Add switch to fiber interface, support fiber_switch in asyncify implementation

Makefile

@@ -20,13 +20,19 @@ endif
 all: hello sieve itersum treesum
 
 .PHONY: hello
-hello: hello_asyncify.wasm hello_wasmfx.wasm
+hello: hello_asyncify.wasm hello_asyncify_switch.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
 
+# new stuff: build with switch
+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
+
 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 +1,70 @@
+// 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 volatile fiber_t hello_fiber;
+static volatile fiber_t world_fiber;
+
+fiber_result_t status;
+
+bool hello_done;
+bool world_done;
+
+
+void* hello(void *arg) {
+  uint32_t i = (uint32_t)(uintptr_t)arg;
+
+  static const char s[] = "hlowrd";
+
+  if (!hello_done){
+    while (i < strlen(s)) {
+      putc(s[i], stdout);
+      i = (uint32_t)(uintptr_t)fiber_switch(world_fiber, (void*)(uintptr_t)i, &status);
+      if (status == FIBER_OK) hello_done = true;
+    }
+  }
+
+  return NULL;
+}
+
+void* world(void *arg) {
+  uint32_t i = (uint32_t)(uintptr_t)arg;
+  static const char s[] = "el ol";
+
+  if (!world_done) {
+    putc(s[i], stdout);
+    i++;
+    i = (uint32_t)(uintptr_t)fiber_switch(hello_fiber, (void*)(uintptr_t)i, &status);
+    if (status == FIBER_OK) world_done = true;
+  }
+
+  return NULL;
+}
+
+int main(void) {
+  fiber_init();
+
+  hello_fiber = fiber_alloc(hello);
+  world_fiber = fiber_alloc(world);
+
+  hello_done = false;
+  world_done = false;
+
+  uint32_t i = 0;
+
+  (void)fiber_resume(hello_fiber, (void*)(uintptr_t)i, &status);
+
+  putc('\n', stdout);
+  fflush(stdout);
+
+  fiber_free(hello_fiber);
+  fiber_free(world_fiber);
+
+  fiber_finalize();
+  return 0;
+}

inc/fiber-switch.h

@@ -0,0 +1,56 @@
+/** A basic fiber interface. **/
+#ifndef WASMFX_FIBER_C_H
+#define WASMFX_FIBER_C_H
+
+#define export(NAME) __attribute__((export_name(NAME)))
+
+/** The signature of a fiber entry point. **/
+typedef void* (*fiber_entry_point_t)(void*);
+
+/** The abstract type of a fiber object. **/
+typedef struct fiber* 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);
+
+/** Yields control to its parent context. This function must be called
+    from within a fiber context. **/
+export("fiber_yield")
+void* fiber_yield(void *arg);
+
+/** Possible status codes for `fiber_switch`. **/
+typedef enum { FIBER_OK = 0, FIBER_YIELD = 1, FIBER_ERROR = 2 } fiber_result_t;
+
+/** Resumes 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 always be `NULL`. **/
+export("fiber_resume")
+void* fiber_resume(fiber_t fiber, void *arg, fiber_result_t *status);
+
+/** 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 always be `NULL`. **/
+export("fiber_switch")
+void* fiber_switch(fiber_t fiber, void *arg, fiber_result_t *status);
+
+/** Initialises the fiber runtime. It must be called exactly once
+    before using any of the other fiber_* functions. **/
+export("fiber_init")
+void fiber_init(void);
+
+/** Tears down the fiber runtime. It must be called after the final
+    use of any of the other fiber_* functions. **/
+export("fiber_finalize")
+void fiber_finalize(void);
+
+#undef export
+#endif