Enrico Fraccaroli
92 lines
2.1 KiB
C
92 lines
2.1 KiB
C
/// MentOS, The Mentoring Operating system project
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/// @file stdlib.c
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/// @brief
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/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#include "system/syscall_types.h"
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#include "stdlib.h"
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#include "string.h"
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#include "assert.h"
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/// @brief Number which identifies a memory area allocated through a call to
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/// malloc(), calloc() or realloc().
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#define MALLOC_MAGIC_NUMBER 0x600DC0DE
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static inline int __malloc_is_valid_ptr(void *ptr)
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{
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return (ptr && (((size_t *)ptr)[-1] == MALLOC_MAGIC_NUMBER));
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}
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size_t malloc_usable_size(void *ptr)
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{
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if (__malloc_is_valid_ptr(ptr))
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return ((size_t *)ptr)[-2];
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return 0;
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}
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void *malloc(unsigned int size)
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{
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size_t *_res, _size = 2 * sizeof(size_t) + size;
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__inline_syscall1(_res, brk, _size);
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_res[0] = size;
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_res[1] = MALLOC_MAGIC_NUMBER;
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return &_res[2];
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}
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void *calloc(size_t num, size_t size)
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{
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void *ptr = malloc(num * size);
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if (ptr) {
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memset(ptr, 0, num * size);
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}
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return ptr;
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}
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void *realloc(void *ptr, size_t size)
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{
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// C standard implementation: When NULL is passed to realloc,
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// simply malloc the requested size and return a pointer to that.
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if (__builtin_expect(ptr == NULL, 0)) {
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return malloc(size);
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}
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// C standard implementation: For a size of zero, free the
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// pointer and return NULL, allocating no new memory.
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if (__builtin_expect(size == 0, 0)) {
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free(ptr);
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return NULL;
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}
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// Get the old size.
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size_t old_size = malloc_usable_size(ptr);
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// Create the new pointer.
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void *newp = malloc(size);
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memset(newp, 0, size);
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memcpy(newp, ptr, old_size);
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free(ptr);
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return newp;
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}
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void free(void *ptr)
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{
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int _res;
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if (__malloc_is_valid_ptr(ptr)) {
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size_t *_ptr = (size_t *)ptr - 2;
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__inline_syscall1(_res, brk, _ptr);
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} else {
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__inline_syscall1(_res, brk, ptr);
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}
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}
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/// Seed used to generate random numbers.
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static int rseed = 0;
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void srand(int x)
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{
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rseed = x;
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}
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int rand()
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{
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return rseed = (rseed * 1103515245U + 12345U) & RAND_MAX;
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}
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