/
Parser.cpp
365 lines (330 loc) · 10.1 KB
/
Parser.cpp
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#include "Parser.h"
#include "Config.h"
#include <stdexcept>
#include <sstream>
namespace cfg
{
Parser::Parser(Config& c)
: config(c), in(nullptr), next_token(NO_TOKEN) {}
Parser::~Parser() {}
void Parser::parse(std::istream& i, const std::string& f, unsigned int l)
{
in = &i;
file = f;
line = l;
// prep the look ahead
std::string dummy;
get_next_token(dummy);
while (next_token != FILE_END)
{
if (next_token == NEWLINE)
{
// skip empty lines
get_next_token(dummy);
}
else
{
parse_section();
}
}
}
Parser::Token Parser::get_next_token(std::string& value)
{
Token token = next_token;
value = next_value;
next_token = lex_token(next_value);
while (next_token == WHITESPACE || next_token == COMMENT)
{
next_token = lex_token(next_value);
}
return token;
}
Parser::Token Parser::lex_token(std::string& value)
{
value.clear();
int c = in->get();
switch (c)
{
case ' ': case '\t': case '\v':
value.push_back(c);
return lex_whitespace(value);
case '\n': case '\r':
value.push_back(c);
return lex_newline(value);
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case '-': case '+':
value.push_back(c);
return lex_number(value);
case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
case 'g': case 'h': case 'i': case 'j': case 'k': case 'l':
case 'm': case 'n': case 'o': case 'p': case 'q': case 'r':
case 's': case 't': case 'u': case 'v': case 'w': case 'x':
case 'y': case 'z':
case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R':
case 'S': case 'T': case 'U': case 'V': case 'W': case 'X':
case 'Y': case 'Z':
case '_':
value.push_back(c);
return lex_identifier(value);
case '"':
return lex_string(value);
case '[':
value = "[";
return OPEN_BRACE;
case ']':
value = "]";
return CLOSE_BRACE;
case '=':
value = "=";
return EQUALS;
case '#':
return lex_comment(value);
case EOF:
return FILE_END;
default:
value.push_back(c);
error("Unexpected " + value + ".");
return ERROR;
}
}
Parser::Token Parser::lex_whitespace(std::string& value)
{
int c = in->get();
while (true)
{
switch (c)
{
case ' ': case '\t': case '\v':
value.push_back(c);
break;
default:
in->unget();
return WHITESPACE;
}
c = in->get();
}
}
Parser::Token Parser::lex_newline(std::string& value)
{
int c = in->get();
line++;
switch (c)
{
case '\n': case '\r':
if (c != value[0])
{
// \r\n or \n\r
value.push_back(c);
}
else
{
// treat \n \n as two newline, obviously
in->unget();
}
return NEWLINE;
default:
in->unget();
return NEWLINE;
}
}
Parser::Token Parser::lex_number(std::string& value)
{
int c = in->get();
while (true)
{
// NOTE: not validating the actual format
switch (c)
{
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case '.':
value.push_back(c);
break;
default:
in->unget();
return NUMBER;
}
c = in->get();
}
}
Parser::Token Parser::lex_identifier(std::string& value)
{
int c = in->get();
while (true)
{
switch (c)
{
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
case 'g': case 'h': case 'i': case 'j': case 'k': case 'l':
case 'm': case 'n': case 'o': case 'p': case 'q': case 'r':
case 's': case 't': case 'u': case 'v': case 'w': case 'x':
case 'y': case 'z':
case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R':
case 'S': case 'T': case 'U': case 'V': case 'W': case 'X':
case 'Y': case 'Z':
case '_': case '-':
value.push_back(c);
break;
default:
in->unget();
return IDENTIFIER;
}
c = in->get();
}
}
Parser::Token Parser::lex_string(std::string& value)
{
int c = in->get();
while (true)
{
switch (c)
{
case '"':
return STRING;
case '\n': case '\r': case EOF:
error("Unexpected newline in string.");
return ERROR;
case '\\':
c = in->get();
switch (c)
{
case '\'':
value.push_back('\'');
break;
case '"':
value.push_back('"');
break;
case '\\':
value.push_back('\\');
break;
case 'a':
value.push_back('\a');
break;
case 'b':
value.push_back('\b');
break;
case 'f':
value.push_back('\f');
break;
case 'n':
value.push_back('\n');
break;
case 'r':
value.push_back('\r');
break;
case 't':
value.push_back('\t');
break;
case 'v':
value.push_back('\v');
break;
default:
error("Unknown escape sequence.");
break;
}
break;
default:
value.push_back(c);
break;
}
c = in->get();
}
}
Parser::Token Parser::lex_comment(std::string& value)
{
int c = in->get();
while (true)
{
switch (c)
{
case '\n': case '\r': case EOF:
return COMMENT;
default:
value.push_back(c);
break;
}
c = in->get();
}
}
void Parser::parse_section()
{
parse_section_header();
while (next_token == IDENTIFIER || next_token == NEWLINE)
{
parse_value_pair();
}
}
void Parser::parse_section_header()
{
std::string value;
Token t = get_next_token(value);
if (t != OPEN_BRACE)
{
error("Expected open breace.");
}
t = get_next_token(value);
if (t != IDENTIFIER)
{
error("Expected identifier.");
}
section = value;
t = get_next_token(value);
if (t != CLOSE_BRACE)
{
error("Expected close brace.");
}
t = get_next_token(value);
if (t != NEWLINE && t != FILE_END)
{
error("Expected newline.");
}
}
void Parser::parse_value_pair()
{
std::string value;
Token t = get_next_token(value);
if (t == NEWLINE)
{
// accept empty line
return;
}
if (t != IDENTIFIER)
{
error("Expected identifier.");
}
std::string name = value;
t = get_next_token(value);
if (t != EQUALS)
{
error("Expected equals.");
}
t = get_next_token(value);
if (t != IDENTIFIER && t != STRING && t != NUMBER)
{
error("Expected identifier or string.");
}
config.set_value(section, name, value);
t = get_next_token(value);
if (t != NEWLINE && t != FILE_END)
{
error("Expected newline.");
}
}
void Parser::error(const std::string& msg)
{
std::stringstream buff;
if (!file.empty())
{
buff << file;
}
buff << "(" << line << "): " << msg;
throw std::runtime_error(buff.str());
}
}