[ADT] Support converting to lowercase string in toHex

[phosek]

Summary

This is useful in certain use-cases such as D51833.

[kristina]

LGTM.

(Really nit-picky comment: I would have done it by keeping an offset aside to add for lower case A-F to a-f and kept the original table as is. Implications of removing static may cause an insignificant increase in code size with bad linkers, just speculating, feel free to ignore)

[phosek]

In D51835#1228387, @kristina wrote:

LGTM.

(Really nit-picky comment: I would have done it by keeping an offset aside to add for lower case A-F to a-f and kept the original table as is. Implications of removing static may cause an insignificant increase in code size with bad linkers, just speculating, feel free to ignore)

Done

[kristina]

LGTM, given that there are already good use cases for it.

llvm/trunk/include/llvm/ADT/StringExtras.h

while (X) {
     X >>= 4;
   }
 
   return std::string(BufPtr, std::end(Buffer));
 }
 
 /// Convert buffer \p Input to its hexadecimal representation.
 /// The returned string is double the size of \p Input.
-inline std::string toHex(StringRef Input) {
+inline std::string toHex(StringRef Input, bool LowerCase = false) {
   static const char *const LUT = "0123456789ABCDEF";
+  const uint8_t Offset = LowerCase ? 32 : 0;
   size_t Length = Input.size();
 
   std::string Output;
   Output.reserve(2 * Length);
   for (size_t i = 0; i < Length; ++i) {
     const unsigned char c = Input[i];
-    Output.push_back(LUT[c >> 4]);
-    Output.push_back(LUT[c & 15]);
+    Output.push_back(LUT[c >> 4] | Offset);
+    Output.push_back(LUT[c & 15] | Offset);
   }
   return Output;
 }
 
-inline std::string toHex(ArrayRef<uint8_t> Input) {
-  return toHex(toStringRef(Input));
+inline std::string toHex(ArrayRef<uint8_t> Input, bool LowerCase = false) {
+  return toHex(toStringRef(Input), LowerCase);
 }
 
 inline uint8_t hexFromNibbles(char MSB, char LSB) {
   unsigned U1 = hexDigitValue(MSB);
   unsigned U2 = hexDigitValue(LSB);
   assert(U1 != -1U && U2 != -1U);
 
   return static_cast<uint8_t>((U1 << 4) | U2);

llvm/trunk/unittests/ADT/StringExtrasTest.cpp

 
 TEST(StringExtrasTest, ToAndFromHex) {
   std::vector<uint8_t> OddBytes = {0x5, 0xBD, 0x0D, 0x3E, 0xCD};
   std::string OddStr = "05BD0D3ECD";
   StringRef OddData(reinterpret_cast<const char *>(OddBytes.data()),
                     OddBytes.size());
   EXPECT_EQ(OddStr, toHex(OddData));
   EXPECT_EQ(OddData, fromHex(StringRef(OddStr).drop_front()));
+  EXPECT_EQ(StringRef(OddStr).lower(), toHex(OddData, true));
 
   std::vector<uint8_t> EvenBytes = {0xA5, 0xBD, 0x0D, 0x3E, 0xCD};
   std::string EvenStr = "A5BD0D3ECD";
   StringRef EvenData(reinterpret_cast<const char *>(EvenBytes.data()),
                      EvenBytes.size());
   EXPECT_EQ(EvenStr, toHex(EvenData));
   EXPECT_EQ(EvenData, fromHex(EvenStr));
+  EXPECT_EQ(StringRef(EvenStr).lower(), toHex(EvenData, true));
 }
 
 TEST(StringExtrasTest, to_float) {
   float F;
   EXPECT_TRUE(to_float("4.7", F));
   EXPECT_FLOAT_EQ(4.7f, F);
 
   double D;