lib/Support/FormatVariadic.cpp

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