[wpiutil] Rewrite StringExtras for std::string_view (#3394)

Remove unused functions and add StringRef-like convenience functions.
Minimize header dependencies.

wpiutil/src/main/native/cpp/llvm/StringExtras.cpp

@@ -1,91 +0,0 @@
-//===-- StringExtras.cpp - Implement the StringExtras header --------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the StringExtras.h header
-//
-//===----------------------------------------------------------------------===//
-
-#include "wpi/StringExtras.h"
-#include "wpi/SmallVector.h"
-#include "wpi/raw_ostream.h"
-using namespace wpi;
-
-/// StrInStrNoCase - Portable version of strcasestr.  Locates the first
-/// occurrence of string 's1' in string 's2', ignoring case.  Returns
-/// the offset of s2 in s1 or npos if s2 cannot be found.
-StringRef::size_type wpi::StrInStrNoCase(StringRef s1, StringRef s2) {
-  size_t N = s2.size(), M = s1.size();
-  if (N > M)
-    return StringRef::npos;
-  for (size_t i = 0, e = M - N + 1; i != e; ++i)
-    if (s1.substr(i, N).equals_lower(s2))
-      return i;
-  return StringRef::npos;
-}
-
-/// getToken - This function extracts one token from source, ignoring any
-/// leading characters that appear in the Delimiters string, and ending the
-/// token at any of the characters that appear in the Delimiters string.  If
-/// there are no tokens in the source string, an empty string is returned.
-/// The function returns a pair containing the extracted token and the
-/// remaining tail string.
-std::pair<StringRef, StringRef> wpi::getToken(StringRef Source,
-                                               StringRef Delimiters) {
-  // Figure out where the token starts.
-  StringRef::size_type Start = Source.find_first_not_of(Delimiters);
-
-  // Find the next occurrence of the delimiter.
-  StringRef::size_type End = Source.find_first_of(Delimiters, Start);
-
-  return std::make_pair(Source.slice(Start, End), Source.substr(End));
-}
-
-/// SplitString - Split up the specified string according to the specified
-/// delimiters, appending the result fragments to the output list.
-void wpi::SplitString(StringRef Source,
-                       SmallVectorImpl<StringRef> &OutFragments,
-                       StringRef Delimiters) {
-  std::pair<StringRef, StringRef> S = getToken(Source, Delimiters);
-  while (!S.first.empty()) {
-    OutFragments.push_back(S.first);
-    S = getToken(S.second, Delimiters);
-  }
-}
-
-void wpi::printEscapedString(StringRef Name, raw_ostream &Out) {
-  for (unsigned i = 0, e = Name.size(); i != e; ++i) {
-    unsigned char C = Name[i];
-    if (isPrint(C) && C != '\\' && C != '"')
-      Out << C;
-    else
-      Out << '\\' << hexdigit(C >> 4) << hexdigit(C & 0x0F);
-  }
-}
-
-void wpi::printHTMLEscaped(StringRef String, raw_ostream &Out) {
-  for (char C : String) {
-    if (C == '&')
-      Out << "&amp;";
-    else if (C == '<')
-      Out << "&lt;";
-    else if (C == '>')
-      Out << "&gt;";
-    else if (C == '\"')
-      Out << "&quot;";
-    else if (C == '\'')
-      Out << "&apos;";
-    else
-      Out << C;
-  }
-}
-
-void wpi::printLowerCase(StringRef String, raw_ostream &Out) {
-  for (const char C : String)
-    Out << toLower(C);
-}

wpiutil/src/main/native/cpp/llvm/StringMap.cpp

@@ -19,6 +19,21 @@
 
 using namespace wpi;
 
+/// HashString - Hash function for strings.
+///
+/// This is the Bernstein hash function.
+//
+// FIXME: Investigate whether a modified bernstein hash function performs
+// better: http://eternallyconfuzzled.com/tuts/algorithms/jsw_tut_hashing.aspx
+//   X*33+c -> X*33^c
+static inline unsigned HashString(std::string_view str,
+                                  unsigned result = 0) noexcept {
+  for (std::string_view::size_type i = 0, e = str.size(); i != e; ++i) {
+    result = result * 33 + static_cast<unsigned char>(str[i]);
+  }
+  return result;
+}
+
 /// Returns the number of buckets to allocate to ensure that the DenseMap can
 /// accommodate \p NumEntries without need to grow().
 static unsigned getMinBucketToReserveForEntries(unsigned NumEntries) {