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A switch-on-string-literal construct that is a nice alternative to
cascading "ifs" of strcmps/memcmps. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85459 91177308-0d34-0410-b5e6-96231b3b80d8
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include/llvm/ADT/StringSwitch.h
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83
include/llvm/ADT/StringSwitch.h
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//===--- 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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// statements 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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/// .Case("violet", Violet)
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/// .Default(UnknownColor);
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/// \endcode
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template<typename 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 result of this switch statement, once known.
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T Result;
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/// \brief Set true when the result of this switch is already known; in this
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/// case, Result is valid.
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bool ResultKnown;
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public:
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explicit StringSwitch(StringRef Str)
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: Str(Str), ResultKnown(false) { }
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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 (!ResultKnown && 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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ResultKnown = true;
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}
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return *this;
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}
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T Default(const T& Value) {
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if (ResultKnown)
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return Result;
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return Value;
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}
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operator T() {
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assert(ResultKnown && "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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