Flash实现中的循环缓冲区 [英] Circular buffer in flash implementation
问题描述
我一直在为嵌入式设备开发数据记录器.目标是存储 定期将一组变量的值存储到外部闪存中. 我的想法是在RAM中创建一个缓冲区.缓冲区的大小将等于 外部闪存的一个扇区中的字节数，即512B. 在规定的时间内，我将用变量的值填充缓冲区，然后 我将此记录存储到外部闪存中.外接闪光灯包含几个 为数据日志存储保留的块.这些块形成循环缓冲区 即，一旦缓冲区已满，最早的记录将被覆盖.
我一直在考虑的第一件事是如何识别 我可以将循环缓冲区用于实际记录存储.根据问题 Flash中的循环缓冲区 我知道我需要在每个记录中附加一个标题.这个头 应该包含一个记录号.
据我正确理解的问题，请回答 Flash中的循环缓冲区一世 插入记录头应大于块数 在为数据日志存储保留的外部闪存中.
为了更好地理解带有包含记录号的标题的想法， 决定编写用于在我的PC而非目标MCU上进行测试的仿真软件.
#define BUFFER_SIZE 8
#define NONE_INDEX BUFFER_SIZE
#define ERASED_BYTE 0x00
unsigned char buffer[BUFFER_SIZE];
void PrintBuffer(unsigned char *buffer){
for(unsigned char index = 0; index < BUFFER_SIZE; index++){
std::cout << std::setw(3); // 3 digits
std::cout << showbase << dec; // in decimal
std::cout << (unsigned short)*(buffer + index) << ", ";
}
std::cout << "\n";
}
void ClearBuffer(unsigned char *buffer, unsigned char length){
for(unsigned char index = 0; index < length; index++){
*(buffer + index) = ERASED_BYTE;
}
}
void Insert2Buffer(unsigned char *buffer, unsigned char elem, unsigned char pos){
*(buffer + pos) = elem;
}
unsigned char FindPosInBuffer(unsigned char *buffer, unsigned char length){
unsigned char curr_hdr;
unsigned char next_hdr;
unsigned char retval = NONE_INDEX; // non-existent index
unsigned char index;
unsigned char next_index;
// searching for erased byte
for(index = 0; index < length; index++){
curr_hdr = *(buffer + index);
if(curr_hdr == ERASED_BYTE){
retval = index;
break;
}
}
// erased byte does not exist - buffer is full i.e. free position is the
// position where a discontinuity in record headers numbers occurs
if(retval == NONE_INDEX){
for(index = 0; index < length; index++){
curr_hdr = *(buffer + index);
next_index = ((index + 1) & (length - 1)); // indices 0 ... 7
next_hdr = *(buffer + next_index);
if((curr_hdr + 1) != next_hdr){
retval = next_index;
break;
}
}
}
return retval;
}
/*
*
*/
int main(int argc, char** argv) {
unsigned char free_pos;
unsigned char elem = 1;
ClearBuffer(buffer, BUFFER_SIZE);
PrintBuffer(buffer);
// inserting into buffer
for(unsigned short insert = 0; insert < 64; insert++){
free_pos = FindPosInBuffer(buffer, BUFFER_SIZE);
Insert2Buffer(buffer, elem, free_pos);
elem++;
// headers 1 ... 16
if(elem == 17){
elem = 1;
}
// headers 1 ... 9 - does not work
//if(elem == 10){
// elem = 1;
//}
PrintBuffer(buffer);
}
return 0;
}
标题1 ... 16:16的输出
0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0,
1, 2, 0, 0, 0, 0, 0, 0,
1, 2, 3, 0, 0, 0, 0, 0,
1, 2, 3, 4, 0, 0, 0, 0,
1, 2, 3, 4, 5, 0, 0, 0,
1, 2, 3, 4, 5, 6, 0, 0,
1, 2, 3, 4, 5, 6, 7, 0,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
1, 10, 11, 12, 13, 14, 15, 16,
1, 2, 11, 12, 13, 14, 15, 16,
1, 2, 3, 12, 13, 14, 15, 16,
1, 2, 3, 4, 13, 14, 15, 16,
1, 2, 3, 4, 5, 14, 15, 16,
1, 2, 3, 4, 5, 6, 15, 16,
1, 2, 3, 4, 5, 6, 7, 16,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
1, 10, 11, 12, 13, 14, 15, 16,
1, 2, 11, 12, 13, 14, 15, 16,
1, 2, 3, 12, 13, 14, 15, 16,
1, 2, 3, 4, 13, 14, 15, 16,
1, 2, 3, 4, 5, 14, 15, 16,
1, 2, 3, 4, 5, 6, 15, 16,
1, 2, 3, 4, 5, 6, 7, 16,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
1, 10, 11, 12, 13, 14, 15, 16,
1, 2, 11, 12, 13, 14, 15, 16,
1, 2, 3, 12, 13, 14, 15, 16,
1, 2, 3, 4, 13, 14, 15, 16,
1, 2, 3, 4, 5, 14, 15, 16,
1, 2, 3, 4, 5, 6, 15, 16,
1, 2, 3, 4, 5, 6, 7, 16,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
标题1 ... 9的输出:
0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0,
1, 2, 0, 0, 0, 0, 0, 0,
1, 2, 3, 0, 0, 0, 0, 0,
1, 2, 3, 4, 0, 0, 0, 0,
1, 2, 3, 4, 5, 0, 0, 0,
1, 2, 3, 4, 5, 6, 0, 0,
1, 2, 3, 4, 5, 6, 7, 0,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
基于对问题 Flash中的循环缓冲区的回答，我认为它足够了具有的最大标头数大于闪存中的块总数.根据我所做的实验，似乎最大报头数必须至少是闪存中块总数的两倍.请问有人告诉我我的最大标题数的想法是否正确吗?预先感谢您的任何建议.
在代码中给出以下这一行:
next_index = ((index + 1) & (length - 1)); // indices 0 ... 7
& (length - 1)部分仅适用于2的幂的length.它实际上是% length的优化，只有length的2的幂才有效.
因此，如果将& (length - 1)部分替换为% length，则它的长度应为9(或其他不是2的幂的数字).
(如果直接使用BUFFER_SIZE而不是将其作为参数length传递，那么只要BUFFER_SIZE为2的幂，编译器很可能会将% length优化为等效的& (length - 1).)
I have been working on data logger for an embedded device. The goal is to store values of a set of variables in periodic manner into the external flash memory. My idea is to create a buffer in RAM. Size of the buffer will be equal to the number of bytes in one sector in the external flash i.e. 512 B. After expiration of prescribed time I will fill the buffer with values of the variables and then I will store this record into the external flash. External flash contains several blocks reserved for the data logs storage. These blocks form a circular buffer i.e. as soon as the buffer is full the oldest records will be overwritten.
First thing I have been thinking about is how to recognize what block in the circular buffer I can use for actual record storage. Based on the question Circular Buffer in Flash I have understood that I need to append a header into each record. This header shall contain a record number.
As far as I understand correctly answer to the question Circular Buffer in Flash the number which I shall insert into the record header should be greater than the number of blocks in the external flash which are reserved for the data logs storage.
For better understanding the idea with headers containing record numbers I have decided to write a simulation software for testing on my pc instead of the target MCU.
#define BUFFER_SIZE 8
#define NONE_INDEX BUFFER_SIZE
#define ERASED_BYTE 0x00
unsigned char buffer[BUFFER_SIZE];
void PrintBuffer(unsigned char *buffer){
for(unsigned char index = 0; index < BUFFER_SIZE; index++){
std::cout << std::setw(3); // 3 digits
std::cout << showbase << dec; // in decimal
std::cout << (unsigned short)*(buffer + index) << ", ";
}
std::cout << "\n";
}
void ClearBuffer(unsigned char *buffer, unsigned char length){
for(unsigned char index = 0; index < length; index++){
*(buffer + index) = ERASED_BYTE;
}
}
void Insert2Buffer(unsigned char *buffer, unsigned char elem, unsigned char pos){
*(buffer + pos) = elem;
}
unsigned char FindPosInBuffer(unsigned char *buffer, unsigned char length){
unsigned char curr_hdr;
unsigned char next_hdr;
unsigned char retval = NONE_INDEX; // non-existent index
unsigned char index;
unsigned char next_index;
// searching for erased byte
for(index = 0; index < length; index++){
curr_hdr = *(buffer + index);
if(curr_hdr == ERASED_BYTE){
retval = index;
break;
}
}
// erased byte does not exist - buffer is full i.e. free position is the
// position where a discontinuity in record headers numbers occurs
if(retval == NONE_INDEX){
for(index = 0; index < length; index++){
curr_hdr = *(buffer + index);
next_index = ((index + 1) & (length - 1)); // indices 0 ... 7
next_hdr = *(buffer + next_index);
if((curr_hdr + 1) != next_hdr){
retval = next_index;
break;
}
}
}
return retval;
}
/*
*
*/
int main(int argc, char** argv) {
unsigned char free_pos;
unsigned char elem = 1;
ClearBuffer(buffer, BUFFER_SIZE);
PrintBuffer(buffer);
// inserting into buffer
for(unsigned short insert = 0; insert < 64; insert++){
free_pos = FindPosInBuffer(buffer, BUFFER_SIZE);
Insert2Buffer(buffer, elem, free_pos);
elem++;
// headers 1 ... 16
if(elem == 17){
elem = 1;
}
// headers 1 ... 9 - does not work
//if(elem == 10){
// elem = 1;
//}
PrintBuffer(buffer);
}
return 0;
}
Output for headers 1 ... 16:
0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0,
1, 2, 0, 0, 0, 0, 0, 0,
1, 2, 3, 0, 0, 0, 0, 0,
1, 2, 3, 4, 0, 0, 0, 0,
1, 2, 3, 4, 5, 0, 0, 0,
1, 2, 3, 4, 5, 6, 0, 0,
1, 2, 3, 4, 5, 6, 7, 0,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
1, 10, 11, 12, 13, 14, 15, 16,
1, 2, 11, 12, 13, 14, 15, 16,
1, 2, 3, 12, 13, 14, 15, 16,
1, 2, 3, 4, 13, 14, 15, 16,
1, 2, 3, 4, 5, 14, 15, 16,
1, 2, 3, 4, 5, 6, 15, 16,
1, 2, 3, 4, 5, 6, 7, 16,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
1, 10, 11, 12, 13, 14, 15, 16,
1, 2, 11, 12, 13, 14, 15, 16,
1, 2, 3, 12, 13, 14, 15, 16,
1, 2, 3, 4, 13, 14, 15, 16,
1, 2, 3, 4, 5, 14, 15, 16,
1, 2, 3, 4, 5, 6, 15, 16,
1, 2, 3, 4, 5, 6, 7, 16,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
1, 10, 11, 12, 13, 14, 15, 16,
1, 2, 11, 12, 13, 14, 15, 16,
1, 2, 3, 12, 13, 14, 15, 16,
1, 2, 3, 4, 13, 14, 15, 16,
1, 2, 3, 4, 5, 14, 15, 16,
1, 2, 3, 4, 5, 6, 15, 16,
1, 2, 3, 4, 5, 6, 7, 16,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 10, 3, 4, 5, 6, 7, 8,
9, 10, 11, 4, 5, 6, 7, 8,
9, 10, 11, 12, 5, 6, 7, 8,
9, 10, 11, 12, 13, 6, 7, 8,
9, 10, 11, 12, 13, 14, 7, 8,
9, 10, 11, 12, 13, 14, 15, 8,
9, 10, 11, 12, 13, 14, 15, 16,
Output for headers 1 ... 9:
0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0,
1, 2, 0, 0, 0, 0, 0, 0,
1, 2, 3, 0, 0, 0, 0, 0,
1, 2, 3, 4, 0, 0, 0, 0,
1, 2, 3, 4, 5, 0, 0, 0,
1, 2, 3, 4, 5, 6, 0, 0,
1, 2, 3, 4, 5, 6, 7, 0,
1, 2, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
9, 2, 3, 4, 5, 6, 7, 8,
9, 3, 3, 4, 5, 6, 7, 8,
9, 4, 3, 4, 5, 6, 7, 8,
9, 5, 3, 4, 5, 6, 7, 8,
9, 6, 3, 4, 5, 6, 7, 8,
9, 7, 3, 4, 5, 6, 7, 8,
9, 8, 3, 4, 5, 6, 7, 8,
9, 9, 3, 4, 5, 6, 7, 8,
9, 1, 3, 4, 5, 6, 7, 8,
Based on the answer to the question Circular Buffer in Flash I thought that it is suficient to have the maximal header number greater than total number of blocks in flash. Based on the experiments I have done it seems that the maximal header number has to be at least double of total number of blocks in flash. Please can anybody tell me whether my idea with maximal header number is correct? Thanks in advance for any suggestions.
Given this line in the code:
next_index = ((index + 1) & (length - 1)); // indices 0 ... 7
The part & (length - 1) only works for a length that is a power of 2. It is effectively an optimisation of % length that is valid only if length is a power of 2.
So if you replace the & (length - 1) part with % length, then it should work for a length of 9 (or any other number that isn't a power of 2).
(If you use BUFFER_SIZE directly rather than passing it as parameter length, then the compiler will most likely optimise % length to the equivalent & (length - 1) whenever BUFFER_SIZE is a power of 2.)
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