Circular Buffer (C)

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HoboBen	Created : 22 April 2011 Edited : 25 April 2011 Language : Monkey Circular Buffer (C)
A fast fixed-size buffer. which you can pretend is "infinite memory" for data that you don't care too much about. When you write to it, it fills up until you start overwriting the oldest data. When reading, it returns the oldest data it has. Ideal for buffering data anywhere a bandwidth is a problem, like text input when you have a low framerate, or streaming real-time sound or video where the past doesn't matter too much. #define BUFFER_SIZE 256 item buffer[BUFFER_SIZE]; int start = 0; int end = 0 int active = 0; void PushToQueue(item p) { buffer[end] = p; end = (end + 1) % BUFFER_SIZE; if (active < BUFFER_SIZE) { active++; } else { /* Overwriting the oldest. Move start to next-oldest / start = (start + 1) % BUFFER_SIZE } } item RetrieveFromQueue(void) { item *p; if (!active) { return NULL; } p = buffer[start]; start = (start + 1) % BUFFER_SIZE; active--; return p; } --v It looks simple, but was a helluva thing to implement as the intuitive solutions (like checking if start == end for detecting emptiness) don't work. So hopefully it saves somebody else the trouble! If you like syntax highlighting, syntax highlighted version (needs JavaScript)

Comments
Monday, 25 April 2011, 14:09
Scherererer	BUFFER_SIZE isn't defined in this snippet, shouldn't it be defined so that it can be used, so that we can change this: item buffer[256] --v to this: #define BUFFER_SIZE 256 / OR const int BUFFER_SIZE = 256; / item buffer[BUFFER_SIZE] --v
Monday, 25 April 2011, 14:50
HoboBen	Whoops! Yes, you're right. Thanks for the correction.

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