1//===--- StringSwitch.h - Switch-on-literal-string Construct --------------===/
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//===----------------------------------------------------------------------===/
8//
9//  This file implements the StringSwitch template, which mimics a switch()
10//  statement whose cases are string literals.
11//
12//===----------------------------------------------------------------------===/
13#ifndef LLVM_ADT_STRINGSWITCH_H
14#define LLVM_ADT_STRINGSWITCH_H
15
16#include "llvm/ADT/StringRef.h"
17#include <cassert>
18#include <cstring>
19
20namespace llvm {
21
22/// \brief A switch()-like statement whose cases are string literals.
23///
24/// The StringSwitch class is a simple form of a switch() statement that
25/// determines whether the given string matches one of the given string
26/// literals. The template type parameter \p T is the type of the value that
27/// will be returned from the string-switch expression. For example,
28/// the following code switches on the name of a color in \c argv[i]:
29///
30/// \code
31/// Color color = StringSwitch<Color>(argv[i])
32///   .Case("red", Red)
33///   .Case("orange", Orange)
34///   .Case("yellow", Yellow)
35///   .Case("green", Green)
36///   .Case("blue", Blue)
37///   .Case("indigo", Indigo)
38///   .Cases("violet", "purple", Violet)
39///   .Default(UnknownColor);
40/// \endcode
41template<typename T, typename R = T>
42class StringSwitch {
43  /// \brief The string we are matching.
44  StringRef Str;
45
46  /// \brief The pointer to the result of this switch statement, once known,
47  /// null before that.
48  const T *Result;
49
50public:
51  explicit StringSwitch(StringRef S)
52  : Str(S), Result(0) { }
53
54  template<unsigned N>
55  StringSwitch& Case(const char (&S)[N], const T& Value) {
56    if (!Result && N-1 == Str.size() &&
57        (std::memcmp(S, Str.data(), N-1) == 0)) {
58      Result = &Value;
59    }
60
61    return *this;
62  }
63
64  template<unsigned N>
65  StringSwitch& EndsWith(const char (&S)[N], const T &Value) {
66    if (!Result && Str.size() >= N-1 &&
67        std::memcmp(S, Str.data() + Str.size() + 1 - N, N-1) == 0) {
68      Result = &Value;
69    }
70
71    return *this;
72  }
73
74  template<unsigned N>
75  StringSwitch& StartsWith(const char (&S)[N], const T &Value) {
76    if (!Result && Str.size() >= N-1 &&
77        std::memcmp(S, Str.data(), N-1) == 0) {
78      Result = &Value;
79    }
80
81    return *this;
82  }
83
84  template<unsigned N0, unsigned N1>
85  StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
86                      const T& Value) {
87    return Case(S0, Value).Case(S1, Value);
88  }
89
90  template<unsigned N0, unsigned N1, unsigned N2>
91  StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
92                      const char (&S2)[N2], const T& Value) {
93    return Case(S0, Value).Case(S1, Value).Case(S2, Value);
94  }
95
96  template<unsigned N0, unsigned N1, unsigned N2, unsigned N3>
97  StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
98                      const char (&S2)[N2], const char (&S3)[N3],
99                      const T& Value) {
100    return Case(S0, Value).Case(S1, Value).Case(S2, Value).Case(S3, Value);
101  }
102
103  template<unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4>
104  StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
105                      const char (&S2)[N2], const char (&S3)[N3],
106                      const char (&S4)[N4], const T& Value) {
107    return Case(S0, Value).Case(S1, Value).Case(S2, Value).Case(S3, Value)
108      .Case(S4, Value);
109  }
110
111  R Default(const T& Value) const {
112    if (Result)
113      return *Result;
114
115    return Value;
116  }
117
118  operator R() const {
119    assert(Result && "Fell off the end of a string-switch");
120    return *Result;
121  }
122};
123
124} // end namespace llvm
125
126#endif // LLVM_ADT_STRINGSWITCH_H
127