io/fdpass: new module for async fd passing.

[ccan] / ccan / io / io_plan.h

diff --git a/ccan/io/io_plan.h b/ccan/io/io_plan.h
index 21a1921734f41e83d2ed836e157e4849496fb8ad..1d503133b6ddb24f4f50cb2e4d12c4fb3e9732d3 100644 (file)
--- a/ccan/io/io_plan.h
+++ b/ccan/io/io_plan.h
@@ -4,9 +4,9 @@
 struct io_conn;
 
 /**
- * union io_plan_arg - scratch space for struct io_plan read/write fns.
+ * union io_plan_union - type for struct io_plan read/write fns.
  */
-union io_plan_arg {
+union io_plan_union {
        char *cp;
        void *vp;
        const void *const_vp;
@@ -14,17 +14,11 @@ union io_plan_arg {
        char c[sizeof(size_t)];
 };
 
-enum io_plan_status {
-       /* As before calling next function. */
-       IO_UNSET,
-       /* Normal. */
-       IO_POLLING,
-       /* Waiting for io_wake */
-       IO_WAITING,
-       /* Always do this. */
-       IO_ALWAYS,
-       /* Closing (both plans will be the same). */
-       IO_CLOSING
+/**
+ * struct io_plan_arg - scratch space for struct io_plan read/write fns.
+ */
+struct io_plan_arg {
+       union io_plan_union u1, u2;
 };
 
 enum io_direction {
@@ -33,26 +27,52 @@ enum io_direction {
 };
 
 /**
- * struct io_plan - one half of I/O to do
- * @status: the status of this plan.
- * @io: function to call when fd becomes read/writable, returns 0 to be
- *      called again, 1 if it's finished, and -1 on error (fd will be closed)
- * @next: the next function which is called if io returns 1.
- * @next_arg: the argument to @next
- * @u1, @u2: scratch space for @io.
+ * io_plan_arg - get a conn's io_plan_arg for a given direction.
+ * @conn: the connection.
+ * @dir: IO_IN or IO_OUT.
+ *
+ * This is how an io helper gets scratch space to store into; you must call
+ * io_set_plan() when you've initialized it.
+ *
+ * Example:
+ * #include <ccan/io/io_plan.h>
+ *
+ * // Simple helper to read a single char.
+ * static int do_readchar(int fd, struct io_plan_arg *arg)
+ * {
+ *     return read(fd, arg->u1.cp, 1) <= 0 ? -1 : 1;
+ * }
+ *
+ * static struct io_plan *io_read_char_(struct io_conn *conn, char *in,
+ *                              struct io_plan *(*next)(struct io_conn*,void*),
+ *                              void *next_arg)
+ * {
+ *     struct io_plan_arg *arg = io_plan_arg(conn, IO_IN);
+ *
+ *     // Store information we need in the plan unions u1 and u2.
+ *     arg->u1.cp = in;
+ *
+ *     return io_set_plan(conn, IO_IN, do_readchar, next, next_arg);
+ * }
  */
-struct io_plan {
-       enum io_plan_status status;
-
-       int (*io)(int fd, struct io_plan *plan);
-
-       struct io_plan *(*next)(struct io_conn *, void *arg);
-       void *next_arg;
-
-       union io_plan_arg u1, u2;
-};
-
-/* Helper to get a conn's io_plan. */
-struct io_plan *io_get_plan(struct io_conn *conn, enum io_direction dir);
+struct io_plan_arg *io_plan_arg(struct io_conn *conn, enum io_direction dir);
 
+/**
+ * io_set_plan - set a conn's io_plan.
+ * @conn: the connection.
+ * @dir: IO_IN or IO_OUT.
+ * @io: the IO function to call when the fd is ready.
+ * @next: the next callback when @io returns 1.
+ * @next_arg: the argument to @next.
+ *
+ * If @conn has debug set, the io function will be called immediately,
+ * so it's important that this be the last thing in your function!
+ *
+ * See also:
+ *     io_get_plan_arg()
+ */
+struct io_plan *io_set_plan(struct io_conn *conn, enum io_direction dir,
+                           int (*io)(int fd, struct io_plan_arg *arg),
+                           struct io_plan *(*next)(struct io_conn *, void *),
+                           void *next_arg);
 #endif /* CCAN_IO_PLAN_H */