Add alloc_size(): every allocator has to be able to answer this, since

free() doesn't have a size arg.

ccan/alloc/alloc.c

@@ -822,6 +822,53 @@ void alloc_free(void *pool, unsigned long poolsize, void *free)
 	}
 }
 
+unsigned long alloc_size(void *pool, unsigned long poolsize, void *p)
+{
+	unsigned long len, pagenum;
+	struct metaheader *mh;
+
+	assert(poolsize >= MIN_SIZE);
+
+	mh = first_mheader(pool, poolsize);
+	assert((char *)p >= (char *)(mh + 1));
+	assert((char *)pool + poolsize > (char *)p);
+
+	pagenum = pool_offset(pool, p) / getpagesize();
+
+	if (get_page_state(pool, pagenum) == SPECIAL) {
+		unsigned long off = (unsigned long)p % getpagesize();
+		uint8_t *metadata = get_page_metadata(pool, pagenum);
+		enum sub_metadata_type type = get_bit_pair(metadata, 0);
+
+		assert(off < SUBPAGE_METAOFF);
+
+		switch (type) {
+		case BITMAP:
+			assert(off % BITMAP_GRANULARITY == 0);
+			off /= BITMAP_GRANULARITY;
+
+			/* Offset by one because first bit used for header. */
+			off++;
+			len = BITMAP_GRANULARITY;
+			while (++off < SUBPAGE_METAOFF / BITMAP_GRANULARITY
+			       && get_bit_pair(metadata, off) == TAKEN)
+				len += BITMAP_GRANULARITY;
+			break;
+		case UNIFORM:
+			len = decode_usize(metadata);
+			break;
+		default:
+			assert(0);
+		}
+	} else {
+		len = getpagesize();
+		while (get_page_state(pool, ++pagenum) == TAKEN)
+			len += getpagesize();
+	}
+
+	return len;
+}
+
 static bool is_metadata_page(void *pool, unsigned long poolsize,
 			     unsigned long page)
 {

ccan/alloc/alloc.h

@@ -7,6 +7,7 @@ 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);
+unsigned long alloc_size(void *pool, unsigned long poolsize, void *p);
 bool alloc_check(void *pool, unsigned long poolsize);
 
 void alloc_visualize(FILE *out, void *pool, unsigned long poolsize);

ccan/alloc/test/run-testsize.c

@@ -0,0 +1,67 @@
+#include "alloc/alloc.h"
+#include "tap/tap.h"
+#include "alloc/alloc.c"
+#include <stdlib.h>
+#include <stdbool.h>
+
+#define POOL_ORD 16
+#define POOL_SIZE (1 << POOL_ORD)
+
+static void invert_bytes(unsigned char *p, unsigned long size)
+{
+	unsigned int i;
+
+	for (i = 0; i < size; i++)
+		p[i] ^= 0xFF;
+}
+
+static bool sizes_ok(void *mem, unsigned long poolsize, void *p[], unsigned num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (alloc_size(mem, poolsize, p[i]) < i)
+			return false;
+	return true;
+}
+
+int main(int argc, char *argv[])
+{
+	void *mem;
+	unsigned int i, num;
+	void *p[POOL_SIZE];
+
+	plan_tests(5);
+
+	/* FIXME: Needs to be page aligned for now. */
+	posix_memalign(&mem, 1 << POOL_ORD, POOL_SIZE);
+
+	alloc_init(mem, POOL_SIZE);
+
+	/* Check that alloc_size() gives reasonable answers. */
+	for (i = 0; i < POOL_SIZE; i++) {
+		p[i] = alloc_get(mem, POOL_SIZE, i, 1);
+		if (!p[i])
+			break;
+		invert_bytes(p[i], alloc_size(mem, POOL_SIZE, p[i]));
+	}
+	ok1(i < POOL_SIZE);
+	num = i;
+	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(sizes_ok(mem, POOL_SIZE, p, num));
+
+	/* Free every second one. */
+	for (i = 0; i < num; i+=2) {
+		alloc_free(mem, POOL_SIZE, p[i]);
+		/* Compact. */
+		if (i + 1 < num) {
+			p[i/2] = p[i + 1];
+			invert_bytes(p[i/2], alloc_size(mem,POOL_SIZE,p[i/2]));
+		}
+	}
+	num /= 2;
+	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(sizes_ok(mem, POOL_SIZE, p, num));
+
+	return exit_status();
+}

ccan/alloc/test/run.c

@@ -49,7 +49,7 @@ int main(int argc, char *argv[])
 	unsigned int i, num, max_size;
 	void *p[POOL_SIZE];
 
-	plan_tests(139);
+	plan_tests(178);
 
 	/* FIXME: Needs to be page aligned for now. */
 	posix_memalign(&mem, 1 << POOL_ORD, POOL_SIZE);
@@ -75,6 +75,7 @@ int main(int argc, char *argv[])
 	ok1(max_size < POOL_SIZE);
 	ok1(max_size > 0);
 	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(alloc_size(mem, POOL_SIZE, p[0]) >= max_size);
 
 	/* Free it, should be able to reallocate it. */
 	alloc_free(mem, POOL_SIZE, p[0]);
@@ -82,6 +83,7 @@ int main(int argc, char *argv[])
 
 	p[0] = alloc_get(mem, POOL_SIZE, max_size, 1);
 	ok1(p[0]);
+	ok1(alloc_size(mem, POOL_SIZE, p[0]) >= max_size);
 	ok1(alloc_check(mem, POOL_SIZE));
 	alloc_free(mem, POOL_SIZE, p[0]);
 	ok1(alloc_check(mem, POOL_SIZE));
@@ -117,12 +119,14 @@ int main(int argc, char *argv[])
 	p[0] = alloc_get(mem, POOL_SIZE, max_size, 1);
 	ok1(p[0]);
 	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(alloc_size(mem, POOL_SIZE, p[0]) >= max_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_size(mem, POOL_SIZE, p[0]) >= max_size);
 	ok1(alloc_check(mem, POOL_SIZE));
 	alloc_free(mem, POOL_SIZE, p[0]);
 	ok1(alloc_check(mem, POOL_SIZE));
@@ -133,6 +137,7 @@ int main(int argc, char *argv[])
 		ok1(p[i]);
 		ok1(((unsigned long)p[i] % (1 << i)) == 0);
 		ok1(alloc_check(mem, POOL_SIZE));
+		ok1(alloc_size(mem, POOL_SIZE, p[i]) >= i);
 	}
 
 	for (i = 0; i < POOL_ORD-1; i++) {
@@ -145,6 +150,7 @@ int main(int argc, char *argv[])
 		p[0] = alloc_get(mem, POOL_SIZE, 1, 1 << i);
 		ok1(p[0]);
 		ok1(alloc_check(mem, POOL_SIZE));
+		ok1(alloc_size(mem, POOL_SIZE, p[i]) >= 1);
 		alloc_free(mem, POOL_SIZE, p[0]);
 		ok1(alloc_check(mem, POOL_SIZE));
 	}
@@ -152,6 +158,7 @@ int main(int argc, char *argv[])
 	/* Alignment check for a 0-byte allocation.  Corner case. */
 	p[0] = alloc_get(mem, POOL_SIZE, 0, 1 << (POOL_ORD - 1));
 	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(alloc_size(mem, POOL_SIZE, p[0]) < POOL_SIZE);
 	alloc_free(mem, POOL_SIZE, p[0]);
 	ok1(alloc_check(mem, POOL_SIZE));
 
@@ -163,6 +170,7 @@ int main(int argc, char *argv[])
 			break;
 	}
 	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(alloc_size(mem, POOL_SIZE, p[i-1]) >= getpagesize());
 
 	/* Sort them. */
 	sort(p, i-1, addr_cmp);
@@ -171,6 +179,7 @@ int main(int argc, char *argv[])
 	for (i = 1; p[i]; i++)
 		alloc_free(mem, POOL_SIZE, p[i]);
 	ok1(alloc_check(mem, POOL_SIZE));
+	ok1(alloc_size(mem, POOL_SIZE, p[0]) >= getpagesize());
 
 	/* Now do a whole heap of subpage allocs. */
 	for (i = 1; i < POOL_SIZE; i++) {
@@ -185,6 +194,7 @@ int main(int argc, char *argv[])
 	ok1(alloc_check(mem, POOL_SIZE));
 	p[0] = alloc_get(mem, POOL_SIZE, 1, 1);
 	ok1(p[0]);
+	ok1(alloc_size(mem, POOL_SIZE, p[0]) >= 1);
 
 	/* Clean up. */
 	for (i = 0; p[i]; i++)