take: new module for parameter ownership.

[ccan] / ccan / take / take.h

diff --git a/ccan/take/take.h b/ccan/take/take.h
new file mode 100644 (file)
index 0000000..b6ac4a9
--- /dev/null
+++ b/ccan/take/take.h
@@ -0,0 +1,116 @@
+/* CC0 (Public domain) - see LICENSE file for details */
+#ifndef CCAN_TAKE_H
+#define CCAN_TAKE_H
+#include "config.h"
+#include <stdbool.h>
+
+/**
+ * take - record a pointer to be consumed by the function its handed to.
+ * @p: the pointer to mark, or NULL.
+ *
+ * This marks a pointer object to be freed by the called function,
+ * which is extremely useful for chaining functions.  It works on
+ * NULL, for pass-through error handling.
+ */
+#define take(p) (take_typeof(p) take_((p)))
+
+/**
+ * taken - check (and un-take) a pointer was passed with take()
+ * @p: the pointer to check.
+ *
+ * A function which accepts take() arguments uses this to see if it
+ * should own the pointer; it will be removed from the take list, so
+ * this only returns true once.
+ *
+ * Example:
+ *     // Silly routine to add 1
+ *     static int *add_one(const int *num)
+ *     {
+ *             int *ret;
+ *             if (taken(num))
+ *                     ret = (int *)num;
+ *             else
+ *                     ret = malloc(sizeof(int));
+ *             if (ret)
+ *                     *ret = (*num) + 1;
+ *             return ret;
+ *     }
+ */
+bool taken(const void *p);
+
+/**
+ * is_taken - check if a pointer was passed with take()
+ * @p: the pointer to check.
+ *
+ * This is like the above, but doesn't remove it from the taken list.
+ *
+ * Example:
+ *     // Silly routine to add 1: doesn't handle taken args!
+ *     static int *add_one_notake(const int *num)
+ *     {
+ *             int *ret = malloc(sizeof(int));
+ *             assert(!is_taken(num));
+ *             if (ret)
+ *                     *ret = (*num) + 1;
+ *             return ret;
+ *     }
+ */
+bool is_taken(const void *p);
+
+/**
+ * taken_any - are there any taken pointers?
+ *
+ * Mainly useful for debugging take() leaks.
+ *
+ * Example:
+ *     static void cleanup(void)
+ *     {
+ *             assert(!taken_any());
+ *     }
+ */
+bool taken_any(void);
+
+/**
+ * take_cleanup - remove all taken pointers from list.
+ *
+ * This is useful in atexit() handlers for valgrind-style leak detection.
+ *
+ * Example:
+ *     static void cleanup2(void)
+ *     {
+ *             take_cleanup();
+ *     }
+ */
+void take_cleanup(void);
+
+/**
+ * take_allocfail - set function to call if we can't reallocated taken array.
+ * @fn: the function.
+ *
+ * If this is not set, then if the array reallocation fails, the
+ * pointer won't be marked taken().  If @fn returns, it is expected to
+ * free the pointer; we return NULL from take() and the function handles
+ * it like any allocation failure.
+ *
+ * Example:
+ *     static void free_on_fail(const void *p)
+ *     {
+ *             free((void *)p);
+ *     }
+ *
+ *     static void init(void)
+ *     {
+ *             take_allocfail(free_on_fail);
+ *     }
+ */
+void take_allocfail(void (*fn)(const void *p));
+
+/* Private functions */
+#if HAVE_TYPEOF
+#define take_typeof(ptr) (__typeof__(ptr))
+#else
+#define take_typeof(ptr)
+#endif
+
+void *take_(const void *p);
+#endif /* CCAN_TAKE_H */