Function _strided_byte_swap

numpy/core/src/multiarray/ctors.c:370–428

}

NPY_NO_EXPORT void
_strided_byte_swap(void *p, npy_intp stride, npy_intp n, int size)
{
    char *a, *b, c = 0;
    int j, m;

    switch(size) {
    case 1: /* no byteswap necessary */
        break;
    case 4:
        if (npy_is_aligned((void*)((npy_intp)p | stride), sizeof(npy_uint32))) {
            for (a = (char*)p; n > 0; n--, a += stride) {
                npy_uint32 * a_ = (npy_uint32 *)a;
                *a_ = npy_bswap4(*a_);
            }
        }
        else {
            for (a = (char*)p; n > 0; n--, a += stride) {
                npy_bswap4_unaligned(a);
            }
        }
        break;
    case 8:
        if (npy_is_aligned((void*)((npy_intp)p | stride), sizeof(npy_uint64))) {
            for (a = (char*)p; n > 0; n--, a += stride) {
                npy_uint64 * a_ = (npy_uint64 *)a;
                *a_ = npy_bswap8(*a_);
            }
        }
        else {
            for (a = (char*)p; n > 0; n--, a += stride) {
                npy_bswap8_unaligned(a);
            }
        }
        break;
    case 2:
        if (npy_is_aligned((void*)((npy_intp)p | stride), sizeof(npy_uint16))) {
            for (a = (char*)p; n > 0; n--, a += stride) {
                npy_uint16 * a_ = (npy_uint16 *)a;
                *a_ = npy_bswap2(*a_);
            }
        }
        else {
            for (a = (char*)p; n > 0; n--, a += stride) {
                npy_bswap2_unaligned(a);
            }
        }
        break;
    default:
        m = size/2;
        for (a = (char *)p; n > 0; n--, a += stride - m) {
            b = a + (size - 1);
            for (j = 0; j < m; j++) {
                c=*a; *a++ = *b; *b-- = c;
            }
        }
        break;
    }