diff --git a/include/llvm/ADT/StringSwitch.h b/include/llvm/ADT/StringSwitch.h new file mode 100644 index 00000000000..d7fac718bb2 --- /dev/null +++ b/include/llvm/ADT/StringSwitch.h @@ -0,0 +1,83 @@ +//===--- StringSwitch.h - Switch-on-literal-string Construct --------------===/ +// +// 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 StringSwitch template, which mimics a switch() +// statements whose cases are string literals. +// +//===----------------------------------------------------------------------===/ +#ifndef LLVM_ADT_STRINGSWITCH_H +#define LLVM_ADT_STRINGSWITCH_H + +#include "llvm/ADT/StringRef.h" +#include +#include + +namespace llvm { + +/// \brief A switch()-like statement whose cases are string literals. +/// +/// The StringSwitch class is a simple form of a switch() statement that +/// determines whether the given string matches one of the given string +/// literals. The template type parameter \p T is the type of the value that +/// will be returned from the string-switch expression. For example, +/// the following code switches on the name of a color in \c argv[i]: +/// +/// \code +/// Color color = StringSwitch(argv[i]) +/// .Case("red", Red) +/// .Case("orange", Orange) +/// .Case("yellow", Yellow) +/// .Case("green", Green) +/// .Case("blue", Blue) +/// .Case("indigo", Indigo) +/// .Case("violet", Violet) +/// .Default(UnknownColor); +/// \endcode +template +class StringSwitch { + /// \brief The string we are matching. + StringRef Str; + + /// \brief The result of this switch statement, once known. + T Result; + + /// \brief Set true when the result of this switch is already known; in this + /// case, Result is valid. + bool ResultKnown; + +public: + explicit StringSwitch(StringRef Str) + : Str(Str), ResultKnown(false) { } + + template + StringSwitch& Case(const char (&S)[N], const T& Value) { + if (!ResultKnown && N-1 == Str.size() && + (std::memcmp(S, Str.data(), N-1) == 0)) { + Result = Value; + ResultKnown = true; + } + + return *this; + } + + T Default(const T& Value) { + if (ResultKnown) + return Result; + + return Value; + } + + operator T() { + assert(ResultKnown && "Fell off the end of a string-switch"); + return Result; + } +}; + +} // end namespace llvm + +#endif // LLVM_ADT_STRINGSWITCH_H \ No newline at end of file