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    SubjectRe: [PATCH] memchr (trivial) optimization

    On Aug 23 2007 19:13, Matt Mackall wrote:
    >
    >And you can do even better with this:
    >
    >void *memchr(const void *s, int c, size_t n)
    >{
    > const unsigned char *p = s, *e = s + n;
    > const unsigned char *e = p + n;

    Uhm, you have two "e"s in there.

    > for (; p < e ; p++)
    > if ((unsigned char)c == *p)
    > return (void *)p;
    >
    > return NULL;
    >}

    Or do it glibc-style

    void *memchr(const void *s, unsigned char c, size_t n)
    {
    ...
    for (; p + 3 < e; p += 4) {
    if (c == p[0])
    return (void *)&p[0];
    if (c == p[1])
    return (void *)&p[1];
    if (c == p[2])
    return (void *)&p[2];
    if (c == p[3])
    return (void *)&p[3];
    }
    ... /* check the rest */
    }


    Jan
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