- try {
- // Check for zero length files because some systems croak when you try to
- // mmap an empty file.
- size_t A_size = FileA.getSize();
- size_t B_size = FileB.getSize();
-
- // If they are both zero sized then they're the same
- if (A_size == 0 && B_size == 0)
+ const sys::FileStatus *FileAStat = FileA.getFileStatus(false, Error);
+ if (!FileAStat)
+ return 2;
+ const sys::FileStatus *FileBStat = FileB.getFileStatus(false, Error);
+ if (!FileBStat)
+ return 2;
+
+ // Check for zero length files because some systems croak when you try to
+ // mmap an empty file.
+ size_t A_size = FileAStat->getSize();
+ size_t B_size = FileBStat->getSize();
+
+ // If they are both zero sized then they're the same
+ if (A_size == 0 && B_size == 0)
+ return 0;
+
+ // If only one of them is zero sized then they can't be the same
+ if ((A_size == 0 || B_size == 0)) {
+ if (Error)
+ *Error = "Files differ: one is zero-sized, the other isn't";
+ return 1;
+ }
+
+ // Now its safe to mmap the files into memory becasue both files
+ // have a non-zero size.
+ sys::MappedFile F1;
+ if (F1.open(FileA, sys::MappedFile::READ_ACCESS, Error))
+ return 2;
+ sys::MappedFile F2;
+ if (F2.open(FileB, sys::MappedFile::READ_ACCESS, Error))
+ return 2;
+ if (!F1.map(Error))
+ return 2;
+ if (!F2.map(Error))
+ return 2;
+
+ // Okay, now that we opened the files, scan them for the first difference.
+ char *File1Start = F1.charBase();
+ char *File2Start = F2.charBase();
+ char *File1End = File1Start+A_size;
+ char *File2End = File2Start+B_size;
+ char *F1P = File1Start;
+ char *F2P = File2Start;
+
+ if (A_size == B_size) {
+ // Are the buffers identical?
+ if (std::memcmp(File1Start, File2Start, A_size) == 0)