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() { }
156