Teach raw_ostream to support hex formatting without a prefix '0x'.

Zachary Turner · Zachary Turner · commit 39571b37a38d · 2015-01-26T18:21:33.000Z
Previously using format_hex() would always print a 0x prior to the hex characters. This allows this to be optional, so that one can choose to print (e.g.) 255 as either 0xFF or just FF. Differential Revision: http://reviews.llvm.org/D7151 llvm-svn: 227108
diff --git a/llvm/include/llvm/Support/Format.h b/llvm/include/llvm/Support/Format.h
@@ -259,21 +259,38 @@ class FormattedNumber {
   unsigned Width;
   bool Hex;
   bool Upper;
+  bool HexPrefix;
   friend class raw_ostream;
 public:
-    FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U)
-      : HexValue(HV), DecValue(DV), Width(W), Hex(H), Upper(U) { }
+  FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U,
+                  bool Prefix)
+      : HexValue(HV), DecValue(DV), Width(W), Hex(H), Upper(U),
+        HexPrefix(Prefix) {}
 };
 
 /// format_hex - Output \p N as a fixed width hexadecimal. If number will not
 /// fit in width, full number is still printed.  Examples:
-///   OS << format_hex(255, 4)        => 0xff
-///   OS << format_hex(255, 4, true)  => 0xFF
-///   OS << format_hex(255, 6)        => 0x00ff
-///   OS << format_hex(255, 2)        => 0xff
-inline FormattedNumber format_hex(uint64_t N, unsigned Width, bool Upper=false) {
+///   OS << format_hex(255, 4)              => 0xff
+///   OS << format_hex(255, 4, true)        => 0xFF
+///   OS << format_hex(255, 6)              => 0x00ff
+///   OS << format_hex(255, 2)              => 0xff
+inline FormattedNumber format_hex(uint64_t N, unsigned Width,
+                                  bool Upper = false) {
   assert(Width <= 18 && "hex width must be <= 18");
-  return FormattedNumber(N, 0, Width, true, Upper);
+  return FormattedNumber(N, 0, Width, true, Upper, true);
+}
+
+/// format_hex_no_prefix - Output \p N as a fixed width hexadecimal. Does not
+/// prepend '0x' to the outputted string.  If number will not fit in width,
+/// full number is still printed.  Examples:
+///   OS << format_hex_no_prefix(255, 4)              => ff
+///   OS << format_hex_no_prefix(255, 4, true)        => FF
+///   OS << format_hex_no_prefix(255, 6)              => 00ff
+///   OS << format_hex_no_prefix(255, 2)              => ff
+inline FormattedNumber format_hex_no_prefix(uint64_t N, unsigned Width,
+                                            bool Upper = false) {
+  assert(Width <= 18 && "hex width must be <= 18");
+  return FormattedNumber(N, 0, Width, true, Upper, false);
 }
 
 /// format_decimal - Output \p N as a right justified, fixed-width decimal. If 
@@ -283,7 +300,7 @@ inline FormattedNumber format_hex(uint64_t N, unsigned Width, bool Upper=false)
 ///   OS << format_decimal(-1, 3)    => " -1"
 ///   OS << format_decimal(12345, 3) => "12345"
 inline FormattedNumber format_decimal(int64_t N, unsigned Width) {
-  return FormattedNumber(0, N, Width, false, false);
+  return FormattedNumber(0, N, Width, false, false, false);
 }
 
 
diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
@@ -410,9 +410,12 @@ raw_ostream &raw_ostream::operator<<(const FormattedString &FS) {
 raw_ostream &raw_ostream::operator<<(const FormattedNumber &FN) {
   if (FN.Hex) {
     unsigned Nibbles = (64 - countLeadingZeros(FN.HexValue)+3)/4;
-    unsigned Width = (FN.Width > Nibbles+2) ? FN.Width : Nibbles+2;
-        
+    unsigned PrefixChars = FN.HexPrefix ? 2 : 0;
+    unsigned Width = std::max(FN.Width, Nibbles + PrefixChars);
+
     char NumberBuffer[20] = "0x0000000000000000";
+    if (!FN.HexPrefix)
+      NumberBuffer[1] = '0';
     char *EndPtr = NumberBuffer+Width;
     char *CurPtr = EndPtr;
     const char A = FN.Upper ? 'A' : 'a';
diff --git a/llvm/unittests/Support/raw_ostream_test.cpp b/llvm/unittests/Support/raw_ostream_test.cpp
@@ -162,6 +162,8 @@ TEST(raw_ostreamTest, FormatHex) {
   EXPECT_EQ("0x1",        printToString(format_hex(1, 3), 3));
   EXPECT_EQ("0x12",       printToString(format_hex(0x12, 3), 4));
   EXPECT_EQ("0x123",      printToString(format_hex(0x123, 3), 5));
+  EXPECT_EQ("FF",         printToString(format_hex_no_prefix(0xFF, 2, true), 4));
+  EXPECT_EQ("ABCD",       printToString(format_hex_no_prefix(0xABCD, 2, true), 4));
   EXPECT_EQ("0xffffffffffffffff",     
                           printToString(format_hex(UINT64_MAX, 18), 18));
   EXPECT_EQ("0x8000000000000000",     
