A faster std.bitmanip.BitArray.opCat

[dlangBugzillaToGithub]

bearophile_hugs reported this on 2012-02-12T11:42:53Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=7487

CC List

• lovelydear

Description

This implements an operator on std.bitmanip.BitArray, to append one or more bits at the beginning:


BitArray opCatAssign(BitArray b)
{
    auto istart = len;
    length = len + b.length;
    for (auto i = istart; i < len; i++)
        this[i] = b[i - istart];
    return this;
}


BitArray opCat_r(bool b)
{
    BitArray r;

    r.length = len + 1;
    r[0] = b;
    for (size_t i = 0; i < len; i++)
        r[1 + i] = this[i];
    return r;
}


I think there are faster ways to perform those operations, that avoid copying single bits, and work mostly with a memmove() on the array of size_t pointed by BitArray.ptr (followed by few single bit copies if necessary).

In my code I have found that opCat_r() to be slow.

[dlangBugzillaToGithub]

lovelydear commented on 2012-04-19T08:55:17Z

See also 7488 and 7490