TokenSpace: fix token wraparound

Fix bug that allocating/freeing a lot of BHandler cause token wraparound
and overwriting existing assigned tokens.

Change-Id: I12527126644bca1793a8475dc487f131e6f83437
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9533
Reviewed-by: waddlesplash <[email protected]>

headers/private/app/TokenSpace.h

@@ -62,7 +62,7 @@ private:
 	typedef std::map<int32, token_info> TokenMap;
 
 			TokenMap			fTokenMap;
-			int32				fTokenCount;
+			int32				fNextToken;
 };
 
 

src/kits/app/TokenSpace.cpp

@@ -20,10 +20,20 @@ BTokenSpace gDefaultTokens;
 	// the default token space - all handlers will go into that one
 
 
+static int32
+get_next_token(int32 token)
+{
+	if (token == INT32_MAX)
+		return 1;
+	else
+		return token + 1;
+}
+
+
 BTokenSpace::BTokenSpace()
 	:
 	BLocker("token space"),
-	fTokenCount(1)
+	fNextToken(1)
 {
 }
 
@@ -39,17 +49,24 @@ BTokenSpace::NewToken(int16 type, void* object)
 	BAutolock locker(this);
 
 	token_info tokenInfo = { type, object, NULL };
-	int32 token = fTokenCount;
+
+	int32 wraparoundToken = fNextToken;
 
 	try {
-		fTokenMap[token] = tokenInfo;
+		for (;;) {
+			int32 token = fNextToken;
+			bool done = fTokenMap.insert(std::pair(token, tokenInfo)).second;
+			fNextToken = get_next_token(token);
+
+			if (done)
+				return token;
+
+			if (fNextToken == wraparoundToken)
+				return -1;
+		}
 	} catch (std::bad_alloc& exception) {
 		return -1;
 	}
-
-	fTokenCount++;
-
-	return token;
 }
 
 
@@ -73,8 +90,8 @@ BTokenSpace::SetToken(int32 token, int16 type, void* object)
 	}
 
 	// this makes sure SetToken() plays more or less nice with NewToken()
-	if (token >= fTokenCount)
+	if (token >= fNextToken)
-		fTokenCount = token + 1;
+		fNextToken = get_next_token(token);
 
 	return true;
 }