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/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* VariableInterpolator.cpp
* Copyright (C) 2011 Simon Newton
*/
#include <ola/Logging.h>
#include <string>
#include "tools/ola_trigger/VariableInterpolator.h"
using std::string;
/**
* Interpolate variables within the Context input the input string.
*/
bool InterpolateVariables(const string &input,
string *output,
const Context &context) {
static const char START_VARIABLE_STRING[] = "${";
static const char END_VARIABLE_STRING[] = "}";
static const char ESCAPE_CHARACTER = '\\';
*output = input;
size_t pos = output->size();
while (true) {
pos = output->rfind(START_VARIABLE_STRING, pos);
if (pos == string::npos)
break;
// found a ${
if (pos != 0 && (*output)[pos - 1] == ESCAPE_CHARACTER) {
// not a real ${
pos = pos - 1;
continue;
}
// search forward for the closing brace
size_t closing = output->find(END_VARIABLE_STRING, pos);
if (closing == string::npos) {
// not found
OLA_WARN << "Variable expansion failed for " << *output << ", missing "
<< END_VARIABLE_STRING << " after character " << pos;
return false;
}
// lookup
size_t variable_name_pos = pos + sizeof(START_VARIABLE_STRING) - 1;
const string variable = output->substr(variable_name_pos,
closing - variable_name_pos);
string value;
if (!context.Lookup(variable, &value)) {
OLA_WARN << "Unknown variable " << variable;
return false;
}
output->replace(pos, closing - pos + 1, value);
}
// finally unescape any braces
for (unsigned i = 0; i < output->size(); i++) {
char c = (*output)[i];
if (c == START_VARIABLE_STRING[0] || c == END_VARIABLE_STRING[0]) {
if (i != 0 && (*output)[i - 1] == ESCAPE_CHARACTER)
output->erase(i - 1, 1);
}
}
return true;
}
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