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.empty() && RepString.front() == ',') {
76     RepString = RepString.drop_front();
77     if (!consumeFieldLayout(RepString, Where, Align, Pad))
78       assert(false && "Invalid replacement field layout specification!");
79   }
80   RepString = RepString.trim();
81   if (!RepString.empty() && RepString.front() == ':') {
82     Options = RepString.drop_front().trim();
83     RepString = StringRef();
84   }
85   RepString = RepString.trim();
86   if (!RepString.empty()) {
87     assert(false && "Unexpected characters found in replacement string!");
88   }
89 
90   return ReplacementItem{Spec, Index, Align, Where, Pad, Options};
91 }
92 
93 std::pair<ReplacementItem, StringRef>
94 formatv_object_base::splitLiteralAndReplacement(StringRef Fmt) {
95   while (!Fmt.empty()) {
96     // Everything up until the first brace is a literal.
97     if (Fmt.front() != '{') {
98       std::size_t BO = Fmt.find_first_of('{');
99       return std::make_pair(ReplacementItem{Fmt.substr(0, BO)}, Fmt.substr(BO));
100     }
101 
102     StringRef Braces = Fmt.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.take_front(NumEscapedBraces);
108       StringRef Right = Fmt.drop_front(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('}');
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('{', 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(1, BC);
131     StringRef Right = Fmt.substr(BC + 1);
132 
133     auto RI = parseReplacementItem(Spec);
134     if (RI)
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     Fmt = Fmt.drop_front(BC + 1);
140   }
141   return std::make_pair(ReplacementItem{Fmt}, StringRef());
142 }
143 
144 SmallVector<ReplacementItem, 2>
145 formatv_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 
156 void detail::format_adapter::anchor() { }
157