Tidy up app::response().

fpdfsdk/src/javascript/app.cpp

Index: fpdfsdk/src/javascript/app.cpp
diff --git a/fpdfsdk/src/javascript/app.cpp b/fpdfsdk/src/javascript/app.cpp
index 3b92a992d9d0be2b46db2266d0e51847b0a34fdd..e40e446e83212784edadb181d5600524794aef90 100644
--- a/fpdfsdk/src/javascript/app.cpp
+++ b/fpdfsdk/src/javascript/app.cpp
@@ -1037,15 +1037,13 @@ FX_BOOL app::response(OBJ_METHOD_PARAMS)
 	CFX_WideString swTitle = L"PDF";
 #endif
 	CFX_WideString swDefault = L"";
-	CFX_WideString swResponse = L"";
 	bool bPassWord = false;
-	
+
 	v8::Isolate* isolate = GetIsolate(cc);
-	
-	int iLength = params.size();	
+
+	int iLength = params.size();
 	if (iLength > 0 && params[0].GetType() == VT_object)
 	{
-		
 		JSObject pObj = (JSObject )params[0];
 		v8::Handle<v8::Value> pValue = JS_GetObjectElement(isolate,pObj,L"cQuestion");
 			swQuestion = CJS_Value(isolate,pValue,GET_VALUE_TYPE(pValue)).operator CFX_WideString();
@@ -1101,22 +1099,31 @@ FX_BOOL app::response(OBJ_METHOD_PARAMS)
 
 	CPDFDoc_Environment* pApp = pContext->GetReaderApp();
 	ASSERT(pApp != NULL);
-	int nLength = 2048;
-	char* pBuff = new char[nLength];
-	nLength = pApp->JS_appResponse(swQuestion, swTitle, swDefault, swLabel, bPassWord, pBuff, nLength);
-	if(nLength<=0)
+
+	const int MAX_INPUT_BYTES = 2048;
+        const int MAX_INPUT_CODE_UNITS = MAX_INPUT_BYTES / 2;
+	unsigned short* pBuff = new unsigned short[MAX_INPUT_CODE_UNITS + 1];
+        if (!pBuff)
+		return FALSE;
+
+	memset(pBuff, 0, MAX_INPUT_BYTES + 2);
+	int nLengthBytes = pApp->JS_appResponse(swQuestion, swTitle, swDefault, swLabel, bPassWord, pBuff, MAX_INPUT_BYTES);
+	if (nLengthBytes <= 0)

[Tom Sepez, 2014/07/29 18:53:37]

hmm.  Just noticed this.  Why do we think that an empty string isn't an OK
response?

[jun_fang, 2014/07/29 19:03:17]

An empty string means that users don't input anythings.So we don't handle it. 

 	{
-		delete[] pBuff;
 		vRet.SetNull();
+		delete[] pBuff;
 		return FALSE;
 	}
-	else
-	{
-		nLength = nLength > sizeof(pBuff) ? sizeof(pBuff) : nLength;
-        vRet = swResponse = CFX_WideString::FromUTF16LE((unsigned short*)pBuff, nLength / 2);
-	}
-	delete[] pBuff;
 
+	// Don't trust the app_response method to actually tell us the length. Instead, stop at U+0000, with which we pre-filled the buffer,
+	// thus avoiding problems with strings containing embedded U+0000 code units.
+	int nCodeUnits;
+	for (nCodeUnits = 0; nCodeUnits < MAX_INPUT_CODE_UNITS; ++nCodeUnits)
+		if (!pBuff[nCodeUnits])
+			break;
+
+	vRet = CFX_WideString::FromUTF16LE(pBuff, nCodeUnits);
+	delete[] pBuff;
 	return TRUE;
 }