summaryrefslogtreecommitdiff
path: root/libc/stdlib/malloc-930716/malloc.c
diff options
context:
space:
mode:
Diffstat (limited to 'libc/stdlib/malloc-930716/malloc.c')
-rw-r--r--libc/stdlib/malloc-930716/malloc.c254
1 files changed, 254 insertions, 0 deletions
diff --git a/libc/stdlib/malloc-930716/malloc.c b/libc/stdlib/malloc-930716/malloc.c
new file mode 100644
index 000000000..e8f7c7004
--- /dev/null
+++ b/libc/stdlib/malloc-930716/malloc.c
@@ -0,0 +1,254 @@
+/* malloc.c - C standard library routine.
+ Copyright (c) 1989, 1993 Michael J. Haertel
+ You may redistribute this library under the terms of the
+ GNU Library General Public License (version 2 or any later
+ version) as published by the Free Software Foundation.
+ THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY EXPRESS OR IMPLIED
+ WARRANTY. IN PARTICULAR, THE AUTHOR MAKES NO REPRESENTATION OR
+ WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY OF THIS
+ SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. */
+
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include "malloc.h"
+
+/* How to really get more memory. */
+void *(*__morecore)(long) = __default_morecore_init;
+
+/* Pointer to the base of the first block. */
+char *_heapbase;
+
+/* Block information table. */
+union info *_heapinfo;
+
+/* Number of info entries. */
+static int heapsize;
+
+/* Search index in the info table. */
+int _heapindex;
+
+/* Limit of valid info table indices. */
+int _heaplimit;
+
+/* Count of large blocks allocated for each fragment size. */
+int _fragblocks[BLOCKLOG];
+
+/* Free lists for each fragment size. */
+struct list _fraghead[BLOCKLOG];
+
+/* Are we experienced? */
+static int initialized;
+
+/* Aligned allocation. */
+static void *
+align(size_t size)
+{
+ void *result;
+ unsigned int adj;
+
+ result = (*__morecore)(size);
+ adj = (unsigned int) ((char *) result - (char *) NULL) % BLOCKSIZE;
+ if (adj != 0) {
+ (*__morecore)(adj = BLOCKSIZE - adj);
+ result = (char *) result + adj;
+ }
+ return result;
+}
+
+/* Set everything up and remember that we have. */
+static int
+initialize(void)
+{
+ heapsize = HEAP / BLOCKSIZE;
+ _heapinfo = align(heapsize * sizeof (union info));
+ if (!_heapinfo)
+ return 0;
+ memset(_heapinfo, 0, heapsize * sizeof (union info));
+ _heapinfo[0].free.size = 0;
+ _heapinfo[0].free.next = _heapinfo[0].free.prev = 0;
+ _heapindex = 0;
+ _heapbase = (char *) _heapinfo;
+ initialized = 1;
+ return 1;
+}
+
+/* Get neatly aligned memory, initializing or growing the
+ heap info table as necessary. */
+static void *
+morecore(size_t size)
+{
+ void *result;
+ union info *newinfo, *oldinfo;
+ int newsize;
+
+ result = align(size);
+ if (!result)
+ return NULL;
+
+ /* Check if we need to grow the info table. */
+ if (BLOCK((char *) result + size) > heapsize) {
+ newsize = heapsize;
+ while (BLOCK((char *) result + size) > newsize)
+ newsize *= 2;
+ newinfo = align(newsize * sizeof (union info));
+ if (!newinfo) {
+ (*__morecore)(-size);
+ return NULL;
+ }
+ memset(newinfo, 0, newsize * sizeof (union info));
+ memcpy(newinfo, _heapinfo, heapsize * sizeof (union info));
+ oldinfo = _heapinfo;
+ newinfo[BLOCK(oldinfo)].busy.type = 0;
+ newinfo[BLOCK(oldinfo)].busy.info.size
+ = BLOCKIFY(heapsize * sizeof (union info));
+ _heapinfo = newinfo;
+#if 0
+ free(oldinfo);
+#else
+ _free_internal (oldinfo);
+#endif
+ heapsize = newsize;
+ }
+
+ _heaplimit = BLOCK((char *) result + size);
+ return result;
+}
+
+/* Allocate memory from the heap. */
+void *
+malloc (size_t size)
+{
+ void *result;
+ int log, block, blocks, i, lastblocks, start;
+ struct list *next;
+
+ if (!initialized && !initialize())
+ return NULL;
+
+ /* Some programs will call malloc (0). We let them pass. */
+#if 0
+ if (size == 0)
+ return NULL;
+#endif
+
+ if (size < sizeof (struct list))
+ size = sizeof (struct list);
+
+ /* Determine the allocation policy based on the request size. */
+ if (size <= BLOCKSIZE / 2) {
+ /* Small allocation to receive a fragment of a block. Determine
+ the logarithm to base two of the fragment size. */
+ --size;
+ for (log = 1; (size >>= 1) != 0; ++log)
+ ;
+
+ /* Look in the fragment lists for a free fragment of the
+ desired size. */
+ if ((next = _fraghead[log].next) != 0) {
+ /* There are free fragments of this size. Pop a fragment
+ out of the fragment list and return it. Update the block's
+ nfree and first counters. */
+ result = next;
+ next->prev->next = next->next;
+ if (next->next)
+ next->next->prev = next->prev;
+ block = BLOCK(result);
+ if (--_heapinfo[block].busy.info.frag.nfree)
+ _heapinfo[block].busy.info.frag.first
+ = (unsigned int) ((char *) next->next - (char *) NULL)
+ % BLOCKSIZE >> log;
+ } else {
+ /* No free fragments of the desired size, so get a new block
+ and break it into fragments, returning the first. */
+ result = malloc(BLOCKSIZE);
+ if (!result)
+ return NULL;
+ ++_fragblocks[log];
+
+ /* Link all fragments but the first into the free list. */
+ next = (struct list *) ((char *) result + (1 << log));
+ next->next = 0;
+ next->prev = &_fraghead[log];
+ _fraghead[log].next = next;
+
+ for (i = 2; i < BLOCKSIZE >> log; ++i) {
+ next = (struct list *) ((char *) result + (i << log));
+ next->next = _fraghead[log].next;
+ next->prev = &_fraghead[log];
+ next->prev->next = next;
+ next->next->prev = next;
+ }
+
+ /* Initialize the nfree and first counters for this block. */
+ block = BLOCK(result);
+ _heapinfo[block].busy.type = log;
+ _heapinfo[block].busy.info.frag.nfree = i - 1;
+ _heapinfo[block].busy.info.frag.first = i - 1;
+ }
+ } else {
+ /* Large allocation to receive one or more blocks. Search
+ the free list in a circle starting at the last place visited.
+ If we loop completely around without finding a large enough
+ space we will have to get more memory from the system. */
+ blocks = BLOCKIFY(size);
+ start = block = _heapindex;
+ while (_heapinfo[block].free.size < blocks) {
+ block = _heapinfo[block].free.next;
+ if (block == start) {
+ /* Need to get more from the system. Check to see if
+ the new core will be contiguous with the final free
+ block; if so we don't need to get as much. */
+ block = _heapinfo[0].free.prev;
+ lastblocks = _heapinfo[block].free.size;
+ if (_heaplimit && block + lastblocks == _heaplimit
+ && (*__morecore)(0) == ADDRESS(block + lastblocks)
+ && morecore((blocks - lastblocks) * BLOCKSIZE)) {
+ /* Note that morecore() can change the location of
+ the final block if it moves the info table and the
+ old one gets coalesced into the final block. */
+ block = _heapinfo[0].free.prev;
+ _heapinfo[block].free.size += blocks - lastblocks;
+ continue;
+ }
+ result = morecore(blocks * BLOCKSIZE);
+ if (!result)
+ return NULL;
+ block = BLOCK(result);
+ _heapinfo[block].busy.type = 0;
+ _heapinfo[block].busy.info.size = blocks;
+ return result;
+ }
+ }
+
+ /* At this point we have found a suitable free list entry.
+ Figure out how to remove what we need from the list. */
+ result = ADDRESS(block);
+ if (_heapinfo[block].free.size > blocks) {
+ /* The block we found has a bit left over, so relink the
+ tail end back into the free list. */
+ _heapinfo[block + blocks].free.size
+ = _heapinfo[block].free.size - blocks;
+ _heapinfo[block + blocks].free.next
+ = _heapinfo[block].free.next;
+ _heapinfo[block + blocks].free.prev
+ = _heapinfo[block].free.prev;
+ _heapinfo[_heapinfo[block].free.prev].free.next
+ = _heapinfo[_heapinfo[block].free.next].free.prev
+ = _heapindex = block + blocks;
+ } else {
+ /* The block exactly matches our requirements, so
+ just remove it from the list. */
+ _heapinfo[_heapinfo[block].free.next].free.prev
+ = _heapinfo[block].free.prev;
+ _heapinfo[_heapinfo[block].free.prev].free.next
+ = _heapindex = _heapinfo[block].free.next;
+ }
+
+ _heapinfo[block].busy.type = 0;
+ _heapinfo[block].busy.info.size = blocks;
+ }
+
+ return result;
+}
generated by cgit v1.2.3 (git 2.46.0) at 2025-11-04 05:11:08 +0000