AK: Simplify Bitmap and implement in terms of BitmapView

Add Bitmap::view() and forward most of the calls to BitmapView since
the code was identical.

Bitmap is now primarily concerned with its dynamically allocated
backing store and BitmapView deals with the rest.

AK/Bitmap.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/BitmapView.h>
 #include <AK/Noncopyable.h>
 #include <AK/Optional.h>
 #include <AK/Platform.h>
@@ -39,35 +40,35 @@ class Bitmap {
     AK_MAKE_NONCOPYABLE(Bitmap);
 
 public:
-    // NOTE: A wrapping Bitmap won't try to free the wrapped data.
-    static Bitmap wrap(u8* data, size_t size)
-    {
-        return Bitmap(data, size);
-    }
+    Bitmap() = default;
 
-    static Bitmap create(size_t size, bool default_value = 0)
+    Bitmap(size_t size, bool default_value)
+        : m_size(size)
     {
-        return Bitmap(size, default_value);
+        VERIFY(m_size != 0);
+        m_data = static_cast<u8*>(kmalloc(size_in_bytes()));
+        fill(default_value);
     }
 
-    static Bitmap create()
+    Bitmap(u8* data, size_t size)
+        : m_data(data)
+        , m_size(size)
     {
-        return Bitmap();
     }
 
+    BitmapView view() { return { m_data, m_size }; }
+    const BitmapView view() const { return { m_data, m_size }; }
+
     Bitmap(Bitmap&& other)
+        : m_data(exchange(other.m_data, nullptr))
+        , m_size(exchange(other.m_size, 0))
     {
-        m_owned = exchange(other.m_owned, false);
-        m_data = exchange(other.m_data, nullptr);
-        m_size = exchange(other.m_size, 0);
     }
 
     Bitmap& operator=(Bitmap&& other)
     {
         if (this != &other) {
-            if (m_owned)
-                kfree(m_data);
-            m_owned = exchange(other.m_owned, false);
+            kfree(m_data);
             m_data = exchange(other.m_data, nullptr);
             m_size = exchange(other.m_size, 0);
         }
@@ -76,18 +77,19 @@ public:
 
     ~Bitmap()
     {
-        if (m_owned)
-            kfree(m_data);
+        kfree(m_data);
         m_data = nullptr;
     }
 
     size_t size() const { return m_size; }
     size_t size_in_bytes() const { return ceil_div(m_size, static_cast<size_t>(8)); }
+
     bool get(size_t index) const
     {
         VERIFY(index < m_size);
         return 0 != (m_data[index / 8] & (1u << (index % 8)));
     }
+
     void set(size_t index, bool value) const
     {
         VERIFY(index < m_size);
@@ -97,56 +99,8 @@ public:
             m_data[index / 8] &= static_cast<u8>(~(1u << (index % 8)));
     }
 
-    size_t count_slow(bool value) const
-    {
-        return count_in_range(0, m_size, value);
-    }
-
-    size_t count_in_range(size_t start, size_t len, bool value) const
-    {
-        VERIFY(start < m_size);
-        VERIFY(start + len <= m_size);
-        if (len == 0)
-            return 0;
-
-        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 };
-
-        size_t count;
-        const u8* first = &m_data[start / 8];
-        const u8* last = &m_data[(start + len) / 8];
-        u8 byte = *first;
-        byte &= bitmask_first_byte[start % 8];
-        if (first == last) {
-            byte &= bitmask_last_byte[(start + len) % 8];
-            count = __builtin_popcount(byte);
-        } else {
-            count = __builtin_popcount(byte);
-            byte = *last;
-            byte &= bitmask_last_byte[(start + len) % 8];
-            count += __builtin_popcount(byte);
-            if (++first < last) {
-                const u32* ptr32 = (const u32*)(((FlatPtr)first + sizeof(u32) - 1) & ~(sizeof(u32) - 1));
-                if ((const u8*)ptr32 > last)
-                    ptr32 = (const u32*)last;
-                while (first < (const u8*)ptr32) {
-                    count += __builtin_popcount(*first);
-                    first++;
-                }
-                const u32* last32 = (const u32*)((FlatPtr)last & ~(sizeof(u32) - 1));
-                while (ptr32 < last32) {
-                    count += __builtin_popcountl(*ptr32);
-                    ptr32++;
-                }
-                for (first = (const u8*)ptr32; first < last; first++)
-                    count += __builtin_popcount(*first);
-            }
-        }
-
-        if (!value)
-            count = len - count;
-        return count;
-    }
+    size_t count_slow(bool value) const { return count_in_range(0, m_size, value); }
+    size_t count_in_range(size_t start, size_t len, bool value) const { return view().count_in_range(start, len, value); }
 
     bool is_null() const { return !m_data; }
 
@@ -155,7 +109,6 @@ public:
 
     void grow(size_t size, bool default_value)
     {
-        VERIFY(m_owned);
         VERIFY(size > m_size);
 
         auto previous_size_bytes = size_in_bytes();
@@ -176,359 +129,35 @@ public:
     }
 
     template<bool VALUE>
-    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 (VALUE)
-                *first |= byte_mask;
-            else
-                *first &= ~byte_mask;
-        } else {
-            if constexpr (VALUE)
-                *first |= byte_mask;
-            else
-                *first &= ~byte_mask;
-            byte_mask = bitmask_last_byte[(start + len) % 8];
-            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) { return view().set_range<VALUE>(start, len); }
+    void set_range(size_t start, size_t len, bool value) { return view().set_range(start, len, value); }
 
-    void set_range(size_t start, size_t len, bool value)
-    {
-        if (value)
-            set_range<true>(start, len);
-        else
-            set_range<false>(start, len);
-    }
+    void fill(bool value) { view().fill(value); }
 
-    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
-    {
-        VERIFY(hint < m_size);
-        const u8* end = &m_data[m_size / 8];
-
-        for (;;) {
-            // We will use hint as what it is: a hint. Because we try to
-            // scan over entire 32 bit words, we may start searching before
-            // the hint!
-            const u32* ptr32 = (const u32*)((FlatPtr)&m_data[hint / 8] & ~(sizeof(u32) - 1));
-            if ((const u8*)ptr32 < &m_data[0]) {
-                ptr32++;
-
-                // m_data isn't aligned, check first bytes
-                size_t start_ptr32 = (const u8*)ptr32 - &m_data[0];
-                size_t i = 0;
-                u8 byte = VALUE ? 0x00 : 0xff;
-                while (i < start_ptr32 && m_data[i] == byte)
-                    i++;
-                if (i < start_ptr32) {
-                    byte = m_data[i];
-                    if constexpr (!VALUE)
-                        byte = ~byte;
-                    VERIFY(byte != 0);
-                    return i * 8 + __builtin_ffs(byte) - 1;
-                }
-            }
-
-            u32 val32 = VALUE ? 0x0 : 0xffffffff;
-            const u32* end32 = (const u32*)((FlatPtr)end & ~(sizeof(u32) - 1));
-            while (ptr32 < end32 && *ptr32 == val32)
-                ptr32++;
-
-            if (ptr32 == end32) {
-                // We didn't find anything, check the remaining few bytes (if any)
-                u8 byte = VALUE ? 0x00 : 0xff;
-                size_t i = (const u8*)ptr32 - &m_data[0];
-                size_t byte_count = m_size / 8;
-                VERIFY(i <= byte_count);
-                while (i < byte_count && m_data[i] == byte)
-                    i++;
-                if (i == byte_count) {
-                    if (hint <= 8)
-                        return {}; // We already checked from the beginning
-
-                    // Try scanning before the hint
-                    end = (const u8*)((FlatPtr)&m_data[hint / 8] & ~(sizeof(u32) - 1));
-                    hint = 0;
-                    continue;
-                }
-                byte = m_data[i];
-                if constexpr (!VALUE)
-                    byte = ~byte;
-                VERIFY(byte != 0);
-                return i * 8 + __builtin_ffs(byte) - 1;
-            }
-
-            // NOTE: We don't really care about byte ordering. We found *one*
-            // free bit, just calculate the position and return it
-            val32 = *ptr32;
-            if constexpr (!VALUE)
-                val32 = ~val32;
-            VERIFY(val32 != 0);
-            return ((const u8*)ptr32 - &m_data[0]) * 8 + __builtin_ffsl(val32) - 1;
-        }
-    }
-
-    Optional<size_t> find_one_anywhere_set(size_t hint = 0) const
-    {
-        return find_one_anywhere<true>(hint);
-    }
-    Optional<size_t> find_one_anywhere_unset(size_t hint = 0) const
-    {
-        return find_one_anywhere<false>(hint);
-    }
-
-    template<bool VALUE>
-    Optional<size_t> find_first() const
-    {
-        size_t byte_count = m_size / 8;
-        size_t i = 0;
-
-        u8 byte = VALUE ? 0x00 : 0xff;
-        while (i < byte_count && m_data[i] == byte)
-            i++;
-        if (i == byte_count)
-            return {};
-
-        byte = m_data[i];
-        if constexpr (!VALUE)
-            byte = ~byte;
-        VERIFY(byte != 0);
-        return i * 8 + __builtin_ffs(byte) - 1;
-    }
+    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); }
 
-    Optional<size_t> find_first_set() const
-    {
-        return find_first<true>();
-    }
-    Optional<size_t> find_first_unset() const
-    {
-        return find_first<false>();
-    }
+    Optional<size_t> find_first_set() const { return view().find_first<true>(); }
+    Optional<size_t> find_first_unset() const { return view().find_first<false>(); }
 
-    // The function will return the next range of unset bits starting from the
-    // @from value.
-    // @from: the position from which the search starts. The var will be
-    //        changed and new value is the offset of the found block.
-    // @min_length: minimum size of the range which will be returned.
-    // @max_length: maximum size of the range which will be returned.
-    //              This is used to increase performance, since the range of
-    //              unset bits can be long, and we don't need the while range,
-    //              so we can stop when we've reached @max_length.
-    inline Optional<size_t> find_next_range_of_unset_bits(size_t& from, size_t min_length = 1, size_t max_length = max_size) const
+    Optional<size_t> find_next_range_of_unset_bits(size_t& from, size_t min_length = 1, size_t max_length = max_size) const
     {
-        if (min_length > max_length) {
-            return {};
-        }
-
-        u32* bitmap32 = (u32*)m_data;
-
-        // Calculating the start offset.
-        size_t start_bucket_index = from / 32;
-        size_t start_bucket_bit = from % 32;
-
-        size_t* start_of_free_chunks = &from;
-        size_t free_chunks = 0;
-
-        for (size_t bucket_index = start_bucket_index; bucket_index < m_size / 32; ++bucket_index) {
-            if (bitmap32[bucket_index] == 0xffffffff) {
-                // Skip over completely full bucket of size 32.
-                if (free_chunks >= min_length) {
-                    return min(free_chunks, max_length);
-                }
-                free_chunks = 0;
-                start_bucket_bit = 0;
-                continue;
-            }
-            if (bitmap32[bucket_index] == 0x0) {
-                // Skip over completely empty bucket of size 32.
-                if (free_chunks == 0) {
-                    *start_of_free_chunks = bucket_index * 32;
-                }
-                free_chunks += 32;
-                if (free_chunks >= max_length) {
-                    return max_length;
-                }
-                start_bucket_bit = 0;
-                continue;
-            }
-
-            u32 bucket = bitmap32[bucket_index];
-            u8 viewed_bits = start_bucket_bit;
-            u32 trailing_zeroes = 0;
-
-            bucket >>= viewed_bits;
-            start_bucket_bit = 0;
-
-            while (viewed_bits < 32) {
-                if (bucket == 0) {
-                    if (free_chunks == 0) {
-                        *start_of_free_chunks = bucket_index * 32 + viewed_bits;
-                    }
-                    free_chunks += 32 - viewed_bits;
-                    viewed_bits = 32;
-                } else {
-                    trailing_zeroes = count_trailing_zeroes_32(bucket);
-                    bucket >>= trailing_zeroes;
-
-                    if (free_chunks == 0) {
-                        *start_of_free_chunks = bucket_index * 32 + viewed_bits;
-                    }
-                    free_chunks += trailing_zeroes;
-                    viewed_bits += trailing_zeroes;
-
-                    if (free_chunks >= min_length) {
-                        return min(free_chunks, max_length);
-                    }
-
-                    // Deleting trailing ones.
-                    u32 trailing_ones = count_trailing_zeroes_32(~bucket);
-                    bucket >>= trailing_ones;
-                    viewed_bits += trailing_ones;
-                    free_chunks = 0;
-                }
-            }
-        }
-
-        if (free_chunks < min_length) {
-            size_t first_trailing_bit = (m_size / 32) * 32;
-            size_t trailing_bits = size() % 32;
-            for (size_t i = 0; i < trailing_bits; ++i) {
-                if (!get(first_trailing_bit + i)) {
-                    if (!free_chunks)
-                        *start_of_free_chunks = first_trailing_bit + i;
-                    if (++free_chunks >= min_length)
-                        return min(free_chunks, max_length);
-                } else {
-                    free_chunks = 0;
-                }
-            }
-            return {};
-        }
-
-        return min(free_chunks, max_length);
+        return view().find_next_range_of_unset_bits(from, min_length, max_length);
     }
 
     Optional<size_t> find_longest_range_of_unset_bits(size_t max_length, size_t& found_range_size) const
     {
-        size_t start = 0;
-        size_t max_region_start = 0;
-        size_t max_region_size = 0;
-
-        while (true) {
-            // Look for the next block which is bigger than currunt.
-            auto length_of_found_range = find_next_range_of_unset_bits(start, max_region_size + 1, max_length);
-            if (length_of_found_range.has_value()) {
-                max_region_start = start;
-                max_region_size = length_of_found_range.value();
-                start += max_region_size;
-            } else {
-                // No ranges which are bigger than current were found.
-                break;
-            }
-        }
-
-        found_range_size = max_region_size;
-        if (max_region_size) {
-            return max_region_start;
-        }
-        return {};
-    }
-
-    Optional<size_t> find_first_fit(size_t minimum_length) const
-    {
-        size_t start = 0;
-        auto length_of_found_range = find_next_range_of_unset_bits(start, minimum_length, minimum_length);
-        if (length_of_found_range.has_value()) {
-            return start;
-        }
-        return {};
-    }
-
-    Optional<size_t> find_best_fit(size_t minimum_length) const
-    {
-        size_t start = 0;
-        size_t best_region_start = 0;
-        size_t best_region_size = max_size;
-        bool found = false;
-
-        while (true) {
-            // Look for the next block which is bigger than requested length.
-            auto length_of_found_range = find_next_range_of_unset_bits(start, minimum_length, best_region_size);
-            if (length_of_found_range.has_value()) {
-                if (best_region_size > length_of_found_range.value() || !found) {
-                    best_region_start = start;
-                    best_region_size = length_of_found_range.value();
-                    found = true;
-                }
-                start += length_of_found_range.value();
-            } else {
-                // There are no ranges which can fit requested length.
-                break;
-            }
-        }
-
-        if (found) {
-            return best_region_start;
-        }
-        return {};
+        return view().find_longest_range_of_unset_bits(max_length, found_range_size);
     }
 
-    Bitmap()
-        : m_size(0)
-        , m_owned(true)
-    {
-        m_data = nullptr;
-    }
-
-    Bitmap(size_t size, bool default_value)
-        : m_size(size)
-        , m_owned(true)
-    {
-        VERIFY(m_size != 0);
-        m_data = reinterpret_cast<u8*>(kmalloc(size_in_bytes()));
-        fill(default_value);
-    }
-
-    Bitmap(u8* data, size_t size)
-        : m_data(data)
-        , m_size(size)
-        , m_owned(false)
-    {
-    }
+    Optional<size_t> find_first_fit(size_t minimum_length) const { return view().find_first_fit(minimum_length); }
+    Optional<size_t> find_best_fit(size_t minimum_length) const { return view().find_best_fit(minimum_length); }
 
-    static constexpr u32 max_size = 0xffffffff;
+    static constexpr size_t max_size = 0xffffffff;
 
 private:
     u8* m_data { nullptr };
     size_t m_size { 0 };
-    bool m_owned { false };
 };
 
 }

Kernel/VM/PhysicalRegion.cpp

@@ -43,7 +43,6 @@ NonnullRefPtr<PhysicalRegion> PhysicalRegion::create(PhysicalAddress lower, Phys
 PhysicalRegion::PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper)
     : m_lower(lower)
     , m_upper(upper)
-    , m_bitmap(Bitmap::create())
 {
 }
 

Userland/DevTools/Profiler/Profile.h

@@ -98,7 +98,7 @@ public:
     void will_track_seen_events(size_t profile_event_count)
     {
         if (m_seen_events.size() != profile_event_count)
-            m_seen_events = Bitmap::create(profile_event_count, false);
+            m_seen_events = Bitmap { profile_event_count, false };
     }
     bool has_seen_event(size_t event_index) const { return m_seen_events.get(event_index); }
     void did_see_event(size_t event_index) { m_seen_events.set(event_index, true); }