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Adjust DiffFilesWithTolerance to help poor cygwin's mmap facility by 

handling zero length files a little more intelligently. If both files are
zero length then we return 0 (true) indicating a match. If only one of the
files is zero length then we return 1 (false) indicating that the files
differ. If the files don't agree in length then they can't match so we
skip the first loop that looks for a quick match.

llvm-svn: 20200
This commit is contained in:
Reid Spencer 2005-02-15 21:47:02 +00:00
parent 5f7c53599e
commit f4425b0208
1 changed files with 24 additions and 8 deletions
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32
llvm/lib/Support/FileUtilities.cpp
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@ -119,7 +119,20 @@ int llvm::DiffFilesWithTolerance(const sys::Path &FileA,
double AbsTol, double RelTol,
std::string *Error) {
try {
// Map in the files into memory.
// Check for zero length files becasue 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)
return 0;
// If only one of them is zero sized then they can't be the same
if ((A_size == 0 || B_size == 0))
return 1;
// Now its safe to mmap the files into memory becasue both files
// have a non-zero size.
sys::MappedFile F1(FileA);
sys::MappedFile F2(FileB);
F1.map();
@ -133,15 +146,18 @@ int llvm::DiffFilesWithTolerance(const sys::Path &FileA,
char *F1P = File1Start;
char *F2P = File2Start;
// Scan for the end of file or first difference.
while (F1P < File1End && F2P < File2End && *F1P == *F2P)
++F1P, ++F2P;
if (A_size == B_size) {
// Scan for the end of file or first difference.
while (F1P < File1End && F2P < File2End && *F1P == *F2P)
++F1P, ++F2P;
// Common case: identifical files.
if (F1P == File1End && F2P == File2End) return 0;
// Common case: identifical files.
if (F1P == File1End && F2P == File2End)
return 0; // Scanned to end, files same
if (AbsTol == 0 && RelTol == 0)
return 1; // Files different!
if (AbsTol == 0 && RelTol == 0)
return 1; // Files different!
}
char *OrigFile1Start = File1Start;
char *OrigFile2Start = File2Start;