win: Add open equivalent

util/file/string_file_writer.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 69 matching lines @@
 
 #ifndef NDEBUG
   // The interface says that |iovecs| is not sacred, so scramble it to make sure
   // that nobody depends on it.
   memset(&(*iovecs)[0], 0xa5, sizeof((*iovecs)[0]) * iovecs->size());
 #endif
 
   return true;
 }
 
-off_t StringFileWriter::Seek(off_t offset, int whence) {
+FileOffset StringFileWriter::Seek(FileOffset offset, int whence) {
   DCHECK(offset_.IsValid());
 
   size_t base_offset;
 
   switch (whence) {
     case SEEK_SET:
       base_offset = 0;
       break;
 
     case SEEK_CUR:
       base_offset = offset_.ValueOrDie();
       break;
 
     case SEEK_END:
       base_offset = string_.size();
       break;
 
     default:
       LOG(ERROR) << "Seek(): invalid whence " << whence;
       return -1;
   }
 
-  off_t base_offset_offt;
+  FileOffset base_offset_offt;
   if (!AssignIfInRange(&base_offset_offt, base_offset)) {
-    LOG(ERROR) << "Seek(): base_offset " << base_offset << " invalid for off_t";
+    LOG(ERROR) << "Seek(): base_offset " << base_offset
+               << " invalid for offset";
     return -1;
   }
-  base::CheckedNumeric<off_t> new_offset(base_offset_offt);
+  base::CheckedNumeric<FileOffset> new_offset(base_offset_offt);
   new_offset += offset;
   if (!new_offset.IsValid()) {
     LOG(ERROR) << "Seek(): new_offset invalid";
     return -1;
   }
-  off_t new_offset_offt = new_offset.ValueOrDie();
+  FileOffset new_offset_offt = new_offset.ValueOrDie();
   size_t new_offset_sizet;
   if (!AssignIfInRange(&new_offset_sizet, new_offset_offt)) {
     LOG(ERROR) << "Seek(): new_offset " << new_offset_offt
                << " invalid for size_t";
     return -1;
   }
 
   offset_ = new_offset_sizet;
 
   return offset_.ValueOrDie();
 }
 
 }  // namespace crashpad