mpw/mpw/environ.re.cpp
2013-05-18 17:24:25 -04:00

127 lines
2.0 KiB
C++

#include <string>
#include <unordered_map>
#include <cstdio>
/*
* #...comment
* var=value
* where value may contain $var and ${var} interpolations.
*
*/
namespace MPW {
std::string EvalString(std::string &s, std::unordered_map<std::string, std::string> &env)
{
std::string rv;
const char *cp = s.c_str();
const char *marker = NULL;
while (*cp)
{
const char *begin = cp;
/*!re2c
re2c:define:YYCTYPE = "char";
re2c:define:YYCURSOR = cp;
re2c:define:YYMARKER = marker;
re2c:yyfill:enable = 0;
re2c:yych:conversion = 1;
re2c:indent:top = 1;
'$' [A-Za-z0-9_]+ {
std::string tmp(begin + 1, cp);
// lookup value...
// append to rv.
auto iter = env.find(tmp);
if (iter != env.end())
{
rv.append(iter->second);
}
continue;
}
'${' [A-Za-z0-9_]+ '}' {
std::string tmp(begin + 2, cp - 1);
auto iter = env.find(tmp);
if (iter != env.end())
{
rv.append(iter->second);
}
continue;
}
. {
rv.push_back(*begin);
continue;
}
[^] {
break;
}
*/
}
return rv;
}
void LoadEnvironment(std::string &envfile, std::unordered_map<std::string, std::string> &env)
{
FILE *fp;
fp = fopen(envfile.c_str(), "r");
if (!fp) return;
for (;;)
{
char *begin;
char *end;
char *iter;
size_t length;
begin = fgetln(fp, &length);
if (!begin) break; // eof or error.
if (!length) continue;
if (begin[0] == '#') continue;
while (length && isspace(begin[length - 1])) --length;
if (!length) continue;
// key=value
// ehh, this could really check for [A-Za-z0-9_]+ '='
end = begin + length;
iter = std::find(begin, end, '=');
if (iter == end || iter == begin)
{
fprintf(stderr, "Invalid Environment entry: %.*s\n", (int)length, begin);
continue;
}
std::string key(begin, iter);
std::string value(iter + 1, end);
value = EvalString(value, env);
//fprintf(stdout, "%s = %s\n", key.c_str(), value.c_str());
// todo -- does this replace an existing value?
env.emplace(key, value);
}
fclose(fp);
}
}