1 //===- CodeExpander.cpp - Expand variables in a string --------------------===//
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 //
9 /// \file Expand the variables in a string.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "CodeExpander.h"
14 #include "CodeExpansions.h"
15 #include "llvm/Support/CommandLine.h"
16 #include "llvm/Support/raw_ostream.h"
17 #include "llvm/TableGen/Error.h"
18 
19 using namespace llvm;
20 
21 void CodeExpander::emit(raw_ostream &OS) const {
22   StringRef Current = Code;
23 
24   while (!Current.empty()) {
25     size_t Pos = Current.find_first_of("$\n\\");
26     if (Pos == StringRef::npos) {
27       OS << Current;
28       Current = "";
29       continue;
30     }
31 
32     OS << Current.substr(0, Pos);
33     Current = Current.substr(Pos);
34 
35     if (Current.startswith("\n")) {
36       OS << "\n" << Indent;
37       Current = Current.drop_front(1);
38       continue;
39     }
40 
41     if (Current.startswith("\\$") || Current.startswith("\\\\")) {
42       OS << Current[1];
43       Current = Current.drop_front(2);
44       continue;
45     }
46 
47     if (Current.startswith("\\")) {
48       Current = Current.drop_front(1);
49       continue;
50     }
51 
52     if (Current.startswith("${")) {
53       StringRef StartVar = Current;
54       Current = Current.drop_front(2);
55       StringRef Var;
56       std::tie(Var, Current) = Current.split("}");
57 
58       // Warn if we split because no terminator was found.
59       StringRef EndVar = StartVar.drop_front(2 /* ${ */ + Var.size());
60       if (EndVar.empty()) {
61         PrintWarning(Loc, "Unterminated expansion '${" + Var + "'");
62         PrintNote("Code: [{" + Code + "}]");
63       }
64 
65       auto ValueI = Expansions.find(Var);
66       if (ValueI == Expansions.end()) {
67         PrintError(Loc,
68                    "Attempt to expand an undeclared variable '" + Var + "'");
69         PrintNote("Code: [{" + Code + "}]");
70       }
71       if (ShowExpansions)
72         OS << "/*$" << Var << "{*/";
73       OS << Expansions.lookup(Var);
74       if (ShowExpansions)
75         OS << "/*}*/";
76       continue;
77     }
78 
79     PrintWarning(Loc, "Assuming missing escape character: \\$");
80     PrintNote("Code: [{" + Code + "}]");
81     OS << "$";
82     Current = Current.drop_front(1);
83   }
84 }
85