From 67dfacdd80791984a11d5ce3a4df8dad3043ed8f Mon Sep 17 00:00:00 2001
From: Marcos Pividori <mpividori@google.com>
Date: Tue, 13 Dec 2016 17:46:32 +0000
Subject: [PATCH] [libFuzzer] Implement DirName() for Windows.

Implement DirName from scratch to avoid dependencies on external libraries.
It's based on MSDN documentation for Naming Files, Paths, and Namespaces.

The algorithm can't simply start from the end and look backwards for the
first separator, because we need to preserve the prefix that represent
the root location. We shouldn't remove anything there. In Windows we
have many different options, like:
 \\Server\Share\ , \ , C: , C:\ , \\?\C:\ , \\?\UNC\Server\Share\
We remove the last separator in the rest of the path, if it exists.

It was implemented to have a similar behaviour to dirname() in linux,
removing trailing separators, returning "." when the path doesn't
contain separators, etc.

Differential Revision: https://reviews.llvm.org/D27579

llvm-svn: 289562
---
 llvm/lib/Fuzzer/FuzzerIOWindows.cpp | 136 +++++++++++++++++++++++++++++++++++-
 1 file changed, 135 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Fuzzer/FuzzerIOWindows.cpp b/llvm/lib/Fuzzer/FuzzerIOWindows.cpp
index df530cd..dd36d06 100644
--- a/llvm/lib/Fuzzer/FuzzerIOWindows.cpp
+++ b/llvm/lib/Fuzzer/FuzzerIOWindows.cpp
@@ -139,8 +139,142 @@ void DeleteFile(const std::string &Path) {
   _unlink(Path.c_str());
 }
 
+static bool IsSeparator(char C) {
+  return C == '\\' || C == '/';
+}
+
+// Parse disk designators, like "C:\". If Relative == true, also accepts: "C:".
+// Returns number of characters considered if successful.
+static size_t ParseDrive(const std::string &FileName, const size_t Offset,
+                         bool Relative = true) {
+  if (Offset + 1 >= FileName.size() || FileName[Offset + 1] != ':')
+    return 0;
+  if (Offset + 2 >= FileName.size() || !IsSeparator(FileName[Offset + 2])) {
+    if (!Relative) // Accept relative path?
+      return 0;
+    else
+      return 2;
+  }
+  return 3;
+}
+
+// Parse a file name, like: SomeFile.txt
+// Returns number of characters considered if successful.
+static size_t ParseFileName(const std::string &FileName, const size_t Offset) {
+  size_t Pos = Offset;
+  const size_t End = FileName.size();
+  for(; Pos < End && !IsSeparator(FileName[Pos]); ++Pos)
+    ;
+  return Pos - Offset;
+}
+
+// Parse a directory ending in separator, like: SomeDir\
+// Returns number of characters considered if successful.
+static size_t ParseDir(const std::string &FileName, const size_t Offset) {
+  size_t Pos = Offset;
+  const size_t End = FileName.size();
+  if (Pos >= End || IsSeparator(FileName[Pos]))
+    return 0;
+  for(; Pos < End && !IsSeparator(FileName[Pos]); ++Pos)
+    ;
+  if (Pos >= End)
+    return 0;
+  ++Pos; // Include separator.
+  return Pos - Offset;
+}
+
+// Parse a servername and share, like: SomeServer\SomeShare\
+// Returns number of characters considered if successful.
+static size_t ParseServerAndShare(const std::string &FileName,
+                                  const size_t Offset) {
+  size_t Pos = Offset, Res;
+  if (!(Res = ParseDir(FileName, Pos)))
+    return 0;
+  Pos += Res;
+  if (!(Res = ParseDir(FileName, Pos)))
+    return 0;
+  Pos += Res;
+  return Pos - Offset;
+}
+
+// Parse the given Ref string from the position Offset, to exactly match the given
+// string Patt.
+// Returns number of characters considered if successful.
+static size_t ParseCustomString(const std::string &Ref, size_t Offset,
+                                const char *Patt) {
+  size_t Len = strlen(Patt);
+  if (Offset + Len > Ref.size())
+    return 0;
+  return Ref.compare(Offset, Len, Patt) == 0 ? Len : 0;
+}
+
+// Parse a location, like:
+// \\?\UNC\Server\Share\  \\?\C:\  \\Server\Share\  \  C:\  C:
+// Returns number of characters considered if successful.
+static size_t ParseLocation(const std::string &FileName) {
+  size_t Pos = 0, Res;
+
+  if ((Res = ParseCustomString(FileName, Pos, R"(\\?\)"))) {
+    Pos += Res;
+    if ((Res = ParseCustomString(FileName, Pos, R"(UNC\)"))) {
+      Pos += Res;
+      if ((Res = ParseServerAndShare(FileName, Pos)))
+        return Pos + Res;
+      return 0;
+    }
+    if ((Res = ParseDrive(FileName, Pos, false)))
+      return Pos + Res;
+    return 0;
+  }
+
+  if (Pos < FileName.size() && IsSeparator(FileName[Pos])) {
+    ++Pos;
+    if (Pos < FileName.size() && IsSeparator(FileName[Pos])) {
+      ++Pos;
+      if ((Res = ParseServerAndShare(FileName, Pos)))
+        return Pos + Res;
+      return 0;
+    }
+    return Pos;
+  }
+
+  if ((Res = ParseDrive(FileName, Pos)))
+    return Pos + Res;
+
+  return Pos;
+}
+
 std::string DirName(const std::string &FileName) {
-  assert(0 && "Unimplemented");
+  size_t LocationLen = ParseLocation(FileName);
+  size_t DirLen = 0, Res;
+  while ((Res = ParseDir(FileName, LocationLen + DirLen)))
+    DirLen += Res;
+  size_t FileLen = ParseFileName(FileName, LocationLen + DirLen);
+
+  if (LocationLen + DirLen + FileLen != FileName.size()) {
+    Printf("DirName() failed for \"%s\", invalid path.\n", FileName.c_str());
+    exit(1);
+  }
+
+  if (DirLen) {
+    --DirLen; // Remove trailing separator.
+    if (!FileLen) { // Path ended in separator.
+      assert(DirLen);
+      // Remove file name from Dir.
+      while (DirLen && !IsSeparator(FileName[LocationLen + DirLen - 1]))
+        --DirLen;
+      if (DirLen) // Remove trailing separator.
+        --DirLen;
+    }
+  }
+
+  if (!LocationLen) { // Relative path.
+    if (!DirLen)
+      return ".";
+    return std::string(".\\").append(FileName, 0, DirLen);
+  }
+
+  return FileName.substr(0, LocationLen + DirLen);
 }
 
 }  // namespace fuzzer
-- 
2.7.4