Add llvm::hexDigitValue to convert single characters to hex.

This is duplicated in a couple places in the codebase. Adopt this in APFloat.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172851 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 0 deletions

diff --git a/include/llvm/ADT/StringExtras.h b/include/llvm/ADT/StringExtras.h
index 9503e0f805..d2887c5c2c 100644
--- a/include/llvm/ADT/StringExtras.h
+++ b/include/llvm/ADT/StringExtras.h
@@ -27,6 +27,17 @@ static inline char hexdigit(unsigned X, bool LowerCase = false) {
   return X < 10 ? '0' + X : HexChar + X - 10;
 }
 
+/// Interpret the given character \p C as a hexadecimal digit and return its
+/// value.
+///
+/// If \p C is not a valid hex digit, -1U is returned.
+static inline unsigned hexDigitValue(char C) {
+  if (C >= '0' && C <= '9') return C-'0';
+  if (C >= 'a' && C <= 'f') return C-'a'+10U;
+  if (C >= 'A' && C <= 'F') return C-'A'+10U;
+  return -1U;
+}
+
 /// utohex_buffer - Emit the specified number into the buffer specified by
 /// BufferEnd, returning a pointer to the start of the string.  This can be used
 /// like this: (note that the buffer must be large enough to handle any number):