Fixed runtime errors.

CMakeLists.txt

@@ -38,9 +38,9 @@ endif ()
 
 set(CMAKE_C_STANDARD 11)
 
-add_executable(CustomHeapManager main.c)
+add_executable(CustomHeapManager
+    src/CHM.c include/CHM.h
+    src/main.c
+)
 
-if (IS_OS_LINUX)
+target_include_directories(CustomHeapManager PUBLIC ${PROJECT_SOURCE_DIR}/include)
-    target_link_options(CustomHeapManager PUBLIC)
-elseif (IS_OS_WINDOWS)
-endif ()

include/CHM.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+
+enum MemMode : unsigned char
+{
+	MEM_MODE_SPEED, // Memory will be allocated more quickly but loses memory efficiency.
+	MEM_MODE_EFFICIENCY, // Memory will be allocated more slowly but gains memory efficiency.
+	MEM_MODE_BALANCED // Memory will be allocated as quickly as possible but also for the sake of memory efficiency.
+};
+
+void set_memory_mode(enum MemMode new_mode);
+
+enum MemMode get_memory_mode();
+
+/// Will find or allocate a memory block appropriately.
+/// @param [in] size The size of the memory block to request.
+/// @returns The allocated memory address on the heap.
+void *malloc(size_t size);
+
+void *realloc(void *ptr, size_t newSize);
+
+/// Will flag the provided memory as free and will defragment other blocks adjacent to it.
+/// @param [in] ptr The memory to flag as free.
+void free(void *ptr);
+
+size_t get_header_size();
+
+/// Will retrieve the current real byte size of the heap.
+/// @returns The size in bytes.
+size_t get_heap_size();
+
+void cleanup_memory();

main.c

@@ -1,280 +0,0 @@
-#include <stddef.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdlib.h>
-
-#define ALIGN16(s) (((s) + 15) & ~0x0F)
-#define BLOCK_SIZE sizeof(struct block)
-#define MINIMUM_BLOCK_SIZE (sizeof(struct block) + 16)
-
-/// The memory block's header.
-struct block
-{
-	size_t size;
-	struct block *prev;
-	struct block *next;
-	int free;
-};
-
-struct block *first = NULL;
-struct block *last = NULL;
-
-/// Extends heap memory upwards, towards zero.
-/// @param [in] s The size of the memory needed aligned by 4 bytes.
-/// @returns The new memory block.
-struct block *extend_heap(size_t s)
-{
-	// Ensure the allocated size is at least the minimum block size
-	if (s < MINIMUM_BLOCK_SIZE)
-		s = MINIMUM_BLOCK_SIZE;
-
-	struct block *b = (struct block *)sbrk(0); // Get the current break
-
-	// Add the size of the block header to the requested size
-	s += BLOCK_SIZE;
-
-	if (sbrk(s) == (void *)-1) // Extend the break by s bytes
-		return NULL;
-
-	b->size = s;
-	b->prev = last;
-	b->next = NULL;
-	b->free = 0;
-
-	if (last)
-		last->next = b;
-
-	last = b;
-
-	return b;
-}
-
-/// Finds the first block that will fit the given size.
-/// @param [in] s The 4 byte aligned size to look for.
-/// @returns The matching available memory block.
-struct block *find_first(size_t s)
-{
-	struct block *current = first;
-	while (current && (!current->free || current->size < s))
-		current = current->next;
-
-	return current;
-}
-
-/// Fragments an existing free memory block into the given size.
-/// @param [in] in The memory block to fragment.
-/// @param [in] s The size of the new memory block.
-/// @returns The new memory block.
-struct block *fragment_block(struct block *in, size_t s)
-{
-	// Calculate the size of the new block, including the block header
-	size_t newBlockSize = s + BLOCK_SIZE;
-
-	// Check if the current block can be split
-	if (in->size <= newBlockSize)
-	{
-		// Cannot split, return the original block
-		return in;
-	}
-
-	// Calculate the size of the remainder block
-	size_t remainderSize = in->size - newBlockSize;
-
-	// Create the new block in the remainder space
-	struct block *newBlock = (struct block *)((char *)(in + 1) + s);
-	newBlock->size = remainderSize;
-	newBlock->prev = in;
-	newBlock->next = in->next;
-	newBlock->free = 1; // Set the new block as free
-
-	// Update the current block to reflect the reduced size
-	in->size = newBlockSize;
-	in->next = newBlock;
-
-	// Insert the new block into the linked list of blocks
-	if (newBlock->next)
-	{
-		newBlock->next->prev = newBlock;
-	}
-
-	return newBlock;
-}
-
-struct block *find_best_fit(size_t s)
-{
-	struct block *current = first;
-	struct block *best_fit = NULL;
-	while (current)
-	{
-		if (current->free && current->size >= s)
-	{
-			if (best_fit && current->size < best_fit->size) // Check for NULL before comparison
-		{
-			{
-				best_fit = current;
-			}
-		}
-		current = current->next;
-	}
-	return best_fit;
-	}
-}
-
-/// Will find or allocate a memory block.
-/// @param [in] size The size of the memory block to request.
-/// @returns The requested memory on the heap.
-/// @todo Fragmenting functionality.
-void *malloc(size_t size)
-{
-	if (size == 0)
-	{
-		return NULL;
-	}
-
-	size = ALIGN16(size);				   // First align the requested size
-	size_t total_size = size + BLOCK_SIZE; // Then add the size of the block header
-
-	struct block *b;
-
-	if (first)
-	{
-		b = find_best_fit(size);
-		if (!b)
-		{
-			b = extend_heap(total_size);
-			if (!b)
-			{
-				return NULL; // Check if heap extension failed
-			}
-		}
-		else if (b->size > total_size + MINIMUM_BLOCK_SIZE)
-		{
-			b = fragment_block(b, size);
-		}
-	}
-	else
-	{
-		b = extend_heap(total_size);
-		if (!b)
-		{
-			return NULL;
-		}
-		first = b;
-	}
-
-	b->free = 0;				   // Mark the block as used
-	return (char *)b + BLOCK_SIZE; // Return a pointer to the usable memory
-}
-
-void *realloc(void *ptr, size_t new_size)
-{
-	if (!ptr)
-	{
-		return malloc(new_size);
-	}
-
-	if (new_size == 0)
-	{
-		free(ptr);
-		return NULL;
-	}
-
-	struct block *b = (struct block *)((char *)ptr - BLOCK_SIZE);
-	if (b->size >= new_size + BLOCK_SIZE)
-	{
-		return ptr; // The block is already big enough
-	}
-
-	void *new_ptr = malloc(new_size);
-	if (!new_ptr)
-	{
-		return NULL; // Allocation failed
-	}
-	memcpy(new_ptr, ptr, b->size - BLOCK_SIZE); // Copy old data to new block, excluding the header size
-	free(ptr);									// Free the old block
-
-	return new_ptr;
-}
-
-/// Will flag the provided memory as free and will defragment other blocks adjacent to it.
-/// @param [in] ptr The memory to flag as free.
-/// @note If all data after the provided memory is free, it will reduce the heap size.
-void my_custom_free(void *ptr)
-{
-    if (!ptr)
-    {
-        return;
-    }
-
-    struct block *b = (struct block *)((char *)ptr - BLOCK_SIZE);
-    if (b->free)
-    {
-        fprintf(stderr, "Double free detected at block %p.\n", ptr);
-        abort(); // Terminate the program immediately due to serious error
-    }
-
-    b->free =  1;
-
-    // Coalesce free blocks
-    while (b->prev && b->prev->free)
-    {
-        // Merge with previous block
-        b->prev->size += BLOCK_SIZE + b->size;
-        b->prev->next = b->next;
-        b = b->prev;
-    }
-
-    // If there is a next block and it's free, merge with it
-    if (b->next && b->next->free)
-    {
-        b->size += BLOCK_SIZE + b->next->size;
-        b->next = b->next->next;
-        if (b->next)
-        {
-            b->next->prev = b;
-        }
-    }
-
-    // After merging, update the 'last' pointer if necessary
-    if (!b->next)
-    {
-        last = b;
-    }
-
-    // Check if we can shrink the heap
-    if (b == last)
-    {
-        // Update 'last' to the previous block or NULL if there's no previous block
-        last = b->prev;
-        if (last)
-        {
-            last->next = NULL;
-        }
-        else
-        {
-            first = NULL;
-        }
-        // Reduce the program break to release the memory
-        sbrk(0 - (b->size + BLOCK_SIZE));
-    }
-}
-
-int main()
-{
-	int *a = (int *)malloc(sizeof(int));
-	int *b = (int *)malloc(sizeof(int));
-
-	*a = 5;
-	*b = 12;
-
-	printf("Test 1: %i\n", *a);
-	printf("Test 2: %i\n", *b);
-	printf("Heap Size: %zu Bytes\n", get_heap_size());
-
-	free(a);
-	free(b);
-
-	int *c = (int *)malloc(sizeof(int));
-
-	return 0;
-}

src/CHM.c

@@ -0,0 +1,426 @@
+#include "CHM.h"
+
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+
+#define ALIGN4(s) (((((s)-1)>>2)<<2)+4)
+#define ALIGN16(s) (((s) + 15) & ~0x0F)
+#define ALIGNMENT 4
+#define BLOCK_SIZE sizeof(struct Block)
+
+/// The memory block's header.
+struct Block
+{
+	size_t size;
+	struct Block *prev;
+	struct Block *next;
+	int free;
+};
+
+enum MemMode mode = MEM_MODE_BALANCED;
+struct Block *first = NULL;
+struct Block *last = NULL;
+
+/// Sets the memory mode for the custom heap manager.
+/// @param [in] new_mode The new mode to use.
+void set_memory_mode(const enum MemMode new_mode)
+{
+	if (new_mode > MEM_MODE_BALANCED)
+	{
+		fprintf(stderr, "The given memory mode, \"%i\", is invalid.", new_mode);
+		return;
+	}
+
+	mode = new_mode;
+}
+
+/// Gets the current memory mode for the custom heap manager.
+/// @returns The current mode.
+enum MemMode get_memory_mode()
+{
+	return mode;
+}
+
+/// Extends heap memory upwards, towards zero.
+/// @param [in] s The size of the memory needed aligned by 4 bytes.
+/// @returns The new memory block.
+struct Block *extend_heap(const size_t s)
+{
+	struct Block* b = (struct Block *)syscall(SYS_brk, NULL);
+
+	if ((void *)syscall(SYS_brk, (char *)(b + 1) + s) == (void *)-1)
+		return NULL;
+
+	b->size = s;
+	b->prev = last;
+	b->next = NULL;
+	b->free = 0;
+
+	if (last)
+		last->next = b;
+
+	last = b;
+
+	return b;
+}
+
+/// Will defragment adjacent memory blocks of the given memory block.
+/// @param [in] in The memory block to defragment for.
+void defragment_adjacent_blocks(struct Block *in)
+{
+	// Go in reverse order to find free memory blocks.
+	while (in->prev && in->prev->free)
+		in = in->prev;
+
+	// Go in forward order to find memory blocks and merge them.
+	while (in->next && in->next->free)
+	{
+		in->size += BLOCK_SIZE + in->next->size;
+		in->next = in->next->next;
+	}
+}
+
+/// Fragments an existing free memory block into the given size.
+/// @param [in] in The memory block to fragment.
+/// @param [in] s The size of the new memory block.
+void fragment_block(struct Block *in, size_t s)
+{
+	// Create the new block in the remainder space
+	struct Block *newBlock = (struct Block *)((char *)(in + 1) + s);
+	newBlock->size = in->size - BLOCK_SIZE - s;
+	newBlock->prev = in;
+	newBlock->next = in->next;
+	newBlock->free = 1;
+
+	// Update the current block to reflect the reduced size
+	in->size = s;
+	in->next = newBlock;
+	in->free = 0;
+}
+
+struct Block *extend_block(struct Block *in, const size_t newSize)
+{
+	if (!in->next)
+	{
+		void *addr = (struct Block *)syscall(SYS_brk, NULL);
+
+		if ((void *)syscall(SYS_brk, (char *)addr + (newSize - in->size)) == (void *)-1)
+			return NULL;
+
+		in->size = newSize;
+
+		return in;
+	}
+
+	size_t totalSize = in->size;
+	struct Block *start = in->prev;
+	struct Block *end = in->next;
+
+	while (start && start->free && totalSize < newSize)
+	{
+		totalSize += BLOCK_SIZE + start->size;
+		if (totalSize >= newSize)
+			break;
+
+		start = in->prev;
+	}
+
+	while (end && end->free && totalSize < newSize)
+	{
+		totalSize += BLOCK_SIZE + end->size;
+		if (totalSize >= newSize)
+			break;
+
+		end = end->next;
+	}
+
+	if (totalSize < newSize || (mode == MEM_MODE_EFFICIENCY && totalSize > newSize))
+		return NULL;
+
+	if (!start)
+		start = in;
+
+	if (!end)
+		end = in;
+
+	struct Block *b = start->next;
+	while (b)
+	{
+		start->size += BLOCK_SIZE + b->size;
+
+		if (b == end)
+			break;
+
+		b = b->next;
+	}
+
+	start->next = end->next;
+	start->free = 0;
+	start->next->prev = start;
+
+	if (!start->next)
+		last = start;
+
+	const size_t remainder = start->size - (BLOCK_SIZE + newSize);
+	if (remainder && !(remainder % ALIGNMENT))
+		fragment_block(start, newSize);
+
+	return start;
+}
+
+/// Finds the first block that will fit the given size.
+/// @param [in] s The memory aligned size to look for.
+/// @returns The matching available memory block.
+struct Block *find_first(const size_t s)
+{
+	const size_t totalSize = BLOCK_SIZE + s;
+	struct Block *current = first;
+	while (current)
+	{
+		if (!current->free || current->size < s)
+		{
+			current = current->next;
+			continue;
+		}
+
+		if (current->size >= s)
+			break;
+
+		current = current->next;
+	}
+
+	return current;
+}
+
+/// Finds the first memory block with more ore equal to the given size and fragments it if necessary.
+/// @param [in] s The memory aligned size to look for.
+/// @returns The matching available memory block.
+struct Block *find_balanced(const size_t s)
+{
+	const size_t totalSize = BLOCK_SIZE + s;
+	struct Block *current = first;
+	while (current)
+	{
+		if (!current->free || current->size < s)
+		{
+			current = current->next;
+			continue;
+		}
+
+		if (current->size == s)
+			break;
+
+		const size_t remainder = current->size - totalSize;
+		if (remainder && !(remainder % ALIGNMENT))
+		{
+			fragment_block(current, s);
+			break;
+		}
+
+		current = current->next;
+	}
+
+	return current;
+}
+
+/// Finds the best fitting memory block with the given size and fragments it if necessary.
+/// @param [in] s The memory aligned size to look for.
+/// @returns The matching available memory block.
+struct Block *find_best_fit(const size_t s)
+{
+	const size_t totalSize = BLOCK_SIZE + s;
+	unsigned char fragment = 0;
+	struct Block *best = NULL;
+	struct Block *current = first;
+
+	while (current)
+	{
+		if (!current->free || current->size < s)
+		{
+			current = current->next;
+			continue;
+		}
+
+		if (current->size == s)
+		{
+			fragment = 0;
+			best = current;
+			break;
+		}
+
+		const size_t remainder = current->size - totalSize;
+		if (best)
+		{
+			if (current->size < best->size && remainder && !(remainder % ALIGNMENT))
+			{
+				fragment = 1;
+				best = current;
+			}
+		}
+		else
+		{
+			if (remainder && !(remainder % ALIGNMENT))
+			{
+				fragment = 1;
+				best = current;
+			}
+		}
+
+		current = current->next;
+	}
+
+	if (best && fragment)
+		fragment_block(best, s);
+
+	return best;
+}
+
+void *malloc(size_t size)
+{
+	if (!size)
+		return NULL;
+
+	size = ALIGN16(size);
+
+	struct Block *b;
+
+	if (first)
+	{
+		switch (mode)
+		{
+			case MEM_MODE_SPEED:
+				b = find_first(size);
+				break;
+			case MEM_MODE_EFFICIENCY:
+				b = find_best_fit(size);
+				break;
+			case MEM_MODE_BALANCED:
+				b = find_balanced(size);
+				break;
+		}
+
+		if (!b)
+		{
+			b = extend_heap(size);
+			if (!b)
+				return NULL;
+		}
+	}
+	else
+	{
+		b = extend_heap(size);
+		if (!b)
+			return NULL;
+
+		first = b;
+		last = b;
+	}
+
+	return b + 1;
+}
+
+void *realloc(void *ptr, size_t newSize)
+{
+	if (!newSize)
+		return NULL;
+
+	if (!ptr)
+		return malloc(newSize);
+
+	newSize = ALIGN16(newSize);
+
+	struct Block *b = (struct Block *)ptr - 1;
+	if (b->free)
+		return NULL;
+
+	if (b->size == newSize)
+		return b + 1;
+
+	const size_t totalSize = BLOCK_SIZE + newSize;
+	const size_t remainder = b->size - totalSize;
+	if (b->size < newSize) // Expand memory block if possible.
+	{
+		if (!extend_block(b, newSize))
+			return NULL;
+
+		return b + 1;
+	}
+	else if (b->size > newSize && remainder && !(remainder % ALIGNMENT)) // Shrink memory block if possible.
+	{
+		fragment_block(b, newSize);
+		return b + 1;
+	}
+
+	return NULL;
+}
+
+void free(void *ptr)
+{
+	if (!ptr)
+		return;
+
+	struct Block *b = (struct Block *)ptr - 1;
+	if (b->free)
+	{
+		fprintf(stderr, "Double free detected for the address %p.\n", ptr);
+		return;
+	}
+
+	b->free = 1;
+
+	if (mode != MEM_MODE_SPEED)
+		defragment_adjacent_blocks(b);
+
+	if (!b->next)
+	{
+		if (!b->prev)
+		{
+			first = NULL;
+			last = NULL;
+		}
+		else
+			last = b;
+
+		syscall(SYS_brk, b);
+	}
+}
+
+size_t get_header_size()
+{
+	return BLOCK_SIZE;
+}
+
+size_t get_heap_size()
+{
+	if (!first || !last)
+		return 0;
+
+	return (char*)last + last->size - (char*)first;
+}
+
+void cleanup_memory()
+{
+	if (!first || !last)
+		return;
+
+	const struct Block *l = last;
+	struct Block *current = first;
+	while (current)
+	{
+		if (!current->free)
+			fprintf(stderr, "Memory at the address %p has not been marked free. Possible memory leak?\n", current + 1);
+
+		if (current == l)
+			break;
+
+		current = current->next;
+	}
+
+	syscall(SYS_brk, first);
+
+	first = NULL;
+	last = NULL;
+}

src/main.c

@@ -0,0 +1,25 @@
+#include "CHM.h"
+
+#include <unistd.h>
+
+int main()
+{
+	set_memory_mode(MEM_MODE_BALANCED);
+
+	int *a = (int *)malloc(sizeof(int));
+	*a = 1;
+	int *b = (int *)malloc(sizeof(int));
+	*b = 2;
+	int *c = (int *)malloc(sizeof(int));
+	*c = 3;
+
+	printf("Heap Size: %zu Bytes\n", get_heap_size());
+
+	free(a);
+	free(b);
+	free(c);
+
+	cleanup_memory();
+
+	return 0;
+}