X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Falloc%2Falloc.h;h=8ffa169f67071c08b0e28acfef9f4d14e9670293;hp=29c29d078873c0fb335432e9c3bf041be3177d96;hb=d9cbd7d4454ae35e4e2f6d18a9469bf26948e4b9;hpb=650c775ff00cccd03fc84e7789a03c51d9839004

diff --git a/ccan/alloc/alloc.h b/ccan/alloc/alloc.h
index 29c29d07..8ffa169f 100644
--- a/ccan/alloc/alloc.h
+++ b/ccan/alloc/alloc.h
@@ -1,13 +1,130 @@
+/* Licensed under LGPLv2.1+ - see LICENSE file for details */
 #ifndef ALLOC_H
 #define ALLOC_H
 #include <stdio.h>
 #include <stdbool.h>
 
+/**
+ * alloc_init - initialize a pool of memory for the allocator.
+ * @pool: the contiguous bytes for the allocator to use
+ * @poolsize: the size of the pool
+ *
+ * This stores all the setup state required to perform allocation within the
+ * pool (there is no external state).  Any previous contents of @pool is
+ * discarded.
+ *
+ * The same @pool and @poolsize arguments must be handed to the other alloc
+ * functions after this.
+ *
+ * If the pool is too small for meaningful allocations, alloc_get will fail.
+ *
+ * Example:
+ *	void *pool = malloc(32*1024*1024);
+ *	if (!pool)
+ *		err(1, "Failed to allocate 32MB");
+ *	alloc_init(pool, 32*1024*1024);
+ */
 void alloc_init(void *pool, unsigned long poolsize);
+
+/**
+ * alloc_get - allocate some memory from the pool
+ * @pool: the contiguous bytes for the allocator to use
+ * @poolsize: the size of the pool
+ * @size: the size of the desired allocation
+ * @align: the alignment of the desired allocation (0 or power of 2)
+ *
+ * This is "malloc" within an initialized pool.
+ *
+ * It will return a unique pointer within the pool (ie. between @pool
+ * and @pool+@poolsize) which meets the alignment requirements of
+ * @align.  Note that the alignment is relative to the start of the pool,
+ * so of @pool is not aligned, the pointer won't be either.
+ *
+ * Returns NULL if there is no contiguous room.
+ *
+ * Example:
+ *	#include <ccan/alignof/alignof.h>
+ *	...
+ *		double *d = alloc_get(pool, 32*1024*1024,
+ *				      sizeof(*d), ALIGNOF(*d));
+ *		if (!d)
+ *			err(1, "Failed to allocate a double");
+ */
 void *alloc_get(void *pool, unsigned long poolsize,
 		unsigned long size, unsigned long align);
+
+/**
+ * alloc_free - free some allocated memory from the pool
+ * @pool: the contiguous bytes for the allocator to use
+ * @poolsize: the size of the pool
+ * @p: the non-NULL pointer returned from alloc_get.
+ *
+ * This is "free" within an initialized pool.  A pointer should only be
+ * freed once, and must be a pointer returned from a successful alloc_get()
+ * call.
+ *
+ * Example:
+ *	alloc_free(pool, 32*1024*1024, d);
+ */
 void alloc_free(void *pool, unsigned long poolsize, void *free);
+
+/**
+ * alloc_size - get the actual size allocated by alloc_get
+ * @pool: the contiguous bytes for the allocator to use
+ * @poolsize: the size of the pool
+ * @p: the non-NULL pointer returned from alloc_get.
+ *
+ * alloc_get() may overallocate, in which case you may use the extra
+ * space exactly as if you had asked for it.
+ *
+ * The return value will always be at least the @size passed to alloc_get().
+ *
+ * Example:
+ *	printf("Allocating a double actually got me %lu bytes\n",
+ *		alloc_size(pool, 32*1024*1024, d));
+ */
+unsigned long alloc_size(void *pool, unsigned long poolsize, void *p);
+
+/**
+ * alloc_check - check the integrity of the allocation pool
+ * @pool: the contiguous bytes for the allocator to use
+ * @poolsize: the size of the pool
+ *
+ * alloc_check() can be used for debugging suspected pool corruption.  It may
+ * be quite slow, but provides some assistance for hard-to-find overruns or
+ * double-frees.  Unlike the rest of the code, it will not crash on corrupted
+ * pools.
+ *
+ * There is an internal function check_fail() which this calls on failure which
+ * is useful for placing breakpoints and gaining more insight into the type
+ * of the corruption detected.
+ *
+ * Example:
+ *	#include <assert.h>
+ *	...
+ *		assert(alloc_check(pool, 32*1024*1024));
+ */
 bool alloc_check(void *pool, unsigned long poolsize);
 
+/**
+ * alloc_visualize - dump information about the allocation pool
+ * @pool: the contiguous bytes for the allocator to use
+ * @poolsize: the size of the pool
+ *
+ * When debugging the allocator itself, it's often useful to see how
+ * the pool is being used.  alloc_visualize() does that, but makes
+ * assumptions about correctness (like the rest of the code) so if you
+ * suspect corruption call alloc_check() first.
+ *
+ * Example:
+ *	d = alloc_get(pool, 32*1024*1024, sizeof(*d), ALIGNOF(*d));
+ *	if (!d) {
+ *		fprintf(stderr, "Allocation failed!\n");
+ *		if (!alloc_check(pool, 32*1024*1024))
+ *			errx(1, "Allocation pool is corrupt");
+ *		alloc_visualize(stderr, pool, 32*1024*1024);
+ *		exit(1);
+ *	}
+ */
 void alloc_visualize(FILE *out, void *pool, unsigned long poolsize);
 #endif /* ALLOC_H */