/**
* slibc — Yet another C library
* Copyright © 2015 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <slibc-alloc.h>
#include <strings.h>
#include <sys/mman.h>
#include <unistd.h>
#include <errno.h>
/**
* Create a new memory allocation on the heap.
* The allocation will not be initialised.
*
* @param size The size of the allocation.
* @return Pointer to the beginning of the new allocation.
* If `size` is zero, this function will either return
* `NULL` (that is what this implement does) or return
* a unique pointer that can later be freed with `free`.
* `NULL` is returned on error, and `errno` is set to
* indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
*/
void* malloc(size_t size)
{
/* TODO implement implementation of malloc */
char* ptr;
size_t full_size;
if (size == 0)
return NULL;
if (__builtin_uaddl_overflow(2 * sizeof(size_t), size, &full_size))
return errno = ENOMEM, NULL;
ptr = mmap(NULL, full_size, (PROT_READ | PROT_WRITE),
(MAP_PRIVATE | MAP_ANONYMOUS), -1, 0);
((size_t*)ptr)[0] = size;
((size_t*)ptr)[1] = 0;
return ptr + 2 * sizeof(size_t);
}
/**
* Variant of `malloc` that clears the allocation with zeroes.
*
* `p = calloc(n, m)` is equivalent to
* `(p = malloc(n * m), p ? (explicit_bzero(p, n * m), p) : NULL)`
*
* @param elem_count The number of elements to allocate.
* @param elem_size The size of each element.
* @return Pointer to the beginning of the new allocation.
* If `elem_count` or `elem_size` is zero, this function
* will either return `NULL` (that is what this implement
* does) or return a unique pointer that can later be
* freed with `free`. `NULL` is returned on error, and
* `errno` is set to indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
*/
void* calloc(size_t elem_count, size_t elem_size)
{
void* ptr;
size_t size;
if (__builtin_umull_overflow(elem_count, elem_size, &size))
return errno = ENOMEM, NULL;
ptr = malloc(size);
if (ptr != NULL)
explicit_bzero(ptr, size);
return ptr;
}
/**
* Variant of `malloc` that extends, or shrinks, an existing allocation,
* if beneficial and possible, or creates a new allocation with the new
* size, copies the data, and frees the old allocation.
*
* On error, `ptr` is not freed.
*
* @param ptr Pointer to the beginning of the old memory allocation.
* The process may crash if it does not point to the
* beginning of a memory allocation on the heap.
* However, if it is `NULL`, this function will behave
* like `malloc`.
* @param size The new allocation size. If zero, this function will
* behave like `free`, and will return `NULL`.
* @return Pointer to the beginning of the new allocation.
* If `size` is zero, `NULL` is returned. On error `NULL`
* is returned and `errno` is set to indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
*/
void* realloc(void* ptr, size_t size)
{
return fast_realloc(ptr, size);
}
/**
* Free a memory allocation.
*
* @param ptr Pointer to the beginning of the memory allocation.
* The process may crash if it does not point to the
* beginning of a memory allocation on the heap.
* However, if it is `NULL`, nothing will happen.
*/
void free(void* ptr)
{
fast_free(ptr);
}
/**
* This function is identical to `free`.
* Any argument beyond the first argument, is ignored.
*
* This function uses variadic arguments because there
* there are multiple conflicting specifications for `cfree`.
*
* @param ptr Pointer to the beginning of the memory allocation.
* The process may crash if it does not point to the
* beginning of a memory allocation on the heap.
* However, if it is `NULL`, nothing will happen.
*/
void cfree(void* ptr, ...)
{
fast_free(ptr);
}
/**
* Variant of `malloc` that returns an address with a
* specified alignment.
*
* It is unspecified how the function works. This implemention
* will allocate a bit of extra memory and shift the returned
* pointer so that it is aligned.
*
* As a GNU-compliant slibc extension, memory allocated
* with this function can be freed with `free`.
*
* @param boundary The alignment.
* @param size The number of bytes to allocated.
* @return Pointer to the beginning of the new allocation.
* If `size` is zero, this function will either return
* `NULL` (that is what this implement does) or return
* a unique pointer that can later be freed with `free`.
* `NULL` is returned on error, and `errno` is set to
* indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
* @throws EINVAL If `boundary` is not a power of two.
*/
void* memalign(size_t boundary, size_t size)
{
char* ptr;
size_t full_size;
size_t address;
size_t shift = 0;
if (!boundary || (__builtin_ffsl(boundary) != boundary))
return errno = EINVAL, NULL;
if (__builtin_uaddl_overflow(boundary - 1, size, &full_size))
return errno = ENOMEM, NULL;
ptr = malloc(full_size);
if (ptr == NULL)
return NULL;
address = (size_t)ptr;
if (address % boundary != 0)
{
shift = boundary - (address % boundary);
ptr += shift;
*(size_t*)(ptr - sizeof(size_t)) = shift;
}
return ptr;
}
/**
* `posix_memalign(p, b, n)` is equivalent to
* `(*p = memalign(b, n), *p ? 0 : errno)`, except
* `boundary` must also be a multiple of `sizeof(void*)`,
* and `errno` is unspecified.
*
* As a GNU-compliant slibc extension, memory allocated
* with this function can be freed with `free`.
*
* @param ptrptr Output parameter for the allocated memory.
* @param boundary The alignment.
* @param size The number of bytes to allocated.
* @return Zero on success, a value for `errno` on error.
*
* @throws ENOMEM The process cannot allocate more memory.
* @throws EINVAL If `boundary` is not a power-of-two multiple of `sizeof(void*)`.
*/
int posix_memalign(void** ptrptr, size_t boundary, size_t size)
{
if (boundary < sizeof(void*))
return EINVAL;
*ptrptr = memalign(boundary, size);
return *ptrptr ? 0 : errno;
}
/**
* `valloc(n)` is equivalent to `memalign(sysconf(_SC_PAGESIZE), n)`.
*
* As a GNU-compliant slibc extension, memory allocated
* with this function can be freed with `free`.
*
* @param size The number of bytes to allocated.
* @return Pointer to the beginning of the new allocation.
* If `size` is zero, this function will either return
* `NULL` (that is what this implement does) or return
* a unique pointer that can later be freed with `free`.
* `NULL` is returned on error, and `errno` is set to
* indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
*/
void* valloc(size_t size)
{
return memalign((size_t)sysconf(_SC_PAGESIZE), size);
}
/**
* This function works like `valloc`, except the allocation size,
* including auxiliary space, is rounded up to the next multiple
* of the page size.
*
* @param size The number of bytes to allocated.
* @return Pointer to the beginning of the new allocation.
* If `size` is zero, this function will either return
* `NULL` (that is what this implement does) or return
* a unique pointer that can later be freed with `free`.
* `NULL` is returned on error, and `errno` is set to
* indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
*/
void* pvalloc(size_t size)
{
size_t boundary = (size_t)sysconf(_SC_PAGESIZE);
size_t full_size = 2 * sizeof(size_t) + boundary - 1 + size;
size_t rounding = 0;
if (full_size % boundary != 0)
rounding = boundary - (full_size % boundary);
if (__builtin_uaddl_overflow(size, rounding, &full_size))
return errno = ENOMEM, NULL;
return memalign(boundary, full_size);
}
/**
* This function is identical to `memalign`,
* except it can be freed with `free`.
*
* Variant of `malloc` that returns an address with a
* specified alignment.
*
* It is unspecified how the function works. This implemention
* will allocate a bit of extra memory and shift the returned
* pointer so that it is aligned.
*
* @param boundary The alignment.
* @param size The number of bytes to allocated.
* @return Pointer to the beginning of the new allocation.
* If `size` is zero, this function will either return
* `NULL` (that is what this implement does) or return
* a unique pointer that can later be freed with `free`.
* `NULL` is returned on error, and `errno` is set to
* indicate the error.
*
* @throws ENOMEM The process cannot allocate more memory.
* @throws EINVAL If `boundary` is not a power of two.
*/
void* aligned_alloc(size_t boundary, size_t size)
{
return memalign(boundary, size);
}
/**
* This function returns the allocation size of
* a memory segment.
*
* `p = malloc(n), malloc_usable_size(p)` will return `n`.
*
* @param segment The memory segment.
* @return The size of the memory segment, 0 if `segment` is `NULL`.
*/
size_t malloc_usable_size(void* segment)
{
return allocsize(segment);
}
