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BitmapView: Disable mutations of the underlying Bitmap

Browse source 
Problem:
- `BitmapView` permits changing the underlying `Bitmap`. This violates
  the idea of a "view" since views are simply overlays which can
  themselves change but do not change the underlying data.

Solution:
- Migrate all non-`const` member functions to Bitmap.
This commit is contained in:
Lenny Maiorani 2021-05-16 18:00:50 -06:00 committed by Andreas Kling
parent ba9b3dc656
commit f25209113f
Notes: sideshowbarker 2024-07-18 17:56:57 +09:00 
Author: https://github.com/ldm5180
Commit: https://github.com/SerenityOS/serenity/commit/f25209113fc
Pull-request: https://github.com/SerenityOS/serenity/pull/7203
Reviewed-by: https://github.com/awesomekling
3 changed files with 82 additions and 97 deletions
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89
AK/Bitmap.h
View file

@ -30,12 +30,6 @@ public:
fill(default_value);
}
Bitmap(u8* data, size_t size)
: m_data(data)
, m_size(size)
{
}
BitmapView view() { return { m_data, m_size }; }
const BitmapView view() const { return { m_data, m_size }; }
@ -108,11 +102,86 @@ public:
}
}
template<bool VALUE>
void set_range(size_t start, size_t len) { return view().set_range<VALUE, false>(start, len); }
void set_range(size_t start, size_t len, bool value) { return view().set_range(start, len, value); }
template<bool VALUE, bool verify_that_all_bits_flip = false>
void set_range(size_t start, size_t len)
{
VERIFY(start < m_size);
VERIFY(start + len <= m_size);
if (len == 0)
return;
void fill(bool value) { view().fill(value); }
static const u8 bitmask_first_byte[8] = { 0xFF, 0xFE, 0xFC, 0xF8, 0xF0, 0xE0, 0xC0, 0x80 };
static const u8 bitmask_last_byte[8] = { 0x0, 0x1, 0x3, 0x7, 0xF, 0x1F, 0x3F, 0x7F };
u8* first = &m_data[start / 8];
u8* last = &m_data[(start + len) / 8];
u8 byte_mask = bitmask_first_byte[start % 8];
if (first == last) {
byte_mask &= bitmask_last_byte[(start + len) % 8];
if constexpr (verify_that_all_bits_flip) {
if constexpr (VALUE) {
VERIFY((*first & byte_mask) == 0);
} else {
VERIFY((*first & byte_mask) == byte_mask);
}
}
if constexpr (VALUE)
*first |= byte_mask;
else
*first &= ~byte_mask;
} else {
if constexpr (verify_that_all_bits_flip) {
if constexpr (VALUE) {
VERIFY((*first & byte_mask) == 0);
} else {
VERIFY((*first & byte_mask) == byte_mask);
}
}
if constexpr (VALUE)
*first |= byte_mask;
else
*first &= ~byte_mask;
byte_mask = bitmask_last_byte[(start + len) % 8];
if constexpr (verify_that_all_bits_flip) {
if constexpr (VALUE) {
VERIFY((*last & byte_mask) == 0);
} else {
VERIFY((*last & byte_mask) == byte_mask);
}
}
if constexpr (VALUE)
*last |= byte_mask;
else
*last &= ~byte_mask;
if (++first < last) {
if constexpr (VALUE)
__builtin_memset(first, 0xFF, last - first);
else
__builtin_memset(first, 0x0, last - first);
}
}
}
void set_range(size_t start, size_t len, bool value)
{
if (value)
set_range<true, false>(start, len);
else
set_range<false, false>(start, len);
}
void set_range_and_verify_that_all_bits_flip(size_t start, size_t len, bool value)
{
if (value)
set_range<true, true>(start, len);
else
set_range<false, true>(start, len);
}
void fill(bool value)
{
__builtin_memset(m_data, value ? 0xff : 0x00, size_in_bytes());
}
Optional<size_t> find_one_anywhere_set(size_t hint = 0) const { return view().find_one_anywhere<true>(hint); }
Optional<size_t> find_one_anywhere_unset(size_t hint = 0) const { return view().find_one_anywhere<false>(hint); }

84
AK/BitmapView.h
View file

@ -6,12 +6,10 @@
#pragma once
#include <AK/Noncopyable.h>
#include <AK/Optional.h>
#include <AK/Platform.h>
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
#include <AK/kmalloc.h>
namespace AK {
@ -95,90 +93,8 @@ public:
bool is_null() const { return !m_data; }
u8* data() { return m_data; }
const u8* data() const { return m_data; }
template<bool VALUE, bool verify_that_all_bits_flip>
void set_range(size_t start, size_t len)
{
VERIFY(start < m_size);
VERIFY(start + len <= m_size);
if (len == 0)
return;
static const u8 bitmask_first_byte[8] = { 0xFF, 0xFE, 0xFC, 0xF8, 0xF0, 0xE0, 0xC0, 0x80 };
static const u8 bitmask_last_byte[8] = { 0x0, 0x1, 0x3, 0x7, 0xF, 0x1F, 0x3F, 0x7F };
u8* first = &m_data[start / 8];
u8* last = &m_data[(start + len) / 8];
u8 byte_mask = bitmask_first_byte[start % 8];
if (first == last) {
byte_mask &= bitmask_last_byte[(start + len) % 8];
if constexpr (verify_that_all_bits_flip) {
if constexpr (VALUE) {
VERIFY((*first & byte_mask) == 0);
} else {
VERIFY((*first & byte_mask) == byte_mask);
}
}
if constexpr (VALUE)
*first |= byte_mask;
else
*first &= ~byte_mask;
} else {
if constexpr (verify_that_all_bits_flip) {
if constexpr (VALUE) {
VERIFY((*first & byte_mask) == 0);
} else {
VERIFY((*first & byte_mask) == byte_mask);
}
}
if constexpr (VALUE)
*first |= byte_mask;
else
*first &= ~byte_mask;
byte_mask = bitmask_last_byte[(start + len) % 8];
if constexpr (verify_that_all_bits_flip) {
if constexpr (VALUE) {
VERIFY((*last & byte_mask) == 0);
} else {
VERIFY((*last & byte_mask) == byte_mask);
}
}
if constexpr (VALUE)
*last |= byte_mask;
else
*last &= ~byte_mask;
if (++first < last) {
if constexpr (VALUE)
__builtin_memset(first, 0xFF, last - first);
else
__builtin_memset(first, 0x0, last - first);
}
}
}
void set_range(size_t start, size_t len, bool value)
{
if (value)
set_range<true, false>(start, len);
else
set_range<false, false>(start, len);
}
void set_range_and_verify_that_all_bits_flip(size_t start, size_t len, bool value)
{
if (value)
set_range<true, true>(start, len);
else
set_range<false, true>(start, len);
}
void fill(bool value)
{
__builtin_memset(m_data, value ? 0xff : 0x00, size_in_bytes());
}
template<bool VALUE>
Optional<size_t> find_one_anywhere(size_t hint = 0) const
{

6
Kernel/Heap/Heap.h
View file

@ -6,7 +6,7 @@
#pragma once
#include <AK/BitmapView.h>
#include <AK/Bitmap.h>
#include <AK/ScopeGuard.h>
#include <AK/TemporaryChange.h>
#include <AK/Vector.h>
@ -32,7 +32,7 @@ public:
Heap(u8* memory, size_t memory_size)
: m_total_chunks(calculate_chunks(memory_size))
, m_chunks(memory)
, m_bitmap(memory + m_total_chunks * CHUNK_SIZE, m_total_chunks)
, m_bitmap(m_total_chunks, false)
{
// To keep the alignment of the memory passed in, place the bitmap
// at the end of the memory block.
@ -153,7 +153,7 @@ private:
size_t m_total_chunks { 0 };
size_t m_allocated_chunks { 0 };
u8* m_chunks { nullptr };
BitmapView m_bitmap;
Bitmap m_bitmap;
};
template<typename ExpandHeap>