llvm/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 #include <cassert>
  10 #include <optional>
  11
  12 using namespace llvm;
  13
  14 static std::optional<AlignStyle> translateLocChar(char C) {
  15   switch (C) {
  16   case '-':
  17     return AlignStyle::Left;
  18   case '=':
  19     return AlignStyle::Center;
  20   case '+':
  21     return AlignStyle::Right;
  22   default:
  23     return std::nullopt;
  24   }
  25   LLVM_BUILTIN_UNREACHABLE;
  26 }
  27
  28 bool formatv_object_base::consumeFieldLayout(StringRef &Spec, AlignStyle &Where,
  29                                              size_t &Align, char &Pad) {
  30   Where = AlignStyle::Right;
  31   Align = 0;
  32   Pad = ' ';
  33   if (Spec.empty())
  34     return true;
  35
  36   if (Spec.size() > 1) {
  37     // A maximum of 2 characters at the beginning can be used for something
  38     // other
  39     // than the width.
  40     // If Spec[1] is a loc char, then Spec[0] is a pad char and Spec[2:...]
  41     // contains the width.
  42     // Otherwise, if Spec[0] is a loc char, then Spec[1:...] contains the width.
  43     // Otherwise, Spec[0:...] contains the width.
  44     if (auto Loc = translateLocChar(Spec[1])) {
  45       Pad = Spec[0];
  46       Where = *Loc;
  47       Spec = Spec.drop_front(2);
  48     } else if (auto Loc = translateLocChar(Spec[0])) {
  49       Where = *Loc;
  50       Spec = Spec.drop_front(1);
  51     }
  52   }
  53
  54   bool Failed = Spec.consumeInteger(0, Align);
  55   return !Failed;
  56 }
  57
  58 std::optional<ReplacementItem>
  59 formatv_object_base::parseReplacementItem(StringRef Spec) {
  60   StringRef RepString = Spec.trim("{}");
  61
  62   // If the replacement sequence does not start with a non-negative integer,
  63   // this is an error.
  64   char Pad = ' ';
  65   std::size_t Align = 0;
  66   AlignStyle Where = AlignStyle::Right;
  67   StringRef Options;
  68   size_t Index = 0;
  69   RepString = RepString.trim();
  70   if (RepString.consumeInteger(0, Index)) {
  71     assert(false && "Invalid replacement sequence index!");
  72     return ReplacementItem{};
  73   }
  74   RepString = RepString.trim();
  75   if (RepString.consume_front(",")) {
  76     if (!consumeFieldLayout(RepString, Where, Align, Pad))
  77       assert(false && "Invalid replacement field layout specification!");
  78   }
  79   RepString = RepString.trim();
  80   if (!RepString.empty() && RepString.front() == ':') {
  81     Options = RepString.drop_front().trim();
  82     RepString = StringRef();
  83   }
  84   RepString = RepString.trim();
  85   if (!RepString.empty()) {
  86     assert(false && "Unexpected characters found in replacement string!");
  87   }
  88
  89   return ReplacementItem{Spec, Index, Align, Where, Pad, Options};
  90 }
  91
  92 std::pair<ReplacementItem, StringRef>
  93 formatv_object_base::splitLiteralAndReplacement(StringRef Fmt) {
  94   while (!Fmt.empty()) {
  95     // Everything up until the first brace is a literal.
  96     if (Fmt.front() != '{') {
  97       std::size_t BO = Fmt.find_first_of('{');
  98       return std::make_pair(ReplacementItem{Fmt.substr(0, BO)}, Fmt.substr(BO));
  99     }
 100
 101     StringRef Braces = Fmt.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.take_front(NumEscapedBraces);
 107       StringRef Right = Fmt.drop_front(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('}');
 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('{', 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(1, BC);
 130     StringRef Right = Fmt.substr(BC + 1);
 131
 132     auto RI = parseReplacementItem(Spec);
 133     if (RI)
 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     Fmt = Fmt.drop_front(BC + 1);
 139   }
 140   return std::make_pair(ReplacementItem{Fmt}, StringRef());
 141 }
 142
 143 SmallVector<ReplacementItem, 2>
 144 formatv_object_base::parseFormatString(StringRef Fmt) {
 145   SmallVector<ReplacementItem, 2> 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() { }