fbFetchPixel_a1b5g5r5 (const FbBits *bits, int offset, miIndexedPtr indexed)
{
    CARD32  pixel = READ((CARD16 *) bits + offset);
    CARD32  a,r,g,b;

    a = (CARD32) ((CARD8) (0 - ((pixel & 0x8000) >> 15))) << 24;
    b = ((pixel & 0x7c00) | ((pixel & 0x7000) >> 5)) >> 7;
    g = ((pixel & 0x03e0) | ((pixel & 0x0380) >> 5)) << 6;
    r = ((pixel & 0x001c) | ((pixel & 0x001f) << 5)) << 14;
    return (a | r | g | b);
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.