SCUMM: Fix off-by-one mistakes in out-of-bounds checks; name some constants

2 files changed, 24 insertions, 11 deletions

diff --git a/engines/scumm/script.cpp b/engines/scumm/script.cpp
index a76461f579..c481fb8a4e 100644
--- a/engines/scumm/script.cpp
+++ b/engines/scumm/script.cpp
@@ -319,6 +319,9 @@ void ScummEngine::runScriptNested(int script) {
 
 	updateScriptPtr();
 
+	if (vm.numNestedScripts >= kMaxScriptNesting)
+		error("Too many nested scripts");
+
 	nest = &vm.nest[vm.numNestedScripts];
 
 	if (_currentScript == 0xFF) {
@@ -334,9 +337,6 @@ void ScummEngine::runScriptNested(int script) {
 
 	vm.numNestedScripts++;
 
-	if (vm.numNestedScripts > ARRAYSIZE(vm.nest))
-		error("Too many nested scripts");
-
 	_currentScript = script;
 	getScriptBaseAddress();
 	resetScriptPointer();
@@ -1284,7 +1284,7 @@ void ScummEngine::beginCutscene(int *args) {
 	vm.slot[scr].cutsceneOverride++;
 
 	++vm.cutSceneStackPointer;
-	if (vm.cutSceneStackPointer > ARRAYSIZE(vm.cutSceneData))
+	if (vm.cutSceneStackPointer >= kMaxCutsceneNum)
 		error("Cutscene stack overflow");
 
 	vm.cutSceneData[vm.cutSceneStackPointer] = args[0];
@@ -1325,7 +1325,7 @@ void ScummEngine::endCutscene() {
 
 void ScummEngine::abortCutscene() {
 	const int idx = vm.cutSceneStackPointer;
-	assert(0 <= idx && idx < 5);
+	assert(0 <= idx && idx < kMaxCutsceneNum);
 
 	uint32 offs = vm.cutScenePtr[idx];
 	if (offs) {
@@ -1344,7 +1344,7 @@ void ScummEngine::abortCutscene() {
 
 void ScummEngine::beginOverride() {
 	const int idx = vm.cutSceneStackPointer;
-	assert(0 <= idx && idx < 5);
+	assert(0 <= idx && idx < kMaxCutsceneNum);
 
 	vm.cutScenePtr[idx] = _scriptPointer - _scriptOrgPointer;
 	vm.cutSceneScript[idx] = _currentScript;
@@ -1361,7 +1361,7 @@ void ScummEngine::beginOverride() {
 
 void ScummEngine::endOverride() {
 	const int idx = vm.cutSceneStackPointer;
-	assert(0 <= idx && idx < 5);
+	assert(0 <= idx && idx < kMaxCutsceneNum);
 
 	vm.cutScenePtr[idx] = 0;
 	vm.cutSceneScript[idx] = 0;
diff --git a/engines/scumm/script.h b/engines/scumm/script.h
index dbfa2630e5..39d5d802b4 100644
--- a/engines/scumm/script.h
+++ b/engines/scumm/script.h
@@ -98,16 +98,29 @@ struct NestedScript {
 	uint8 slot;
 };
 
+enum {
+	/**
+	 * The maximal number of cutscenes that can be active
+	 * in parallel (i.e. nested).
+	 */
+	kMaxCutsceneNum = 5,
+
+	/**
+	 * The maximal 'nesting' level for scripts.
+	 */
+	kMaxScriptNesting = 15
+};
+
 struct VirtualMachineState {
-	uint32 cutScenePtr[5];
-	byte cutSceneScript[5];
-	int16 cutSceneData[5];
+	uint32 cutScenePtr[kMaxCutsceneNum];
+	byte cutSceneScript[kMaxCutsceneNum];
+	int16 cutSceneData[kMaxCutsceneNum];
 	int16 cutSceneScriptIndex;
 	byte cutSceneStackPointer;
 	ScriptSlot slot[NUM_SCRIPT_SLOT];
 	int32 localvar[NUM_SCRIPT_SLOT][26];
 
-	NestedScript nest[15];
+	NestedScript nest[kMaxScriptNesting];
 	byte numNestedScripts;
 };