lib/Support/FormatVariadic.cpp

   1 //===- FormatVariadic.cpp - Format string parsing and analysis ----*-C++-*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //===----------------------------------------------------------------------===//
   7
   8 #include "llvm/Support/FormatVariadic.h"
   9
  10 using namespace llvm;
  11
  12 static Optional<AlignStyle> translateLocChar(char C) {
  13   switch (C) {
  14   case '-':
  15     return AlignStyle::Left;
  16   case '=':
  17     return AlignStyle::Center;
  18   case '+':
  19     return AlignStyle::Right;
  20   default:
  21     return None;
  22   }
  23   LLVM_BUILTIN_UNREACHABLE;
  24 }
  25
  26 bool formatv_object_base::consumeFieldLayout(StringRef &Spec, AlignStyle &Where,
  27                                              size_t &Align, char &Pad) {
  28   Where = AlignStyle::Right;
  29   Align = 0;
  30   Pad = ' ';
  31   if (Spec.empty())
  32     return true;
  33
  34   if (Spec.size() > 1) {
  35     // A maximum of 2 characters at the beginning can be used for something
  36     // other
  37     // than the width.
  38     // If Spec[1] is a loc char, then Spec[0] is a pad char and Spec[2:...]
  39     // contains the width.
  40     // Otherwise, if Spec[0] is a loc char, then Spec[1:...] contains the width.
  41     // Otherwise, Spec[0:...] contains the width.
  42     if (auto Loc = translateLocChar(Spec[1])) {
  43       Pad = Spec[0];
  44       Where = *Loc;
  45       Spec = Spec.drop_front(2);
  46     } else if (auto Loc = translateLocChar(Spec[0])) {
  47       Where = *Loc;
  48       Spec = Spec.drop_front(1);
  49     }
  50   }
  51
  52   bool Failed = Spec.consumeInteger(0, Align);
  53   return !Failed;
  54 }
  55
  56 Optional<ReplacementItem>
  57 formatv_object_base::parseReplacementItem(StringRef Spec) {
  58   StringRef RepString = Spec.trim("{}");
  59
  60   // If the replacement sequence does not start with a non-negative integer,
  61   // this is an error.
  62   char Pad = ' ';
  63   std::size_t Align = 0;
  64   AlignStyle Where = AlignStyle::Right;
  65   StringRef Options;
  66   size_t Index = 0;
  67   RepString = RepString.trim();
  68   if (RepString.consumeInteger(0, Index)) {
  69     assert(false && "Invalid replacement sequence index!");
  70     return ReplacementItem{};
  71   }
  72   RepString = RepString.trim();
  73   if (!RepString.empty() && RepString.front() == ',') {
  74     RepString = RepString.drop_front();
  75     if (!consumeFieldLayout(RepString, Where, Align, Pad))
  76       assert(false && "Invalid replacement field layout specification!");
  77   }
  78   RepString = RepString.trim();
  79   if (!RepString.empty() && RepString.front() == ':') {
  80     Options = RepString.drop_front().trim();
  81     RepString = StringRef();
  82   }
  83   RepString = RepString.trim();
  84   if (!RepString.empty()) {
  85     assert(false && "Unexpected characters found in replacement string!");
  86   }
  87
  88   return ReplacementItem{Spec, Index, Align, Where, Pad, Options};
  89 }
  90
  91 std::pair<ReplacementItem, StringRef>
  92 formatv_object_base::splitLiteralAndReplacement(StringRef Fmt) {
  93   std::size_t From = 0;
  94   while (From < Fmt.size() && From != StringRef::npos) {
  95     std::size_t BO = Fmt.find_first_of('{', From);
  96     // Everything up until the first brace is a literal.
  97     if (BO != 0)
  98       return std::make_pair(ReplacementItem{Fmt.substr(0, BO)}, Fmt.substr(BO));
  99
 100     StringRef Braces =
 101         Fmt.drop_front(BO).take_while([](char C) { return C == '{'; });
 102     // If there is more than one brace, then some of them are escaped.  Treat
 103     // these as replacements.
 104     if (Braces.size() > 1) {
 105       size_t NumEscapedBraces = Braces.size() / 2;
 106       StringRef Middle = Fmt.substr(BO, NumEscapedBraces);
 107       StringRef Right = Fmt.drop_front(BO + NumEscapedBraces * 2);
 108       return std::make_pair(ReplacementItem{Middle}, Right);
 109     }
 110     // An unterminated open brace is undefined.  We treat the rest of the string
 111     // as a literal replacement, but we assert to indicate that this is
 112     // undefined and that we consider it an error.
 113     std::size_t BC = Fmt.find_first_of('}', BO);
 114     if (BC == StringRef::npos) {
 115       assert(
 116           false &&
 117           "Unterminated brace sequence.  Escape with {{ for a literal brace.");
 118       return std::make_pair(ReplacementItem{Fmt}, StringRef());
 119     }
 120
 121     // Even if there is a closing brace, if there is another open brace before
 122     // this closing brace, treat this portion as literal, and try again with the
 123     // next one.
 124     std::size_t BO2 = Fmt.find_first_of('{', BO + 1);
 125     if (BO2 < BC)
 126       return std::make_pair(ReplacementItem{Fmt.substr(0, BO2)},
 127                             Fmt.substr(BO2));
 128
 129     StringRef Spec = Fmt.slice(BO + 1, BC);
 130     StringRef Right = Fmt.substr(BC + 1);
 131
 132     auto RI = parseReplacementItem(Spec);
 133     if (RI.hasValue())
 134       return std::make_pair(*RI, Right);
 135
 136     // If there was an error parsing the replacement item, treat it as an
 137     // invalid replacement spec, and just continue.
 138     From = BC + 1;
 139   }
 140   return std::make_pair(ReplacementItem{Fmt}, StringRef());
 141 }
 142
 143 std::vector<ReplacementItem>
 144 formatv_object_base::parseFormatString(StringRef Fmt) {
 145   std::vector<ReplacementItem> Replacements;
 146   ReplacementItem I;
 147   while (!Fmt.empty()) {
 148     std::tie(I, Fmt) = splitLiteralAndReplacement(Fmt);
 149     if (I.Type != ReplacementType::Empty)
 150       Replacements.push_back(I);
 151   }
 152   return Replacements;
 153 }
 154
 155 void detail::format_adapter::anchor() { }