X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftcon%2Ftcon.h;h=1dbadafc9726716e6d19d82794ab22b461ef4903;hp=5b38c7193406fa1ccae181dbfde21849ace70601;hb=0ddea4131eca28437638cdaf9394324fafab33da;hpb=5c451bbbed80e3bcb1f6be4301026ece01ab1309

diff --git a/ccan/tcon/tcon.h b/ccan/tcon/tcon.h
index 5b38c719..1dbadafc 100644
--- a/ccan/tcon/tcon.h
+++ b/ccan/tcon/tcon.h
@@ -1,19 +1,21 @@
-/* Placed into the public domain */
+/* CC0 (Public domain) - see LICENSE file for details */
 #ifndef CCAN_TCON_H
 #define CCAN_TCON_H
 #include "config.h"
 
+#include <stddef.h>
+
 /**
  * TCON - declare a _tcon type containing canary variables.
  * @decls: the semi-colon separated list of type canaries.
  *
  * This declares a _tcon member for a structure.  It should be the
  * last element in your structure; with sufficient compiler support it
- * will not use any actual storage.  tcon_to_raw() will compare
+ * will not use any actual storage.  tcon_check() will compare
  * expressions with one of these "type canaries" to cause warnings if
  * the container is misused.
  *
- * A type of "void *" will allow tcon_to_raw() to pass on any (pointer) type.
+ * A type of "void *" will allow tcon_check() to pass on any (pointer) type.
  *
  * Example:
  *	// Simply typesafe linked list.
@@ -42,6 +44,77 @@
 #define TCON(decls) struct { decls; } _tcon[1]
 #endif
 
+/**
+ * TCON_WRAP - declare a wrapper type containing a base type and type canaries
+ * @basetype: the base type to wrap
+ * @decls: the semi-colon separated list of type canaries.
+ *
+ * This expands to a new type which includes the given base type, and
+ * also type canaries, similar to those created with TCON.
+ *
+ * The embedded base type value can be accessed using tcon_unwrap().
+ *
+ * Differences from using TCON()
+ * - The wrapper type will take either the size of the base type, or
+ *   the size of a single pointer, whichever is greater (regardless of
+ *   compiler)
+ * - A TCON_WRAP type may be included in another structure, and need
+ *   not be the last element.
+ *
+ * A type of "void *" will allow tcon_check() to pass on any (pointer) type.
+ *
+ * Example:
+ *	// Simply typesafe linked list.
+ *	struct list_head {
+ *		struct list_head *prev, *next;
+ *	};
+ *
+ *	typedef TCON_WRAP(struct list_head, char *canary) string_list_t;
+ *
+ *	// More complex: mapping from one type to another.
+ *	struct map {
+ *		void *contents;
+ *	};
+ *
+ *	typedef TCON_WRAP(struct map, char *charp_canary; int int_canary)
+ *		int_to_string_map_t;
+ */
+#define TCON_WRAP(basetype, decls) \
+	union {			   \
+		basetype _base;	   \
+		struct {	   \
+			decls;	   \
+		} *_tcon;	   \
+	}
+
+/**
+ * TCON_WRAP_INIT - an initializer for a variable declared with TCON_WRAP
+ * @...: Initializer for the base type (treated as variadic so commas
+ *       can be included)
+ *
+ * Converts converts an initializer suitable for a base type into one
+ * suitable for that type wrapped with TCON_WRAP.
+ *
+ * Example:
+ *	TCON_WRAP(int, char *canary) canaried_int = TCON_WRAP_INIT(17);
+ */
+#define TCON_WRAP_INIT(...)			\
+	{ ._base = __VA_ARGS__, }
+
+/**
+ * tcon_unwrap - Access the base type of a TCON_WRAP
+ * @ptr: pointer to an object declared with TCON_WRAP
+ *
+ * tcon_unwrap() returns a pointer to the base type of the TCON_WRAP()
+ * object pointer to by @ptr.
+ *
+ * Example:
+ *	TCON_WRAP(int, char *canary) canaried_int;
+ *
+ *	*tcon_unwrap(&canaried_int) = 17;
+ */
+#define tcon_unwrap(ptr) (&((ptr)->_base))
+
 /**
  * tcon_check - typecheck a typed container
  * @x: the structure containing the TCON.
@@ -61,6 +134,72 @@
 #define tcon_check(x, canary, expr)				\
 	(sizeof((x)->_tcon[0].canary == (expr)) ? (x) : (x))
 
+/**
+ * tcon_check_ptr - typecheck a typed container
+ * @x: the structure containing the TCON.
+ * @canary: which canary to check against.
+ * @expr: the expression whose type must match &TCON (not evaluated)
+ *
+ * This macro is used to check that the expression is a pointer to the type
+ * expected for this structure (note the "useless" sizeof() argument
+ * which contains this comparison with the type canary), or NULL.
+ *
+ * It evaluates to @x so you can chain it.
+ */
+#define tcon_check_ptr(x, canary, expr)				\
+	(sizeof(&(x)->_tcon[0].canary == (expr)) ? (x) : (x))
+
+
+/**
+ * tcon_type - the type within a container (or void *)
+ * @x: the structure containing the TCON.
+ * @canary: which canary to check against.
+ */
+#if HAVE_TYPEOF
+#define tcon_type(x, canary) __typeof__((x)->_tcon[0].canary)
+#else
+#define tcon_type(x, canary) void *
+#endif
+
+/**
+ * tcon_sizeof - the size of type within a container
+ * @x: the structure containing the TCON.
+ * @canary: which canary to check against.
+ */
+#define tcon_sizeof(x, canary) sizeof((x)->_tcon[0].canary)
+
+/**
+ * TCON_VALUE - encode an integer value in a type canary
+ * @canary: name of the value canary
+ * @val: positive integer compile time constant value
+ *
+ * This macro can be included inside the declarations in a TCON() or
+ * TCON_WRAP(), constructing a special "type" canary which encodes the
+ * integer value @val (which must be a compile time constant, and a
+ * positive integer in the range of size_t).
+ */
+#define TCON_VALUE(canary, val)	char _value_##canary[val]
+
+/**
+ * tcon_value - retrieve the value of a TCON_VALUE canary
+ * @x: the structure containing the TCON
+ * @canary: name of the value canary
+ *
+ * This macros expands to the value previously encoded into a TCON
+ * using TCON_VALUE().
+ */
+#define tcon_value(x, canary)	tcon_sizeof(x, _value_##canary)
+
+/**
+ * tcon_ptr_type - pointer to the type within a container (or void *)
+ * @x: the structure containing the TCON.
+ * @canary: which canary to check against.
+ */
+#if HAVE_TYPEOF
+#define tcon_ptr_type(x, canary) __typeof__(&(x)->_tcon[0].canary)
+#else
+#define tcon_ptr_type(x, canary) void *
+#endif
 
 /**
  * tcon_cast - cast to a canary type for this container (or void *)
@@ -72,10 +211,157 @@
  * platform doesn't HAVE_TYPEOF, then it casts to void * (which will
  * cause a warning if the user doesn't expect a pointer type).
  */
+#define tcon_cast(x, canary, expr) ((tcon_type((x), canary))(expr))
+#define tcon_cast_ptr(x, canary, expr) ((tcon_ptr_type((x), canary))(expr))
+
+/**
+ * TCON_CONTAINER - encode information on a specific member of a
+ *                  containing structure into a "type" canary
+ * @canary: name of the container canary
+ * @container: type of the container structure
+ * @member: name of the member
+ *
+ * Used in the declarations in TCON() or TCON_WRAP(), encode a
+ * "container canary".  This encodes the type of @container, the type
+ * of @member within it (with sufficient compiler support) and the
+ * offset of @member within @container.
+ */
 #if HAVE_TYPEOF
-#define tcon_cast(x, canary, expr) ((__typeof__((x)->_tcon[0].canary))(expr))
+#define TCON_CONTAINER(canary, container, member)			\
+	container _container_##canary;					\
+	typeof(((container *)0)->member) _member_##canary;		\
+	TCON_VALUE(_offset_##canary, offsetof(container, member))
 #else
-#define tcon_cast(x, canary, expr) ((void *)(expr))
+#define TCON_CONTAINER(canary, container, member)			\
+	container _container_##canary;					\
+	TCON_VALUE(_offset_##canary, offsetof(container, member))
 #endif
 
+/**
+ * tcon_container_check
+ * tcon_container_check_ptr
+ * tcon_container_type
+ * tcon_container_ptr_type
+ * tcon_container_sizeof
+ * tcon_container_cast
+ * tcon_container_cast_ptr
+ * @x: the structure containing the TCON.
+ * @canary: which container canary to check against.
+ *
+ * As tcon_check / tcon_check_ptr / tcon_type / tcon_ptr_type /
+ * tcon_sizeof / tcon_cast / tcon_cast_ptr, but use the type of the
+ * "container" type declared with TCON_CONTAINER, instead of a simple
+ * canary.
+ */
+#define tcon_container_check(x, canary, expr)		\
+	tcon_check(x, _container_##canary, expr)
+#define tcon_container_check_ptr(x, canary, expr)	\
+	tcon_check_ptr(x, _container_##canary, expr)
+#define tcon_container_type(x, canary)		\
+	tcon_type(x, _container_##canary)
+#define tcon_container_ptr_type(x, canary)	\
+	tcon_ptr_type(x, _container_##canary)
+#define tcon_container_sizeof(x, canary)	\
+	tcon_sizeof(x, _container_##canary)
+#define tcon_container_cast(x, canary, expr)	\
+	tcon_cast(x, _container_##canary, expr)
+#define tcon_container_cast_ptr(x, canary, expr)	\
+	tcon_cast_ptr(x, _container_##canary, expr)
+
+/**
+ * tcon_member_check
+ * tcon_member_check_ptr
+ * tcon_member_type
+ * tcon_member_ptr_type
+ * tcon_member_sizeof
+ * tcon_member_cast
+ * tcon_member_cast_ptr
+ * @x: the structure containing the TCON.
+ * @canary: which container canary to check against.
+ *
+ * As tcon_check / tcon_check_ptr / tcon_type / tcon_ptr_type /
+ * tcon_sizeof / tcon_cast / tcon_cast_ptr, but use the type of the
+ * "member" type declared with TCON_CONTAINER, instead of a simple
+ * canary.
+ */
+#define tcon_member_check(x, canary, expr)	\
+	tcon_check(x, _member_##canary, expr)
+#define tcon_member_check_ptr(x, canary, expr)		\
+	tcon_check_ptr(x, _member_##canary, expr)
+#define tcon_member_type(x, canary)		\
+	tcon_type(x, _member_##canary)
+#define tcon_member_ptr_type(x, canary)	\
+	tcon_ptr_type(x, _member_##canary)
+#define tcon_member_sizeof(x, canary)	\
+	tcon_sizeof(x, _member_##canary)
+#define tcon_member_cast(x, canary, expr)	\
+	tcon_cast(x, _member_##canary, expr)
+#define tcon_member_cast_ptr(x, canary, expr)	\
+	tcon_cast_ptr(x, _member_##canary, expr)
+
+/**
+ * tcon_offset - the offset of a member within a container, as
+ *               declared with TCON_CONTAINER
+ * @x: the structure containing the TCON.
+ * @canary: which container canary to check against.
+ */
+#define tcon_offset(x, canary)			\
+	tcon_value((x), _offset_##canary)
+
+/**
+ * tcon_container_of - get pointer to enclosing structure based on a
+ *                     container canary
+ * @x: the structure containing the TCON
+ * @canary: the name of the container canary
+ * @member_ptr: pointer to a member of the container
+ *
+ * @member_ptr must be a pointer to the member of a container
+ * structure previously recorded in @canary with TCON_CONTAINER.
+ *
+ * tcon_container_of() evaluates to a pointer to the container
+ * structure.  With sufficient compiler support, the pointer will be
+ * correctly typed, and the type of @member_ptr will be verified.
+ *
+ * Returns NULL if @member_ptr is NULL.
+ */
+#define tcon_container_of(x, canary, member_ptr)			\
+	tcon_container_cast_ptr(					\
+		tcon_member_check_ptr((x), canary, (member_ptr)),	\
+		canary, tcon_container_of_((member_ptr),		\
+					   tcon_offset((x), canary)))
+
+static inline void *tcon_container_of_(void *member_ptr, size_t offset)
+{
+	return member_ptr ? (char *)member_ptr - offset : NULL;
+}
+
+
+/**
+ * tcon_member_of - get pointer to enclosed member structure based on a
+ *                  container canary
+ * @x: the structure containing the TCON
+ * @canary: the name of the container canary
+ * @container_ptr: pointer to a container
+ *
+ * @container_ptr must be a pointer to a container structure
+ * previously recorded in @canary with TCON_CONTAINER.
+ *
+ * tcon_member_of() evaluates to a pointer to the member of the
+ * container recorded in @canary. With sufficient compiler support,
+ * the pointer will be correctly typed, and the type of @container_ptr
+ * will be verified.
+ *
+ * Returns NULL if @container_ptr is NULL.
+ */
+#define tcon_member_of(x, canary, container_ptr)			\
+	tcon_member_cast_ptr(						\
+		tcon_container_check_ptr((x), canary, (container_ptr)),	\
+		canary, tcon_member_of_((container_ptr),		\
+					tcon_offset((x), canary)))
+static inline void *tcon_member_of_(void *container_ptr, size_t offset)
+{
+	return container_ptr ? (char *)container_ptr + offset : NULL;
+}
+
+
 #endif /* CCAN_TCON_H */