Initial cut at file/mem allocator (pages only)

alloc/_info.c

+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * alloc - memory allocator routines
+ *
+ * The alloc module implements a simple allocator which you can use to
+ * dynamically allocate space within a region of memory.  This can be useful
+ * for suballocations within a given region, or a memory-mapped file.
+ *
+ * All metadata is kept within the memory handed to the allocator: you only
+ * need hand the pointer and the size of the memory to each call.
+ *
+ * The region contents is always in offsets, so it can be mapped in different
+ * places, but is not endian-safe.
+ *
+ * Example:
+ *	#include <sys/mman.h>
+ *	#include <unistd.h>
+ *	#include <sys/types.h>
+ *	#include <err.h>
+ *	#include "alloc/alloc.h"
+ *
+ *	static void usage(const char *name)
+ *	{
+ *		errx(1, "Usage: %s --create <mapfile>\n"
+ *		     " %s --check <mapfile>\n"
+ *		     " %s --alloc <mapfile>\n"
+ *		     " %s --free=<offset> <mapfile>\n", name, name, name);
+ *	}
+ *
+ *	// Create a memory mapped file, and allocate from within it
+ *	int main(int argc, char *argv[])
+ *	{
+ *		void *a, *p;
+ *		int fd;
+ *		enum { CREATE, CHECK, ALLOC, FREE } cmd;
+ *
+ *		if (argc != 3)
+ *			usage(argv[0]);
+ *
+ *		if (strcmp(argv[1], "--create") == 0)
+ *			cmd = CREATE;
+ *		else if (strcmp(argv[1], "--check") == 0)
+ *			cmd = CHECK;
+ *		else if (strcmp(argv[1], "--alloc") == 0)
+ *			cmd = ALLOC;
+ *		else if (strncmp(argv[1], "--free=", strlen("--free=")) == 0)
+ *			cmd = FREE;
+ *		else
+ *			usage(argv[0]);
+ *
+ *		if (cmd == CREATE) {
+ *			fd = open(argv[2], O_RDWR|O_CREAT|O_EXCL, 0600);
+ *			if (fd < 0)
+ *				err(1, "Could not create %s", argv[2]);
+ *			if (ftruncate(fd, 1048576) != 0)
+ *				err(1, "Could not set length on %s", argv[2]);
+ *		} else {
+ *			fd = open(argv[2], O_RDWR);
+ *			if (fd < 0)
+ *				err(1, "Could not open %s", argv[2]);
+ *		}
+ *
+ *		a = mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_SHARED, fd,0);
+ *		if (a == MAP_FAILED)
+ *			err(1, "Could not map %s", argv[2]);
+ *
+ *		switch (cmd) {
+ *		case CREATE:
+ *			alloc_init(a, 1048576);
+ *			break;
+ *		case CHECK:
+ *			if (!alloc_check(a, 1048576))
+ *				err(1, "Region is corrupt");
+ *			break;
+ *		case ALLOC:
+ *			p = alloc_get(a, 1048576, 1024, 16);
+ *			if (!p)
+ *				errx(1, "Could not allocate");
+ *			printf("%zu\n", (char *)p - (char *)a);
+ *			break;
+ *		case FREE:
+ *			p = (char *)a + atol(argv[1] + strlen("--free="));
+ *			alloc_free(a, 1048576, p);
+ *			break;
+ *		}
+ *		return 0;
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		return 0;
+	}
+
+	return 1;
+}

alloc/alloc.c

+#include <unistd.h>
+#include <stdint.h>
+#include <string.h>
+#include <limits.h>
+#include <assert.h>
+#include "alloc.h"
+
+/* FIXME: Doesn't handle non-page-aligned poolsize. */
+/* FIXME: Doesn't handle sub-page allocations. */
+
+#define MIN_SIZE (getpagesize() * 2)
+
+enum page_state
+{
+	FREE,
+	TAKEN,
+	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)
+{
+	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[page * 2 / CHAR_BIT] &= ~(3 << (page * 2 % CHAR_BIT));
+	bits[page * 2 / CHAR_BIT] |= ((uint8_t)s << (page * 2 % CHAR_BIT));
+}
+
+static unsigned long metadata_length(void *pool, unsigned long poolsize)
+{
+	return ((poolsize / getpagesize() * 2 / CHAR_BIT) + getpagesize() - 1)
+		& ~(getpagesize() - 1);
+}
+
+void *alloc_get(void *pool, unsigned long poolsize,
+		unsigned long size, unsigned long align)
+{
+	unsigned long i, free, want, metalen;
+
+	if (poolsize < MIN_SIZE)
+		return NULL;
+
+	/* FIXME: Necessary for this. */
+	if (size == 0)
+		size = 1;
+
+	want = (size + getpagesize() - 1) / getpagesize();
+	metalen = metadata_length(pool, poolsize);
+
+	free = 0;
+	for (i = 0; i < (poolsize - metalen) / getpagesize(); i++) {
+		switch (get_page_state(pool, i)) {
+		case FREE:
+			if (++free >= want) {
+				unsigned int j;
+				char *ret = (char *)pool + metalen
+					+ (i - want + 1) * getpagesize();
+
+				if ((unsigned long)ret % align)
+					continue;
+
+				for (j = i; j > i - want + 1; j--)
+					set_page_state(pool, j, TAKEN);
+				set_page_state(pool, i - want + 1, TAKEN_START);
+				return ret;
+			}
+			break;
+		case TAKEN_START:
+		case TAKEN:
+			free = 0;
+			break;
+		}
+	}
+
+	return NULL;
+}
+
+void alloc_free(void *pool, unsigned long poolsize, void *free)
+{
+	unsigned long pagenum, metalen;
+
+	if (poolsize < MIN_SIZE)
+		return;
+
+	if (!free)
+		return;
+
+	metalen = metadata_length(pool, poolsize);
+
+	assert(free > pool && (char *)pool + poolsize > (char *)free);
+	assert((unsigned long)free % getpagesize() == 0);
+
+	pagenum = ((char *)free - (char *)pool - metalen) / getpagesize();
+
+	assert(get_page_state(pool, pagenum) == TAKEN_START);
+	set_page_state(pool, pagenum, FREE);
+	while (get_page_state(pool, ++pagenum) == TAKEN)
+		set_page_state(pool, pagenum, FREE);
+}
+
+bool alloc_check(void *pool, unsigned long poolsize)
+{
+	unsigned int i, metalen;
+	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++) {
+		enum page_state state = get_page_state(pool, i);
+		switch (state) {
+		case FREE:
+		case TAKEN_START:
+			break;
+		case TAKEN:
+			if (last_state == FREE)
+				return false;
+			break;
+		default:
+			return false;
+		}
+		last_state = state;
+	}
+	return true;
+}

alloc/alloc.h

+#ifndef ALLOC_H
+#define ALLOC_H
+#include <stdbool.h>
+
+void alloc_init(void *pool, unsigned long poolsize);
+void *alloc_get(void *pool, unsigned long poolsize,
+		unsigned long size, unsigned long align);
+void alloc_free(void *pool, unsigned long poolsize, void *free);
+bool alloc_check(void *pool, unsigned long poolsize);
+
+#endif /* ALLOC_H */

alloc/test/run.c

+#include "alloc/alloc.h"
+#include "tap.h"
+#include "alloc/alloc.c"
+#include <stdlib.h>
+
+#define POOL_ORD 16
+#define POOL_SIZE (1 << POOL_ORD)
+
+#define sort(p, num, cmp) \
+	qsort((p), (num), sizeof(*p), (int(*)(const void *, const void *))cmp)
+
+static int addr_cmp(void **a, void **b)
+{
+	return (*a) - (*b);
+}
+
+static bool unique(void *p[], unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 1; i < num; i++)
+		if (p[i] == p[i-1])
+			return false;
+	return true;
+}	
+
+int main(int argc, char *argv[])
+{
+	void *mem;
+	unsigned int i, num, max_size;
+	void *p[POOL_SIZE];
+
+	plan_tests(141);
+
+	/* FIXME: Needs to be page aligned for now. */
+	posix_memalign(&mem, getpagesize(), POOL_SIZE);
+
+	/* Small pool, all allocs fail, even 0-length. */
+	alloc_init(mem, 0);
+	ok1(alloc_check(mem, 0));
+	ok1(alloc_get(mem, 0, 1, 1) == NULL);
+	ok1(alloc_get(mem, 0, 128, 1) == NULL);
+	ok1(alloc_get(mem, 0, 0, 1) == NULL);
+
+	/* Free of NULL should work. */
+	alloc_free(mem, 0, NULL);
+
+	alloc_init(mem, POOL_SIZE);
+	ok1(alloc_check(mem, POOL_SIZE));
+	/* Find largest allocation which works. */
+	for (max_size = POOL_SIZE * 2; max_size; max_size--) {
+		p[0] = alloc_get(mem, POOL_SIZE, max_size, 1);
+		if (p[0])
+			break;
+	}
+	ok1(max_size < POOL_SIZE);
+	ok1(max_size > 0);
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	/* Free it, should be able to reallocate it. */
+	alloc_free(mem, POOL_SIZE, p[0]);
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	p[0] = alloc_get(mem, POOL_SIZE, max_size, 1);
+	ok1(p[0]);
+	ok1(alloc_check(mem, POOL_SIZE));
+	alloc_free(mem, POOL_SIZE, p[0]);
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	/* Allocate a whole heap. */
+	for (i = 0; i < POOL_SIZE; i++) {
+		p[i] = alloc_get(mem, POOL_SIZE, 1, 1);
+		if (!p[i])
+			break;
+	}
+
+	num = i;
+	/* Can't allocate this many. */
+	ok1(num != POOL_SIZE);
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	/* Sort them. */
+	sort(p, num, addr_cmp);
+
+	/* Uniqueness check */
+	ok1(unique(p, num));
+
+	/* Free every second one. */
+	for (i = 0; i < num; i += 2) {
+		alloc_free(mem, POOL_SIZE, p[i]);
+		ok1(alloc_check(mem, POOL_SIZE));
+	}
+	for (i = 1; i < num; i += 2) {
+		alloc_free(mem, POOL_SIZE, p[i]);
+		ok1(alloc_check(mem, POOL_SIZE));
+	}
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	/* Should be able to reallocate max size. */
+	p[0] = alloc_get(mem, POOL_SIZE, max_size, 1);
+	ok1(p[0]);
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	/* Re-initializing should be the same as freeing everything */
+	alloc_init(mem, POOL_SIZE);
+	ok1(alloc_check(mem, POOL_SIZE));
+	p[0] = alloc_get(mem, POOL_SIZE, max_size, 1);
+	ok1(p[0]);
+	ok1(alloc_check(mem, POOL_SIZE));
+	alloc_free(mem, POOL_SIZE, p[0]);
+	ok1(alloc_check(mem, POOL_SIZE));
+
+	/* Alignment constraints should be met, as long as powers of two */
+	for (i = 0; i < POOL_ORD-2 /* FIXME: Should be -1 */; i++) {
+		p[i] = alloc_get(mem, POOL_SIZE, i, 1 << i);
+		ok1(p[i]);
+		ok1(((unsigned long)p[i] % (1 << i)) == 0);
+		ok1(alloc_check(mem, POOL_SIZE));
+	}
+
+	for (i = 0; i < POOL_ORD-2 /* FIXME: Should be -1 */; i++) {
+		alloc_free(mem, POOL_SIZE, p[i]);
+		ok1(alloc_check(mem, POOL_SIZE));
+	}
+
+	/* Alignment constraints for a single-byte allocation. */
+	for (i = 0; i < POOL_ORD; i++) {
+		p[0] = alloc_get(mem, POOL_SIZE, 1, 1 << i);
+		ok1(p[0]);
+		ok1(alloc_check(mem, POOL_SIZE));
+		alloc_free(mem, POOL_SIZE, p[0]);
+		ok1(alloc_check(mem, POOL_SIZE));
+	}
+
+	return exit_status();
+}