provide a "strtoull" operation that works on StringRef's.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82322 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/StringRef.cpp

@@ -11,3 +11,66 @@
 using namespace llvm;
 
 const size_t StringRef::npos;
+
+static bool GetAsUnsignedInteger(StringRef Str, unsigned Radix,
+                                 unsigned long long &Result) {
+  // Autosense radix if not specified.
+  if (Radix == 0) {
+    if (Str[0] != '0') {
+      Radix = 10;
+    } else {
+      if (Str.size() < 2) {
+        Radix = 8;
+      } else {
+        if (Str[1] == 'x') {
+          Str = Str.substr(2);
+          Radix = 16;
+        } else if (Str[1] == 'b') {
+          Str = Str.substr(2);
+          Radix = 2;
+        } else {
+          Radix = 8;
+        }
+      }
+    }
+  }
+  
+  // Empty strings (after the radix autosense) are invalid.
+  if (Str.empty()) return true;
+  
+  // Parse all the bytes of the string given this radix.  Watch for overflow.
+  Result = 0;
+  while (!Str.empty()) {
+    unsigned CharVal;
+    if (Str[0] >= '0' && Str[0] <= '9')
+      CharVal = Str[0]-'0';
+    else if (Str[0] >= 'a' && Str[0] <= 'z')
+      CharVal = Str[0]-'a'+10;
+    else if (Str[0] >= 'A' && Str[0] <= 'Z')
+      CharVal = Str[0]-'A'+10;
+    else
+      return true;
+    
+    // If the parsed value is larger than the integer radix, the string is
+    // invalid.
+    if (CharVal >= Radix)
+      return true;
+    
+    // Add in this character.
+    unsigned long long PrevResult = Result;
+    Result = Result*Radix+CharVal;
+    
+    // Check for overflow.
+    if (Result < PrevResult)
+      return true;
+
+    Str = Str.substr(1);
+  }
+  
+  return false;
+}
+
+bool StringRef::getAsInteger(unsigned Radix, unsigned long long &Result) const {
+  return GetAsUnsignedInteger(*this, Radix, Result);
+}
+