/*
 * Copyright (c) 2011, 2012 Nicira Networks.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>

#include <inttypes.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>

#include "byte-order.h"
#include "random.h"
#include "util.h"

static void
check_log_2_floor(uint32_t x, int n)
{
    if (log_2_floor(x) != n) {
        fprintf(stderr, "log_2_floor(%"PRIu32") is %d but should be %d\n",
                x, log_2_floor(x), n);
        abort();
    }
}

static void
check_ctz(uint32_t x, int n)
{
    if (ctz(x) != n) {
        fprintf(stderr, "ctz(%"PRIu32") is %d but should be %d\n",
                x, ctz(x), n);
        abort();
    }
}

/* Returns the sum of the squares of the first 'n' positive integers. */
static unsigned int
sum_of_squares(int n)
{
    return n * (n + 1) * (2 * n + 1) / 6;
}

static void
check_bitwise_copy(void)
{
    unsigned int n_loops;
    int src_ofs;
    int dst_ofs;
    int n_bits;

    n_loops = 0;
    for (n_bits = 0; n_bits <= 64; n_bits++) {
        for (src_ofs = 0; src_ofs < 64 - n_bits; src_ofs++) {
            for (dst_ofs = 0; dst_ofs < 64 - n_bits; dst_ofs++) {
                ovs_be64 src = htonll(random_uint64());
                ovs_be64 dst = htonll(random_uint64());
                ovs_be64 orig_dst = dst;
                ovs_be64 expect;

                if (n_bits == 64) {
                    expect = dst;
                } else {
                    uint64_t mask = (UINT64_C(1) << n_bits) - 1;
                    expect = orig_dst & ~htonll(mask << dst_ofs);
                    expect |= htonll(((ntohll(src) >> src_ofs) & mask)
                                     << dst_ofs);
                }

                bitwise_copy(&src, sizeof src, src_ofs,
                             &dst, sizeof dst, dst_ofs,
                             n_bits);
                if (expect != dst) {
                    fprintf(stderr,"copy_bits(0x%016"PRIx64",8,%d, "
                            "0x%016"PRIx64",8,%d, %d) yielded 0x%016"PRIx64" "
                            "instead of the expected 0x%016"PRIx64"\n",
                            ntohll(src), src_ofs,
                            ntohll(orig_dst), dst_ofs,
                            n_bits,
                            ntohll(dst), ntohll(expect));
                    abort();
                }

                n_loops++;
            }
        }
    }

    if (n_loops != sum_of_squares(64)) {
        abort();
    }
}

static void
check_bitwise_zero(void)
{
    unsigned int n_loops;
    int dst_ofs;
    int n_bits;

    n_loops = 0;
    for (n_bits = 0; n_bits <= 64; n_bits++) {
        for (dst_ofs = 0; dst_ofs < 64 - n_bits; dst_ofs++) {
            ovs_be64 dst = htonll(random_uint64());
            ovs_be64 orig_dst = dst;
            ovs_be64 expect;

            if (n_bits == 64) {
                expect = htonll(0);
            } else {
                uint64_t mask = (UINT64_C(1) << n_bits) - 1;
                expect = orig_dst & ~htonll(mask << dst_ofs);
            }

            bitwise_zero(&dst, sizeof dst, dst_ofs, n_bits);
            if (expect != dst) {
                fprintf(stderr,"bitwise_zero(0x%016"PRIx64",8,%d, %d) "
                        "yielded 0x%016"PRIx64" "
                        "instead of the expected 0x%016"PRIx64"\n",
                        ntohll(orig_dst), dst_ofs,
                        n_bits,
                        ntohll(dst), ntohll(expect));
                abort();
            }

            n_loops++;
        }
    }

    if (n_loops != 64 * (64 + 1) / 2) {
        abort();
    }
}

int
main(void)
{
    int n;

    for (n = 0; n < 32; n++) {
        /* Check minimum x such that f(x) == n. */
        check_log_2_floor(1 << n, n);
        check_ctz(1 << n, n);

        /* Check maximum x such that f(x) == n. */
        check_log_2_floor((1 << n) | ((1 << n) - 1), n);
        check_ctz(UINT32_MAX << n, n);

        /* Check a random value in the middle. */
        check_log_2_floor((random_uint32() & ((1 << n) - 1)) | (1 << n), n);
        check_ctz((random_uint32() | 1) << n, n);
    }

    /* Check ctz(0).
     * (log_2_floor(0) is undefined.) */
    check_ctz(0, 32);

    check_bitwise_copy();

    check_bitwise_zero();

    return 0;
}