include/wvtask.h

   1 /* -*- Mode: C++ -*-
   2  * Worldvisions Weaver Software:
   3  *   Copyright (C) 1997-2002 Net Integration Technologies, Inc.
   4  *
   5  * A set of classes that provide co-operative multitasking support.  By
   6  * default there's no scheduler -- you have to provide it yourself.  As it
   7  * stands, this is just a convenient way to switch from one context to
   8  * another when you know exactly what you want to do.
   9  *
  10  * This is mainly intended for use by WvStream, but that's probably not the
  11  * only possible use... see also WvCont.
  12  */
  13 #ifndef __WVTASK_H
  14 #define __WVTASK_H
  15
  16 #ifdef _WIN32
  17
  18 #include "wvwin32task.h"
  19
  20 #else
  21
  22 #include "wvstring.h"
  23 #include "wvlinklist.h"
  24 #include "wvstreamsdebugger.h"
  25 #include "wvstringlist.h"
  26 #include "setjmp.h"
  27 #include <ucontext.h>
  28
  29 #define WVTASK_MAGIC 0x123678
  30
  31 class WvTaskMan;
  32
  33 /** Represents a single thread of control. */
  34 class WvTask
  35 {
  36     friend class WvTaskMan;
  37
  38     // you might think it would be useful to have this return an int, since
  39     // yield() and run() both return int.  But that ends up being more
  40     // confusing than you think, because if you call task1->run(), and he
  41     // calls task2->run(), and task2 calls yield(), then task1->run() returns
  42     // the value *task2* passed to yield!  So we avoid the confusion by not
  43     // using return values here, which discourages people from thinking of
  44     // them as return values.
  45     typedef void TaskFunc(void *userdata);
  46
  47     static int taskcount, numtasks, numrunning;
  48     int magic_number, *stack_magic;
  49     WvString name;
  50     int tid;
  51
  52     size_t stacksize;
  53     void *stack;
  54     bool running, recycled;
  55
  56     WvTaskMan &man;
  57     ucontext_t mystate; // used for resuming the task
  58     ucontext_t func_call, func_return;
  59
  60     TaskFunc *func;
  61     void *userdata;
  62
  63     WvTask(WvTaskMan &_man, size_t _stacksize = 64*1024);
  64
  65 public:
  66     virtual ~WvTask();
  67
  68     void start(WvStringParm _name, TaskFunc *_func, void *_userdata);
  69     bool isrunning() const
  70         { return running; }
  71     void recycle();
  72     int get_tid() const { return tid; }
  73     WvString get_name() const { return name; }
  74 };
  75
  76
  77 DeclareWvList(WvTask);
  78
  79 /** Provides co-operative multitasking support among WvTask instances. */
  80 class WvTaskMan
  81 {
  82     friend class WvTask;
  83
  84     static WvTaskMan *singleton;
  85     static int links;
  86
  87     static int magic_number;
  88     static WvTaskList all_tasks, free_tasks;
  89
  90     static void get_stack(WvTask &task, size_t size);
  91     static void stackmaster();
  92     static void _stackmaster();
  93     static void do_task();
  94     static void call_func(WvTask *task);
  95
  96     static char *stacktop;
  97     static ucontext_t stackmaster_task;
  98
  99     static WvTask *stack_target;
 100     static ucontext_t get_stack_return;
 101
 102     static WvTask *current_task;
 103     static ucontext_t toplevel;
 104
 105     WvTaskMan();
 106     virtual ~WvTaskMan();
 107
 108 #ifdef ENABLE_DELETE_DETECTOR
 109     friend void operator &&<WvTaskMan>(CheckIObject, const WvTaskMan *);
 110 #endif
 111
 112 public:
 113     /// get/dereference the singleton global WvTaskMan
 114     static WvTaskMan *get();
 115     static void unlink();
 116
 117     WvTask *start(WvStringParm name,
 118                   WvTask::TaskFunc *func, void *userdata,
 119                   size_t stacksize = 64*1024);
 120
 121     // run() and yield() return the 'val' passed to run() when this task
 122     // was started.
 123     static int run(WvTask &task, int val = 1);
 124     static int yield(int val = 1);
 125
 126     static WvTask *whoami()
 127         { return current_task; }
 128
 129     static const void *current_top_of_stack();
 130     static size_t current_stacksize_limit();
 131
 132 private:
 133     static WvString debugger_tasks_run_cb(WvStringParm, WvStringList &,
 134             WvStreamsDebugger::ResultCallback, void *);
 135 };
 136
 137
 138 #endif // ifdef _WIN32
 139 #endif // __WVTASK_H