Aegisub/aegisub/libaegisub/common/cajun/reader.cpp

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/**********************************************
License: BSD
Project Webpage: http://cajun-jsonapi.sourceforge.net/
Author: Terry Caton
***********************************************/
#include "libaegisub/cajun/reader.h"
#ifndef LAGI_PRE
#include <cassert>
#include <set>
#include <sstream>
#endif
/*
TODO:
* better documentation
* unicode character decoding
*/
namespace json {
std::istream& operator >> (std::istream& istr, UnknownElement& elementRoot) {
Reader::Read(elementRoot, istr);
return istr;
}
/// Wrapper around istream to keep track of document/line offsets
class Reader::InputStream {
std::istream& m_iStr;
Location m_Location;
public:
InputStream(std::istream& iStr) : m_iStr(iStr) { }
int Get() {
assert(!m_iStr.eof());
int c = m_iStr.get();
++m_Location.m_nDocOffset;
if (c == '\n') {
++m_Location.m_nLine;
m_Location.m_nLineOffset = 0;
}
else {
++m_Location.m_nLineOffset;
}
return c;
}
int Peek() {
assert(!m_iStr.eof());
return m_iStr.peek();
}
bool EOS() {
m_iStr.peek(); // apparently eof flag isn't set until a character read is attempted. whatever.
return m_iStr.eof();
}
Location const& GetLocation() const { return m_Location; }
};
class Reader::TokenStream {
Tokens const& m_Tokens;
Tokens::const_iterator m_itCurrent;
public:
TokenStream(Tokens const& tokens) : m_Tokens(tokens), m_itCurrent(tokens.begin())
{ }
Token const& Peek() {
assert(!EOS());
return *m_itCurrent;
}
Token const& Get() {
assert(!EOS());
return *m_itCurrent++;
}
bool EOS() const { return m_itCurrent == m_Tokens.end(); }
};
void Reader::Read(UnknownElement& unknown, std::istream& istr) {
Reader reader;
Tokens tokens;
InputStream inputStream(istr);
reader.Scan(tokens, inputStream);
TokenStream tokenStream(tokens);
unknown = reader.Parse(tokenStream);
if (!tokenStream.EOS()) {
Token const& token = tokenStream.Peek();
throw ParseException("Expected End of token stream; found " + token.sValue, token.locBegin, token.locEnd);
}
}
void Reader::Scan(Tokens& tokens, InputStream& inputStream) {
while (EatWhiteSpace(inputStream), !inputStream.EOS()) {
// if all goes well, we'll create a token each pass
Token token;
token.locBegin = inputStream.GetLocation();
// gives us null-terminated string
std::string sChar;
sChar.push_back(inputStream.Peek());
switch (sChar[0]) {
case '{':
token.sValue = sChar[0];
MatchExpectedString(sChar, inputStream);
token.nType = Token::TOKEN_OBJECT_BEGIN;
break;
case '}':
token.sValue = sChar[0];
MatchExpectedString(sChar, inputStream);
token.nType = Token::TOKEN_OBJECT_END;
break;
case '[':
token.sValue = sChar[0];
MatchExpectedString(sChar, inputStream);
token.nType = Token::TOKEN_ARRAY_BEGIN;
break;
case ']':
token.sValue = sChar[0];
MatchExpectedString(sChar, inputStream);
token.nType = Token::TOKEN_ARRAY_END;
break;
case ',':
token.sValue = sChar[0];
MatchExpectedString(sChar, inputStream);
token.nType = Token::TOKEN_NEXT_ELEMENT;
break;
case ':':
token.sValue = sChar[0];
MatchExpectedString(sChar, inputStream);
token.nType = Token::TOKEN_MEMBER_ASSIGN;
break;
case '"':
MatchString(token.sValue, inputStream);
token.nType = Token::TOKEN_STRING;
break;
case '-':
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
MatchNumber(token.sValue, inputStream);
token.nType = Token::TOKEN_NUMBER;
break;
case 't':
token.sValue = "true";
MatchExpectedString(token.sValue, inputStream);
token.nType = Token::TOKEN_BOOLEAN;
break;
case 'f':
token.sValue = "false";
MatchExpectedString(token.sValue, inputStream);
token.nType = Token::TOKEN_BOOLEAN;
break;
case 'n':
token.sValue = "null";
MatchExpectedString(token.sValue, inputStream);
token.nType = Token::TOKEN_NULL;
break;
default:
throw ScanException("Unexpected character in stream: " + sChar, inputStream.GetLocation());
}
token.locEnd = inputStream.GetLocation();
tokens.push_back(token);
}
}
void Reader::EatWhiteSpace(InputStream& inputStream) {
while (!inputStream.EOS() && ::isspace(inputStream.Peek()))
inputStream.Get();
}
void Reader::MatchExpectedString(std::string const& sExpected, InputStream& inputStream) {
std::string::const_iterator it(sExpected.begin()), itEnd(sExpected.end());
for ( ; it != itEnd; ++it) {
if (inputStream.EOS() || // did we reach the end before finding what we're looking for...
inputStream.Get() != *it) // ...or did we find something different?
{
throw ScanException("Expected string: " + sExpected, inputStream.GetLocation());
}
}
}
void Reader::MatchString(std::string& string, InputStream& inputStream) {
MatchExpectedString("\"", inputStream);
while (!inputStream.EOS() && inputStream.Peek() != '"') {
char c = inputStream.Get();
// escape?
if (c == '\\' && !inputStream.EOS()) { // shouldn't have reached the end yet
c = inputStream.Get();
switch (c) {
case '/': string.push_back('/'); break;
case '"': string.push_back('"'); break;
case '\\': string.push_back('\\'); break;
case 'b': string.push_back('\b'); break;
case 'f': string.push_back('\f'); break;
case 'n': string.push_back('\n'); break;
case 'r': string.push_back('\r'); break;
case 't': string.push_back('\t'); break;
case 'u': // TODO: what do we do with this?
default:
throw ScanException("Unrecognized escape sequence found in string: \\" + c, inputStream.GetLocation());
}
}
else {
string.push_back(c);
}
}
// eat the last '"' that we hopefully just peeked
MatchExpectedString("\"", inputStream);
}
void Reader::MatchNumber(std::string& sNumber, InputStream& inputStream) {
const char sNumericChars[] = "0123456789.eE-+";
std::set<char> numericChars;
numericChars.insert(sNumericChars, sNumericChars + sizeof(sNumericChars));
while (!inputStream.EOS()&& numericChars.count(inputStream.Peek()))
sNumber.push_back(inputStream.Get());
}
UnknownElement Reader::Parse(Reader::TokenStream& tokenStream) {
if (tokenStream.EOS())
throw ParseException("Unexpected end of token stream", Location(), Location()); // nowhere to point to
Token const& token = tokenStream.Peek();
switch (token.nType) {
case Token::TOKEN_OBJECT_BEGIN: return ParseObject(tokenStream);
case Token::TOKEN_ARRAY_BEGIN: return ParseArray(tokenStream);
case Token::TOKEN_STRING: return ParseString(tokenStream);
case Token::TOKEN_NUMBER: return ParseNumber(tokenStream);
case Token::TOKEN_BOOLEAN: return ParseBoolean(tokenStream);
case Token::TOKEN_NULL: return ParseNull(tokenStream);
default:
throw ParseException("Unexpected token: " + token.sValue, token.locBegin, token.locEnd);
}
}
UnknownElement Reader::ParseObject(Reader::TokenStream& tokenStream) {
MatchExpectedToken(Token::TOKEN_OBJECT_BEGIN, tokenStream);
Object object;
while (!tokenStream.EOS() && tokenStream.Peek().nType != Token::TOKEN_OBJECT_END) {
// first the member name. save the token in case we have to throw an exception
Token const& tokenName = tokenStream.Peek();
std::string const& name = MatchExpectedToken(Token::TOKEN_STRING, tokenStream);
if (object.count(name))
throw ParseException("Duplicate object member token: " + name, tokenName.locBegin, tokenName.locEnd);
// ...then the key/value separator...
MatchExpectedToken(Token::TOKEN_MEMBER_ASSIGN, tokenStream);
// ...then the value itself (can be anything).
object[name] = Parse(tokenStream);
if (!tokenStream.EOS() && tokenStream.Peek().nType != Token::TOKEN_OBJECT_END)
MatchExpectedToken(Token::TOKEN_NEXT_ELEMENT, tokenStream);
}
MatchExpectedToken(Token::TOKEN_OBJECT_END, tokenStream);
return object;
}
UnknownElement Reader::ParseArray(Reader::TokenStream& tokenStream) {
MatchExpectedToken(Token::TOKEN_ARRAY_BEGIN, tokenStream);
Array array;
while (!tokenStream.EOS() && tokenStream.Peek().nType != Token::TOKEN_ARRAY_END)
{
array.push_back(Parse(tokenStream));
if (!tokenStream.EOS() && tokenStream.Peek().nType != Token::TOKEN_ARRAY_END)
MatchExpectedToken(Token::TOKEN_NEXT_ELEMENT, tokenStream);
}
MatchExpectedToken(Token::TOKEN_ARRAY_END, tokenStream);
return array;
}
UnknownElement Reader::ParseString(Reader::TokenStream& tokenStream) {
return MatchExpectedToken(Token::TOKEN_STRING, tokenStream);
}
UnknownElement Reader::ParseNumber(Reader::TokenStream& tokenStream) {
Token const& currentToken = tokenStream.Peek(); // might need this later for throwing exception
std::string const& sValue = MatchExpectedToken(Token::TOKEN_NUMBER, tokenStream);
// First try to parse it as an int
std::istringstream iStr(sValue);
int64_t iValue;
iStr >> iValue;
// If the entire token was consumed then it's not a double
if (iStr.eof())
return iValue;
// Try again as a double
iStr.seekg(0, std::ios::beg);
double dValue;
iStr >> dValue;
// If there's still stuff left in the token then it's malformed
if (!iStr.eof())
throw ParseException("Unexpected character in NUMBER token: " + iStr.peek(), currentToken.locBegin, currentToken.locEnd);
return dValue;
}
UnknownElement Reader::ParseBoolean(Reader::TokenStream& tokenStream) {
return MatchExpectedToken(Token::TOKEN_BOOLEAN, tokenStream) == "true";
}
UnknownElement Reader::ParseNull(Reader::TokenStream& tokenStream) {
MatchExpectedToken(Token::TOKEN_NULL, tokenStream);
return Null();
}
std::string const& Reader::MatchExpectedToken(Token::Type nExpected, Reader::TokenStream& tokenStream) {
if (tokenStream.EOS())
throw ParseException("Unexpected End of token stream", Location(), Location()); // nowhere to point to
Token const& token = tokenStream.Get();
if (token.nType != nExpected)
throw ParseException("Unexpected token: " + token.sValue, token.locBegin, token.locEnd);
return token.sValue;
}
}