memset predates (by quite a bit) the addition of function prototypes to C. Without a prototype, you can’t pass a char to a function — when/if you try, it’ll be promoted to int when you pass it, and what the function receives is an int. It’s also worth noting that in C, (but not in … Read more
Oddly, the reason this works with -1 is exactly the same as the reason that this works with zeros: in two’s complement binary representation, -1 has 1s in all its bits, regardless of the size of the integer, so filling in a region with bytes filled with all 1s produces a region of -1 signed … Read more
From your question + the compiler-generated asm from your answer: fill(0) is an ERMSB rep stosb which will use 256b stores in an optimized microcoded loop. (Works best if the buffer is aligned, probably to at least 32B or maybe 64B). fill(1) is a simple 128-bit movaps vector store loop. Only one store can execute … Read more
It may be used for call chaining like: char a[200]; strcpy(memset(a, 0, 200), “bla”);
memset(array, 0, sizeof(array[0][0]) * m * n); Where m and n are the width and height of the two-dimensional array (in your example, you have a square two-dimensional array, so m == n).
You could use Enumerable.Repeat: byte[] a = Enumerable.Repeat((byte)10, 100).ToArray(); The first parameter is the element you want repeated, and the second parameter is the number of times to repeat it. This is OK for small arrays but you should use the looping method if you are dealing with very large arrays and performance is a … Read more
memset (from <string.h>) is probably the fastest standard way, since it’s usually a routine written directly in assembly and optimized by hand. memset(myarray, 0, sizeof(myarray)); // for automatically-allocated arrays memset(myarray, 0, N*sizeof(*myarray)); // for heap-allocated arrays, where N is the number of elements By the way, in C++ the idiomatic way would be to use … Read more
I don’t see any reason to prefer bzero over memset. memset is a standard C function while bzero has never been a C standard function. The rationale is probably because you can achieve exactly the same functionality using memset function. Now regarding efficiency, compilers like gcc use builtin implementations for memset which switch to a … Read more