CXFA_FMStringExpression: int16_t is not a good type for a string index.

Use early return while we're at it.

Bug: 716519
Change-Id: I4630d8b6121266c76a53f0171ba6dfd307da725a
Reviewed-on: https://pdfium-review.googlesource.com/4611
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

2 files changed, 54 insertions, 20 deletions

diff --git a/xfa/fxfa/fm2js/xfa_simpleexpression.cpp b/xfa/fxfa/fm2js/xfa_simpleexpression.cpp
index 872fe7e2e8..fabdaa60f0 100644
--- a/xfa/fxfa/fm2js/xfa_simpleexpression.cpp
+++ b/xfa/fxfa/fm2js/xfa_simpleexpression.cpp
@@ -153,28 +153,29 @@ CXFA_FMStringExpression::~CXFA_FMStringExpression() {}
 
 void CXFA_FMStringExpression::ToJavaScript(CFX_WideTextBuf& javascript) {
   CFX_WideString tempStr(m_wsString);
-  if (tempStr.GetLength() > 2) {
-    javascript.AppendChar(L'\"');
-    wchar_t oneChar;
-    for (int16_t i = 1; i < tempStr.GetLength() - 1; i++) {
-      oneChar = tempStr[i];
-      switch (oneChar) {
-        case L'\"': {
-          i++;
-          javascript << L"\\\"";
-        } break;
-        case 0x0d:
-          break;
-        case 0x0a: {
-          javascript << L"\\n";
-        } break;
-        default: { javascript.AppendChar(oneChar); } break;
-      }
-    }
-    javascript.AppendChar(L'\"');
-  } else {
+  if (tempStr.GetLength() <= 2) {
     javascript << tempStr;
+    return;
+  }
+  javascript.AppendChar(L'\"');
+  for (int32_t i = 1; i < tempStr.GetLength() - 1; i++) {
+    wchar_t oneChar = tempStr[i];
+    switch (oneChar) {
+      case L'\"':
+        i++;
+        javascript << L"\\\"";
+        break;
+      case 0x0d:
+        break;
+      case 0x0a:
+        javascript << L"\\n";
+        break;
+      default:
+        javascript.AppendChar(oneChar);
+        break;
+    }
   }
+  javascript.AppendChar(L'\"');
 }
 
 CXFA_FMIdentifierExpression::CXFA_FMIdentifierExpression(
diff --git a/xfa/fxfa/fm2js/xfa_simpleexpression_unittest.cpp b/xfa/fxfa/fm2js/xfa_simpleexpression_unittest.cpp
index 160c4a12c4..b1b96e03d5 100644
--- a/xfa/fxfa/fm2js/xfa_simpleexpression_unittest.cpp
+++ b/xfa/fxfa/fm2js/xfa_simpleexpression_unittest.cpp
@@ -7,6 +7,7 @@
 #include <memory>
 #include <utility>
 
+#include "core/fxcrt/fx_string.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/test_support.h"
 #include "third_party/base/ptr_util.h"
@@ -41,3 +42,35 @@ TEST(FMCallExpressionTest, more_than_32_arguments) {
 
   EXPECT_EQ(result.AsStringC(), js.AsStringC());
 }
+
+TEST(FMStringExpressionTest, Empty) {
+  CFX_WideTextBuf accumulator;
+  CXFA_FMStringExpression(1, CFX_WideStringC()).ToJavaScript(accumulator);
+  EXPECT_EQ(L"", accumulator.AsStringC());
+}
+
+TEST(FMStringExpressionTest, Short) {
+  CFX_WideTextBuf accumulator;
+  CXFA_FMStringExpression(1, L"a").ToJavaScript(accumulator);
+  EXPECT_EQ(L"a", accumulator.AsStringC());
+}
+
+TEST(FMStringExpressionTest, Medium) {
+  CFX_WideTextBuf accumulator;
+  CXFA_FMStringExpression(1, L".abcd.").ToJavaScript(accumulator);
+  EXPECT_EQ(L"\"abcd\"", accumulator.AsStringC());
+}
+
+TEST(FMStringExpressionTest, Long) {
+  CFX_WideTextBuf accumulator;
+  std::vector<CFX_WideStringC::UnsignedType> vec(140000, L'A');
+  CXFA_FMStringExpression(1, CFX_WideStringC(vec)).ToJavaScript(accumulator);
+  EXPECT_EQ(140000, accumulator.GetLength());
+}
+
+TEST(FMStringExpressionTest, Quoted) {
+  CFX_WideTextBuf accumulator;
+  CXFA_FMStringExpression(1, L".Simon says \"\"run\"\".")
+      .ToJavaScript(accumulator);
+  EXPECT_EQ(L"\"Simon says \\\"run\\\"\"", accumulator.AsStringC());
+}