tools/gn/string_utils.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "tools/gn/string_utils.h"
   6
   7 #include "tools/gn/err.h"
   8 #include "tools/gn/scope.h"
   9 #include "tools/gn/token.h"
  10 #include "tools/gn/tokenizer.h"
  11 #include "tools/gn/value.h"
  12
  13 namespace {
  14
  15 // Constructs an Err indicating a range inside a string. We assume that the
  16 // token has quotes around it that are not counted by the offset.
  17 Err ErrInsideStringToken(const Token& token, size_t offset, size_t size,
  18                          const std::string& msg,
  19                          const std::string& help = std::string()) {
  20   // The "+1" is skipping over the " at the beginning of the token.
  21   int int_offset = static_cast<int>(offset);
  22   Location begin_loc(token.location().file(),
  23                      token.location().line_number(),
  24                      token.location().char_offset() + int_offset + 1);
  25   Location end_loc(token.location().file(),
  26                    token.location().line_number(),
  27                    token.location().char_offset() + int_offset + 1 +
  28                    static_cast<int>(size));
  29   return Err(LocationRange(begin_loc, end_loc), msg, help);
  30 }
  31
  32 // Given the character input[i] indicating the $ in a string, locates the
  33 // identifier and places its range in |*identifier|, and updates |*i| to
  34 // point to the last character consumed.
  35 //
  36 // On error returns false and sets the error.
  37 bool LocateInlineIdenfitier(const Token& token,
  38                             const char* input, size_t size,
  39                             size_t* i,
  40                             base::StringPiece* identifier,
  41                             Err* err) {
  42   size_t dollars_index = *i;
  43   (*i)++;
  44   if (*i == size) {
  45     *err = ErrInsideStringToken(token, dollars_index, 1, "$ at end of string.",
  46         "I was expecting an identifier after the $.");
  47     return false;
  48   }
  49
  50   bool has_brackets;
  51   if (input[*i] == '{') {
  52     (*i)++;
  53     if (*i == size) {
  54       *err = ErrInsideStringToken(token, dollars_index, 2,
  55           "${ at end of string.",
  56           "I was expecting an identifier inside the ${...}.");
  57       return false;
  58     }
  59     has_brackets = true;
  60   } else {
  61     has_brackets = false;
  62   }
  63
  64   // First char is special.
  65   if (!Tokenizer::IsIdentifierFirstChar(input[*i])) {
  66     *err = ErrInsideStringToken(
  67         token, dollars_index, *i - dollars_index + 1,
  68         "$ not followed by an identifier char.",
  69         "It you want a literal $ use \"\\$\".");
  70     return false;
  71   }
  72   size_t begin_offset = *i;
  73   (*i)++;
  74
  75   // Find the first non-identifier char following the string.
  76   while (*i < size && Tokenizer::IsIdentifierContinuingChar(input[*i]))
  77     (*i)++;
  78   size_t end_offset = *i;
  79
  80   // If we started with a bracket, validate that there's an ending one. Leave
  81   // *i pointing to the last char we consumed (backing up one).
  82   if (has_brackets) {
  83     if (*i == size) {
  84       *err = ErrInsideStringToken(token, dollars_index, *i - dollars_index,
  85                                   "Unterminated ${...");
  86       return false;
  87     } else if (input[*i] != '}') {
  88       *err = ErrInsideStringToken(token, *i, 1, "Not an identifier in string expansion.",
  89           "The contents of ${...} should be an identifier. "
  90           "This character is out of sorts.");
  91       return false;
  92     }
  93     // We want to consume the bracket but also back up one, so *i is unchanged.
  94   } else {
  95     (*i)--;
  96   }
  97
  98   *identifier = base::StringPiece(&input[begin_offset],
  99                                   end_offset - begin_offset);
 100   return true;
 101 }
 102
 103 bool AppendIdentifierValue(Scope* scope,
 104                            const Token& token,
 105                            const base::StringPiece& identifier,
 106                            std::string* output,
 107                            Err* err) {
 108   const Value* value = scope->GetValue(identifier, true);
 109   if (!value) {
 110     // We assume the identifier points inside the token.
 111     *err = ErrInsideStringToken(
 112         token, identifier.data() - token.value().data() - 1, identifier.size(),
 113         "Undefined identifier in string expansion.",
 114         std::string("\"") + identifier + "\" is not currently in scope.");
 115     return false;
 116   }
 117
 118   output->append(value->ToString(false));
 119   return true;
 120 }
 121
 122 }  // namespace
 123
 124 bool ExpandStringLiteral(Scope* scope,
 125                          const Token& literal,
 126                          Value* result,
 127                          Err* err) {
 128   DCHECK(literal.type() == Token::STRING);
 129   DCHECK(literal.value().size() > 1);  // Should include quotes.
 130   DCHECK(result->type() == Value::STRING);  // Should be already set.
 131
 132   // The token includes the surrounding quotes, so strip those off.
 133   const char* input = &literal.value().data()[1];
 134   size_t size = literal.value().size() - 2;
 135
 136   std::string& output = result->string_value();
 137   output.reserve(size);
 138   for (size_t i = 0; i < size; i++) {
 139     if (input[i] == '\\') {
 140       if (i < size - 1) {
 141         switch (input[i + 1]) {
 142           case '\\':
 143           case '"':
 144           case '$':
 145             output.push_back(input[i + 1]);
 146             i++;
 147             continue;
 148           default:  // Everything else has no meaning: pass the literal.
 149             break;
 150         }
 151       }
 152       output.push_back(input[i]);
 153     } else if (input[i] == '$') {
 154       base::StringPiece identifier;
 155       if (!LocateInlineIdenfitier(literal, input, size, &i, &identifier, err))
 156         return false;
 157       if (!AppendIdentifierValue(scope, literal, identifier, &output, err))
 158         return false;
 159     } else {
 160       output.push_back(input[i]);
 161     }
 162   }
 163   return true;
 164 }
 165
 166 std::string RemovePrefix(const std::string& str, const std::string& prefix) {
 167   CHECK(str.size() >= prefix.size() &&
 168         str.compare(0, prefix.size(), prefix) == 0);
 169   return str.substr(prefix.size());
 170 }