Format.h revision ffbbf314f1740b9d73c5af1ad1aa3e731dac026b 
1//===- Format.h - Efficient printf-style formatting for streams -*- C++ -*-===//
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//
10// This file implements the format() function, which can be used with other
11// LLVM subsystems to provide printf-style formatting.  This gives all the power
12// and risk of printf.  This can be used like this (with raw_ostreams as an
13// example):
14//
15//    OS << "mynumber: " << format("%4.5f", 1234.412) << '\n';
16//
17// Or if you prefer:
18//
19//  OS << format("mynumber: %4.5f\n", 1234.412);
20//
21//===----------------------------------------------------------------------===//
22
23#ifndef LLVM_SUPPORT_FORMAT_H
24#define LLVM_SUPPORT_FORMAT_H
25
26#include <cstdio>
27#ifdef WIN32
28#define snprintf _snprintf
29#endif
30
31namespace llvm {
32
33/// format_object_base - This is a helper class used for handling formatted
34/// output.  It is the abstract base class of a templated derived class.
35class format_object_base {
36protected:
37  const char *Fmt;
38  virtual void home(); // Out of line virtual method.
39
40  /// snprint - Call snprintf() for this object, on the given buffer and size.
41  virtual int snprint(char *Buffer, unsigned BufferSize) const = 0;
42
43public:
44  format_object_base(const char *fmt) : Fmt(fmt) {}
45  virtual ~format_object_base() {}
46
47  /// print - Format the object into the specified buffer.  On success, this
48  /// returns the length of the formatted string.  If the buffer is too small,
49  /// this returns a length to retry with, which will be larger than BufferSize.
50  unsigned print(char *Buffer, unsigned BufferSize) const {
51    assert(BufferSize && "Invalid buffer size!");
52
53    // Print the string, leaving room for the terminating null.
54    int N = snprint(Buffer, BufferSize);
55
56    // VC++ and old GlibC return negative on overflow, just double the size.
57    if (N < 0)
58      return BufferSize*2;
59
60    // Other impls yield number of bytes needed, not including the final '\0'.
61    if (unsigned(N) >= BufferSize)
62      return N+1;
63
64    // Otherwise N is the length of output (not including the final '\0').
65    return N;
66  }
67};
68
69/// format_object1 - This is a templated helper class used by the format
70/// function that captures the object to be formated and the format string. When
71/// actually printed, this synthesizes the string into a temporary buffer
72/// provided and returns whether or not it is big enough.
73template <typename T>
74class format_object1 : public format_object_base {
75  T Val;
76public:
77  format_object1(const char *fmt, const T &val)
78    : format_object_base(fmt), Val(val) {
79  }
80
81  virtual int snprint(char *Buffer, unsigned BufferSize) const {
82    return snprintf(Buffer, BufferSize, Fmt, Val);
83  }
84};
85
86/// format_object2 - This is a templated helper class used by the format
87/// function that captures the object to be formated and the format string. When
88/// actually printed, this synthesizes the string into a temporary buffer
89/// provided and returns whether or not it is big enough.
90template <typename T1, typename T2>
91class format_object2 : public format_object_base {
92  T1 Val1;
93  T2 Val2;
94public:
95  format_object2(const char *fmt, const T1 &val1, const T2 &val2)
96  : format_object_base(fmt), Val1(val1), Val2(val2) {
97  }
98
99  virtual int snprint(char *Buffer, unsigned BufferSize) const {
100    return snprintf(Buffer, BufferSize, Fmt, Val1, Val2);
101  }
102};
103
104/// format_object3 - This is a templated helper class used by the format
105/// function that captures the object to be formated and the format string. When
106/// actually printed, this synthesizes the string into a temporary buffer
107/// provided and returns whether or not it is big enough.
108template <typename T1, typename T2, typename T3>
109class format_object3 : public format_object_base {
110  T1 Val1;
111  T2 Val2;
112  T3 Val3;
113public:
114  format_object3(const char *fmt, const T1 &val1, const T2 &val2,const T3 &val3)
115    : format_object_base(fmt), Val1(val1), Val2(val2), Val3(val3) {
116  }
117
118  virtual int snprint(char *Buffer, unsigned BufferSize) const {
119    return snprintf(Buffer, BufferSize, Fmt, Val1, Val2, Val3);
120  }
121};
122
123/// format - This is a helper function that is used to produce formatted output.
124/// This is typically used like:  OS << format("%0.4f", myfloat) << '\n';
125template <typename T>
126inline format_object1<T> format(const char *Fmt, const T &Val) {
127  return format_object1<T>(Fmt, Val);
128}
129
130/// format - This is a helper function that is used to produce formatted output.
131/// This is typically used like:  OS << format("%0.4f", myfloat) << '\n';
132template <typename T1, typename T2>
133inline format_object2<T1, T2> format(const char *Fmt, const T1 &Val1,
134                                     const T2 &Val2) {
135  return format_object2<T1, T2>(Fmt, Val1, Val2);
136}
137
138/// format - This is a helper function that is used to produce formatted output.
139/// This is typically used like:  OS << format("%0.4f", myfloat) << '\n';
140template <typename T1, typename T2, typename T3>
141  inline format_object3<T1, T2, T3> format(const char *Fmt, const T1 &Val1,
142                                           const T2 &Val2, const T3 &Val3) {
143  return format_object3<T1, T2, T3>(Fmt, Val1, Val2, Val3);
144}
145
146} // end namespace llvm
147
148#endif
149