forked from KolibriOS/kolibrios
101 lines
3.6 KiB
C
101 lines
3.6 KiB
C
#include <string.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <sys/ksys.h>
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#include "_mem.h"
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// Macro to align a value to a specified alignment.
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// Ensures that the allocated memory is aligned to a certain boundary (e.g., 16 bytes).
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#define __mem_align(value, align) ((value + align - 1) & ~(align - 1))
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void* malloc(size_t size)
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{
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// Handle zero-size allocation.
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if (size == 0) {
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return NULL;
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}
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// Align the size to 16 bytes.
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size = __mem_align(size, 16);
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struct mem_node* current_node = __mem_node; // Start at the head of the linked list.
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struct mem_node* new_node = NULL; // Pointer to the new node that will be created.
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// Iterate through the linked list of memory nodes.
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while (current_node != NULL) {
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// Check if the current node has enough free space for the requested size.
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if (size + sizeof(struct mem_node) <= current_node->free) {
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// Calculate the used memory in current node
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const size_t s = GET_MEM_NODE_USED_MEM(current_node);
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// Create a new memory node after the current node's used space.
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new_node = (struct mem_node*)(GET_MEM_NODE_PTR(current_node) + s);
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// Set the size of the new node.
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new_node->size = current_node->free - sizeof(struct mem_node);
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// Update current node's size
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current_node->size = s;
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// Mark current node as used.
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current_node->free = 0;
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break; // Found a suitable node, exit the loop.
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}
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current_node = current_node->next; // Move to the next node in the list.
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}
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// If no suitable node was found in the existing list:
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if (new_node == NULL) {
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// Calculate the size of the new block, including the mem_block header, mem_node header and alignment.
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const size_t s = __mem_align(size + sizeof(struct mem_block) + sizeof(struct mem_node), ALLOC_BLOCK_SIZE);
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// Allocate a new block of memory using the ksys_alloc function (presumably a kernel-level allocation function).
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struct mem_block* block = (struct mem_block*)_ksys_alloc(s);
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// Check if the allocation was successful.
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if (block == NULL) {
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__errno = ENOMEM; // Set the error number to indicate memory allocation failure.
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return NULL; // Return NULL to indicate allocation failure.
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}
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// Create a new memory node after the mem_block header.
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new_node = (struct mem_node*)(block + sizeof(struct mem_block));
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// Set the size of the new node.
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new_node->size = s - sizeof(struct mem_block) - sizeof(struct mem_node);
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}
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// Set the free space in the new node.
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new_node->free = new_node->size - size;
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// Set the last pointer of the new node to the current node.
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new_node->last = current_node;
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// Link the new node into the linked list.
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if (current_node != NULL) {
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// Set the next pointer of the current node to the new node.
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new_node->next = current_node->next;
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// Update the last pointer of the next node, if it exists.
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if (current_node->next != NULL) {
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current_node->next->last = new_node;
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}
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current_node->next = new_node;
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} else {
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// If the current node is NULL, the new node is the first node in the list.
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new_node->next = NULL;
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}
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// If the linked list was empty, set the head to the new node.
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if (__mem_node == NULL) {
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__mem_node = new_node;
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}
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// Return a pointer to the user data area of the new node.
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return GET_MEM_NODE_PTR(new_node);
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}
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#undef __mem_align
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