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1 //===- FormatVariadic.cpp - Format string parsing and analysis ----*-C++-*-===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //===----------------------------------------------------------------------===//
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8
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9 #include "llvm/Support/FormatVariadic.h"
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10
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11 using namespace llvm;
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12
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13 static Optional<AlignStyle> translateLocChar(char C) {
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14 switch (C) {
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15 case '-':
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16 return AlignStyle::Left;
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17 case '=':
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18 return AlignStyle::Center;
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19 case '+':
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20 return AlignStyle::Right;
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21 default:
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22 return None;
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23 }
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24 LLVM_BUILTIN_UNREACHABLE;
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25 }
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26
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27 bool formatv_object_base::consumeFieldLayout(StringRef &Spec, AlignStyle &Where,
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28 size_t &Align, char &Pad) {
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29 Where = AlignStyle::Right;
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30 Align = 0;
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31 Pad = ' ';
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32 if (Spec.empty())
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33 return true;
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34
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35 if (Spec.size() > 1) {
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36 // A maximum of 2 characters at the beginning can be used for something
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37 // other
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38 // than the width.
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39 // If Spec[1] is a loc char, then Spec[0] is a pad char and Spec[2:...]
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40 // contains the width.
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41 // Otherwise, if Spec[0] is a loc char, then Spec[1:...] contains the width.
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42 // Otherwise, Spec[0:...] contains the width.
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43 if (auto Loc = translateLocChar(Spec[1])) {
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44 Pad = Spec[0];
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45 Where = *Loc;
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46 Spec = Spec.drop_front(2);
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47 } else if (auto Loc = translateLocChar(Spec[0])) {
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48 Where = *Loc;
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49 Spec = Spec.drop_front(1);
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50 }
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51 }
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52
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53 bool Failed = Spec.consumeInteger(0, Align);
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54 return !Failed;
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55 }
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56
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57 Optional<ReplacementItem>
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58 formatv_object_base::parseReplacementItem(StringRef Spec) {
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59 StringRef RepString = Spec.trim("{}");
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60
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61 // If the replacement sequence does not start with a non-negative integer,
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62 // this is an error.
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63 char Pad = ' ';
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64 std::size_t Align = 0;
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65 AlignStyle Where = AlignStyle::Right;
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66 StringRef Options;
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67 size_t Index = 0;
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68 RepString = RepString.trim();
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69 if (RepString.consumeInteger(0, Index)) {
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70 assert(false && "Invalid replacement sequence index!");
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71 return ReplacementItem{};
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72 }
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73 RepString = RepString.trim();
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74 if (!RepString.empty() && RepString.front() == ',') {
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75 RepString = RepString.drop_front();
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76 if (!consumeFieldLayout(RepString, Where, Align, Pad))
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77 assert(false && "Invalid replacement field layout specification!");
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78 }
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79 RepString = RepString.trim();
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80 if (!RepString.empty() && RepString.front() == ':') {
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81 Options = RepString.drop_front().trim();
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82 RepString = StringRef();
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83 }
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84 RepString = RepString.trim();
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85 if (!RepString.empty()) {
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86 assert(false && "Unexpected characters found in replacement string!");
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87 }
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88
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89 return ReplacementItem{Spec, Index, Align, Where, Pad, Options};
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90 }
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91
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92 std::pair<ReplacementItem, StringRef>
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93 formatv_object_base::splitLiteralAndReplacement(StringRef Fmt) {
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94 std::size_t From = 0;
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95 while (From < Fmt.size() && From != StringRef::npos) {
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96 std::size_t BO = Fmt.find_first_of('{', From);
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97 // Everything up until the first brace is a literal.
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98 if (BO != 0)
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99 return std::make_pair(ReplacementItem{Fmt.substr(0, BO)}, Fmt.substr(BO));
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100
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101 StringRef Braces =
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102 Fmt.drop_front(BO).take_while([](char C) { return C == '{'; });
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103 // If there is more than one brace, then some of them are escaped. Treat
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104 // these as replacements.
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105 if (Braces.size() > 1) {
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106 size_t NumEscapedBraces = Braces.size() / 2;
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107 StringRef Middle = Fmt.substr(BO, NumEscapedBraces);
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108 StringRef Right = Fmt.drop_front(BO + NumEscapedBraces * 2);
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109 return std::make_pair(ReplacementItem{Middle}, Right);
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110 }
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111 // An unterminated open brace is undefined. We treat the rest of the string
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112 // as a literal replacement, but we assert to indicate that this is
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113 // undefined and that we consider it an error.
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114 std::size_t BC = Fmt.find_first_of('}', BO);
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115 if (BC == StringRef::npos) {
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116 assert(
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117 false &&
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118 "Unterminated brace sequence. Escape with {{ for a literal brace.");
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119 return std::make_pair(ReplacementItem{Fmt}, StringRef());
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120 }
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121
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122 // Even if there is a closing brace, if there is another open brace before
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123 // this closing brace, treat this portion as literal, and try again with the
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124 // next one.
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125 std::size_t BO2 = Fmt.find_first_of('{', BO + 1);
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126 if (BO2 < BC)
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127 return std::make_pair(ReplacementItem{Fmt.substr(0, BO2)},
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128 Fmt.substr(BO2));
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129
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130 StringRef Spec = Fmt.slice(BO + 1, BC);
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131 StringRef Right = Fmt.substr(BC + 1);
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132
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133 auto RI = parseReplacementItem(Spec);
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134 if (RI.hasValue())
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135 return std::make_pair(*RI, Right);
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136
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137 // If there was an error parsing the replacement item, treat it as an
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138 // invalid replacement spec, and just continue.
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139 From = BC + 1;
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140 }
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141 return std::make_pair(ReplacementItem{Fmt}, StringRef());
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142 }
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143
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144 std::vector<ReplacementItem>
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145 formatv_object_base::parseFormatString(StringRef Fmt) {
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146 std::vector<ReplacementItem> Replacements;
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147 ReplacementItem I;
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148 while (!Fmt.empty()) {
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149 std::tie(I, Fmt) = splitLiteralAndReplacement(Fmt);
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150 if (I.Type != ReplacementType::Empty)
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151 Replacements.push_back(I);
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152 }
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153 return Replacements;
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154 }
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