From 8d532c51318bad2436880ecac972c9dfa3996c9b Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Tue, 30 Dec 2003 10:40:49 +0000
Subject: Rework malloc.  The new default implementation is based on dlmalloc
 from Doug Lea.  It is about 2x faster than the old malloc-930716, and behave
 itself much better -- it will properly release memory back to the system, and
 it uses a combination of brk() for small allocations and mmap() for larger
 allocations.  -Erik

---
 libc/stdlib/malloc-standard/memalign.c | 126 +++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 libc/stdlib/malloc-standard/memalign.c

(limited to 'libc/stdlib/malloc-standard/memalign.c')

diff --git a/libc/stdlib/malloc-standard/memalign.c b/libc/stdlib/malloc-standard/memalign.c
new file mode 100644
index 000000000..bd9536272
--- /dev/null
+++ b/libc/stdlib/malloc-standard/memalign.c
@@ -0,0 +1,126 @@
+/*
+  This is a version (aka dlmalloc) of malloc/free/realloc written by
+  Doug Lea and released to the public domain.  Use, modify, and
+  redistribute this code without permission or acknowledgement in any
+  way you wish.  Send questions, comments, complaints, performance
+  data, etc to dl@cs.oswego.edu
+
+  VERSION 2.7.2 Sat Aug 17 09:07:30 2002  Doug Lea  (dl at gee)
+
+  Note: There may be an updated version of this malloc obtainable at
+           ftp://gee.cs.oswego.edu/pub/misc/malloc.c
+  Check before installing!
+
+  Hacked up for uClibc by Erik Andersen <andersen@codepoet.org>
+*/
+
+#include <features.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include "malloc.h"
+
+
+/* ------------------------------ memalign ------------------------------ */
+void* memalign(size_t alignment, size_t bytes)
+{
+    size_t nb;             /* padded  request size */
+    char*           m;              /* memory returned by malloc call */
+    mchunkptr       p;              /* corresponding chunk */
+    char*           brk;            /* alignment point within p */
+    mchunkptr       newp;           /* chunk to return */
+    size_t newsize;        /* its size */
+    size_t leadsize;       /* leading space before alignment point */
+    mchunkptr       remainder;      /* spare room at end to split off */
+    unsigned long    remainder_size; /* its size */
+    size_t size;
+
+    /* If need less alignment than we give anyway, just relay to malloc */
+
+    if (alignment <= MALLOC_ALIGNMENT) return malloc(bytes);
+
+    /* Otherwise, ensure that it is at least a minimum chunk size */
+
+    if (alignment <  MINSIZE) alignment = MINSIZE;
+
+    /* Make sure alignment is power of 2 (in case MINSIZE is not).  */
+    if ((alignment & (alignment - 1)) != 0) {
+	size_t a = MALLOC_ALIGNMENT * 2;
+	while ((unsigned long)a < (unsigned long)alignment) a <<= 1;
+	alignment = a;
+    }
+
+    LOCK;
+    checked_request2size(bytes, nb);
+
+    /* Strategy: find a spot within that chunk that meets the alignment
+     * request, and then possibly free the leading and trailing space.  */
+
+
+    /* Call malloc with worst case padding to hit alignment. */
+
+    m  = (char*)(malloc(nb + alignment + MINSIZE));
+
+    if (m == 0) {
+	UNLOCK;
+	return 0; /* propagate failure */
+    }
+
+    p = mem2chunk(m);
+
+    if ((((unsigned long)(m)) % alignment) != 0) { /* misaligned */
+
+	/*
+	   Find an aligned spot inside chunk.  Since we need to give back
+	   leading space in a chunk of at least MINSIZE, if the first
+	   calculation places us at a spot with less than MINSIZE leader,
+	   we can move to the next aligned spot -- we've allocated enough
+	   total room so that this is always possible.
+	   */
+
+	brk = (char*)mem2chunk((unsigned long)(((unsigned long)(m + alignment - 1)) &
+		    -((signed long) alignment)));
+	if ((unsigned long)(brk - (char*)(p)) < MINSIZE)
+	    brk += alignment;
+
+	newp = (mchunkptr)brk;
+	leadsize = brk - (char*)(p);
+	newsize = chunksize(p) - leadsize;
+
+	/* For mmapped chunks, just adjust offset */
+	if (chunk_is_mmapped(p)) {
+	    newp->prev_size = p->prev_size + leadsize;
+	    set_head(newp, newsize|IS_MMAPPED);
+	    UNLOCK;
+	    return chunk2mem(newp);
+	}
+
+	/* Otherwise, give back leader, use the rest */
+	set_head(newp, newsize | PREV_INUSE);
+	set_inuse_bit_at_offset(newp, newsize);
+	set_head_size(p, leadsize);
+	free(chunk2mem(p));
+	p = newp;
+
+	assert (newsize >= nb &&
+		(((unsigned long)(chunk2mem(p))) % alignment) == 0);
+    }
+
+    /* Also give back spare room at the end */
+    if (!chunk_is_mmapped(p)) {
+	size = chunksize(p);
+	if ((unsigned long)(size) > (unsigned long)(nb + MINSIZE)) {
+	    remainder_size = size - nb;
+	    remainder = chunk_at_offset(p, nb);
+	    set_head(remainder, remainder_size | PREV_INUSE);
+	    set_head_size(p, nb);
+	    free(chunk2mem(remainder));
+	}
+    }
+
+    check_inuse_chunk(p);
+    UNLOCK;
+    return chunk2mem(p);
+}
+
-- 
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