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
11using namespace llvm;
12
13static 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
27bool 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
57Optional<ReplacementItem>
58formatv_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
92std::pair<ReplacementItem, StringRef>
93formatv_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
144SmallVector<ReplacementItem, 2>
145formatv_object_base::parseFormatString(StringRef Fmt) {
146  SmallVector<ReplacementItem, 2> 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}
155
156void detail::format_adapter::anchor() { }
157