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
translateLocChar(char C)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
consumeFieldLayout(StringRef & Spec,AlignStyle & Where,size_t & Align,char & Pad)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>
parseReplacementItem(StringRef Spec)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.consume_front(",")) {
76 if (!consumeFieldLayout(RepString, Where, Align, Pad))
77 assert(false && "Invalid replacement field layout specification!");
78 }
79 RepString = RepString.trim();
80 if (RepString.consume_front(":")) {
81 Options = RepString.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>
splitLiteralAndReplacement(StringRef Fmt)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)
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>
parseFormatString(StringRef Fmt)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
anchor()155 void support::detail::format_adapter::anchor() {}
156