Add APIs for limited use of document tagged code.

fpdfsdk/fpdfdoc.cpp

Index: fpdfsdk/fpdfdoc.cpp
diff --git a/fpdfsdk/fpdfdoc.cpp b/fpdfsdk/fpdfdoc.cpp
index 254be3f883acca4fc25fadd3bb971ec0812fd0c5..2dcf606a7cb79f476df34c7d8477fbc8eeaa39ee 100644
--- a/fpdfsdk/fpdfdoc.cpp
+++ b/fpdfsdk/fpdfdoc.cpp
@@ -64,7 +64,7 @@ unsigned long Utf16EncodeMaybeCopyAndReturnLength(const CFX_WideString& text,
                                                   unsigned long buflen) {
   CFX_ByteString encodedText = text.UTF16LE_Encode();
   unsigned long len = encodedText.GetLength();
-  if (buffer && buflen >= len)
+  if (buffer && len <= buflen)
     FXSYS_memcpy(buffer, encodedText.c_str(), len);
   return len;
 }
@@ -186,7 +186,7 @@ DLLEXPORT unsigned long STDCALL FPDFAction_GetFilePath(FPDF_ACTION pDict,
   CPDF_Action action(ToDictionary(static_cast<CPDF_Object*>(pDict)));
   CFX_ByteString path = action.GetFilePath().UTF8Encode();
   unsigned long len = path.GetLength() + 1;
-  if (buffer && buflen >= len)
+  if (buffer && len <= buflen)
     FXSYS_memcpy(buffer, path.c_str(), len);
   return len;
 }
@@ -203,7 +203,7 @@ DLLEXPORT unsigned long STDCALL FPDFAction_GetURIPath(FPDF_DOCUMENT document,
   CPDF_Action action(ToDictionary(static_cast<CPDF_Object*>(pDict)));
   CFX_ByteString path = action.GetURI(pDoc);
   unsigned long len = path.GetLength() + 1;
-  if (buffer && buflen >= len)
+  if (buffer && len <= buflen)
     FXSYS_memcpy(buffer, path.c_str(), len);
   return len;
 }