1 files changed, 95 insertions, 0 deletions
diff --git a/Userland/Libraries/LibC/mallocdefs.h b/Userland/Libraries/LibC/mallocdefs.h
new file mode 100644
index 0000000000..d639c512cd
--- /dev/null
+++ b/Userland/Libraries/LibC/mallocdefs.h
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/InlineLinkedList.h>
+#include <AK/Types.h>
+
+#define MAGIC_PAGE_HEADER 0x42657274     // 'Bert'
+#define MAGIC_BIGALLOC_HEADER 0x42697267 // 'Birg'
+#define MALLOC_SCRUB_BYTE 0xdc
+#define FREE_SCRUB_BYTE 0xed
+
+static constexpr unsigned short size_classes[] = { 8, 16, 32, 64, 128, 256, 500, 1016, 2032, 4088, 8184, 16376, 32752, 0 };
+static constexpr size_t num_size_classes = (sizeof(size_classes) / sizeof(unsigned short)) - 1;
+
+struct CommonHeader {
+    size_t m_magic;
+    size_t m_size;
+};
+
+struct BigAllocationBlock : public CommonHeader {
+    BigAllocationBlock(size_t size)
+    {
+        m_magic = MAGIC_BIGALLOC_HEADER;
+        m_size = size;
+    }
+    unsigned char* m_slot[0];
+};
+
+struct FreelistEntry {
+    FreelistEntry* next;
+};
+
+struct ChunkedBlock
+    : public CommonHeader
+    , public InlineLinkedListNode<ChunkedBlock> {
+
+    static constexpr size_t block_size = 64 * KiB;
+    static constexpr size_t block_mask = ~(block_size - 1);
+
+    ChunkedBlock(size_t bytes_per_chunk)
+    {
+        m_magic = MAGIC_PAGE_HEADER;
+        m_size = bytes_per_chunk;
+        m_free_chunks = chunk_capacity();
+        m_freelist = (FreelistEntry*)chunk(0);
+        for (size_t i = 0; i < chunk_capacity(); ++i) {
+            auto* entry = (FreelistEntry*)chunk(i);
+            if (i != chunk_capacity() - 1)
+                entry->next = (FreelistEntry*)chunk(i + 1);
+            else
+                entry->next = nullptr;
+        }
+    }
+
+    ChunkedBlock* m_prev { nullptr };
+    ChunkedBlock* m_next { nullptr };
+    FreelistEntry* m_freelist { nullptr };
+    size_t m_free_chunks { 0 };
+    [[gnu::aligned(8)]] unsigned char m_slot[0];
+
+    void* chunk(size_t index)
+    {
+        return &m_slot[index * m_size];
+    }
+    bool is_full() const { return m_free_chunks == 0; }
+    size_t bytes_per_chunk() const { return m_size; }
+    size_t free_chunks() const { return m_free_chunks; }
+    size_t used_chunks() const { return chunk_capacity() - m_free_chunks; }
+    size_t chunk_capacity() const { return (block_size - sizeof(ChunkedBlock)) / m_size; }
+};