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      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 
     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   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.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     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() { }
    156