = %f\n",y,(cb_ptr->quoteBuffer[y].time),(cb_ptr->quoteBuffer[y].rate));
}
}
}
}
static cbuf *cbuf_init(void)
{
return calloc(1, sizeof(cbuf));
}
int main(void)
{
cbuf *cb1;
cb1 = cbuf_init() ;
cbuf_update(&cb1, 60, 1.291) ;
cbuf_update(&cb1, 63, 1.287) ;
cbuf_update(&cb1, 63, 1.231) ;
cbuf_update(&cb1, 69, 1.229) ;
cbuf_update(&cb1, 72, 1.247) ;
cbuf_update(&cb1,361,1.291);
cbuf_update(&cb1, 411, 1.291) ;
cbuf_update(&cb1, 412, 1.281) ;
cbuf_update(&cb1, 413, 1.292) ;
cbuf_update(&cb1, 414, 1.284) ;
cbuf_update(&cb1, 414, 1.290) ;
cbuf_update(&cb1, 511, 1.241) ;
cbuf_update(&cb1, 512, 1.251) ;
cbuf_update(&cb1, 513, 1.232) ;
cbuf_update(&cb1, 514, 1.202) ;
cbuf_update(&cb1, 517, 1.119) ;
cbuf_update(&cb1, 551, 1.080) ;
cbuf_update(&cb1, 552, 1.081) ;
cbuf_update(&cb1, 553, 1.079) ;
cbuf_update(&cb1, 554, 1.088) ;
cbuf_update(&cb1, 561, 1.072) ;
cbuf_update(&cb1, 562, 1.113) ;
cbuf_update(&cb1, 563, 1.091) ;
cbuf_update(&cb1, 564, 1.092) ;
cbuf_update(&cb1, 571, 1.089) ;
cbuf_update(&cb1, 572, 1.073) ;
cbuf_update(&cb1, 573, 1.061) ;
cbuf_update(&cb1, 574, 1.111) ;
cbuf_update(&cb1, 581, 1.119) ;
cbuf_update(&cb1, 582, 1.123) ;
cbuf_update(&cb1, 583, 1.151) ;
cbuf_update(&cb1, 584, 1.153) ;
cbuf_dump(cb1);
cbuf_update(&cb1, 750, 1.200) ;
cbuf_dump(cb1) ;
cbuf_update(&cb1, 818, 1.210) ;
cbuf_dump(cb1) ;
cbuf_update(&cb1, 868, 1.230) ;
cbuf_dump(cb1) ;
cbuf_update(&cb1, 878, 1.230) ;
cbuf_dump(cb1) ;
cbuf_update(&cb1, 900, 1.240) ;
cbuf_dump(cb1) ;
cbuf_update(&cb1, 2000, 1.240) ;
cbuf_dump(cb1) ;
return 0;
}