[ccan] [PATCH 2/3] generator: Generators for C
David Gibson
david at gibson.dropbear.id.au
Mon Feb 15 23:13:23 AEDT 2016
Generators are a limited form of co-routine, which people may be familiar
with from Python. This module adds an implementation of generators for C.
Signed-off-by: David Gibson <david at gibson.dropbear.id.au>
---
ccan/generator/LICENSE | 1 +
ccan/generator/_info | 71 ++++++++++++
ccan/generator/generator.c | 54 ++++++++++
ccan/generator/generator.h | 202 +++++++++++++++++++++++++++++++++++
ccan/generator/test/api.c | 62 +++++++++++
ccan/generator/test/compile_fail-1.c | 21 ++++
ccan/generator/test/compile_fail-2.c | 21 ++++
ccan/generator/test/compile_fail-3.c | 24 +++++
ccan/generator/test/compile_fail-4.c | 23 ++++
ccan/generator/test/compile_fail-5.c | 21 ++++
ccan/generator/test/example-gens.c | 10 ++
ccan/generator/test/example-gens.h | 8 ++
12 files changed, 518 insertions(+)
create mode 120000 ccan/generator/LICENSE
create mode 100644 ccan/generator/_info
create mode 100644 ccan/generator/generator.c
create mode 100644 ccan/generator/generator.h
create mode 100644 ccan/generator/test/api.c
create mode 100644 ccan/generator/test/compile_fail-1.c
create mode 100644 ccan/generator/test/compile_fail-2.c
create mode 100644 ccan/generator/test/compile_fail-3.c
create mode 100644 ccan/generator/test/compile_fail-4.c
create mode 100644 ccan/generator/test/compile_fail-5.c
create mode 100644 ccan/generator/test/example-gens.c
create mode 100644 ccan/generator/test/example-gens.h
diff --git a/ccan/generator/LICENSE b/ccan/generator/LICENSE
new file mode 120000
index 0000000..dc314ec
--- /dev/null
+++ b/ccan/generator/LICENSE
@@ -0,0 +1 @@
+../../licenses/LGPL-2.1
\ No newline at end of file
diff --git a/ccan/generator/_info b/ccan/generator/_info
new file mode 100644
index 0000000..a6570e3
--- /dev/null
+++ b/ccan/generator/_info
@@ -0,0 +1,71 @@
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * generator - generators for C
+ *
+ * Generators are a limited form of coroutines, which provide a useful
+ * way of expressing certain problems, while being much simpler to
+ * understand than general coroutines.
+ *
+ * Instead of returning a single value, a generator can "yield" a
+ * value at various points during its execution. Whenever it yields,
+ * the "calling" function resumes and obtains the newly yielded value
+ * to work with. When the caller asks for the next value from the
+ * generator, the generator resumes execution from the last yield and
+ * continues onto the next.
+ *
+ * Example:
+ * #include <stdio.h>
+ * #include <ccan/generator/generator.h>
+ *
+ * generator_def_static(simple_gen, int)
+ * {
+ * generator_yield(1);
+ * generator_yield(3);
+ * generator_yield(17);
+ * }
+ *
+ * int main(int argc, char *argv[])
+ * {
+ * generator_t(int) gen = simple_gen();
+ * int *ret;
+ *
+ * while ((ret = generator_next(gen)) != NULL) {
+ * printf("Generator returned %d\n", *ret);
+ * }
+ *
+ * return 0;
+ * }
+ *
+ * Author: David Gibson <david at gibson.dropbear.id.au>
+ * License: LGPL (v2.1 or any later version)
+ *
+ * Ccanlint:
+ * // We need several gcc extensions
+ * objects_build_without_features FAIL
+ * tests_compile_without_features FAIL
+ * tests_helpers_compile_without_features FAIL
+ */
+int main(int argc, char *argv[])
+{
+ /* Expect exactly one argument */
+ if (argc != 2)
+ return 1;
+
+ if (strcmp(argv[1], "depends") == 0) {
+ printf("ccan/build_assert\n");
+ printf("ccan/ptrint\n");
+ printf("ccan/alignof\n");
+ printf("ccan/cppmagic\n");
+ return 0;
+ }
+
+ if (strcmp(argv[1], "testdepends") == 0) {
+ printf("ccan/str\n");
+ return 0;
+ }
+
+ return 1;
+}
diff --git a/ccan/generator/generator.c b/ccan/generator/generator.c
new file mode 100644
index 0000000..d217665
--- /dev/null
+++ b/ccan/generator/generator.c
@@ -0,0 +1,54 @@
+/* Licensed LGPLv2.1+ - see LICENSE file for details */
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+#include <ccan/alignof/alignof.h>
+
+#include <ccan/generator/generator.h>
+
+#define DEFAULT_STATE_SIZE 8192
+#define STATE_ALIGN ALIGNOF(struct generator_)
+
+void *generator_new_(generator_wrapper_ *fn, size_t retsize)
+{
+ char *base;
+ size_t size = DEFAULT_STATE_SIZE;
+ void *ret;
+ struct generator_ *gen;
+
+ base = malloc(size);
+ if (!base)
+ abort();
+
+ retsize = (retsize + STATE_ALIGN) & ~(STATE_ALIGN - 1);
+ ret = base + size - retsize;
+ gen = (struct generator_ *)ret - 1;
+
+ gen->base = base;
+ gen->complete = false;
+
+ getcontext(&gen->gen);
+
+ gen->gen.uc_stack.ss_sp = gen->base;
+ gen->gen.uc_stack.ss_size = (char *)gen - base;
+
+ if (HAVE_POINTER_SAFE_MAKECONTEXT) {
+ makecontext(&gen->gen, (void *)fn, 1, ret);
+ } else {
+ ptrdiff_t si = ptr2int(ret);
+ ptrdiff_t mask = (1UL << (sizeof(int) * 8)) - 1;
+ int lo = si & mask;
+ int hi = si >> (sizeof(int) * 8);
+
+ makecontext(&gen->gen, (void *)fn, 2, lo, hi);
+ }
+
+ return ret;
+}
+
+void generator_free_(void *ret)
+{
+ struct generator_ *gen = generator_state_(ret);
+ free(gen->base);
+}
diff --git a/ccan/generator/generator.h b/ccan/generator/generator.h
new file mode 100644
index 0000000..6b2bd92
--- /dev/null
+++ b/ccan/generator/generator.h
@@ -0,0 +1,202 @@
+/* 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 */
diff --git a/ccan/generator/test/api.c b/ccan/generator/test/api.c
new file mode 100644
index 0000000..a5770fd
--- /dev/null
+++ b/ccan/generator/test/api.c
@@ -0,0 +1,62 @@
+#include <ccan/generator/generator.h>
+#include <ccan/tap/tap.h>
+#include <ccan/str/str.h>
+
+#include "example-gens.h"
+
+generator_def_static(genx, const char *)
+{
+ generator_yield("one");
+ generator_yield("two");
+ generator_yield("three");
+ generator_yield("four");
+}
+
+static void test1(void)
+{
+ generator_t(int) state1 = gen1();
+ int *ret;
+
+ ok1((ret = generator_next(state1)) != NULL);
+ ok1(*ret == 1);
+ ok1((ret = generator_next(state1)) != NULL);
+ ok1(*ret == 3);
+ ok1((ret = generator_next(state1)) != NULL);
+ ok1(*ret == 17);
+ ok1((ret = generator_next(state1)) == NULL);
+
+ /* Test that things don't go bad if we try to invoke an
+ * already completed generator */
+ ok1((ret = generator_next(state1)) == NULL);
+
+ generator_free(state1);
+}
+
+static void testx(void)
+{
+ generator_t(const char *) statex = genx();
+ const char *val;
+
+ ok1(generator_next_val(val, statex));
+ ok1(streq(val, "one"));
+ ok1(generator_next_val(val, statex));
+ ok1(streq(val, "two"));
+ ok1(generator_next_val(val, statex));
+ ok1(streq(val, "three"));
+ ok1(generator_next_val(val, statex));
+ ok1(streq(val, "four"));
+ ok1(!generator_next_val(val, statex));
+ generator_free(statex);
+}
+
+int main(void)
+{
+ /* This is how many tests you plan to run */
+ plan_tests(8 + 9);
+
+ test1();
+ testx();
+
+ /* This exits depending on whether all tests passed */
+ return exit_status();
+}
diff --git a/ccan/generator/test/compile_fail-1.c b/ccan/generator/test/compile_fail-1.c
new file mode 100644
index 0000000..38e623a
--- /dev/null
+++ b/ccan/generator/test/compile_fail-1.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <ccan/generator/generator.h>
+
+#include <ccan/generator/generator.c>
+
+#include "example-gens.h"
+
+int main(int argc, char *argv[])
+{
+#ifdef FAIL
+ int *g = gen1();
+#else
+ generator_t(int) g = gen1();
+#endif
+
+ printf("%d", *generator_next(g));
+
+ exit(0);
+}
diff --git a/ccan/generator/test/compile_fail-2.c b/ccan/generator/test/compile_fail-2.c
new file mode 100644
index 0000000..7f24131
--- /dev/null
+++ b/ccan/generator/test/compile_fail-2.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <ccan/generator/generator.h>
+
+#include <ccan/generator/generator.c>
+
+#include "example-gens.h"
+
+int main(int argc, char *argv[])
+{
+#ifdef FAIL
+ generator_t(char) g = gen1();
+#else
+ generator_t(int) g = gen1();
+#endif
+
+ printf("%d", *generator_next(g));
+
+ exit(0);
+}
diff --git a/ccan/generator/test/compile_fail-3.c b/ccan/generator/test/compile_fail-3.c
new file mode 100644
index 0000000..9347efc
--- /dev/null
+++ b/ccan/generator/test/compile_fail-3.c
@@ -0,0 +1,24 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <ccan/generator/generator.h>
+
+#include <ccan/generator/generator.c>
+
+generator_def_static(intgen, int)
+{
+#ifdef FAIL
+ generator_yield("a");
+#else
+ generator_yield(1);
+#endif
+}
+
+int main(int argc, char *argv[])
+{
+ generator_t(int) g = intgen();
+
+ printf("%d", *generator_next(g));
+
+ exit(0);
+}
diff --git a/ccan/generator/test/compile_fail-4.c b/ccan/generator/test/compile_fail-4.c
new file mode 100644
index 0000000..f7297cf
--- /dev/null
+++ b/ccan/generator/test/compile_fail-4.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <ccan/generator/generator.h>
+
+#include <ccan/generator/generator.c>
+
+#include "example-gens.h"
+
+int main(int argc, char *argv[])
+{
+ generator_t(int) g = gen1();
+#ifdef FAIL
+ char *val;
+#else
+ int val;
+#endif
+
+ generator_next_val(val, g);
+ printf("%d", val);
+
+ exit(0);
+}
diff --git a/ccan/generator/test/compile_fail-5.c b/ccan/generator/test/compile_fail-5.c
new file mode 100644
index 0000000..ba8ced9
--- /dev/null
+++ b/ccan/generator/test/compile_fail-5.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <ccan/generator/generator.h>
+
+#include <ccan/generator/generator.c>
+
+#include "example-gens.h"
+
+int main(int argc, char *argv[])
+{
+#ifdef FAIL
+ int *g = NULL;
+#else
+ generator_t(int) g = gen1();
+#endif
+
+ generator_free(g);
+
+ exit(0);
+}
diff --git a/ccan/generator/test/example-gens.c b/ccan/generator/test/example-gens.c
new file mode 100644
index 0000000..c554011
--- /dev/null
+++ b/ccan/generator/test/example-gens.c
@@ -0,0 +1,10 @@
+#include <ccan/generator/generator.h>
+
+#include "example-gens.h"
+
+generator_def(gen1, int)
+{
+ generator_yield(1);
+ generator_yield(3);
+ generator_yield(17);
+}
diff --git a/ccan/generator/test/example-gens.h b/ccan/generator/test/example-gens.h
new file mode 100644
index 0000000..cf4ce3b
--- /dev/null
+++ b/ccan/generator/test/example-gens.h
@@ -0,0 +1,8 @@
+#ifndef _EXAMPLE_GENS_H
+#define _EXAMPLE_GENS_H
+
+#include <ccan/generator/generator.h>
+
+generator_declare(gen1, int);
+
+#endif /* _EXAMPLE_GENS_H */
--
2.5.0
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