TONY: Beginnings of refactoring Tony engine's threads to use coroutines

1 files changed, 271 insertions, 0 deletions

diff --git a/engines/tony/coroutine.h b/engines/tony/coroutine.h
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+++ b/engines/tony/coroutine.h
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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef TONY_COROUTINE_H
+#define TONY_COROUTINE_H
+
+#include "common/scummsys.h"
+#include "common/util.h"	// for SCUMMVM_CURRENT_FUNCTION
+
+namespace Tony {
+
+/**
+ * @defgroup TonyCoroutines	Coroutine support for Tony engine
+ *
+ * The following is loosely based on an article by Simon Tatham:
+ *   <http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html>.
+ * However, many improvements and tweaks have been made, in particular
+ * by taking advantage of C++ features not available in C.
+ */
+//@{
+
+
+// Enable this macro to enable some debugging support in the coroutine code.
+//#define COROUTINE_DEBUG	1
+
+/**
+ * The core of any coroutine context which captures the 'state' of a coroutine.
+ * Private use only.
+ */
+struct CoroBaseContext {
+	int _line;
+	int _sleep;
+	CoroBaseContext *_subctx;
+#if COROUTINE_DEBUG
+	const char *_funcName;
+#endif
+	CoroBaseContext(const char *func);
+	~CoroBaseContext();
+};
+
+typedef CoroBaseContext *CoroContext;
+
+
+// FIXME: Document this!
+extern CoroContext nullContext;
+
+/**
+ * Wrapper class which holds a pointer to a pointer to a CoroBaseContext.
+ * The interesting part is the destructor, which kills the context being held,
+ * but ONLY if the _sleep val of that context is zero. This way, a coroutine
+ * can just 'return' w/o having to worry about freeing the allocated context
+ * (in Simon Tatham's original code, one had to use a special macro to
+ * return from a coroutine).
+ */
+class CoroContextHolder {
+	CoroContext &_ctx;
+public:
+	CoroContextHolder(CoroContext &ctx) : _ctx(ctx) {
+		assert(ctx);
+		assert(ctx->_sleep >= 0);
+		ctx->_sleep = 0;
+	}
+	~CoroContextHolder() {
+		if (_ctx && _ctx->_sleep == 0) {
+			delete _ctx;
+			_ctx = 0;
+		}
+	}
+};
+
+
+#define CORO_PARAM    CoroContext &coroParam
+
+
+/**
+ * Begin the declaration of a coroutine context.
+ * This allows declaring variables which are 'persistent' during the
+ * lifetime of the coroutine. An example use would be:
+ *
+ *  CORO_BEGIN_CONTEXT;
+ *    int var;
+ *    char *foo;
+ *  CORO_END_CONTEXT(_ctx);
+ *
+ * It is not possible to initialize variables here, due to the way this
+ * macro is implemented. Furthermore, to use the variables declared in
+ * the coroutine context, you have to access them via the context variable
+ * name that was specified as parameter to CORO_END_CONTEXT, e.g.
+ *   _ctx->var = 0;
+ *
+ * @see CORO_END_CONTEXT
+ *
+ * @note We declare a variable 'DUMMY' to allow the user to specify an 'empty'
+ * context, and so compilers won't complain about ";" following the macro.
+ */
+#define CORO_BEGIN_CONTEXT  \
+	struct CoroContextTag : CoroBaseContext { \
+		CoroContextTag() : CoroBaseContext(SCUMMVM_CURRENT_FUNCTION) {} \
+		int DUMMY
+
+/**
+ * End the declaration of a coroutine context.
+ * @param x	name of the coroutine context
+ * @see CORO_BEGIN_CONTEXT
+ */
+#define CORO_END_CONTEXT(x)    } *x = (CoroContextTag *)coroParam
+
+/**
+ * Begin the code section of a coroutine.
+ * @param x	name of the coroutine context
+ * @see CORO_BEGIN_CODE
+ */
+#define CORO_BEGIN_CODE(x) \
+		if (&coroParam == &nullContext) assert(!nullContext);\
+		if (!x) {coroParam = x = new CoroContextTag();}\
+		CoroContextHolder tmpHolder(coroParam);\
+		switch (coroParam->_line) { case 0:;
+
+/**
+ * End the code section of a coroutine.
+ * @see CORO_END_CODE
+ */
+#define CORO_END_CODE \
+			if (&coroParam == &nullContext) { \
+				delete nullContext; \
+				nullContext = NULL; \
+			} \
+		}
+
+/**
+ * Sleep for the specified number of scheduler cycles.
+ */
+#define CORO_SLEEP(delay) do {\
+			coroParam->_line = __LINE__;\
+			coroParam->_sleep = delay;\
+			assert(&coroParam != &nullContext);\
+			return; case __LINE__:;\
+		} while (0)
+
+#define CORO_GIVE_WAY do { g_scheduler->giveWay(); CORO_SLEEP(1); } while (0)
+#define CORO_RESCHEDULE do { g_scheduler->reschedule(); CORO_SLEEP(1); } while (0)
+
+/**
+ * Stop the currently running coroutine and all calling coroutines.
+ *
+ * This sets _sleep to -1 rather than 0 so that the context doesn't get
+ * deleted by CoroContextHolder, since we want CORO_INVOKE_ARGS to
+ * propogate the _sleep value and return immediately (the scheduler will
+ * then delete the entire coroutine's state, including all subcontexts).
+ */
+#define CORO_KILL_SELF() \
+		do { if (&coroParam != &nullContext) { coroParam->_sleep = -1; } return; } while (0)
+
+
+/**
+ * This macro is to be used in conjunction with CORO_INVOKE_ARGS and
+ * similar macros for calling coroutines-enabled subroutines.
+ */
+#define CORO_SUBCTX   coroParam->_subctx
+
+/**
+ * Invoke another coroutine.
+ *
+ * If the subcontext still exists after the coroutine is invoked, it has
+ * either yielded/slept or killed itself, and so we copy the _sleep value
+ * to our own context and return (execution will continue at the case
+ * statement below, where we loop and call the coroutine again).
+ * If the subcontext is null, the coroutine ended normally, and we can
+ * simply break out of the loop and continue execution.
+ *
+ * @param subCoro	name of the coroutine-enabled function to invoke
+ * @param ARGS		list of arguments to pass to subCoro
+ *
+ * @note ARGS must be surrounded by parentheses, and the first argument
+ *       in this list must always be CORO_SUBCTX. For example, the
+ *       regular function call
+ *          myFunc(a, b);
+ *       becomes the following:
+ *          CORO_INVOKE_ARGS(myFunc, (CORO_SUBCTX, a, b));
+ */
+#define CORO_INVOKE_ARGS(subCoro, ARGS)  \
+		do {\
+			coroParam->_line = __LINE__;\
+			coroParam->_subctx = 0;\
+			do {\
+				subCoro ARGS;\
+				if (!coroParam->_subctx) break;\
+				coroParam->_sleep = coroParam->_subctx->_sleep;\
+				assert(&coroParam != &nullContext);\
+				return; case __LINE__:;\
+			} while (1);\
+		} while (0)
+
+/**
+ * Invoke another coroutine. Similar to CORO_INVOKE_ARGS,
+ * but allows specifying a return value which is returned
+ * if invoked coroutine yields (thus causing the current
+ * coroutine to yield, too).
+ */
+#define CORO_INVOKE_ARGS_V(subCoro, RESULT, ARGS)  \
+		do {\
+			coroParam->_line = __LINE__;\
+			coroParam->_subctx = 0;\
+			do {\
+				subCoro ARGS;\
+				if (!coroParam->_subctx) break;\
+				coroParam->_sleep = coroParam->_subctx->_sleep;\
+				assert(&coroParam != &nullContext);\
+				return RESULT; case __LINE__:;\
+			} while (1);\
+		} while (0)
+
+/**
+ * Convenience wrapper for CORO_INVOKE_ARGS for invoking a coroutine
+ * with no parameters.
+ */
+#define CORO_INVOKE_0(subCoroutine) \
+			CORO_INVOKE_ARGS(subCoroutine,(CORO_SUBCTX))
+
+/**
+ * Convenience wrapper for CORO_INVOKE_ARGS for invoking a coroutine
+ * with one parameter.
+ */
+#define CORO_INVOKE_1(subCoroutine, a0) \
+			CORO_INVOKE_ARGS(subCoroutine,(CORO_SUBCTX,a0))
+
+/**
+ * Convenience wrapper for CORO_INVOKE_ARGS for invoking a coroutine
+ * with two parameters.
+ */
+#define CORO_INVOKE_2(subCoroutine, a0,a1) \
+			CORO_INVOKE_ARGS(subCoroutine,(CORO_SUBCTX,a0,a1))
+
+/**
+ * Convenience wrapper for CORO_INVOKE_ARGS for invoking a coroutine
+ * with three parameters.
+ */
+#define CORO_INVOKE_3(subCoroutine, a0,a1,a2) \
+			CORO_INVOKE_ARGS(subCoroutine,(CORO_SUBCTX,a0,a1,a2))
+
+/**
+ * Convenience wrapper for CORO_INVOKE_ARGS for invoking a coroutine
+ * with four parameters.
+ */
+#define CORO_INVOKE_4(subCoroutine, a0,a1,a2,a3) \
+			CORO_INVOKE_ARGS(subCoroutine,(CORO_SUBCTX,a0,a1,a2,a3))
+
+//@}
+
+} // End of namespace Tony
+
+#endif		// TONY_COROUTINE_H