mirror of
https://github.com/cc65/cc65.git
synced 2024-10-31 20:06:11 +00:00
175 lines
7.6 KiB
C
175 lines
7.6 KiB
C
/*****************************************************************************/
|
|
/* */
|
|
/* posix_memalign */
|
|
/* */
|
|
/* Allocate an aligned memory block */
|
|
/* */
|
|
/* */
|
|
/* */
|
|
/* (C) 2004-2005 Ullrich von Bassewitz */
|
|
/* Roemerstrasse 52 */
|
|
/* D-70794 Filderstadt */
|
|
/* EMail: uz@cc65.org */
|
|
/* */
|
|
/* */
|
|
/* This software is provided "as-is," without any expressed or implied */
|
|
/* warranty. In no event will the authors be held liable for any damages */
|
|
/* arising from the use of this software. */
|
|
/* */
|
|
/* Permission is granted to anyone to use this software for any purpose, */
|
|
/* including commercial applications, and to alter it and redistribute it */
|
|
/* freely, subject to the following restrictions: */
|
|
/* */
|
|
/* 1. The origin of this software must not be misrepresented; you must not */
|
|
/* claim that you wrote the original software. If you use this software */
|
|
/* in a product, an acknowledgment in the product documentation would be */
|
|
/* appreciated, but is not required. */
|
|
/* 2. Alterred source versions must be marked plainly as such, and must not */
|
|
/* be misrepresented as being the original software. */
|
|
/* 3. This notice may not be removed or alterred from any source */
|
|
/* distribution. */
|
|
/* */
|
|
/*****************************************************************************/
|
|
|
|
|
|
|
|
#include <stddef.h> /* define NULL */
|
|
#include <stdlib.h> /* declare function's prototype */
|
|
#include <_heap.h>
|
|
|
|
#include <errno.h>
|
|
#define EOK 0 /* No errors (non-standard name) */
|
|
|
|
|
|
|
|
/* This is a very simple version of an aligned memory allocator. We will
|
|
** allocate a greater block, so that we can place the aligned block (that is
|
|
** returned) within it. We use our knowledge about the internal heap
|
|
** structures to free the unused parts of the bigger block (the two chunks
|
|
** below and above the aligned block).
|
|
*/
|
|
|
|
|
|
|
|
int __fastcall__ posix_memalign (void** memptr, size_t alignment, size_t size)
|
|
/* Allocate a block of memory with the given "size", which is aligned to a
|
|
** memory address that is a multiple of "alignment". "alignment" MUST NOT be
|
|
** zero, and MUST be a power of two; otherwise, this function will return
|
|
** EINVAL. The function returns ENOMEM if not enough memory is available
|
|
** to satisfy the request. "memptr" must point to a variable; that variable
|
|
** will return the address of the allocated memory. Use free() to release that
|
|
** allocated block.
|
|
*/
|
|
{
|
|
size_t rawsize;
|
|
size_t uppersize;
|
|
size_t lowersize;
|
|
register struct usedblock* b; /* points to raw Block */
|
|
register struct usedblock* u; /* points to User block */
|
|
register struct usedblock* p; /* Points to upper block */
|
|
|
|
/* Handle requests for zero-sized blocks */
|
|
if (size == 0) {
|
|
*memptr = NULL;
|
|
return EINVAL;
|
|
}
|
|
|
|
/* Test alignment: is it a power of two? There must be only one bit set. */
|
|
if (alignment == 0 || (alignment & --alignment) != 0) {
|
|
*memptr = NULL;
|
|
return EINVAL;
|
|
}
|
|
|
|
/* Augment the block size up to the alignment, and allocate memory.
|
|
** We don't need to account for the additional admin. data that's needed to
|
|
** manage the used block, because the block returned by malloc() has that
|
|
** overhead added one time; and, the worst thing that might happen is that
|
|
** we cannot free the upper and lower blocks.
|
|
*/
|
|
b = malloc (size + alignment);
|
|
|
|
/* Handle out-of-memory */
|
|
if (b == NULL) {
|
|
*memptr = NULL;
|
|
return ENOMEM;
|
|
}
|
|
|
|
/* Create (and return) a new pointer that points to the user-visible
|
|
** aligned block.
|
|
*/
|
|
u = *memptr = (struct usedblock*) (((unsigned)b + alignment) & ~alignment);
|
|
|
|
/* Get a pointer to the (raw) upper block */
|
|
p = (struct usedblock*) ((char*)u + size);
|
|
|
|
/* Get the raw-block pointer, which is located just below the visible
|
|
** unaligned block. The first word of this raw block is the total size
|
|
** of the block, including the admin. space.
|
|
*/
|
|
b = (b-1)->start;
|
|
rawsize = b->size;
|
|
|
|
/* Check if we can free the space above the user block. That is the case
|
|
** if the size of the block is at least sizeof (struct freeblock) bytes,
|
|
** and the size of the remaining block is at least that size, too.
|
|
** If the upper block is smaller, then we just will pass it to the caller,
|
|
** together with the requested aligned block.
|
|
*/
|
|
uppersize = rawsize - (lowersize = (char*)p - (char*)b);
|
|
if (uppersize >= sizeof (struct freeblock) &&
|
|
lowersize >= sizeof (struct freeblock)) {
|
|
|
|
/* Setup the usedblock structure */
|
|
p->size = uppersize;
|
|
p->start = p;
|
|
|
|
/* Generate a pointer to the (upper) user space, and free that block */
|
|
free (p + 1);
|
|
|
|
/* Decrease the raw-block size by the amount of space just freed */
|
|
rawsize = lowersize;
|
|
}
|
|
|
|
/* Check if we can free the space below the user block. That is the case
|
|
** if the size of the block is at least sizeof (struct freeblock) bytes,
|
|
** and the size of the remaining block is at least that size, too. If the
|
|
** lower block is smaller, we just will pass it to the caller, together
|
|
** with the requested aligned block.
|
|
** Beware: We need an additional struct usedblock, in the lower block,
|
|
** which is part of the block that is passed back to the caller.
|
|
*/
|
|
lowersize = ((char*)u - (char*)b) - sizeof (struct usedblock);
|
|
if ( lowersize >= sizeof (struct freeblock) &&
|
|
(rawsize - lowersize) >= sizeof (struct freeblock)) {
|
|
|
|
/* b already points to the raw lower-block.
|
|
** Set up the usedblock structure.
|
|
*/
|
|
b->size = lowersize;
|
|
b->start = b;
|
|
|
|
/* Generate a pointer to the (lower) user space, and free that block */
|
|
free (b + 1);
|
|
|
|
/* Decrease the raw-block size by the amount of space just freed */
|
|
rawsize -= lowersize;
|
|
|
|
/* Set b to the raw user-block (that will be returned) */
|
|
b = u - 1;
|
|
}
|
|
|
|
/* u points to the user-visible block, while b points to the raw block,
|
|
** and rawsize contains the length of the raw block. Set up the usedblock
|
|
** structure, but beware: If we didn't free the lower block, then it is
|
|
** split; which means that we must use b to write the size,
|
|
** and u to write the start field.
|
|
*/
|
|
b->size = rawsize;
|
|
(u-1)->start = b;
|
|
|
|
return EOK;
|
|
}
|
|
|
|
|
|
|