Reduce signed/unsigned comparison warnings

core/fxcodec/codec/fx_codec_flate.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fxcodec/codec/codec_int.h"
 
 #include <algorithm>
 #include <memory>
 
+#include "core/fxcrt/include/fx_ext.h"
 #include "core/include/fxcodec/fx_codec.h"
 #include "core/include/fxcodec/fx_codec_flate.h"
 #include "third_party/zlib_v128/zlib.h"
 
 extern "C" {
 static void* my_alloc_func(void* opaque,
                            unsigned int items,
                            unsigned int size) {
   return FX_Alloc2D(uint8_t, items, size);
 }
@@ skipping 913 matching lines @@
       predictor_type = 1;
     }
   }
   if (bLZW) {
     {
       std::unique_ptr<CLZWDecoder> decoder(new CLZWDecoder);
       dest_size = (FX_DWORD)-1;
       offset = src_size;
       int err = decoder->Decode(NULL, dest_size, src_buf, offset, bEarlyChange);
       if (err || dest_size == 0 || dest_size + 1 < dest_size) {
-        return static_cast<FX_DWORD>(-1);
+        return FX_INVALID_OFFSET;
       }
     }
     {
       std::unique_ptr<CLZWDecoder> decoder(new CLZWDecoder);
       dest_buf = FX_Alloc(uint8_t, dest_size + 1);
       dest_buf[dest_size] = '\0';
       decoder->Decode(dest_buf, dest_size, src_buf, offset, bEarlyChange);
     }
   } else {
     FlateUncompress(src_buf, src_size, estimated_size, dest_buf, dest_size,
                     offset);
   }
   if (predictor_type == 0) {
     return offset;
   }
   FX_BOOL ret = TRUE;
   if (predictor_type == 2) {
     ret = PNG_Predictor(dest_buf, dest_size, Colors, BitsPerComponent, Columns);
   } else if (predictor_type == 1) {
     ret =
         TIFF_Predictor(dest_buf, dest_size, Colors, BitsPerComponent, Columns);
   }
-  return ret ? offset : static_cast<FX_DWORD>(-1);
+  return ret ? offset : FX_INVALID_OFFSET;
 }
 FX_BOOL CCodec_FlateModule::Encode(const uint8_t* src_buf,
                                    FX_DWORD src_size,
                                    int predictor,
                                    int Colors,
                                    int BitsPerComponent,
                                    int Columns,
                                    uint8_t*& dest_buf,
                                    FX_DWORD& dest_size) {
   if (predictor != 2 && predictor < 10) {
@@ skipping 19 matching lines @@
                                    FX_DWORD src_size,
                                    uint8_t*& dest_buf,
                                    FX_DWORD& dest_size) {
   dest_size = src_size + src_size / 1000 + 12;
   dest_buf = FX_Alloc(uint8_t, dest_size);
   unsigned long temp_size = dest_size;
   FPDFAPI_FlateCompress(dest_buf, &temp_size, src_buf, src_size);
   dest_size = (FX_DWORD)temp_size;
   return TRUE;
 }