var.cpp

/*
AutoHotkey

Copyright 2003-2009 Chris Mallett (support@autohotkey.com)

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.
*/

#include "stdafx.h" // pre-compiled headers
#include "defines.h"
#include "script_object.h"
#include "var.h"
#include "globaldata.h" // for g_script
#include <utility>


// Init static vars:
TCHAR Var::sEmptyString[] = _T(""); // For explanation, see its declaration in .h file.


ResultType Var::AssignHWND(HWND aWnd)
{
	return Assign((size_t)aWnd);
}



ResultType Var::Assign(Var &aVar)
// Assign some other variable to the "this" variable.
// source_var->Type() must be VAR_NORMAL, but this->Type() can be VAR_VIRTUAL.
// Returns OK or FAIL.
{
	Var &target_var = *ResolveAlias();
	Var &source_var = *aVar.ResolveAlias();

	if (source_var.mAttrib & VAR_ATTRIB_UNINITIALIZED)
	{
		target_var.Uninitialize();
		return OK;
	}

	switch (source_var.mAttrib & VAR_ATTRIB_TYPES) // This switch() method should squeeze a little more performance out of it compared to doing "&" for every attribute.  Only works for attributes that are mutually-exclusive, which these are.
	{
	case VAR_ATTRIB_IS_INT64:
		return target_var.Assign(source_var.mContentsInt64);
	case VAR_ATTRIB_IS_DOUBLE:
		return target_var.Assign(source_var.mContentsDouble);
	case VAR_ATTRIB_IS_OBJECT:
		return target_var.Assign(source_var.mObject);
	}
	// Otherwise:
	return target_var.Assign(source_var.mCharContents, source_var._CharLength()); // Pass length to improve performance. It isn't necessary to call Contents()/Length() because they must be already up-to-date because there is no binary number to update them from (if there were, the above would have returned).  Also, caller ensured Type()==VAR_NORMAL.
}



ResultType Var::Assign(ExprTokenType &aToken)
// Returns OK or FAIL.
// Writes aToken's value into aOutputVar based on the type of the token.
// Caller must ensure that aToken.symbol is an operand (not an operator or other symbol).
{
	if (mType == VAR_VIRTUAL)
	{
		if (aToken.symbol == SYM_MISSING)
			return g_script.RuntimeError(ERR_INVALID_ASSIGNMENT);
		return AssignVirtual(aToken);
	}
	switch (aToken.symbol)
	{
	case SYM_STRING:  return Assign(aToken.marker, aToken.marker_length);
	case SYM_INTEGER: return Assign(aToken.value_int64); // Listed first for performance because it's Likely the most common from our callers.
	case SYM_VAR:     return Assign(*aToken.var);
	case SYM_OBJECT:  return Assign(aToken.object);
	case SYM_FLOAT:   return Assign(aToken.value_double); // Listed last because it's probably the least common.
	default:
		ASSERT(!"Unhandled symbol");
	case SYM_MISSING:
		return Uninitialize() ? OK : FAIL;
	}
	// Since above didn't return, it can only be SYM_STRING.
	return Assign(aToken.marker, aToken.marker_length);
}



ResultType Var::AssignVirtual(ExprTokenType &aValue)
{
	if (!mVV->Set) // Might be impossible due to prior validation of assignments/output vars.
		return g_script.VarIsReadOnlyError(this);
	FuncResult result_token;
	mVV->Set(result_token, mName, aValue);
	return result_token.Result();
}



ResultType Var::PopulateVirtualVar()
{
	FuncResult result_token;
	result_token.symbol = SYM_INTEGER; // For _f_return_i() and consistency with BIFs.
	mVV->Get(result_token, mName);
	if (result_token.Exited())
		return FAIL;
	if (result_token.mem_to_free)
	{
		_AcceptNewMem(result_token.mem_to_free, result_token.marker_length);
		mAttrib |= VAR_ATTRIB_VIRTUAL_OPEN;
		return OK;
	}
	size_t length;
	LPTSTR value = TokenToString(result_token, result_token.buf, &length);
	if (!AssignString(nullptr, length))
		return FAIL;
	tmemcpy(mCharContents, value, length + 1);
	return OK;
}



void Var::UpdateAlias(Var *aTargetVar)
// Caller must ensure that aTargetVar isn't NULL.
// When this function actually converts a normal variable into an alias , the variable's old
// attributes (especially mContents and mCapacity) are hidden/suppressed by virtue of all Var::
// methods obeying VAR_ALIAS and resolving it to be the target variable.  This prevents a memory
// leak in a case where a UDF is defined to provide a default value for a ByRef parameter, and is
// called both with and without that parameter.
{
	IObject *ref = aTargetVar->mType == VAR_ALIAS && aTargetVar->IsObject()
		? aTargetVar->mObject : nullptr;

	// BELOW IS THE MEANS BY WHICH ALIASES AREN'T ALLOWED TO POINT TO OTHER ALIASES, ONLY DIRECTLY TO
	// THE TARGET VAR.
	// Resolve aliases-to-aliases for performance.  A caller may ask to create an alias
	// to an alias when a function calls another function and passes to it one of its own
	// byref-params, or if the target var has had its reference taken with GetRef().
	while (aTargetVar->mType == VAR_ALIAS)
		aTargetVar = aTargetVar->mAliasFor;

	// The following is done only after the above in case there's ever a way for the above
	// to circle back to become this variable.
	// Prevent potential infinite loops in other methods by refusing to change an alias
	// to point to itself.
	if (aTargetVar == this)
		return;

	SetAliasDirect(aTargetVar);
	
	// Done last in case it causes interruption:
	ASSERT(!IsObject());
	//if (IsObject())
	//	ReleaseObject();
	if (ref)
	{
		_SetObject(ref);
		ref->AddRef();
	}
}



void Var::UpdateAlias(VarRef *aTargetVar)
{
	ASSERT(!IsObject());
	SetAliasDirect(aTargetVar);
	_SetObject(aTargetVar);
	aTargetVar->AddRef();
}



IObject *Var::GetRef()
{
	auto target_var = this;
	if (mType == VAR_ALIAS)
	{
		if (mAttrib & VAR_ATTRIB_IS_OBJECT)
		{
			mObject->AddRef();
			return mObject;
		}
		target_var = mAliasFor;
	}
	auto ref = new VarRef();
	if (!target_var->MoveToNewFreeVar(*ref))
	{
		ref->Release();
		return nullptr;
	}
	if (mType == VAR_ALIAS)
		target_var->UpdateAlias(ref);
	UpdateAlias(ref);
	return ref;
}



ResultType Var::MoveToNewFreeVar(Var &aFV)
{
	ASSERT(aFV.mType == VAR_NORMAL && mType == VAR_NORMAL);
	ASSERT(aFV.mHowAllocated == ALLOC_MALLOC);
	aFV.mName = mName;   // For error reporting.
	aFV.mScope = mScope | VAR_VARREF; // Flag it as a VarRef to allow ToReturnValue to safely optimize.
	if (mAttrib & VAR_ATTRIB_TYPES)
	{
		aFV.mContentsInt64 = mContentsInt64;
		aFV.mAttrib = (mAttrib & (VAR_ATTRIB_TYPES | VAR_ATTRIB_CACHE))
			| VAR_ATTRIB_CONTENTS_OUT_OF_DATE;
		mAttrib &= ~VAR_ATTRIB_TYPES; // Mainly to remove VAR_ATTRIB_IS_OBJECT.
	}
#if 0
	// The following is currently not used because:
	//  - It causes the capacity of the variable to change (possibly reset to 0), which is bad if
	//    VarSetStrCapacity(&v, n) was used.  GetRef() wouldn't have been called by it because of
	//    optimization of OutputVar parameters.
	//  - At worst, a small amount of memory per unique variable is reserved and won't be reused
	//    from this point on, the same as if its capacity increased beyond MAX_ALLOC_SIMPLE.
	//  - If the variable isn't empty, it's likely that this action will be repeateded each time
	// 	  the function is called; i.e. malloc will be used by aFV.Assign() and the string will be
	// 	  copied, when it would be more efficient to malloc at a earlier point and swap vs. copy.
	//  - In the most common cases, GetRef() is used when capacity is 0.
	// An alternative would be to change VarSetStrCapacity() to always GetRef(), but that would be
	// detrimental for optimizing string concatenation, which is its recommended purpose.
	else if (mHowAllocated == ALLOC_SIMPLE && !(mScope & (VAR_GLOBAL | VAR_LOCAL_STATIC)))
	{
		// Don't transfer a SimpleHeap buffer to freevars since that would cause the
		// buffer to be lost permanently when the freevar is deleted (such as after
		// the function returns and the VarRef's reference count reaches 0).
		if (!aFV.Assign(mCharContents, CharLength()))
			return FAIL;
		//mAttrib = VAR_ATTRIB_UNINITIALIZED;
		//*mCharContents = '\0';
		//mByteLength = 0;
		return OK;
	}
#endif
	else
	{
		if (!(mAttrib & VAR_ATTRIB_UNINITIALIZED))
		{
			aFV.mAttrib &= ~VAR_ATTRIB_UNINITIALIZED;
			mAttrib |= VAR_ATTRIB_UNINITIALIZED;
		}
	}
	std::swap(aFV.mHowAllocated, mHowAllocated);
	std::swap(aFV.mByteContents, mByteContents);
	std::swap(aFV.mByteCapacity, mByteCapacity);
	std::swap(aFV.mByteLength, mByteLength);
	return OK;
}



ResultType Var::GetClipboardAll(void **aData, size_t *aDataSize)
{
	*aData = NULL; // Set default in case of early return or empty data.
	*aDataSize = 0;

	if (!g_clip.Open())
		return g_script.RuntimeError(CANT_OPEN_CLIPBOARD_READ);

	// Calculate the size needed:
	// EnumClipboardFormats() retrieves all formats, including synthesized formats that don't
	// actually exist on the clipboard but are instead constructed on demand.  Unfortunately,
	// there doesn't appear to be any way to reliably determine which formats are real and
	// which are synthesized (if there were such a way, a large memory savings could be
	// realized by omitting the synthesized formats from the saved version). One thing that
	// is certain is that the "real" format(s) come first and the synthesized ones afterward.
	// However, that's not quite enough because although it is recommended that apps store
	// the primary/preferred format first, the OS does not enforce this.  For example, testing
	// shows that the apps do not have to store CF_UNICODETEXT prior to storing CF_TEXT,
	// in which case the clipboard might have inaccurate CF_TEXT as the first element and
	// more accurate/complete (non-synthesized) CF_UNICODETEXT stored as the next.
	// In spite of the above, the below seems likely to be accurate 99% or more of the time,
	// which seems worth it given the large savings of memory that are achieved, especially
	// for large quantities of text or large images. Confidence is further raised by the
	// fact that MSDN says there's no advantage/reason for an app to place multiple formats
	// onto the clipboard if those formats are available through synthesis.
	// And since CF_TEXT always(?) yields synthetic CF_OEMTEXT and CF_UNICODETEXT, and
	// probably (but less certainly) vice versa: if CF_TEXT is listed first, it might certainly
	// mean that the other two do not need to be stored.  There is some slight doubt about this
	// in a situation where an app explicitly put CF_TEXT onto the clipboard and then followed
	// it with CF_UNICODETEXT that isn't synthesized, nor does it match what would have been
	// synthesized. However, that seems extremely unlikely (it would be much more likely for
	// an app to store CF_UNICODETEXT *first* followed by custom/non-synthesized CF_TEXT, but
	// even that might be unheard of in practice).  So for now -- since there is no documentation
	// to be found about this anywhere -- it seems best to omit some of the most common
	// synthesized formats:
	// CF_TEXT is the first of three text formats to appear: Omit CF_OEMTEXT and CF_UNICODETEXT.
	//    (but not vice versa since those are less certain to be synthesized)
	//    (above avoids using four times the amount of memory that would otherwise be required)
	//    UPDATE: Only the first text format is included now, since MSDN says there is no
	//    advantage/reason to having multiple non-synthesized text formats on the clipboard.
	//    UPDATE: MS Word 2010 (and perhaps other versions) stores CF_TEXT before CF_UNICODETEXT,
	//    even when CF_TEXT is incomplete/inaccurate. Since there's no way to know whether it was
	//    synthesized, it is now stored unconditionally. CF_TEXT and CF_OEMTEXT are discarded to
	//    save memory and because they should always be synthesized correctly.
	// CF_DIB: Always omit this if CF_DIBV5 is available (which must be present on Win2k+, at least
	// as a synthesized format, whenever CF_DIB is present?) This policy seems likely to avoid
	// the issue where CF_DIB occurs first yet CF_DIBV5 that comes later is *not* synthesized,
	// perhaps simply because the app stored DIB prior to DIBV5 by mistake (though there is
	// nothing mandatory, so maybe it's not really a mistake). Note: CF_DIBV5 supports alpha
	// channel / transparency, and perhaps other things, and it is likely that when synthesized,
	// no information of the original CF_DIB is lost. Thus, when CF_DIBV5 is placed back onto
	// the clipboard, any app that needs CF_DIB will have it synthesized back to the original
	// data (hopefully). It's debatable whether to do it that way or store whichever comes first
	// under the theory that an app would never store both formats on the clipboard since MSDN
	// says: "If the system provides an automatic type conversion for a particular clipboard format,
	// there is no advantage to placing the conversion format(s) on the clipboard."
	HGLOBAL hglobal;
	UINT size; // Make it 32-bit even on x64 to allow clipboard data to be used between x86 and x64.
	UINT format;
	VarSizeType space_needed;
	UINT dib_format_to_omit = 0;
	BOOL save_null_data;
	// Start space_needed off at 4 to allow room for guaranteed final termination of the variable's contents.
	// The termination must be of the same size as format because a single-byte terminator would
	// be read in as a format of 0x00?????? where ?????? is an access violation beyond the buffer.
	for (space_needed = sizeof(format), format = 0; format = EnumClipboardFormats(format);)
	{
		switch (format)
		{
		case CF_BITMAP:
		case CF_ENHMETAFILE:
		case CF_DSPENHMETAFILE:
			// These formats appear to be specific handle types, not always safe to call GlobalSize() for.
			continue;
		}
		// No point in calling GetLastError() since it would never be executed because the loop's
		// condition breaks on zero return value.
		if (format == CF_TEXT || format == CF_OEMTEXT // This format is excluded in favour of CF_UNICODETEXT.
			|| format == dib_format_to_omit) // ... or this format was marked excluded by a prior iteration.
			continue;
		// GetClipboardData() causes Task Manager to report a (sometimes large) increase in
		// memory utilization for the script, which is odd since it persists even after the
		// clipboard is closed.  However, when something new is put onto the clipboard by the
		// the user or any app, that memory seems to get freed automatically.  Also, 
		// GetClipboardData(49356) fails in MS Visual C++ when the copied text is greater than
		// about 200 KB (but GetLastError() returns ERROR_SUCCESS).  When pasting large sections
		// of colorized text into MS Word, it can't get the colorized text either (just the plain
		// text). Because of this example, it seems likely it can fail in other places or under
		// other circumstances, perhaps by design of the app. Therefore, be tolerant of failures
		// because partially saving the clipboard seems much better than aborting the operation.
		if (hglobal = g_clip.GetClipboardDataTimeout(format, &save_null_data))
		{
			space_needed += (VarSizeType)(sizeof(format) + sizeof(size) + GlobalSize(hglobal)); // The total amount of storage space required for this item.
			if (!dib_format_to_omit)
			{
				if (format == CF_DIB)
					dib_format_to_omit = CF_DIBV5;
				else if (format == CF_DIBV5)
					dib_format_to_omit = CF_DIB;
			}
			// Currently CF_ENHMETAFILE isn't supported, so no need for this section:
			//if (!meta_format_to_omit) // Checked for the same reasons as dib_format_to_omit.
			//{
			//	if (format == CF_ENHMETAFILE)
			//		meta_format_to_omit = CF_METAFILEPICT;
			//	else if (format == CF_METAFILEPICT)
			//		meta_format_to_omit = CF_ENHMETAFILE;
			//}
		}
		else if (save_null_data)
			space_needed += (VarSizeType)(sizeof(format) + sizeof(size));
		//else omit this format from consideration.
	}

	if (space_needed == sizeof(format)) // This works because even a single empty format requires space beyond sizeof(format) for storing its format+size.
	{
		g_clip.Close();
		return OK;
	}

	if (space_needed & 1)
		++space_needed; // Ensure it's a multiple of WCHAR.

	LPVOID binary_contents;
	
	// Allocate buffer.
	*aData = binary_contents = malloc(space_needed);
	
	if (!binary_contents)
	{
		g_clip.Close();
		return MemoryError();
	}

	// Retrieve and store all the clipboard formats.  Because failures of GetClipboardData() are now
	// tolerated, it seems safest to recalculate the actual size (actual_space_needed) of the data
	// in case it varies from that found in the estimation phase.  This is especially necessary in
	// case GlobalLock() ever fails, since that isn't even attempted during the estimation phase.
	// Otherwise, the variable's mLength member would be set to something too high (the estimate),
	// which might cause problems elsewhere.
	LPVOID hglobal_locked;
	VarSizeType added_size, actual_space_used;
	for (actual_space_used = sizeof(format), format = 0; format = EnumClipboardFormats(format);)
	{
		switch (format)
		{
		case CF_BITMAP:
		case CF_ENHMETAFILE:
		case CF_DSPENHMETAFILE:
			// These formats appear to be specific handle types, not always safe to call GlobalSize() for.
			continue;
		}
		// No point in calling GetLastError() since it would never be executed because the loop's
		// condition breaks on zero return value.
		if (format == CF_TEXT || format == CF_OEMTEXT
			|| format == dib_format_to_omit /*|| format == meta_format_to_omit*/)
			continue;
		// Although the GlobalSize() documentation implies that a valid HGLOBAL should not be zero in
		// size, it does happen, at least in MS Word and for CF_BITMAP.  Therefore, in order to save
		// the clipboard as accurately as possible, also save formats whose size is zero.  Note that
		// GlobalLock() fails to work on hglobals of size zero, so don't do it for them.
		hglobal = g_clip.GetClipboardDataTimeout(format, &save_null_data);
		if (hglobal)
			size = (UINT)GlobalSize(hglobal); // Data >= 4GB seems extremely unlikely, and couldn't be detected by 32-bit processes anyway, so there's no checking for overflow on x64.
		else if (save_null_data)
			size = 0; // This format usually has NULL data.
		else
			continue; // GetClipboardData() failed: skip this format.
		if (!size || (hglobal_locked = GlobalLock(hglobal))) // Size of zero or lock succeeded: Include this format.
		{
			// Any changes made to how things are stored here should also be made to the size-estimation
			// phase so that space_needed matches what is done here:
			added_size = (VarSizeType)(sizeof(format) + sizeof(size) + size);
			actual_space_used += added_size;
			if (actual_space_used > space_needed) // Tolerate incorrect estimate by omitting formats that won't fit.
				actual_space_used -= added_size;
			else
			{
				*(UINT *)binary_contents = format;
				binary_contents = (char *)binary_contents + sizeof(format);
				*(SIZE_T *)binary_contents = size;
				binary_contents = (char *)binary_contents + sizeof(size);
				if (size)
				{
					memcpy(binary_contents, hglobal_locked, size);
					binary_contents = (char *)binary_contents + size;
				}
				//else hglobal_locked is not valid, so don't reference it or unlock it.
			}
			if (size)
				GlobalUnlock(hglobal); // hglobal not hglobal_locked.
		}
	}
	g_clip.Close();
	*(UINT *)binary_contents = 0; // Final termination (must be UINT, see above).

	*aDataSize = (DWORD)actual_space_used;
	return OK;
}



ResultType Var::SetClipboardAll(void *aData, size_t aDataSize)
{
	if (!g_clip.Open())
		return g_script.RuntimeError(CANT_OPEN_CLIPBOARD_WRITE);
	EmptyClipboard(); // Failure is not checked for since it's probably impossible under these conditions.

	// In case the variable contents are incomplete or corrupted (such as having been read in from a
	// bad file with FileRead), prevent reading beyond the end of the variable:
	LPVOID next, binary_contents = aData;
	LPVOID binary_contents_max = (char *)binary_contents + aDataSize; // The last accessible byte, which should be the last byte of the (UINT)0 terminator.
	HGLOBAL hglobal;
	LPVOID hglobal_locked;
	UINT format;
	UINT size;

	while ((next = (char *)binary_contents + sizeof(format)) <= binary_contents_max
		&& (format = *(UINT *)binary_contents)) // Get the format.  Relies on short-circuit boolean order.
	{
		binary_contents = next;
		if ((next = (char *)binary_contents + sizeof(size)) > binary_contents_max)
			break;
		size = *(UINT *)binary_contents; // Get the size of this format's data.
		binary_contents = next;
		if ((next = (char *)binary_contents + size) > binary_contents_max)
			break;
		// v1.1.16: Always allocate a non-zero amount, since testing shows that SetClipboardData()
		// fails when passed a zero-length HGLOBAL, at least on Windows 8.  Zero-initialize using
		// GMEM_ZEROINIT since GlobalAlloc() might return a block larger than requested.  Although
		// it isn't necessarily safer (depending on what programs do with this format), it should
		// at least be more consistent than leaving it uninitialized, if anything ever uses it.
		if (   !(hglobal = GlobalAlloc(GMEM_MOVEABLE | GMEM_ZEROINIT, size + (size == 0)))   )
		{
			g_clip.Close();
			return MemoryError();
		}
		if (size) // i.e. Don't try to lock memory of size zero.  It's not needed.
		{
			if (   !(hglobal_locked = GlobalLock(hglobal))   )
			{
				GlobalFree(hglobal);
				g_clip.Close();
				return g_script.RuntimeError(ERR_INTERNAL_CALL); // Generic msg since so rare.
			}
			memcpy(hglobal_locked, binary_contents, size);
			GlobalUnlock(hglobal);
			binary_contents = next;
		}
		//else hglobal is just an empty format, but store it for completeness/accuracy (e.g. CF_BITMAP).
		SetClipboardData(format, hglobal); // The system now owns hglobal.
	}

	return g_clip.Close();
}



ResultType Var::AssignString(LPCTSTR aBuf, VarSizeType aLength, bool aExactSize)
// Returns OK or FAIL.
// If aBuf isn't NULL, caller must ensure that aLength is either VARSIZE_MAX (which tells us that the
// entire strlen() of aBuf should be used) or an explicit length (can be zero) that the caller must
// ensure is less than or equal to the total length of aBuf (if less, only a substring is copied).
// If aBuf is NULL, the variable will be set up to handle a string of at least aLength
// in length.  In addition, if the var is the clipboard, it will be prepared for writing.
// Any existing contents of this variable will be destroyed regardless of whether aBuf is NULL.
// Note that aBuf's memory can safely overlap with that of this->Contents() because in that case the
// new length of the contents will always be less than or equal to the old length, and thus no
// reallocation/expansion is needed (such an expansion would free the source before it could be
// written to the destination).  This is because callers pass in an aBuf that is either:
// 1) Between this->Contents() and its terminator.
// 2) Equal to this->Contents() but with aLength passed in as shorter than this->Length().
//
// Caller can omit both params to set a var to be empty-string, but in that case, if the variable
// is of large capacity, its memory will not be freed.  This is by design because it allows the
// caller to exploit its knowledge of whether the var's large capacity is likely to be needed
// again in the near future, thus reducing the expected amount of memory fragmentation.
// To explicitly free the memory, use Assign("").
{
	if (mType == VAR_ALIAS)
		// For maintainability, it seems best not to use the following method:
		//    Var &var = *(mType == VAR_ALIAS ? mAliasFor : this);
		// If that were done, bugs would be easy to introduce in a long function like this one
		// if your forget at use the implicit "this" by accident.  So instead, just call self.
		return mAliasFor->AssignString(aBuf, aLength, aExactSize);

	bool do_assign = true;        // Set defaults.
	bool free_it_if_large = true; //
	if (!aBuf)
		if (aLength == VARSIZE_MAX) // Caller omitted this param too, so it wants to assign empty string.
		{
			free_it_if_large = false;
			aLength = 0; // aBuf is set to "" further below.
		}
		else // Caller gave a NULL buffer to signal us to ensure the var is at least aLength in capacity.
			do_assign = false;
	else // Caller provided a non-NULL buffer.
		if (aLength == VARSIZE_MAX) // Caller wants us to determine its length.
			aLength = (mCharContents == aBuf) ? _CharLength() : (VarSizeType)_tcslen(aBuf); // v1.0.45: Added optimization check: (mContents == aBuf).  v1.1.09.03: Replaced CharLength() with _CharLength() to avoid updating contents (probably only applicable when aBuf == Var::sEmptyString).
		//else leave aLength as the caller-specified value in case it's explicitly shorter than the apparent length.
	if (!aBuf)
		aBuf = _T("");  // From here on, make sure it's the empty string for all uses (read-only empty string vs. sEmptyString seems more appropriate in this case).

	size_t space_needed = aLength + 1; // +1 for the zero terminator.
	size_t space_needed_in_bytes = space_needed * sizeof(TCHAR);

	if (mType == VAR_VIRTUAL)
	{
		if (do_assign)
			return AssignVirtual(ExprTokenType(const_cast<LPTSTR>(aBuf), aLength));
		// Since above didn't return, the caller wants to allocate some temporary memory for
		// writing the value into, and should call Close() in order to commit the actual value.
	}
	else if (mType == VAR_CONSTANT) // Might be impossible due to prior validation of assignments/output vars.
		return g_script.VarIsReadOnlyError(this);

	if (space_needed < 2) // Variable is being assigned the empty string (or a deref that resolves to it).
	{
		Free(free_it_if_large ? VAR_FREE_IF_LARGE : VAR_NEVER_FREE); // This also makes the variable blank and removes VAR_ATTRIB_OFTEN_REMOVED.
		return OK;
	}

	if (mAttrib & VAR_ATTRIB_IS_OBJECT)
		ReleaseObject(); // This removes the attribute prior to calling Release() and potentially __Delete().

	// The below is done regardless of whether the section that follows it fails and returns early because
	// it's the correct thing to do in all cases.
	// For simplicity, this is done unconditionally even though it should be needed only
	// when do_assign is true. It's the caller's responsibility to turn on the binary-clip
	// attribute (if appropriate) by calling Var::Close() with the right option.
	mAttrib &= ~(VAR_ATTRIB_OFTEN_REMOVED | VAR_ATTRIB_IS_OBJECT);
	// HOWEVER, other things like making mLength 0 and mContents blank are not done here for performance
	// reasons (it seems too rare that early return/failure will occur below, since it's only due to
	// out-of-memory... and even if it does happen, there are probably no consequences to leaving the variable
	// the way it is now (rather than forcing it to be blank) since the script thread that caused the error
	// will be ended.

	if (space_needed_in_bytes > mByteCapacity)
	{
		size_t new_size; // Use a new name, rather than overloading space_needed, for maintainability.
		char *new_mem;

		switch (mHowAllocated)
		{
		case ALLOC_NONE:
		case ALLOC_SIMPLE:
			if (space_needed_in_bytes <= _TSIZE(MAX_ALLOC_SIMPLE))
			{
				// v1.0.31: Conserve memory within large arrays by allowing elements of length 3 or 7, for such
				// things as the storage of boolean values, or the storage of short numbers (it's best to use
				// multiples of 4 for size due to byte alignment in SimpleHeap; e.g. lengths of 3 and 7).
				// Because the above checked that space_needed > mCapacity, the capacity will increase but
				// never decrease in this section, which prevent a memory leak by only ever wasting a maximum
				// of 4+8+MAX_ALLOC_SIMPLE for each variable (and then only in the worst case -- in the average
				// case, it saves memory by avoiding the overhead incurred for each separate malloc'd block).
				if (space_needed_in_bytes <= _TSIZE(4)) // Even for aExactSize, it seems best to prevent variables from having only a zero terminator in them because that would usually waste 3 bytes due to byte alignment in SimpleHeap.
					new_size = _TSIZE(4); // v1.0.45: Increased from 2 to 4 to exploit byte alignment in SimpleHeap.
				else if (aExactSize) // Allows VarSetStrCapacity() to make more flexible use of SimpleHeap.
					new_size = space_needed_in_bytes;
				else
				{
					if (space_needed_in_bytes <= _TSIZE(8))
						new_size = _TSIZE(8); // v1.0.45: Increased from 7 to 8 to exploit 32-bit alignment in SimpleHeap.
					else // space_needed <= MAX_ALLOC_SIMPLE
						new_size = _TSIZE(MAX_ALLOC_SIMPLE);
				}
				// In the case of mHowAllocated==ALLOC_SIMPLE, the following will allocate another block
				// from SimpleHeap even though the var already had one. This is by design because it can
				// happen only a limited number of times per variable. See comments further above for details.
				if (   !(new_mem = (char *) SimpleHeap::Malloc(new_size))   )
					return MemoryError(); // Leave all var members unchanged so that they're consistent with each other. Don't bother making the var blank and its length zero for reasons described higher above.
				mHowAllocated = ALLOC_SIMPLE;  // In case it was previously ALLOC_NONE. This step must be done only after the alloc succeeded.
				break;
			}
			// ** ELSE DON'T BREAK, JUST FALL THROUGH TO THE NEXT CASE. **
			// **
		case ALLOC_MALLOC: // Can also reach here by falling through from above.
			// This case can happen even if space_needed is less than MAX_ALLOC_SIMPLE
			// because once a var becomes ALLOC_MALLOC, it should never change to
			// one of the other alloc modes.  See comments higher above for explanation.
			new_size = space_needed_in_bytes; // Below relies on this being initialized unconditionally.
			if (!aExactSize)
			{
				// Allow a little room for future expansion to cut down on the number of
				// free's and malloc's we expect to have to do in the future for this var:
				if (new_size < _TSIZE(16)) // v1.0.45.03: Added this new size to prevent all local variables in a recursive
					new_size = _TSIZE(16); // function from having a minimum size of MAX_PATH.  16 seems like a good size because it holds nearly any number.  It seems counterproductive to go too small because each malloc, no matter how small, could have around 40 bytes of overhead.
				else if (new_size < _TSIZE(MAX_PATH))
					new_size = _TSIZE(MAX_PATH);  // An amount that will fit all standard filenames seems good.
				else if (new_size < _TSIZE(160 * 1024)) // MAX_PATH to 160 KB or less -> 10% extra.
					new_size = (size_t)(new_size * 1.1);
				else if (new_size < _TSIZE(1600 * 1024))  // 160 to 1600 KB -> 16 KB extra
					new_size += _TSIZE(16 * 1024);
				else if (new_size < _TSIZE(6400 * 1024)) // 1600 to 6400 KB -> 1% extra
					new_size += (new_size / 100); // Produces smaller code than (new_size * 1.01) and benchmarks the same.
				else  // 6400 KB or more: Cap the extra margin at some reasonable compromise of speed vs. mem usage: 64 KB
					new_size += _TSIZE(64 * 1024);
			}
			//else space_needed was already verified higher above to be within bounds.

			// In case the old memory area is large, free it before allocating the new one.  This reduces
			// the peak memory load on the system and reduces the chance of an actual out-of-memory error.
			bool memory_was_freed;
			if (memory_was_freed = (mHowAllocated == ALLOC_MALLOC && mByteCapacity)) // Verified correct: 1) Both are checked because it might have fallen through from case ALLOC_SIMPLE; 2) mCapacity indicates for certain whether mContents contains the empty string.
				free(mByteContents); // The other members are left temporarily out-of-sync for performance (they're resync'd only if an error occurs).
			//else mContents contains a "" or it points to memory on SimpleHeap, so don't attempt to free it.

			if (  !(new_mem = (char *)malloc(new_size))  )
			{
				if (memory_was_freed) // Resync members to reflect the fact that it was freed (it's done this way for performance).
				{
					mByteCapacity = 0;             // Invariant: Anyone setting mCapacity to 0 must also set
					mCharContents = sEmptyString;  // mContents to the empty string.
				}
				else
				{
					// IMPORTANT: It's the empty string (a constant) or it points to memory on SimpleHeap, so don't
					// change mContents/Capacity (that would cause a memory leak for reasons described elsewhere).
					// Make the var empty for the following reasons:
					//  1) This condition could be caused by the script requesting a very high (possibly invalid)
					//     capacity with VarSetStrCapacity().  The script might be handling the failure using TRY/CATCH,
					//     so we want the result to be sane.
					//  2) It's safer and more maintainable.  For instance, VarSetStrCapacity() sets length to 0, which
					//     can produce bad/undefined results if there is no null-terminator at mCharContents[Length()]
					//     as some other parts of the code assume.
					//  3) It's more consistent.  If this var contained a binary number or object, it has already
					//     been cleared by "mAttrib &=" above.
					*mCharContents = '\0'; // If it's sEmptyString, that's okay too because it's writable.
				}
				mByteLength = 0; // mAttrib was already updated higher above.
				return MemoryError(); // since an error is most likely to occur at runtime.
			}

			// Below is necessary because it might have fallen through from case ALLOC_SIMPLE.
			// This step must be done only after the alloc succeeded (because otherwise, want to keep it
			// set to ALLOC_SIMPLE (fall-through), if that's what it was).
			mHowAllocated = ALLOC_MALLOC;
			break;
		} // switch()

		// Since above didn't return, the alloc succeeded.  Because that's true, all the members (except those
		// set in their sections above) are updated together so that they stay consistent with each other:
		mByteContents = new_mem;
		mByteCapacity = (VarSizeType)new_size;
	} // if (space_needed > mCapacity)

	if (do_assign)
	{
		// Above has ensured that space_needed is either strlen(aBuf)-1 or the length of some
		// substring within aBuf starting at aBuf.  However, aBuf might overlap mContents or
		// even be the same memory address (due to something like GlobalVar := YieldGlobalVar(),
		// in which case ACT_ASSIGNEXPR calls us to assign GlobalVar to GlobalVar).
		if (mCharContents != aBuf)
		{
			// Don't use strlcpy() or such because:
			// 1) Caller might have specified that only part of aBuf's total length should be copied.
			// 2) mContents and aBuf might overlap (see above comment), in which case strcpy()'s result
			//    is undefined, but memmove() is guaranteed to work (and performs about the same).
			tmemmove(mCharContents, aBuf, aLength); // Some callers such as RegEx routines might rely on this copying binary zeroes over rather than stopping at the first binary zero.
		}
		//else nothing needs to be done since source and target are identical.  Some callers probably rely on
		// this optimization.
		mCharContents[aLength] = '\0'; // v1.0.45: This is now done unconditionally in case caller wants to shorten a variable's existing contents (no known callers do this, but it helps robustness).
	}
	else // Caller only wanted the variable resized as a preparation for something it will do later.
	{
		// Init for greater robustness/safety (the ongoing conflict between robustness/redundancy and performance).
		// This has been in effect for so long that some callers probably rely on it.
		*mCharContents = '\0'; // If it's sEmptyString, that's okay too because it's writable.
		// We've done everything except the actual assignment.  Let the caller handle that.
		// Also, the length will be set below to the expected length in case the caller
		// doesn't override this.
		// Below: Already verified that the length value will fit into VarSizeType.
	}

	if (mType == VAR_VIRTUAL)
	{
		// This tells Contents() not to call mVV->Get():
		mAttrib |= VAR_ATTRIB_VIRTUAL_OPEN;
	}

	// Writing to union is safe because above already ensured that "this" isn't an alias.
	mByteLength = aLength * sizeof(TCHAR); // aLength was verified accurate higher above.
	return OK;
}



ResultType Var::AssignBinaryNumber(__int64 aNumberAsInt64, VarAttribType aAttrib)
{
	if (mType == VAR_ALIAS)
		return mAliasFor->AssignBinaryNumber(aNumberAsInt64, aAttrib);

	if (mType == VAR_VIRTUAL)
	{
		// Virtual vars have no binary number cache, as their value may be calculated on-demand.
		// Additionally, THE CACHE MUST NOT BE USED due to the union containing mVV.
		ExprTokenType value;
		value.symbol = (aAttrib & VAR_ATTRIB_IS_INT64) ? SYM_INTEGER : SYM_FLOAT;
		value.value_int64 = aNumberAsInt64;
		return AssignVirtual(value);
	}
	else if (mType == VAR_CONSTANT) // Might be impossible due to prior validation of assignments/output vars.
		return g_script.VarIsReadOnlyError(this);

	if (mAttrib & VAR_ATTRIB_IS_OBJECT) // mObject will be overwritten below via the union.
		ReleaseObject(); // This removes the attribute prior to calling Release() and potentially __Delete().

	mContentsInt64 = aNumberAsInt64;
	mAttrib &= ~(VAR_ATTRIB_TYPES | VAR_ATTRIB_NOT_NUMERIC | VAR_ATTRIB_UNINITIALIZED);
	mAttrib |= (VAR_ATTRIB_CONTENTS_OUT_OF_DATE | aAttrib); // Must be done prior to below.  aAttrib indicates the type of binary number.
	return OK;
}



ResultType Var::AssignSkipAddRef(IObject *aValueToAssign)
{
	if (mType == VAR_ALIAS)
		return mAliasFor->AssignSkipAddRef(aValueToAssign);

	if (mType == VAR_VIRTUAL)
	{
		auto result = AssignVirtual(ExprTokenType(aValueToAssign));
		aValueToAssign->Release(); // Caller wanted us to take responsibility for this.
		return result;
	}

	Free(); // If var contains an object, this will Release() it.  It will also clear any string contents and free memory if appropriate.
		
	// Already done by Free() above:
	//mAttrib &= ~(VAR_ATTRIB_OFTEN_REMOVED | VAR_ATTRIB_UNINITIALIZED);

	_SetObject(aValueToAssign);
	
	return OK;
}



void Var::Get(ResultToken &aResultToken)
{
	if (mType == VAR_ALIAS)
		return mAliasFor->Get(aResultToken);
	ASSERT(mType == VAR_VIRTUAL);
	mVV->Get(aResultToken, mName);
}



void Var::Free(int aWhenToFree, bool aClearAliasesAndRequireInit)
// The name "Free" is a little misleading because this function:
// ALWAYS sets the variable to be blank (except for static variables and aExcludeAliases==true).
// BUT ONLY SOMETIMES frees the memory, depending on various factors described further below.
// Caller must be aware that ALLOC_SIMPLE (due to its nature) is never freed.
// aClearAliasesAndRequireInit may be split into two if any caller ever wants to pass
// true for one and not the other.
{
	// Not checked because VAR_VIRTUAL uses this to free its temporary buffer:
	//if (mType != VAR_NORMAL) // For robustness, since callers generally shouldn't call it this way.
	//	return;

	if (mType == VAR_ALIAS) // For simplicity and reduced code size, just make a recursive call to self.
	{
		if (!aClearAliasesAndRequireInit)
		{
			// For maintainability, it seems best not to use the following method:
			//    Var &var = *(mType == VAR_ALIAS ? mAliasFor : this);
			// If that were done, bugs would be easy to introduce in a long function like this one
			// if your forget at use the implicit "this" by accident.  So instead, just call self.
			mAliasFor->Free(aWhenToFree);
			return;
		}
		mType = VAR_NORMAL; // Revert alias to normal variable.
	}

	mByteLength = 0; // Writing to union is safe because above already ensured that "this" isn't an alias.
	// Even if it isn't free'd, variable will be made blank.  So it seems proper to always remove
	// the uninitialized attribute (since *we* are initializing it).  Some callers may rely on us
	// removing these attributes:
	mAttrib &= ~VAR_ATTRIB_OFTEN_REMOVED;

	if (aClearAliasesAndRequireInit)
		// Caller requires this var to be considered uninitialized from now on.  This attribute may
		// have been removed above, but there was no cost involved.  It might not have been set in
		// the first place, so we must add it here anyway:
		mAttrib |= VAR_ATTRIB_UNINITIALIZED;

	if (mAttrib & VAR_ATTRIB_IS_OBJECT)
	{
		ReleaseObject(); // This removes the attribute prior to calling Release() and potentially __Delete().
		return; // Best to return at this point since Release() may have caused reentry into this function.
	}

	switch (mHowAllocated)
	{
	// Shouldn't be necessary to check the following because by definition, ALLOC_NONE
	// means mContents==sEmptyString (this policy is enforced in other places).
	//
	//case ALLOC_NONE:
	//	mContents = sEmptyString;
	//	break;

	case ALLOC_SIMPLE:
		// Don't set to sEmptyString because then we'd have a memory leak.  i.e. once a var becomes
		// ALLOC_SIMPLE, it should never become ALLOC_NONE again (though it can become ALLOC_MALLOC).
		*mCharContents = '\0';
		break;

	case ALLOC_MALLOC:
		// Setting a var whose contents are very large to be nothing or blank is currently the
		// only way to free up the memory of that var.  Shrinking it dynamically seems like it
		// might introduce too much memory fragmentation and overhead (since in many cases,
		// it would likely need to grow back to its former size in the near future).  So we
		// only free relatively large vars:
		if (mByteCapacity)
		{
			// aWhenToFree==VAR_FREE_IF_LARGE: the memory is not freed if it is a small area because
			// it might help reduce memory fragmentation and improve performance in cases where
			// the memory will soon be needed again (in which case one free+malloc is saved).
			if (   aWhenToFree == VAR_ALWAYS_FREE
				|| aWhenToFree == VAR_FREE_IF_LARGE && mByteCapacity > (4 * 1024)   )
			{
				free(mByteContents);
				mByteCapacity = 0;             // Invariant: Anyone setting mCapacity to 0 must also set
				mCharContents = sEmptyString;  // mContents to the empty string.
				// BUT DON'T CHANGE mHowAllocated to ALLOC_NONE (see comments further below).
			}
			else // Don't actually free it, but make it blank (callers rely on this).
				*mCharContents = '\0';
		}
		//else mCapacity==0, so mContents is already the empty string, so don't attempt to free
		// it or assign to it. It was the responsibility of whoever set mCapacity to 0 to ensure mContents
		// was set properly (which is why it's not done here).

		// But do not change mHowAllocated to be ALLOC_NONE because it would cause a
		// a memory leak in this sequence of events:
		// var1 is assigned something short enough to make it ALLOC_SIMPLE
		// var1 is assigned something large enough to require malloc()
		// var1 is set to empty string and its mem is thus free()'d by the above.
		// var1 is once again assigned something short enough to make it ALLOC_SIMPLE
		// The last step above would be a problem because the 2nd ALLOC_SIMPLE can't
		// reclaim the spot in SimpleHeap that had been in use by the first.  In other
		// words, when a var makes the transition from ALLOC_SIMPLE to ALLOC_MALLOC,
		// its ALLOC_SIMPLE memory is lost to the system until the program exits.
		// But since this loss occurs at most once per distinct variable name,
		// it's not considered a memory leak because the loss can't exceed a fixed
		// amount regardless of how long the program runs.  The reason for all of this
		// is that allocating dynamic memory is costly: it causes system memory fragmentation,
		// (especially if a var were to be malloc'd and free'd thousands of times in a loop)
		// and small-sized mallocs have a large overhead: it's been said that every block
		// of dynamic mem, even those of size 1 or 2, incurs about 40 bytes of overhead
		// (and testing of SimpleHeap supports this).
		// UPDATE: Yes it's true that a script could create an unlimited number of new variables
		// by constantly using different dynamic names when creating them.  But it's still supportable
		// that there's no memory leak because even if the worst-case series of events mentioned
		// higher above occurs for every variable, only a fixed amount of memory is ever lost per
		// variable.  So you could think of the lost memory as part of the basic overhead of creating
		// a variable (since variables are never truly destroyed, just their contents freed).
		// The odds against all of these worst-case factors occurring simultaneously in anything other
		// than a theoretical test script seem nearly astronomical.
		break;
	} // switch()
}



ResultType Var::AppendIfRoom(LPTSTR aStr, VarSizeType aLength)
// Returns OK if there's room enough to append aStr and it succeeds.
// Returns FAIL otherwise (also returns FAIL for VAR_VIRTUAL).
// Environment variables aren't supported here; instead, aStr is appended directly onto the actual/internal
// contents of the "this" variable.
{
	if (mType == VAR_ALIAS)
		return mAliasFor->AppendIfRoom(aStr, aLength);
	if (mType != VAR_NORMAL // e.g. VAR_VIRTUAL. Some callers do call it this way, but even if not it should be kept for maintainability.
		|| IsObject()) // Let caller free it; not worth handling here.
		return FAIL; // CHECK THIS FIRST, BEFORE BELOW, BECAUSE CALLERS ALWAYS WANT IT TO BE A FAILURE.
	if (aLength)
	{
		VarSizeType var_length = Length(); // Get the apparent length because one caller is a concat that wants consistent behavior of the .= operator regardless of whether this shortcut succeeds or not.
		VarSizeType new_length = var_length + aLength;
		if (new_length >= _CharCapacity()) // Not enough room.
			return FAIL;
		tmemmove(mCharContents + var_length, aStr, aLength);  // mContents was updated via Length() above. Use memmove() vs. memcpy() in case there's any overlap between source and dest.
		mCharContents[new_length] = '\0'; // Terminate it as a separate step in case caller passed a length shorter than the apparent length of aStr.
		mByteLength = new_length * sizeof(TCHAR);
	}
	// Even if nothing was appended above, set the attributes so n:=1,n.="" produces a String, not an Integer.
	// If this is a binary-clip variable, appending has probably "corrupted" it; so don't allow it to ever be
	// put back onto the clipboard as binary data (the routine that does that is designed to detect corruption,
	// but it might not be perfect since corruption is so rare).  Also remove the other flags that are no longer
	// appropriate:
	mAttrib &= ~VAR_ATTRIB_OFTEN_REMOVED; // This also removes VAR_ATTRIB_NOT_NUMERIC because appending some digits to an empty variable would make it numeric.
	return OK;
}



ResultType Var::Append(LPTSTR aStr, VarSizeType aLength)
// Caller must ensure that Type() == VAR_NORMAL.
{
	if (mType == VAR_ALIAS)
		return mAliasFor->Append(aStr, aLength);
	if (AppendIfRoom(aStr, aLength))
		return OK;
	// Since above didn't return, we need to allocate space and postpone freeing our current value
	// until after it is copied into the new buffer.  The following relies on AppendIfRoom() always
	// succeeding if there is room and the var has non-zero length; otherwise AssignString() would
	// null-terminate the old contents at position 0 and the result would be incorrect.
	LPTSTR old_contents = mCharContents; // Caller has ensured UpdateContents() was called if necessary.
	VarSizeType old_length = _CharLength();
	VarSizeType old_capacity = (mHowAllocated == ALLOC_MALLOC) ? mByteCapacity : 0;
	if (old_capacity)
		mByteCapacity = 0; // Prevent the call below from freeing it.
	if (!AssignString(NULL, _CharLength() + aLength))
	{
		mByteCapacity = old_capacity; // Restore this since the contents are being left as is.
		return FAIL;
	}
	tmemcpy(mCharContents, old_contents, old_length);
	tmemcpy(mCharContents + old_length, aStr, aLength + 1);
	if (old_capacity)
		free(old_contents);
	return OK;
}



void Var::AcceptNewMem(LPTSTR aNewMem, VarSizeType aLength)
// Caller provides a new malloc'd memory block (currently must be non-NULL).  That block and its
// contents are directly hung onto this variable in place of its old block, which is freed (except
// in the case of VAR_VIRTUAL, in which case the memory is passed to mVV->Set() then freed).
// This function was added in v1.0.45 to aid callers in improving performance.
{
	if (mType == VAR_ALIAS)
		return mAliasFor->AcceptNewMem(aNewMem, aLength);
	if (mType != VAR_NORMAL)
	{
		Assign(aNewMem, aLength);
		free(aNewMem); // Caller gave it to us to take charge of, but we have no further use for it.
	}
	else // VAR_NORMAL
		_AcceptNewMem(aNewMem, aLength);
}



void Var::_AcceptNewMem(LPTSTR aNewMem, VarSizeType aLength)
// Called by AcceptNewMem() when mType == VAR_NORMAL.
// Called by PopulateVirtualVar() when mType == VAR_VIRTUAL.
{
	Free(VAR_ALWAYS_FREE); // Release the variable's old memory. This also removes flags VAR_ATTRIB_OFTEN_REMOVED.
	mHowAllocated = ALLOC_MALLOC; // Must always be this type to avoid complications and possible memory leaks.
	mByteContents = (char *) aNewMem;
	if (aLength == VARSIZE_MAX)
		aLength = _tcslen(aNewMem);
	mByteLength = aLength * sizeof(TCHAR);
	ASSERT( mByteLength + sizeof(TCHAR) <= _msize(aNewMem) );
	mByteCapacity = (VarSizeType)_msize(aNewMem); // Get actual capacity in case it's a lot bigger than aLength+1. _msize() is only about 36 bytes of code and probably a very fast call.
	// Already done by Free() above:
	//mAttrib &= ~VAR_ATTRIB_OFTEN_REMOVED; // New memory is always non-binary-clip.  A new parameter could be added to change this if it's ever needed.

	// Shrink the memory if there's a lot of wasted space because the extra capacity is seldom utilized
	// in real-world scripts.
	// A simple rule seems best because shrinking is probably fast regardless of the sizes involved,
	// plus and there's considerable rarity to ever needing capacity beyond what's in a variable
	// (concat/append is one example).  This will leave a large percentage of extra space in small variables,
	// but in those rare cases when a script needs to create thousands of such variables, there may be a
	// current or future way to shrink an existing variable to contain only its current length, such as
	// VarShrink().
	if (mByteCapacity - mByteLength > 64)
	{
		// _expand() is only about 75 bytes of uncompressed code size and probably performs very quickly
		// when shrinking.  MSDN implies that when shrinking, failure won't happen unless something is
		// terribly wrong (e.g. corrupted heap), but it's known to fail in other cases, such as when
		// called by AutoHotkey running as a Windows store app.
		if (_expand(mByteContents, mByteLength + sizeof(TCHAR)))
			// Update capacity only after successfully shrinking:
			mByteCapacity = mByteLength + sizeof(TCHAR);
		// The block is left unchanged on failure, so in that case leave everything as is.
	}
}



void Var::SetLengthFromContents()
// Function added in v1.0.43.06.  It updates the mLength member to reflect the actual current length of mContents.
// Caller must ensure that Type() is VAR_NORMAL.
{
	if (mType == VAR_ALIAS)
		return mAliasFor->SetLengthFromContents();
	if (mAttrib & VAR_ATTRIB_CONTENTS_OUT_OF_DATE)
	{
		UpdateContents(); // Set contents and length based on numeric value.
		return;
	}
	size_t length = 0;
	LPTSTR contents = mCharContents;
	size_t max_count = mByteCapacity / sizeof(TCHAR);
	// Since the performance cost is low, ensure the string is terminated at the limit of its
	// capacity (helps prevent crashes if DLL function didn't do its job and terminate the string,
	// or when a function is called that deliberately doesn't terminate the string, such as
	// RtlMoveMemory()).
	if (max_count == 0)
		max_count = 1; // Contents() == Var::sEmptyString in this case, so check it hasn't been tampered with.
	length = _tcsnlen(contents, max_count);
	if (length == max_count)
		g_script.CriticalError(ERR_STRING_NOT_TERMINATED, mName);
	mByteLength = _TSIZE(length);
}



ResultType Var::BackupFunctionVars(UserFunc &aFunc, VarBkp *&aVarBackup, int &aVarBackupCount)
// All parameters except the first are output parameters that are set for our caller (though caller
// is responsible for having initialized aVarBackup to NULL).
// If there is nothing to backup, only the aVarBackupCount is changed (to zero).
// Returns OK or FAIL.
{
	if (   !(aVarBackupCount = aFunc.mVars.mCount)   )  // Nothing needs to be backed up.
		return OK; // Leave aVarBackup set to NULL as set by the caller.

	// NOTES ABOUT MALLOC(): Apparently, the implementation of malloc() is quite good, at least for small blocks
	// needed to back up 50 or less variables.  It nearly as fast as alloca(), at least when the system
	// isn't under load and has the memory to spare without swapping.  Therefore, the attempt to use alloca to
	// speed up recursive script-functions didn't result in enough of a speed-up (only 1 to 5%) to be worth the
	// added complexity.
	// Since Var is not a POD struct (it contains private members, a custom constructor, etc.), the VarBkp
	// POD struct is used to hold the backup because it's probably better performance than using Var's
	// constructor to create each backup array element.
	if (   !(aVarBackup = (VarBkp *)malloc(aVarBackupCount * sizeof(VarBkp)))   ) // Caller will take care of freeing it.
		return FAIL;

	int i;
	aVarBackupCount = 0;  // Init only once prior to both loops. aVarBackupCount is being "overloaded" to track the current item in aVarBackup, BUT ALSO its being updated to an actual count in case some statics are omitted from the array.

	// Note that Backup() does not make the variable empty after backing it up because that is something
	// that must be done by our caller at a later stage.
	for (i = 0; i < aFunc.mVars.mCount; ++i)
		aFunc.mVars.mItem[i]->Backup(aVarBackup[aVarBackupCount++]);
	return OK;
}



void Var::Backup(VarBkp &aVarBkp)
// Caller must not call this function for static variables because it's not equipped to deal with them
// (they don't need to be backed up or restored anyway).
// This method is used rather than struct copy (=) because it's of expected higher performance than
// using the Var::constructor to make a copy of each var.  Also note that something like memcpy()
// can't be used on Var objects since they're not POD (e.g. they have a constructor and they have
// private members).
{
	aVarBkp.mVar = this; // Allows the restoration process to always know its target without searching.
	aVarBkp.mByteContents = mByteContents;
	aVarBkp.mContentsInt64 = mContentsInt64; // This also copies the other members of the union: mContentsDouble, mObject.
	aVarBkp.mByteLength = mByteLength; // Since it's a union, it might actually be backing up mAliasFor (happens at least for recursive functions that pass parameters ByRef).
	aVarBkp.mByteCapacity = mByteCapacity;
	aVarBkp.mHowAllocated = mHowAllocated; // This might be ALLOC_SIMPLE or ALLOC_NONE if backed up variable was at the lowest layer of the call stack.
	aVarBkp.mAttrib = mAttrib;
	aVarBkp.mType = mType; // Fix for v1.0.47.06: Must also back up and restore mType in case an optional ByRef parameter is omitted by one call by specified by another thread that interrupts the first thread's call.
	// Once the backup is made, Free() is not called because the whole point of the backup is to
	// preserve the original memory/contents of each variable.  Instead, clear the variable
	// completely and set it up to become ALLOC_MALLOC in case anything actually winds up using
	// the variable prior to the restoration of the backup.  In other words, ALLOC_SIMPLE and NONE
	// retained (if present) because that would cause a memory leak when multiple layers are all
	// allowed to use ALLOC_SIMPLE yet none are ever able to free it (the bottommost layer is
	// allowed to use ALLOC_SIMPLE because that's a fixed/constant amount of memory gets freed
	// when the program exits).
	// Now reset this variable (caller has ensured it's non-static) to create a "new layer" for it, keeping
	// its backup intact but allowing this variable (or formal parameter) to be given a new value in the future:
	mByteCapacity = 0;             // Invariant: Anyone setting mCapacity to 0 must also set...
	mCharContents = sEmptyString;  // ...mContents to the empty string.
	mByteLength = 0;
	mType = VAR_NORMAL;
	mHowAllocated = ALLOC_MALLOC; // Never NONE because that would permit SIMPLE. See comments higher above.
	mAttrib = VAR_ATTRIB_UNINITIALIZED; // The function's new recursion layer should consider this var uninitialized, even if it was initialized by the previous layer.
}



void Var::Restore(VarBkp &aVarBkp)
{
	mByteContents = aVarBkp.mByteContents;
	mContentsInt64 = aVarBkp.mContentsInt64; // This also copies the other members of the union: mContentsDouble, mObject.
	mByteLength = aVarBkp.mByteLength; // Since it's a union, it might actually be restoring mAliasFor, which is desired.
	mByteCapacity = aVarBkp.mByteCapacity;
	mHowAllocated = aVarBkp.mHowAllocated; // This might be ALLOC_SIMPLE or ALLOC_NONE if backed-up variable was at the lowest layer of the call stack.
	mAttrib = aVarBkp.mAttrib;
	mType = aVarBkp.mType;
}



void Var::FreeAndRestoreFunctionVars(UserFunc &aFunc, VarBkp *&aVarBackup, int &aVarBackupCount)
{
	int i;
	for (i = 0; i < aFunc.mVars.mCount; ++i)
		aFunc.mVars.mItem[i]->Free(VAR_ALWAYS_FREE, true); // Pass "true" to exclude aliases, since their targets should not be freed (they don't belong to this function). Also resets the "uninitialized" attribute.

	// The freeing (above) MUST be done prior to the restore-from-backup below (otherwise there would be
	// a memory leak).  Static variables are never backed up and thus do not exist in the aVarBackup array.
	// This is because by definition, the contents of statics are not freed or altered by the calling procedure
	// (regardless how recursive or multi-threaded the function is).
	if (aVarBackup) // This is the indicator that a backup was made; thus a restore is also needed.
	{
		for (i = 0; i < aVarBackupCount; ++i) // Static variables were never backed up so they won't be in this array. See comments above.
		{
			VarBkp &bkp = aVarBackup[i];
			bkp.mVar->Restore(bkp);
		}
		free(aVarBackup);
		aVarBackup = NULL; // Some callers want this reset; it's an indicator of whether the next function call in this expression (if any) will have a backup.
	}
}



// Used by the debugger.
void VarBkp::ToToken(ExprTokenType &aValue)
{
	switch (mAttrib & VAR_ATTRIB_TYPES)
	{
	case VAR_ATTRIB_IS_OBJECT: aValue.SetValue(mObject); break;
	case VAR_ATTRIB_IS_INT64: aValue.SetValue(mContentsInt64); break;
	case VAR_ATTRIB_IS_DOUBLE: aValue.SetValue(mContentsDouble); break;
	default:
		if (mAttrib & VAR_ATTRIB_UNINITIALIZED)
			aValue.symbol = SYM_MISSING;
		else
			aValue.SetValue(mCharContents, mByteLength / sizeof(TCHAR));
	}
}



// Without __declspec(noinline), this produced larger code than the original, which had
// the code essentially repeated in ValidateName().  There's no good reason to inline
// this function (or other functions which are only called to display an error dialog).
__declspec(noinline)
ResultType DisplayNameError(LPCTSTR aErrorFormat, int aDisplayError, LPCTSTR aName)
{
	if (!aDisplayError)
		return FAIL;
	static LPCTSTR sErrorSubject[] = VALIDATENAME_SUBJECTS;
	TCHAR msg[512];
	sntprintf(msg, _countof(msg), aErrorFormat
		, sErrorSubject[VALIDATENAME_SUBJECT_INDEX(aDisplayError)]
		, aName);
	return g_script.ScriptError(msg);
}



ResultType Var::ValidateName(LPCTSTR aName, int aDisplayError)
// Returns OK or FAIL.
{
	if (!*aName) return FAIL; // Shouldn't be called this way.
	
	// Seems best to disallow variables that start with numbers for purity, to allow
	// something like 1e3 to be scientific notation, and possibly other reasons.
	if (*aName >= '0' && *aName <= '9')
	{
		return DisplayNameError(_T("This %s name starts with a number, which is not allowed:\n\"%-1.300s\""), aDisplayError, aName);
	}
	if (*find_identifier_end(aName) != '\0')
	{
		return DisplayNameError(_T("The following %s name contains an illegal character:\n\"%-1.300s\""), aDisplayError, aName);
	}
	if (aDisplayError == DISPLAY_METHOD_ERROR || aDisplayError == DISPLAY_GROUP_ERROR)
		return OK;
	// Reserve names of control flow statements.  Aside from being more "pure" and allowing
	// future improvements, it should also help catch syntax errors such as "if (foo) break".
	// Note that since these statements allow parentheses, they only get here for variable names.
	// Reserve operator keywords.  This makes ACT_ASSIGNEXPR more consistent with ACT_EXPRESSION,
	// such as for "and := 1" vs. "(and := 1)", though a different error message is given.
	if (   Script::ConvertActionType(aName)
		|| Script::ConvertWordOperator(aName, _tcslen(aName))
		|| !_tcsicmp(aName, _T("True")) || !_tcsicmp(aName, _T("False"))
		|| !_tcsicmp(aName, _T("local")) || !_tcsicmp(aName, _T("global")) || !_tcsicmp(aName, _T("static")))
	{
		return DisplayNameError(_T("The following reserved word must not be used as a %s name:\n\"%-1.300s\""), aDisplayError, aName);
	}
	// Otherwise:
	return OK;
}



ResultType Var::AssignStringFromCodePage(LPCSTR aBuf, int aLength, UINT aCodePage)
{
#ifndef UNICODE
	// Not done since some callers have a more effective optimization in place:
	//if (aCodePage == CP_ACP || aCodePage == GetACP())
		// Avoid unnecessary conversion (ACP -> UTF16 -> ACP).
		//return AssignString(aBuf, aLength, true, false);
	// Convert from specified codepage to UTF-16,
	CStringWCharFromChar wide_buf(aBuf, aLength, aCodePage);
	// then back to the active codepage:
	return AssignStringToCodePage(wide_buf, wide_buf.GetLength(), CP_ACP);
#else
	int iLen = MultiByteToWideChar(aCodePage, 0, aBuf, aLength, NULL, 0);
	if (iLen > 0) {
		if (!AssignString(NULL, iLen, true))
			return FAIL;
		LPWSTR aContents = Contents(TRUE);
		iLen = MultiByteToWideChar(aCodePage, 0, aBuf, aLength, (LPWSTR) aContents, iLen);
		// A return value of 0 is not ambiguous here, but any failure is more likely to occur
		// in the first call.  For consistency (see below), let the var be blank on error.
		if (aLength == -1 && iLen)
			--iLen; // Exclude the null-terminator.
		else
			aContents[iLen] = 0;
		SetCharLength(iLen);
	}
	else
		Assign(); // Return value is ambiguous in this case: may be zero-length input or an error.  For simplicity, return OK.
	return OK;
#endif
}



ResultType Var::AssignStringToCodePage(LPCWSTR aBuf, int aLength, UINT aCodePage, DWORD aFlags, char aDefChar)
{
	char *pDefChar;
	if (aCodePage == CP_UTF8 || aCodePage == CP_UTF7) {
		pDefChar = NULL;
		aFlags = 0;
	}
	else
		pDefChar = &aDefChar;
	int iLen = WideCharToMultiByte(aCodePage, aFlags, aBuf, aLength, NULL, 0, pDefChar, NULL);
	if (iLen > 0) {
		if (!SetCapacity(iLen, true))
			return FAIL;
		LPSTR aContents = (LPSTR) Contents(TRUE);
		iLen = WideCharToMultiByte(aCodePage, aFlags, aBuf, aLength, aContents, iLen, pDefChar, NULL);
		aContents[iLen] = 0;
		if (!iLen)
			return FAIL;
#ifndef UNICODE
		SetCharLength(aContents[iLen - 1] ? iLen : iLen - 1);
#endif
	}
	else
		Assign();
	return OK;
}



LPTSTR ResultToken::Malloc(LPTSTR aValue, size_t aLength)
{
	if (aLength == -1)
		aLength = _tcslen(aValue);
	if (  !(mem_to_free = tmalloc(aLength + 1))  )
		return NULL;
	symbol = SYM_STRING;
	marker_length = aLength;
	return tmemcpy(marker = mem_to_free, aValue, aLength + 1); // +1 to include the null-terminator.
}



ResultType Var::InitializeConstant()
{
	// Caller has verified !IsInitialized() && Type() == VAR_CONSTANT.
	Var &var = *ResolveAlias();
	ASSERT(var.mType == VAR_CONSTANT && var.IsObject() && dynamic_cast<::Object*>(var.mObject));
	var.mAttrib &= ~VAR_ATTRIB_UNINITIALIZED; // Only make one attempt; prevents infinite recursion.
	FuncResult result_token;
	auto cls = (::Object*)var.mObject;
	cls->AddRef(); // Necessary because Construct() calls Release() on failure.
	auto result = cls->Construct(result_token, nullptr, 0);
	if (result == OK)
		cls->Release();
	return result;
}