1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.

use super::{Buffer, MutableBuffer};
use crate::util::bit_util::ceil;

/// Apply a bitwise operation `op` to four inputs and return the result as a Buffer.
/// The inputs are treated as bitmaps, meaning that offsets and length are specified in number of bits.
pub fn bitwise_quaternary_op_helper<F>(
    buffers: [&Buffer; 4],
    offsets: [usize; 4],
    len_in_bits: usize,
    op: F,
) -> Buffer
where
    F: Fn(u64, u64, u64, u64) -> u64,
{
    let first_chunks = buffers[0].bit_chunks(offsets[0], len_in_bits);
    let second_chunks = buffers[1].bit_chunks(offsets[1], len_in_bits);
    let third_chunks = buffers[2].bit_chunks(offsets[2], len_in_bits);
    let fourth_chunks = buffers[3].bit_chunks(offsets[3], len_in_bits);

    let chunks = first_chunks
        .iter()
        .zip(second_chunks.iter())
        .zip(third_chunks.iter())
        .zip(fourth_chunks.iter())
        .map(|(((first, second), third), fourth)| op(first, second, third, fourth));
    // Soundness: `BitChunks` is a `BitChunks` iterator which
    // correctly reports its upper bound
    let mut buffer = unsafe { MutableBuffer::from_trusted_len_iter(chunks) };

    let remainder_bytes = ceil(first_chunks.remainder_len(), 8);
    let rem = op(
        first_chunks.remainder_bits(),
        second_chunks.remainder_bits(),
        third_chunks.remainder_bits(),
        fourth_chunks.remainder_bits(),
    );
    // we are counting its starting from the least significant bit, to to_le_bytes should be correct
    let rem = &rem.to_le_bytes()[0..remainder_bytes];
    buffer.extend_from_slice(rem);

    buffer.into()
}

/// Apply a bitwise operation `op` to two inputs and return the result as a Buffer.
/// The inputs are treated as bitmaps, meaning that offsets and length are specified in number of bits.
pub fn bitwise_bin_op_helper<F>(
    left: &Buffer,
    left_offset_in_bits: usize,
    right: &Buffer,
    right_offset_in_bits: usize,
    len_in_bits: usize,
    mut op: F,
) -> Buffer
where
    F: FnMut(u64, u64) -> u64,
{
    let left_chunks = left.bit_chunks(left_offset_in_bits, len_in_bits);
    let right_chunks = right.bit_chunks(right_offset_in_bits, len_in_bits);

    let chunks = left_chunks
        .iter()
        .zip(right_chunks.iter())
        .map(|(left, right)| op(left, right));
    // Soundness: `BitChunks` is a `BitChunks` iterator which
    // correctly reports its upper bound
    let mut buffer = unsafe { MutableBuffer::from_trusted_len_iter(chunks) };

    let remainder_bytes = ceil(left_chunks.remainder_len(), 8);
    let rem = op(left_chunks.remainder_bits(), right_chunks.remainder_bits());
    // we are counting its starting from the least significant bit, to to_le_bytes should be correct
    let rem = &rem.to_le_bytes()[0..remainder_bytes];
    buffer.extend_from_slice(rem);

    buffer.into()
}

/// Apply a bitwise operation `op` to one input and return the result as a Buffer.
/// The input is treated as a bitmap, meaning that offset and length are specified in number of bits.
pub fn bitwise_unary_op_helper<F>(
    left: &Buffer,
    offset_in_bits: usize,
    len_in_bits: usize,
    mut op: F,
) -> Buffer
where
    F: FnMut(u64) -> u64,
{
    // reserve capacity and set length so we can get a typed view of u64 chunks
    let mut result =
        MutableBuffer::new(ceil(len_in_bits, 8)).with_bitset(len_in_bits / 64 * 8, false);

    let left_chunks = left.bit_chunks(offset_in_bits, len_in_bits);

    let result_chunks = result.typed_data_mut::<u64>().iter_mut();

    result_chunks
        .zip(left_chunks.iter())
        .for_each(|(res, left)| {
            *res = op(left);
        });

    let remainder_bytes = ceil(left_chunks.remainder_len(), 8);
    let rem = op(left_chunks.remainder_bits());
    // we are counting its starting from the least significant bit, to to_le_bytes should be correct
    let rem = &rem.to_le_bytes()[0..remainder_bytes];
    result.extend_from_slice(rem);

    result.into()
}

pub fn buffer_bin_and(
    left: &Buffer,
    left_offset_in_bits: usize,
    right: &Buffer,
    right_offset_in_bits: usize,
    len_in_bits: usize,
) -> Buffer {
    bitwise_bin_op_helper(
        left,
        left_offset_in_bits,
        right,
        right_offset_in_bits,
        len_in_bits,
        |a, b| a & b,
    )
}

pub fn buffer_bin_or(
    left: &Buffer,
    left_offset_in_bits: usize,
    right: &Buffer,
    right_offset_in_bits: usize,
    len_in_bits: usize,
) -> Buffer {
    bitwise_bin_op_helper(
        left,
        left_offset_in_bits,
        right,
        right_offset_in_bits,
        len_in_bits,
        |a, b| a | b,
    )
}

pub fn buffer_unary_not(
    left: &Buffer,
    offset_in_bits: usize,
    len_in_bits: usize,
) -> Buffer {
    bitwise_unary_op_helper(left, offset_in_bits, len_in_bits, |a| !a)
}