--- /dev/null
+/* Licensed under LGPLv2.1+ - see LICENSE file for details */
+#ifndef CCAN_GENERATOR_H
+#define CCAN_GENERATOR_H
+#include "config.h"
+
+#if !HAVE_UCONTEXT
+#error Generators require working ucontext.h functions
+#endif
+
+#if !HAVE_TYPEOF
+#error Generators require typeof
+#endif
+
+#if !HAVE_STATEMENT_EXPR
+#error Generators require statement expressions
+#endif
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <ucontext.h>
+
+#include <ccan/ptrint/ptrint.h>
+#include <ccan/build_assert/build_assert.h>
+#include <ccan/cppmagic/cppmagic.h>
+
+/*
+ * Internals - included just for the use of inlines and macros
+ */
+
+struct generator_ {
+ ucontext_t gen;
+ ucontext_t caller;
+ bool complete;
+ void *base;
+};
+
+static inline struct generator_ *generator_state_(const void *ret)
+{
+ return (struct generator_ *)ret - 1;
+}
+
+struct generator_incomplete_;
+
+#define generator_rtype_(gen_) \
+ typeof((*(gen_))((struct generator_incomplete_ *)NULL))
+
+#if HAVE_POINTER_SAFE_MAKECONTEXT
+#define generator_wrapper_args_() void *ret
+#else
+#define generator_wrapper_args_() int lo, int hi
+#endif
+typedef void generator_wrapper_(generator_wrapper_args_());
+
+void *generator_new_(generator_wrapper_ *fn, size_t retsize);
+void generator_free_(void *ret);
+
+/*
+ * API
+ */
+
+/**
+ * generator_t - type for an in-progress generator
+ * @rtype: type of values the generator yield
+ */
+#define generator_t(rtype_) \
+ typeof(rtype_ (*)(struct generator_incomplete_ *))
+
+/**
+ * generator_declare - declare (but don't define) a generator function
+ * @name: name for the generator
+ * @rtype: return type for the generator
+ *
+ * Declares (as an extern) a generator function named @name, which
+ * will yield return values of type @rtype.
+ *
+ * Example:
+ * generator_declare(count_to_3, int);
+ */
+#define generator_declare(name_, rtype_) \
+ generator_t(rtype_) name_(void)
+
+/**
+ * generator_def - define a generator function
+ * @name: name for the generator
+ * @rtype: return type for the generator
+ *
+ * Define a generator function named @name yielding return values of
+ * type @rtype. The generator_def() line is followed immediately by a
+ * block containing the generator's code.
+ *
+ * Example:
+ * generator_def(count_to_3, int)
+ * {
+ * generator_yield(1);
+ * generator_yield(2);
+ * generator_yield(3);
+ * }
+ */
+#define generator_def_(name_, rtype_, storage_) \
+ static void name_##_generator_(rtype_ *ret_); \
+ static void name_##_generator__(generator_wrapper_args_()) \
+ { \
+ struct generator_ *gen; \
+ CPPMAGIC_IFELSE(HAVE_POINTER_SAFE_MAKECONTEXT) \
+ () \
+ (ptrdiff_t hilo = ((ptrdiff_t)hi << (8*sizeof(int))) \
+ + (ptrdiff_t)lo; \
+ rtype_ *ret = (rtype_ *)int2ptr(hilo); \
+ BUILD_ASSERT(sizeof(struct generator_ *) \
+ <= 2*sizeof(int));) \
+ gen = generator_state_(ret); \
+ name_##_generator_(ret); \
+ gen->complete = true; \
+ setcontext(&gen->caller); \
+ assert(0); \
+ } \
+ storage_ generator_t(rtype_) name_(void) \
+ { \
+ return generator_new_(name_##_generator__, \
+ sizeof(rtype_)); \
+ } \
+ static void name_##_generator_(rtype_ *ret_)
+#define generator_def(name_, rtype_) \
+ generator_def_(name_, rtype_, )
+
+/**
+ * generator_def_static - define a private / local generator function
+ * @name: name for the generator
+ * @rtype: return type for the generator
+ *
+ * As generator_def, but the resulting generator function will be
+ * local to this module.
+ */
+#define generator_def_static(name_, rtype_) \
+ generator_def_(name_, rtype_, static)
+
+/**
+ * generator_yield - yield (return) a value from a generator
+ * @val: value to yield
+ *
+ * Invoke only from within a generator. Yield the given value to the
+ * caller. This will stop execution of the generator code until the
+ * caller next invokes generator_next(), at which point it will
+ * continue from the generator_yield statement.
+ */
+#define generator_yield(val_) \
+ do { \
+ struct generator_ *gen_ = generator_state_(ret_); \
+ int rc; \
+ *(ret_) = (val_); \
+ rc = swapcontext(&gen_->gen, &gen_->caller); \
+ assert(rc == 0); \
+ } while (0)
+
+/**
+ * generator_next - get next value from a generator
+ * @gen: a generator state variable
+ *
+ * Returns a pointer to a (correctly typed) buffer containing the next
+ * value yielded by @gen, or NULL if @gen is finished. The buffer
+ * contents is only valid until the next time @gen is called or
+ * manipulated.
+ */
+static inline void *generator_next_(void *ret_)
+{
+ struct generator_ *gen = generator_state_(ret_);
+ int rc;
+
+ if (gen->complete)
+ return NULL;
+
+ rc = swapcontext(&gen->caller, &gen->gen);
+ assert(rc == 0);
+
+ return gen->complete ? NULL : ret_;
+}
+#define generator_next(gen_) \
+ ((generator_rtype_(gen_) *)generator_next_(gen_))
+
+/**
+ * generator_next_val - store next value from a generator
+ * @val: a variable of type suitable to store the generator's return
+ * type (lvalue)
+ * @gen: a generator state variable
+ *
+ * Returns 'true' if @gen yielded a new value, false if @gen is
+ * complete. If a new value was yielded, it is stored in @val.
+ */
+#define generator_next_val(val_, gen_) \
+ ({ \
+ generator_rtype_(gen_) *ret; \
+ ret = generator_next(gen_); \
+ if (ret) \
+ (val_) = *ret; \
+ !!ret; \
+ })
+
+#define generator_free(gen_) \
+ generator_free_((generator_rtype_(gen_) *)(gen_))
+
+#endif /* CCAN_GENERATOR_H */
projects / ccan / blobdiff