memset.c File Reference

Fill block of memory with a constant value. More...

#include "amathc.h"

Include dependency graph for memset.c:

Go to the source code of this file.

Typedefs
typedef uintptr_t	mem_ptr

Functions
void	MemSet (void *dst0, int c0, unsigned int length)
	Fill block of memory with a constant value. More...

Detailed Description

Fill block of memory with a constant value.

Code originate from FreeBSD base, revision 229286.

The original source code can be obtained from: https://svnweb.freebsd.org/base/head/lib/libc/string/memset.c?revision=229286

Definition in file memset.c.

Typedef Documentation

mem_ptr

typedef uintptr_t mem_ptr

Definition at line 51 of file memset.c.

Function Documentation

MemSet()

void MemSet	(	void *	dst0,
		int	c0,
		unsigned int	length
	)

Fill block of memory with a constant value.

Definition at line 56 of file memset.c.

{
    unsigned char* dst = (unsigned char*) dst0;
    unsigned int t;
    unsigned int c;

    /*
     * If not enough words, just fill bytes.  A length >= 2 words
     * guarantees that at least one of them is `complete' after
     * any necessary alignment.  For instance:
     *
     *  |-----------|-----------|-----------|
     *  |00|01|02|03|04|05|06|07|08|09|0A|00|
     *            ^---------------------^
     *       dst         dst+length-1
     *
     * but we use a minimum of 3 here since the overhead of the code
     * to do word writes is substantial.
     */
    if (length < 3 * wsize)
    {
        while (length != 0)
        {
            *dst++ = c0;
            --length;
        }
    }

    if ((c = (unsigned char)c0) != 0)
    { /* Fill the word. */
        c = (c << 8) | c; /* u_int is 16 bits. */
#if UINT_MAX > 0xffff
        c = (c << 16) | c;  /* u_int is 32 bits. */
#endif
#if UINT_MAX > 0xffffffff
        c = (c << 32) | c;  /* u_int is 64 bits. */
#endif
    }

    /* Align destination by filling in bytes. */
    if ((t = (mem_ptr)dst & wmask) != 0)
    {
        t = wsize - t;
        length -= t;
        do
        {
            *dst++ = c0;
        }
        while (--t != 0);
    }

    /* Fill words.  Length was >= 2*words so we know t >= 1 here. */
    t = length / wsize;
    do
    {
        *(unsigned int*)dst = c;
        dst += wsize;
    }
    while (--t != 0);

    /* Mop up trailing bytes, if any. */
    t = length & wmask;
    if (t != 0)
        do
        {
            *dst++ = c0;
        }
        while (--t != 0);
}