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parser.cpp 2.89 KB
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#include "parser.h"
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#include "scanner.h"
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#include "token.h"
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#include "exceptions.h"
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#include <sstream>
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namespace YAML
{
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	Parser::Parser(std::istream& in): m_pScanner(0)
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	{
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		Load(in);
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	}

	Parser::~Parser()
	{
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		delete m_pScanner;
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	}

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	Parser::operator bool() const
	{
		return m_pScanner->PeekNextToken() != 0;
	}

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	void Parser::Load(std::istream& in)
	{
		delete m_pScanner;
		m_pScanner = new Scanner(in);
		m_state.Reset();
	}

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	// GetNextDocument
	// . Reads the next document in the queue (of tokens).
	// . Throws (ScannerException|ParserException)s on errors.
	void Parser::GetNextDocument(Node& document)
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	{
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		// clear node
		document.Clear();

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		// first read directives
		ParseDirectives();

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		// we better have some tokens in the queue
		if(!m_pScanner->PeekNextToken())
			return;

		// first eat doc start (optional)
		if(m_pScanner->PeekNextToken()->type == TT_DOC_START)
			m_pScanner->EatNextToken();

		// now parse our root node
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		document.Parse(m_pScanner, m_state);
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		// and finally eat any doc ends we see
		while(m_pScanner->PeekNextToken() && m_pScanner->PeekNextToken()->type == TT_DOC_END)
			m_pScanner->EatNextToken();
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	}

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	// ParseDirectives
	// . Reads any directives that are next in the queue.
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	void Parser::ParseDirectives()
	{
		bool readDirective = false;

		while(1) {
			Token *pToken = m_pScanner->PeekNextToken();
			if(!pToken || pToken->type != TT_DIRECTIVE)
				break;

			// we keep the directives from the last document if none are specified;
			// but if any directives are specific, then we reset them
			if(!readDirective)
				m_state.Reset();

			readDirective = true;
			HandleDirective(pToken->value, pToken->params);
			m_pScanner->PopNextToken();
		}
	}

	void Parser::HandleDirective(const std::string& name, const std::vector <std::string>& params)
	{
		if(name == "YAML")
			HandleYamlDirective(params);
		else if(name == "TAG")
			HandleTagDirective(params);
	}

	// HandleYamlDirective
	// . Should be of the form 'major.minor' (like a version number)
	void Parser::HandleYamlDirective(const std::vector <std::string>& params)
	{
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		if(params.size() != 1)
			throw BadYAMLDirective();
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		std::stringstream str(params[0]);
		str >> m_state.version.major;
		str.get();
		str >> m_state.version.minor;
		if(!str)
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			throw BadYAMLDirective();  // TODO: or throw if there are any more characters in the stream?
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		// TODO: throw on major > 1? warning on major == 1, minor > 2?
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	}

	void Parser::HandleTagDirective(const std::vector <std::string>& params)
	{
		if(params.size() != 2)
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			throw BadTAGDirective();
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		std::string handle = params[0], prefix = params[1];
		m_state.tags[handle] = prefix;
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	}
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	void Parser::PrintTokens(std::ostream& out)
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	{
		while(1) {
			Token *pToken = m_pScanner->GetNextToken();
			if(!pToken)
				break;

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			out << *pToken << std::endl;
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		}
	}
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}