139 lines
4.7 KiB
C
139 lines
4.7 KiB
C
/*************************************************************************
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* *
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* Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith. *
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* All rights reserved. Email: russ@q12.org Web: www.q12.org *
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* *
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* This library is free software; you can redistribute it and/or *
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* modify it under the terms of EITHER: *
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* (1) The GNU Lesser General Public License as published by the Free *
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* Software Foundation; either version 2.1 of the License, or (at *
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* your option) any later version. The text of the GNU Lesser *
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* General Public License is included with this library in the *
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* file LICENSE.TXT. *
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* (2) The BSD-style license that is included with this library in *
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* the file LICENSE-BSD.TXT. *
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* *
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* This library is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files *
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* LICENSE.TXT and LICENSE-BSD.TXT for more details. *
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* *
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*************************************************************************/
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/* this comes from the `reuse' library. copy any changes back to the source.
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these stack allocation functions are a replacement for alloca(), except that
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they allocate memory from a separate pool.
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advantages over alloca():
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- consecutive allocations are guaranteed to be contiguous with increasing
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address.
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- functions can allocate stack memory that is returned to the caller,
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in other words pushing and popping stack frames is optional.
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disadvantages compared to alloca():
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- less portable
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- slightly slower, although still orders of magnitude faster than malloc().
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- longjmp() and exceptions do not deallocate stack memory (but who cares?).
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just like alloca():
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- using too much stack memory does not fail gracefully, it fails with a
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segfault.
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*/
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#ifndef _ODE_STACK_H_
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#define _ODE_STACK_H_
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#ifdef WIN32
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#include "windows.h"
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#endif
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struct dStack {
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char *base; // bottom of the stack
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int size; // maximum size of the stack
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char *pointer; // current top of the stack
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char *frame; // linked list of stack frame ptrs
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# ifdef WIN32 // stuff for windows:
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int pagesize; // - page size - this is ASSUMED to be a power of 2
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int committed; // - bytes committed in allocated region
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#endif
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// initialize the stack. `max_size' is the maximum size that the stack can
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// reach. on unix and windows a `virtual' memory block of this size is
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// mapped into the address space but does not actually consume physical
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// memory until it is referenced - so it is safe to set this to a high value.
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void init (int max_size);
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// destroy the stack. this unmaps any virtual memory that was allocated.
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void destroy();
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// allocate `size' bytes from the stack and return a pointer to the allocated
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// memory. `size' must be >= 0. the returned pointer will be aligned to the
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// size of a long int.
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char * alloc (int size)
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{
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char *ret = pointer;
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pointer += ((size-1) | (sizeof(long int)-1) )+1;
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# ifdef WIN32
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// for windows we need to commit pages as they are required
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if ((pointer-base) > committed) {
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committed = ((pointer-base-1) | (pagesize-1))+1; // round up to pgsize
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VirtualAlloc (base,committed,MEM_COMMIT,PAGE_READWRITE);
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}
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# endif
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return ret;
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}
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// return the address that will be returned by the next call to alloc()
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char *nextAlloc()
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{
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return pointer;
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}
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// push and pop the current size of the stack. pushFrame() saves the current
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// frame pointer on the stack, and popFrame() retrieves it. a typical
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// stack-using function will bracket alloc() calls with pushFrame() and
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// popFrame(). both functions return the current stack pointer - this should
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// be the same value for the two bracketing calls. calling popFrame() too
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// many times will result in a segfault.
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char * pushFrame()
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{
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char *newframe = pointer;
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char **addr = (char**) alloc (sizeof(char*));
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*addr = frame;
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frame = newframe;
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return newframe;
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/* OLD CODE
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*((char**)pointer) = frame;
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frame = pointer;
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char *ret = pointer;
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pointer += sizeof(char*);
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return ret;
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*/
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}
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char * popFrame()
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{
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pointer = frame;
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frame = *((char**)pointer);
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return pointer;
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}
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};
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#endif
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