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89 lines
3.1 KiB
C
89 lines
3.1 KiB
C
#ifndef COROUTINE_ASYNCIFY_CONTEXT_H
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#define COROUTINE_ASYNCIFY_CONTEXT_H
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/*
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This is a coroutine implementation based on Binaryen's Asyncify transformation for WebAssembly.
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This implementation is built on low-level ucontext-like API in wasm/fiber.c
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This file is an adapter for the common coroutine interface and for stack manipulation.
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wasm/fiber.c doesn't take care of stack to avoid duplicate management with this adapter.
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* See also: wasm/fiber.c
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*/
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#include <stddef.h>
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#include <stdio.h>
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#include "wasm/asyncify.h"
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#include "wasm/machine.h"
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#include "wasm/fiber.h"
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#define COROUTINE void __attribute__((__noreturn__))
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static const int ASYNCIFY_CORO_DEBUG = 0;
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struct coroutine_context
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{
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rb_wasm_fiber_context fc;
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void *argument;
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struct coroutine_context *from;
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void *current_sp;
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void *stack_base;
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size_t size;
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};
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typedef COROUTINE(* coroutine_start)(struct coroutine_context *from, struct coroutine_context *self);
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COROUTINE coroutine_trampoline(void * _start, void * _context);
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static inline void coroutine_initialize_main(struct coroutine_context * context)
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{
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if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] entry (context = %p)\n", __func__, context);
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// NULL fiber entry means it's the main fiber, and handled specially.
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rb_wasm_init_context(&context->fc, NULL, NULL, NULL);
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// mark the main fiber has already started
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context->fc.is_started = true;
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}
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static inline void coroutine_initialize(struct coroutine_context *context, coroutine_start start, void *stack, size_t size)
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{
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if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] entry (context = %p, stack = %p ... %p)\n", __func__, context, stack, (char *)stack + size);
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rb_wasm_init_context(&context->fc, coroutine_trampoline, start, context);
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// record the initial stack pointer position to restore it after resumption
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context->current_sp = (char *)stack + size;
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context->stack_base = stack;
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context->size = size;
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}
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static inline struct coroutine_context * coroutine_transfer(struct coroutine_context * current, struct coroutine_context * target)
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{
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if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] entry (current = %p, target = %p)\n", __func__, current, target);
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struct coroutine_context * previous = target->from;
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target->from = current;
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if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] current->current_sp = %p -> %p\n", __func__, current->current_sp, rb_wasm_get_stack_pointer());
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// record the current stack pointer position to restore it after resumption
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current->current_sp = rb_wasm_get_stack_pointer();
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// suspend the current coroutine and resume another coroutine
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rb_wasm_swapcontext(¤t->fc, &target->fc);
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// after the original coroutine resumed
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rb_wasm_set_stack_pointer(current->current_sp);
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target->from = previous;
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return target;
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}
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static inline void coroutine_destroy(struct coroutine_context * context)
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{
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if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] entry (context = %p)\n", __func__, context);
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context->stack_base = NULL;
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context->size = 0;
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context->from = NULL;
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}
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#endif /* COROUTINE_ASYNCIFY_CONTEXT_H */
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