From 53ad16b79a6cf2ef4f94e282cf5fc0d50b37d2b1 Mon Sep 17 00:00:00 2001
From: Rain <rain.by.zhou@gmail.com>
Date: Sat, 22 Jan 2022 21:03:38 +0800
Subject: [PATCH] add cops impl

Signed-off-by: Rain <rain.by.zhou@gmail.com>
---
 .gitignore       |  2 ++
 build.sh         |  3 +++
 context.cpp      | 28 ++++++++++++++++++++
 context.h        | 68 ++++++++++++++++++++++++++++++++++++++++++++++++
 main.cpp         | 26 ++++++++++++++++++
 switch_context.S | 48 ++++++++++++++++++++++++++++++++++
 6 files changed, 175 insertions(+)
 create mode 100755 build.sh
 create mode 100644 context.cpp
 create mode 100644 context.h
 create mode 100644 main.cpp
 create mode 100644 switch_context.S

diff --git a/.gitignore b/.gitignore
index 259148f..e7790e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,8 @@
 # Prerequisites
 *.d
 
+cops
+
 # Compiled Object files
 *.slo
 *.lo
diff --git a/build.sh b/build.sh
new file mode 100755
index 0000000..c2105ca
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+g++ -g -std=c++17 -I. *.cpp *.S -o cops
diff --git a/context.cpp b/context.cpp
new file mode 100644
index 0000000..176b694
--- /dev/null
+++ b/context.cpp
@@ -0,0 +1,28 @@
+#include <context.h>
+#include <iostream>
+
+namespace cops{
+
+static coro_t def([](){});
+coro_t* current = &def;
+
+void main(coro_t* coro, context from) {
+  coro->next_->ctx_ = from;
+  coro->fn_();
+  coro->switch_out();
+}
+
+void coro_t::switch_out() {
+  current = next_;
+  context from = switch_context(next_, next_->ctx_);
+  next_ = static_cast<coro_t*>(from);
+  next_->ctx_ = from;
+}
+
+void coro_t::switch_in() {
+  next_ = current;
+  current = this;
+  ctx_ = switch_context(this, ctx_);
+}
+
+}
diff --git a/context.h b/context.h
new file mode 100644
index 0000000..2084e93
--- /dev/null
+++ b/context.h
@@ -0,0 +1,68 @@
+#pragma once
+
+#include <memory>
+#include <functional>
+#include <stdint.h>
+
+namespace cops {
+class coro_t;
+}
+
+using context = void*;
+
+extern "C"
+context switch_context(cops::coro_t* to, context ctx);
+extern "C"
+context make_context(context sp, void* entry);
+
+namespace cops {
+
+class stack_t {
+public:
+  stack_t(size_t size = 64 * 1024) : size_(size) {
+    sp_ = new char[size_];
+  }
+  ~stack_t() {
+    delete[] sp_;
+  }
+
+  void* sp() {
+    return sp_ + size_ - 1;
+  }
+
+private:
+  char* sp_;
+  size_t size_;
+};
+
+class coro_t {
+public:
+  using Fn = std::function<void(void)>;
+
+  explicit coro_t(Fn&& fn)
+    : fn_(std::forward<Fn>(fn)) {
+  }
+  ~coro_t() {
+  }
+
+  void switch_out();
+  void switch_in();
+
+public:
+  context ctx_;
+  coro_t* next_;
+  stack_t stack_;
+  Fn fn_;
+};
+
+extern coro_t* current;
+void main(coro_t* coro, context ctx);
+
+template <class Fn>
+std::unique_ptr<coro_t> make_coro(Fn&& fn) {
+  auto coro = std::make_unique<coro_t>(std::forward<Fn>(fn));
+  coro->ctx_ = make_context(coro->stack_.sp(), (void*)main);
+  return coro;
+}
+
+} // cops
diff --git a/main.cpp b/main.cpp
new file mode 100644
index 0000000..4d4a10d
--- /dev/null
+++ b/main.cpp
@@ -0,0 +1,26 @@
+#include <iostream>
+#include <context.h>
+
+int main() {
+  std::unique_ptr<cops::coro_t> coro;
+  std::unique_ptr<cops::coro_t> sub_coro;
+  coro = cops::make_coro([&sub_coro]() {
+      std::cout << "coro" << std::endl;
+      cops::current->switch_out();
+      sub_coro = cops::make_coro([]() {
+          std::cout << "sub_coro" << std::endl;
+          cops::current->switch_out();
+          std::cout << "sub_coro exit" << std::endl;
+        });
+      sub_coro->switch_in();
+      std::cout << "coro exit" << std::endl;
+    });
+  std::cout << "main" << std::endl;
+  coro->switch_in();
+  std::cout << "main" << std::endl;
+  coro->switch_in();
+  std::cout << "main" << std::endl;
+  sub_coro->switch_in();
+  std::cout << "exit" << std::endl;
+  return 0;
+}
diff --git a/switch_context.S b/switch_context.S
new file mode 100644
index 0000000..352dba0
--- /dev/null
+++ b/switch_context.S
@@ -0,0 +1,48 @@
+.file "switch_context.S"
+.text
+.globl switch_context
+.type switch_context,@function
+.align 16
+switch_context:
+    leaq  -56(%rsp), %rsp
+    movq  %rdi, (%rsp)    /* save suspended coro_t* */
+
+    movq  %r12, 8(%rsp)
+    movq  %r13, 16(%rsp)
+    movq  %r14, 24(%rsp)
+    movq  %r15, 32(%rsp)
+    movq  %rbx, 40(%rsp)
+    movq  %rbp, 48(%rsp)
+
+    movq  %rsp, %rax     /* return suspended context */
+
+    movq  %rsi, %rsp     /* restore context */
+    movq  56(%rsp), %r8  /* return point */
+
+    movq  8(%rsp), %r12
+    movq  16(%rsp), %r13
+    movq  24(%rsp), %r14
+    movq  32(%rsp), %r15
+    movq  40(%rsp), %rbx
+    movq  48(%rsp), %rbp
+
+    leaq  64(%rsp), %rsp
+
+    movq  %rax, %rsi    /* for main(coro_t*, context) 2rd argument */
+
+    jmp  *%r8
+.size switch_context,.-switch_context
+.section .note.GNU-stack,"",%progbits
+
+.text
+.globl make_context
+.type make_context,@function
+.align 16
+make_context:
+    andq  $-16, %rdi      /* 16 bytes align for movdqa */
+    leaq  -56(%rdi), %rdi
+    movq  %rsi, 56(%rdi)  /* set entry */
+    movq  %rdi, %rax      /* return updated context */
+    retq
+.size make_context,.-make_context
+.section .note.GNU-stack,"",%progbits