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/**
* Implementation of a bit array.
*
* Copyright: Copyright (C) 1999-2025 by The D Language Foundation, All Rights Reserved
* Authors: $(LINK2 https://www.digitalmars.com, Walter Bright)
* License: $(LINK2 https://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
* Source: $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/root/bitarray.d, root/_bitarray.d)
* Documentation: https://dlang.org/phobos/dmd_root_array.html
* Coverage: https://codecov.io/gh/dlang/dmd/src/master/src/dmd/root/bitarray.d
*/
module dmd.root.bitarray;
import core.stdc.stdio;
import core.stdc.string;
import dmd.root.rmem;
struct BitArray
{
alias Chunk_t = size_t;
enum ChunkSize = Chunk_t.sizeof;
enum BitsPerChunk = ChunkSize * 8;
size_t length() const @nogc nothrow pure @safe
{
return len;
}
void length(size_t nlen) nothrow pure
{
immutable ochunks = chunks(len);
immutable nchunks = chunks(nlen);
if (ochunks != nchunks)
{
ptr = cast(size_t*)mem.xrealloc_noscan(ptr, nchunks * ChunkSize);
}
if (nchunks > ochunks)
ptr[ochunks .. nchunks] = 0;
if (nlen & (BitsPerChunk - 1))
ptr[nchunks - 1] &= (cast(Chunk_t)1 << (nlen & (BitsPerChunk - 1))) - 1;
len = nlen;
}
void opAssign(const ref BitArray b) nothrow pure
{
if (!len)
length(b.len);
assert(len == b.len);
memcpy(ptr, b.ptr, bytes(len));
}
bool opIndex(size_t idx) const @nogc nothrow pure
{
import core.bitop : bt;
assert(idx < len);
return !!bt(ptr, idx);
}
void opIndexAssign(bool val, size_t idx) @nogc nothrow pure
{
import core.bitop : btc, bts;
assert(idx < len);
if (val)
bts(ptr, idx);
else
btc(ptr, idx);
}
bool opEquals(const ref BitArray b) const @nogc nothrow pure
{
return len == b.len && memcmp(ptr, b.ptr, bytes(len)) == 0;
}
void zero() @nogc nothrow pure
{
memset(ptr, 0, bytes(len));
}
/******
* Returns:
* true if no bits are set
*/
bool isZero() @nogc nothrow pure
{
const nchunks = chunks(len);
foreach (i; 0 .. nchunks)
{
if (ptr[i])
return false;
}
return true;
}
void or(const ref BitArray b) @nogc nothrow pure
{
assert(len == b.len);
const nchunks = chunks(len);
foreach (i; 0 .. nchunks)
ptr[i] |= b.ptr[i];
}
/* Swap contents of `this` with `b`
*/
void swap(ref BitArray b) @nogc nothrow pure
{
assert(len == b.len);
const nchunks = chunks(len);
foreach (i; 0 .. nchunks)
{
const chunk = ptr[i];
ptr[i] = b.ptr[i];
b.ptr[i] = chunk;
}
}
~this() nothrow pure
{
debug
{
// Stomp the allocated memory
const nchunks = chunks(len);
foreach (i; 0 .. nchunks)
{
ptr[i] = cast(Chunk_t)0xFEFEFEFE_FEFEFEFE;
}
}
mem.xfree(ptr);
debug
{
// Set to implausible values
len = cast(size_t)0xFEFEFEFE_FEFEFEFE;
ptr = cast(size_t*)cast(size_t)0xFEFEFEFE_FEFEFEFE;
}
}
private:
size_t len; // length in bits
size_t *ptr;
/// Returns: The amount of chunks used to store len bits
static size_t chunks(const size_t len) @nogc nothrow pure @safe
{
return (len + BitsPerChunk - 1) / BitsPerChunk;
}
/// Returns: The amount of bytes used to store len bits
static size_t bytes(const size_t len) @nogc nothrow pure @safe
{
return chunks(len) * ChunkSize;
}
}
nothrow pure unittest
{
BitArray array;
array.length = 20;
assert(array[19] == 0);
array[10] = 1;
assert(array[10] == 1);
array[10] = 0;
assert(array[10] == 0);
assert(array.length == 20);
BitArray a,b;
assert(a != array);
a.length = 200;
assert(a != array);
assert(a.isZero());
a[100] = true;
b.length = 200;
b[100] = true;
assert(a == b);
a.length = 300;
b.length = 300;
assert(a == b);
b[299] = true;
assert(a != b);
assert(!a.isZero());
a.swap(b);
assert(a[299] == true);
assert(b[299] == false);
a = b;
assert(a == b);
}
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