Add switch to fiber interface, support fiber_switch in asyncify implementation

Makefile

@@ -20,13 +20,23 @@ endif
 all: hello sieve itersum treesum
 
 .PHONY: hello
-hello: hello_asyncify.wasm hello_wasmfx.wasm
+hello: hello_asyncify.wasm hello_asyncify_switch.wasm racecar.wasm hello_wasmfx.wasm
 
 hello_asyncify.wasm: inc/fiber.h src/asyncify/asyncify_impl.c examples/hello.c
 	$(WASICC) -DSTACK_POOL_SIZE=$(STACK_POOL_SIZE) -DASYNCIFY_DEFAULT_STACK_SIZE=$(ASYNCIFY_DEFAULT_STACK_SIZE) src/asyncify/asyncify_impl.c $(WASIFLAGS) examples/hello.c -o hello_asyncfiy.pre.wasm
 	$(ASYNCIFY) hello_asyncfiy.pre.wasm -o hello_asyncify.wasm
 	chmod +x hello_asyncify.wasm
 
+hello_asyncify_switch.wasm: inc/fiber_switch.h src/asyncify/asyncify_switch_impl.c examples/hello_switch.c
+	$(WASICC) -DSTACK_POOL_SIZE=$(STACK_POOL_SIZE) -DASYNCIFY_DEFAULT_STACK_SIZE=$(ASYNCIFY_DEFAULT_STACK_SIZE) src/asyncify/asyncify_switch_impl.c $(WASIFLAGS) examples/hello_switch.c -o hello_asyncfiy_switch.pre.wasm
+	$(ASYNCIFY) hello_asyncfiy_switch.pre.wasm -o hello_asyncify_switch.wasm
+	chmod +x hello_asyncify_switch.wasm
+
+racecar.wasm: inc/fiber_switch.h src/asyncify/asyncify_switch_impl.c examples/racecar.c
+	$(WASICC) -DSTACK_POOL_SIZE=$(STACK_POOL_SIZE) -DASYNCIFY_DEFAULT_STACK_SIZE=$(ASYNCIFY_DEFAULT_STACK_SIZE) src/asyncify/asyncify_switch_impl.c $(WASIFLAGS) examples/racecar.c -o racecar.pre.wasm
+	$(ASYNCIFY) racecar.pre.wasm -o racecar.wasm
+	chmod +x racecar.wasm
+
 hello_wasmfx.wasm: inc/fiber.h src/wasmfx/imports.wat src/wasmfx/wasmfx_impl.c examples/hello.c
 	$(WASICC) $(SHADOW_STACK_FLAG) -DWASMFX_CONT_SHADOW_STACK_SIZE=$(WASMFX_CONT_SHADOW_STACK_SIZE) -DWASMFX_CONT_TABLE_INITIAL_CAPACITY=$(WASMFX_CONT_TABLE_INITIAL_CAPACITY) -Wl,--export-table,--export-memory,--export=__stack_pointer src/wasmfx/wasmfx_impl.c $(WASIFLAGS) examples/hello.c -o hello_wasmfx.pre.wasm
 	$(WASM_INTERP) -d -i src/wasmfx/imports.wat -o fiber_wasmfx_imports.wasm

examples/hello_switch.c

@@ -0,0 +1,74 @@
+// Cooperative printing of "hello world"
+#include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fiber_switch.h>
+
+static fiber_t hello_fiber;
+static fiber_t world_fiber;
+
+static bool hello_done;
+static bool world_done;
+
+
+void* hello(void *arg, fiber_t main_fiber) {
+  uint32_t i = (uint32_t)(uintptr_t)arg;
+
+  static const char s[] = "hlowrd";
+
+  do  {
+    putc(s[i], stdout);
+    i = (uint32_t)(uintptr_t)fiber_switch(world_fiber, (void*)(uintptr_t)i, &hello_fiber);
+  } while (!world_done && world_fiber != NULL);
+
+  hello_done = true;
+  fiber_return_switch(main_fiber, (void*)(uintptr_t)i);
+  return NULL;
+}
+
+void* world(void *arg, fiber_t  __attribute__((unused))main_fiber) {
+  uint32_t i = (uint32_t)(uintptr_t)arg;
+  static const char s[] = "el ol";
+
+  do {
+    putc(s[i], stdout);
+    i++;
+    i = (uint32_t)(uintptr_t)fiber_switch(hello_fiber, (void*)(uintptr_t)i, &world_fiber);
+  } while (i < strlen(s));
+
+  world_done = true;
+  fiber_switch(hello_fiber, (void*)(uintptr_t)i, &world_fiber);
+  return NULL;
+}
+
+void *prog(void * __attribute__((unused))result, fiber_t dummy) {
+
+  hello_fiber = fiber_alloc((fiber_entry_point_t)hello);
+  world_fiber = fiber_alloc((fiber_entry_point_t)world);
+
+  hello_done = false;
+  world_done = false;
+
+  uint32_t i = 0;
+
+  // Initial switch must be from *some* fiber, so we use dummy.
+  (void)fiber_switch(hello_fiber, (void*)(uintptr_t)i, &dummy);
+
+  putc('\n', stdout);
+  fflush(stdout);
+
+  fiber_free(hello_fiber);
+  fiber_free(world_fiber);
+
+  return NULL;
+}
+
+int main(int __attribute__((unused)) argc, char * __attribute__((unused))argv[]) {
+
+  void *result = fiber_main(prog, NULL);
+
+  return (int)(intptr_t)result;
+}

examples/racecar.c

@@ -0,0 +1,65 @@
+// Cooperative printing of "racecar"
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fiber_switch.h>
+
+static volatile fiber_t main_fiber;
+static volatile fiber_t rr;
+static volatile fiber_t cc;
+static volatile fiber_t aa;
+static volatile fiber_t e;
+
+void* rr_func(void *__attribute__((unused))arg, fiber_t main_fiber) {
+  putc('r', stdout);
+  fiber_switch(aa, NULL, &rr);
+  putc('r', stdout);
+  fiber_return_switch(main_fiber, NULL);
+  return NULL;
+}
+
+void* aa_func(void *__attribute__((unused))arg, fiber_t  __attribute__((unused))dummy) {
+  putc('a', stdout);
+  fiber_switch(cc, NULL, &aa);
+  putc('a', stdout);
+  fiber_return_switch(rr, NULL);
+  return NULL;
+}
+
+void* cc_func(void *__attribute__((unused))arg, fiber_t  __attribute__((unused))dummy) {
+  putc('c', stdout);
+  fiber_switch(e, NULL, &cc);
+  putc('c', stdout);
+  fiber_return_switch(aa, NULL);
+  return NULL;
+}
+
+void* e_func(void *__attribute__((unused))arg, fiber_t  __attribute__((unused))dummy) {
+  putc('e', stdout);
+  fiber_return_switch(cc, NULL);
+  return NULL;
+}
+
+void *prog(void * __attribute__((unused))result, fiber_t  __attribute__((unused))dummy) {
+
+    rr = fiber_alloc(rr_func);
+    aa = fiber_alloc(aa_func);
+    cc = fiber_alloc(cc_func);
+    e = fiber_alloc(e_func);
+
+    (void)fiber_switch(rr, NULL, &main_fiber);
+
+    putc('\n', stdout);
+    fflush(stdout);
+
+    return NULL;
+}
+
+int main(int __attribute__((unused)) argc, char * __attribute__((unused))argv[]) {
+
+  void *result = fiber_main(prog, NULL);
+
+  return (int)(intptr_t)result;
+}

inc/fiber_switch.h

@@ -0,0 +1,48 @@
+/** A basic fiber interface. **/
+#ifndef WASMFX_FIBER_C_H
+#define WASMFX_FIBER_C_H
+
+#define export(NAME) __attribute__((export_name(NAME)))
+
+/** The abstract type of a fiber object. **/
+typedef struct fiber* fiber_t;
+
+/** The signature of a fiber entry point. **/
+/** take void* void* instead? 
+ * first pointer: argument in switch
+ * second pointer: switched_from fiber_t
+*/
+typedef void* (*fiber_entry_point_t)(void*, fiber_t);
+
+/** Allocates a new fiber with the default stack size. **/
+export("fiber_alloc")
+fiber_t fiber_alloc(fiber_entry_point_t entry);
+
+/** Reclaims the memory occupied by the fiber object. **/
+export("fiber_free")
+void fiber_free(fiber_t fiber);
+
+
+/** Possible status codes for `fiber_switch`. **/
+typedef enum { FIBER_OK = 0, FIBER_SWITCH = 1, FIBER_ERROR = 2 } fiber_result_t;
+
+
+/** Switches to a given `fiber` with argument `arg`, returning some value
+    of type `void*`. The output parameter `status` indicates whether
+    the fiber ran to completion (`FIBER_OK`), yielded control
+    (`FIBER_YIELD`), or failed (`FIBER_ERROR`), in the latter case the
+    return value will be undefined. **/
+export("fiber_switch")
+void* fiber_switch(fiber_t fiber, void *arg, volatile fiber_t *switched_from);
+
+/** Switches to `target` and destroys currently executing `fiber`. **/
+// todo: attribute no return
+export("fiber_return_switch")
+void fiber_return_switch(fiber_t target, void *arg);
+
+/** Runs the provided `main` function in a fiber context. **/
+export("fiber_main")
+void *fiber_main(void *(*main)(void*,fiber_t), void* arg);
+
+#undef export
+#endif