Comments on: Interrupt Safe Ring Buffer Library http://steve.kargs.net/software/interrupt-safe-ring-buffer-library/ Open Source Software Haven Mon, 16 Jan 2012 07:36:14 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Lei http://steve.kargs.net/software/interrupt-safe-ring-buffer-library/comment-page-1/#comment-82773 Lei Fri, 01 Jul 2011 23:30:41 +0000 http://steve.kargs.net/?p=116#comment-82773 The absolute index method only wraps around then the buffer size is a divisor of the counter's capacity. So if the buffer size is a power of two and a unsigned integer counter is used, the counter would always wrap around. The absolute index method only wraps around then the buffer size is a divisor of the counter’s capacity. So if the buffer size is a power of two and a unsigned integer counter is used, the counter would always wrap around.

]]> By: skarg http://steve.kargs.net/software/interrupt-safe-ring-buffer-library/comment-page-1/#comment-69091 skarg Sat, 08 Jan 2011 13:44:03 +0000 http://steve.kargs.net/?p=116#comment-69091 Hi Joaquim, head minus tail will only return zero when they are equal, which is the only time that the buffer is empty, even if the value of head reaches the maximum value of an unsigned integer. The concept is exploiting unsigned integer overflow in C: http://en.wikipedia.org/wiki/Integer_overflow "In the C programming language, signed integer overflow causes undefined behavior, while unsigned integer overflow causes the number to be reduced modulo a power of two, meaning that unsigned integers "wrap around" on overflow. " There is more discussion of the various types of Circular Buffers at Wikipedia from the link in the article: http://en.wikipedia.org/wiki/Circular_buffer Best Regards, Steve Hi Joaquim,

head minus tail will only return zero when they are equal, which is the only time that the buffer is empty, even if the value of head reaches the maximum value of an unsigned integer.

The concept is exploiting unsigned integer overflow in C:
http://en.wikipedia.org/wiki/Integer_overflow
“In the C programming language, signed integer overflow causes undefined behavior, while unsigned integer overflow causes the number to be reduced modulo a power of two, meaning that unsigned integers “wrap around” on overflow. ”

There is more discussion of the various types of Circular Buffers at Wikipedia from the link in the article:
http://en.wikipedia.org/wiki/Circular_buffer

Best Regards,

Steve

]]> By: Joaquim Torres http://steve.kargs.net/software/interrupt-safe-ring-buffer-library/comment-page-1/#comment-10991 Joaquim Torres Mon, 27 Apr 2009 16:16:05 +0000 http://steve.kargs.net/?p=116#comment-10991 What happens when head reaches the max value of an int and returns to zero? I think inuse() will return a wrong value. What happens when head reaches the max value of an int and returns to zero? I think inuse() will return a wrong value.

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