Allocator now has metadata.

alloc/_info.c

@@ -95,6 +95,7 @@ int main(int argc, char *argv[])
 		return 1;
 
 	if (strcmp(argv[1], "depends") == 0) {
+		printf("build_assert\n");
 		return 0;
 	}
 

alloc/alloc.c

@@ -4,12 +4,26 @@
 #include <limits.h>
 #include <assert.h>
 #include "alloc.h"
+#include "build_assert/build_assert.h"
+#include "config.h"
+
+#if HAVE_ALIGNOF
+#define ALIGNOF(t) __alignof__(t)
+#else
+/* Alignment by measuring structure padding. */
+#define ALIGNOF(t) (sizeof(struct { char c; t _h; }) - 1 - sizeof(t))
+#endif
 
 /* FIXME: Doesn't handle non-page-aligned poolsize. */
-/* FIXME: Doesn't handle sub-page allocations. */
 
+/* FIXME: Reduce. */
 #define MIN_SIZE (getpagesize() * 2)
 
+/* Metadata looks like this:
+ * <unsigned long metalen> <page states> <align-pad> [<1-byte-len> <free|bit|uniform> bits...]* [unsigned long next]. 
+ */
+
+#define BITS_PER_PAGE 2
 enum page_state
 {
 	FREE,
@@ -17,65 +31,82 @@ enum page_state
 	TAKEN_START,
 };
 
-void alloc_init(void *pool, unsigned long poolsize)
-{
-	uint8_t *bits = pool;
-	unsigned int pages = poolsize / getpagesize();
-
-	if (poolsize < MIN_SIZE)
-		return;
-
-	memset(bits, 0, (pages * 2 + CHAR_BIT - 1)/ CHAR_BIT);
-}
-
 static enum page_state get_page_state(const uint8_t *bits, unsigned long page)
 {
+	bits += sizeof(unsigned long);
 	return bits[page * 2 / CHAR_BIT] >> (page * 2 % CHAR_BIT) & 3;
 }
 
 static void set_page_state(uint8_t *bits, unsigned long page, enum page_state s)
 {
+	bits += sizeof(unsigned long);
 	bits[page * 2 / CHAR_BIT] &= ~(3 << (page * 2 % CHAR_BIT));
 	bits[page * 2 / CHAR_BIT] |= ((uint8_t)s << (page * 2 % CHAR_BIT));
 }
 
+/* Assumes a is a power of two. */
+static unsigned long align_up(unsigned long x, unsigned long a)
+{
+	return (x + a - 1) & ~(a - 1);
+}
+
+static unsigned long div_up(unsigned long x, unsigned long a)
+{
+	return (x + a - 1) / a;
+}
+
 static unsigned long metadata_length(void *pool, unsigned long poolsize)
 {
-	return ((poolsize / getpagesize() * 2 / CHAR_BIT) + getpagesize() - 1)
-		& ~(getpagesize() - 1);
+	return *(unsigned long *)pool;
 }
 
-void *alloc_get(void *pool, unsigned long poolsize,
-		unsigned long size, unsigned long align)
+void alloc_init(void *pool, unsigned long poolsize)
 {
-	long i;
-	unsigned long free, want, metalen;
+	/* FIXME: Alignment assumptions about pool. */
+	unsigned long *metalen = pool, pages, pagestatebytes, i;
 
 	if (poolsize < MIN_SIZE)
-		return NULL;
+		return;
 
-	/* FIXME: Necessary for this. */
-	if (size == 0)
-		size = 1;
+	pages = poolsize / getpagesize();
 
-	want = (size + getpagesize() - 1) / getpagesize();
-	metalen = metadata_length(pool, poolsize);
+	/* First comes the metadata length, then 2 bits per page, then
+	 * the next pointer. */
+	pagestatebytes = div_up(pages * BITS_PER_PAGE, CHAR_BIT);
+	*metalen = sizeof(*metalen)
+		+ align_up(pagestatebytes, ALIGNOF(unsigned long))
+		+ sizeof(unsigned long);
+
+	/* Mark all the bits FREE to start, and zero the next pointer. */
+	BUILD_ASSERT(FREE == 0);
+	memset(metalen + 1, 0, *metalen - sizeof(*metalen));
+
+	/* Mark the metadata page(s) allocated. */
+	set_page_state(pool, 0, TAKEN_START);
+	for (i = 1; i < div_up(*metalen, getpagesize()); i++)
+		set_page_state(pool, i, TAKEN);
+}
+
+static void *alloc_get_pages(void *pool, unsigned long poolsize,
+			     unsigned long pages, unsigned long align)
+{
+	long i;
+	unsigned long free;
 
 	free = 0;
 	/* We allocate from far end, to increase ability to expand metadata. */
-	for (i = (poolsize - metalen) / getpagesize() - 1; i >= 0; i--) {
+	for (i = poolsize / getpagesize() - 1; i >= 0; i--) {
 		switch (get_page_state(pool, i)) {
 		case FREE:
-			if (++free >= want) {
+			if (++free >= pages) {
 				unsigned long j;
-				char *ret = (char *)pool + metalen
-					+ i * getpagesize();
+				char *ret = (char *)pool + i * getpagesize();
 
 				/* They might ask for multi-page alignment. */
 				if ((unsigned long)ret % align)
 					continue;
 
-				for (j = i+1; j < i + want; j++)
+				for (j = i+1; j < i + pages; j++)
 					set_page_state(pool, j, TAKEN);
 				set_page_state(pool, i, TAKEN_START);
 				return ret;
@@ -91,22 +122,37 @@ void *alloc_get(void *pool, unsigned long poolsize,
 	return NULL;
 }
 
+void *alloc_get(void *pool, unsigned long poolsize,
+		unsigned long size, unsigned long align)
+{
+	if (poolsize < MIN_SIZE)
+		return NULL;
+
+	if (size >= getpagesize() || align > getpagesize()) {
+		unsigned long pages = (size + getpagesize()-1) / getpagesize();
+		return alloc_get_pages(pool, poolsize, pages, align);
+	}
+
+	/* FIXME: Sub-page allocations. */
+	return alloc_get_pages(pool, poolsize, 1, align);
+}
+
 void alloc_free(void *pool, unsigned long poolsize, void *free)
 {
 	unsigned long pagenum, metalen;
 
-	if (poolsize < MIN_SIZE)
-		return;
-
 	if (!free)
 		return;
 
+	assert(poolsize >= MIN_SIZE);
+
 	metalen = metadata_length(pool, poolsize);
 
-	assert(free > pool && (char *)pool + poolsize > (char *)free);
+	assert((char *)free >= (char *)pool + metalen);
+	assert((char *)pool + poolsize > (char *)free);
 	assert((unsigned long)free % getpagesize() == 0);
 
-	pagenum = ((char *)free - (char *)pool - metalen) / getpagesize();
+	pagenum = ((char *)free - (char *)pool) / getpagesize();
 
 	assert(get_page_state(pool, pagenum) == TAKEN_START);
 	set_page_state(pool, pagenum, FREE);
@@ -116,15 +162,33 @@ void alloc_free(void *pool, unsigned long poolsize, void *free)
 
 bool alloc_check(void *pool, unsigned long poolsize)
 {
-	unsigned int i, metalen;
+	unsigned long i, metalen, pagestatebytes;
 	enum page_state last_state = FREE;
 
 	if (poolsize < MIN_SIZE)
 		return true;
 
 	metalen = metadata_length(pool, poolsize);
-	for (i = 0; i < (poolsize - metalen) / getpagesize(); i++) {
+	if (get_page_state(pool, 0) != TAKEN_START)
+		return false;
+
+	pagestatebytes = div_up(poolsize / getpagesize() * BITS_PER_PAGE,
+				CHAR_BIT);
+	if (metalen < (sizeof(unsigned long)
+		       + align_up(pagestatebytes, ALIGNOF(unsigned long))
+		       + sizeof(unsigned long)))
+		return false;
+
+	for (i = 1; i < poolsize / getpagesize(); i++) {
 		enum page_state state = get_page_state(pool, i);
+
+		/* Metadata pages will be marked TAKEN. */
+		if (i < div_up(metalen, getpagesize())) {
+			if (get_page_state(pool, 0) != TAKEN)
+				return false;
+			continue;
+		}
+
 		switch (state) {
 		case FREE:
 		case TAKEN_START:

config.h

@@ -1,5 +1,6 @@
 /* Simple config.h for gcc. */
 #define HAVE_TYPEOF 1
+#define HAVE_ALIGNOF 1
 #define HAVE_STATEMENT_EXPR 1
 #define HAVE_BUILTIN_EXPECT 1
 #define HAVE_ATTRIBUTE_PRINTF 1