add a couple of helpers to the Triple class for decoding

the darwin version string.  This should help consolidate
the variety of weird functions we have scattered around the
codebase that do stuff like this.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78792 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/Triple.cpp

@@ -209,6 +209,71 @@ StringRef Triple::getOSAndEnvironmentName() const {
   return Tmp.split('-').second;                      // Strip second component
 }
 
+static unsigned EatNumber(StringRef &Str) {
+  assert(!Str.empty() && Str[0] >= '0' && Str[0] <= '9' && "Not a number");
+  unsigned Result = Str[0]-'0';
+  
+  // Eat the digit.
+  Str = Str.substr(1);
+  
+  // Handle "darwin11".
+  if (Result == 1 && !Str.empty() && Str[0] >= '0' && Str[0] <= '9') {
+    Result = Result*10 + (Str[0] - '0');
+    // Eat the digit.
+    Str = Str.substr(1);
+  }
+  
+  return Result;
+}
+
+/// getDarwinNumber - Parse the 'darwin number' out of the specific target
+/// triple.  For example, if we have darwin8.5 return 8,5,0.  If any entry is
+/// not defined, return 0's.  This requires that the triple have an OSType of
+/// darwin before it is called.
+void Triple::getDarwinNumber(unsigned &Maj, unsigned &Min,
+                             unsigned &Revision) const {
+  assert(getOS() == Darwin && "Not a darwin target triple!");
+  StringRef OSName = getOSName();
+  assert(OSName.startswith("darwin") && "Unknown darwin target triple!");
+  
+  // Strip off "darwin".
+  OSName = OSName.substr(6);
+  
+  Maj = Min = Revision = 0;
+
+  if (OSName.empty() || OSName[0] < '0' || OSName[0] > '9')
+    return;
+
+  // The major version is the first digit.
+  Maj = EatNumber(OSName);
+  if (OSName.empty()) return;
+  
+  // Handle minor version: 10.4.9 -> darwin8.9.
+  if (OSName[0] != '.')
+    return;
+  
+  // Eat the '.'.
+  OSName = OSName.substr(1);
+
+  if (OSName.empty() || OSName[0] < '0' || OSName[0] > '9')
+    return;
+  
+  Min = EatNumber(OSName);
+  if (OSName.empty()) return;
+
+  // Handle revision darwin8.9.1
+  if (OSName[0] != '.')
+    return;
+  
+  // Eat the '.'.
+  OSName = OSName.substr(1);
+  
+  if (OSName.empty() || OSName[0] < '0' || OSName[0] > '9')
+    return;
+
+  Revision = EatNumber(OSName);
+}
+
 void Triple::setTriple(const Twine &Str) {
   Data = Str.str();
   Arch = InvalidArch;