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127 lines
3.8 KiB
C++
127 lines
3.8 KiB
C++
//===--- StringSwitch.h - Switch-on-literal-string Construct --------------===/
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===/
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//
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// This file implements the StringSwitch template, which mimics a switch()
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// statement whose cases are string literals.
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//
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//===----------------------------------------------------------------------===/
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#ifndef LLVM_ADT_STRINGSWITCH_H
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#define LLVM_ADT_STRINGSWITCH_H
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#include "llvm/ADT/StringRef.h"
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#include <cassert>
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#include <cstring>
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namespace llvm {
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/// \brief A switch()-like statement whose cases are string literals.
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///
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/// The StringSwitch class is a simple form of a switch() statement that
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/// determines whether the given string matches one of the given string
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/// literals. The template type parameter \p T is the type of the value that
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/// will be returned from the string-switch expression. For example,
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/// the following code switches on the name of a color in \c argv[i]:
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///
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/// \code
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/// Color color = StringSwitch<Color>(argv[i])
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/// .Case("red", Red)
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/// .Case("orange", Orange)
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/// .Case("yellow", Yellow)
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/// .Case("green", Green)
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/// .Case("blue", Blue)
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/// .Case("indigo", Indigo)
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/// .Cases("violet", "purple", Violet)
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/// .Default(UnknownColor);
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/// \endcode
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template<typename T, typename R = T>
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class StringSwitch {
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/// \brief The string we are matching.
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StringRef Str;
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/// \brief The pointer to the result of this switch statement, once known,
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/// null before that.
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const T *Result;
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public:
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explicit StringSwitch(StringRef Str)
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: Str(Str), Result(0) { }
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template<unsigned N>
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StringSwitch& Case(const char (&S)[N], const T& Value) {
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if (!Result && N-1 == Str.size() &&
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(std::memcmp(S, Str.data(), N-1) == 0)) {
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Result = &Value;
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}
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return *this;
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}
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template<unsigned N>
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StringSwitch& EndsWith(const char (&S)[N], const T &Value) {
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if (!Result && Str.size() >= N-1 &&
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std::memcmp(S, Str.data() + Str.size() + 1 - N, N-1) == 0) {
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Result = &Value;
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}
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return *this;
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}
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template<unsigned N>
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StringSwitch& StartsWith(const char (&S)[N], const T &Value) {
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if (!Result && Str.size() >= N-1 &&
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std::memcmp(S, Str.data(), N-1) == 0) {
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Result = &Value;
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}
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return *this;
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}
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template<unsigned N0, unsigned N1>
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StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
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const T& Value) {
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return Case(S0, Value).Case(S1, Value);
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}
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template<unsigned N0, unsigned N1, unsigned N2>
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StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
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const char (&S2)[N2], const T& Value) {
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return Case(S0, Value).Case(S1, Value).Case(S2, Value);
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}
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template<unsigned N0, unsigned N1, unsigned N2, unsigned N3>
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StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
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const char (&S2)[N2], const char (&S3)[N3],
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const T& Value) {
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return Case(S0, Value).Case(S1, Value).Case(S2, Value).Case(S3, Value);
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}
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template<unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4>
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StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
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const char (&S2)[N2], const char (&S3)[N3],
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const char (&S4)[N4], const T& Value) {
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return Case(S0, Value).Case(S1, Value).Case(S2, Value).Case(S3, Value)
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.Case(S4, Value);
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}
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R Default(const T& Value) const {
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if (Result)
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return *Result;
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return Value;
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}
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operator R() const {
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assert(Result && "Fell off the end of a string-switch");
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return *Result;
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}
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};
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} // end namespace llvm
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#endif // LLVM_ADT_STRINGSWITCH_H
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