stream.cpp

#include "stream.h"
#include <iostream>
#include "exp.h"

#ifndef YAML_PREFETCH_SIZE
#define YAML_PREFETCH_SIZE 2048
#endif

#define S_ARRAY_SIZE( A ) (sizeof(A)/sizeof(*(A)))
#define S_ARRAY_END( A ) ((A) + S_ARRAY_SIZE(A))

#define CP_REPLACEMENT_CHARACTER (0xFFFD)

namespace YAML
{
	enum UtfIntroState {
		uis_start,
		uis_utfbe_b1,
		uis_utf32be_b2,
		uis_utf32be_bom3,
		uis_utf32be,
		uis_utf16be,
		uis_utf16be_bom1,
		uis_utfle_bom1,
		uis_utf16le_bom2,
		uis_utf32le_bom3,
		uis_utf16le,
		uis_utf32le,
		uis_utf8_imp,
		uis_utf16le_imp,
		uis_utf32le_imp3,
		uis_utf8_bom1,
		uis_utf8_bom2,
		uis_utf8,
		uis_error
	};

	enum UtfIntroCharType {
		uict00,
		uictBB,
		uictBF,
		uictEF,
		uictFE,
		uictFF,
		uictAscii,
		uictOther,
		uictMax
	};

	static bool s_introFinalState[] = {
		false, //uis_start
		false, //uis_utfbe_b1
		false, //uis_utf32be_b2
		false, //uis_utf32be_bom3
		true,  //uis_utf32be
		true,  //uis_utf16be
		false, //uis_utf16be_bom1
		false, //uis_utfle_bom1
		false, //uis_utf16le_bom2
		false, //uis_utf32le_bom3
		true,  //uis_utf16le
		true,  //uis_utf32le
		false, //uis_utf8_imp
		false, //uis_utf16le_imp
		false, //uis_utf32le_imp3
		false, //uis_utf8_bom1
		false, //uis_utf8_bom2
		true,  //uis_utf8
		true,  //uis_error
	};

	static UtfIntroState s_introTransitions[][uictMax] = {
		// uict00,           uictBB,           uictBF,           uictEF,           uictFE,           uictFF,           uictAscii,        uictOther
		  {uis_utfbe_b1,     uis_utf8,         uis_utf8,         uis_utf8_bom1,    uis_utf16be_bom1, uis_utfle_bom1,   uis_utf8_imp,     uis_utf8},
		  {uis_utf32be_b2,   uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf16be,      uis_utf8},
		  {uis_utf32be,      uis_utf8,         uis_utf8,         uis_utf8,         uis_utf32be_bom3, uis_utf8,         uis_utf8,         uis_utf8},
		  {uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf32be,      uis_utf8,         uis_utf8},
		  {uis_utf32be,      uis_utf32be,      uis_utf32be,      uis_utf32be,      uis_utf32be,      uis_utf32be,      uis_utf32be,      uis_utf32be},
		  {uis_utf16be,      uis_utf16be,      uis_utf16be,      uis_utf16be,      uis_utf16be,      uis_utf16be,      uis_utf16be,      uis_utf16be},
		  {uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf16be,      uis_utf8,         uis_utf8},
		  {uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf16le_bom2, uis_utf8,         uis_utf8,         uis_utf8},
		  {uis_utf32le_bom3, uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le},
		  {uis_utf32le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le},
		  {uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le},
		  {uis_utf32le,      uis_utf32le,      uis_utf32le,      uis_utf32le,      uis_utf32le,      uis_utf32le,      uis_utf32le,      uis_utf32le},
		  {uis_utf16le_imp,  uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8},
		  {uis_utf32le_imp3, uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le},
		  {uis_utf32le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le,      uis_utf16le},
		  {uis_utf8,         uis_utf8_bom2,    uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8},
		  {uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8},
		  {uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8,         uis_utf8},
	};

	static char s_introUngetCount[][uictMax] = {
		// uict00, uictBB, uictBF, uictEF, uictFE, uictFF, uictAscii, uictOther
		  {0,      1,      1,      0,      0,      0,      0,         1},
		  {0,      2,      2,      2,      2,      2,      2,         2},
		  {3,      3,      3,      3,      0,      3,      3,         3},
		  {4,      4,      4,      4,      4,      0,      4,         4},
		  {1,      1,      1,      1,      1,      1,      1,         1},
		  {1,      1,      1,      1,      1,      1,      1,         1},
		  {2,      2,      2,      2,      2,      0,      2,         2},
		  {2,      2,      2,      2,      0,      2,      2,         2},
		  {0,      1,      1,      1,      1,      1,      1,         1},
		  {0,      2,      2,      2,      2,      2,      2,         2},
		  {1,      1,      1,      1,      1,      1,      1,         1},
		  {1,      1,      1,      1,      1,      1,      1,         1},
		  {0,      2,      2,      2,      2,      2,      2,         2},
		  {0,      3,      3,      3,      3,      3,      3,         3},
		  {4,      4,      4,      4,      4,      4,      4,         4},
		  {2,      0,      2,      2,      2,      2,      2,         2},
		  {3,      3,      0,      3,      3,      3,      3,         3},
		  {1,      1,      1,      1,      1,      1,      1,         1},
	};

	inline UtfIntroCharType IntroCharTypeOf(std::istream::int_type ch)
	{
		if (std::istream::traits_type::eof() == ch) {
			return uictOther;
		}

		switch (ch) {
		case 0: return uict00;
		case 0xBB: return uictBB;
		case 0xBF: return uictBF;
		case 0xEF: return uictEF;
		case 0xFE: return uictFE;
		case 0xFF: return uictFF;
		}

		if ((ch > 0) && (ch < 0xFF)) {
			return uictAscii;
		}

		return uictOther;
	}

	inline char Utf8Adjust(unsigned long ch, unsigned char lead_bits, unsigned char rshift)
	{
		const unsigned char header = ((1 << lead_bits) - 1) << (8 - lead_bits);
		const unsigned char mask = (0xFF >> (lead_bits + 1));
		return static_cast<char>(static_cast<unsigned char>(
			header | ((ch >> rshift) & mask)
			));
	}

	inline void QueueUnicodeCodepoint(std::deque<char>& q, unsigned long ch)
	{
		// We are not allowed to queue the Stream::eof() codepoint, so
		// replace it with CP_REPLACEMENT_CHARACTER
		if (static_cast<unsigned long>(Stream::eof()) == ch)
		{
			ch = CP_REPLACEMENT_CHARACTER;
		}

		if (ch < 0x80)
		{
			q.push_back(Utf8Adjust(ch, 0, 0));
		}
		else if (ch < 0x800)
		{
			q.push_back(Utf8Adjust(ch, 2, 6));
			q.push_back(Utf8Adjust(ch, 1, 0));
		}
		else if (ch < 0x10000)
		{
			q.push_back(Utf8Adjust(ch, 3, 12));
			q.push_back(Utf8Adjust(ch, 1, 6));
			q.push_back(Utf8Adjust(ch, 1, 0));
		}
		else
		{
			q.push_back(Utf8Adjust(ch, 4, 18));
			q.push_back(Utf8Adjust(ch, 1, 12));
			q.push_back(Utf8Adjust(ch, 1, 6));
			q.push_back(Utf8Adjust(ch, 1, 0));
		}
	}

	Stream::Stream(std::istream& input)
		: m_input(input),
		m_pPrefetched(new unsigned char[YAML_PREFETCH_SIZE]), 
		m_nPrefetchedAvailable(0), m_nPrefetchedUsed(0)
	{
		typedef std::istream::traits_type char_traits;

		if(!input)
			return;

		// Determine (or guess) the character-set by reading the BOM, if any.  See
		// the YAML specification for the determination algorithm.
		char_traits::int_type intro[4];
		int nIntroUsed = 0;
		UtfIntroState state = uis_start;
		for(; !s_introFinalState[state]; ) {
			std::istream::int_type ch = input.get();
			intro[nIntroUsed++] = ch;
			UtfIntroCharType charType = IntroCharTypeOf(ch);
			UtfIntroState newState = s_introTransitions[state][charType];
			int nUngets = s_introUngetCount[state][charType];
			if(nUngets > 0) {
				input.clear();
				for(; nUngets > 0; --nUngets) {
					if(char_traits::eof() != intro[--nIntroUsed])
						input.putback(char_traits::to_char_type(intro[nIntroUsed]));
				}
			}
			state = newState;
		}

		switch (state) {
		case uis_utf8: m_charSet = utf8; break;
		case uis_utf16le: m_charSet = utf16le; break;
		case uis_utf16be: m_charSet = utf16be; break;
		case uis_utf32le: m_charSet = utf32le; break;
		case uis_utf32be: m_charSet = utf32be; break;
		default: m_charSet = utf8; break;
		}

		ReadAheadTo(0);
	}

	Stream::~Stream()
	{
		delete[] m_pPrefetched;
	}

	char Stream::peek() const
	{
		if (m_readahead.empty())
		{
			return Stream::eof();
		}

		return m_readahead[0];
	}
	
	Stream::operator bool() const
	{
		return m_input.good() || (!m_readahead.empty() && m_readahead[0] != Stream::eof());
	}

	// get
	// . Extracts a character from the stream and updates our position
	char Stream::get()
	{
		char ch = peek();
		AdvanceCurrent();
		m_mark.column++;
		
		if(ch == '\n') {
			m_mark.column = 0;
			m_mark.line++;
		}
		
		return ch;
	}

	// get
	// . Extracts 'n' characters from the stream and updates our position
	std::string Stream::get(int n)
	{
		std::string ret;
		ret.reserve(n);
		for(int i=0;i<n;i++)
			ret += get();
		return ret;
	}

	// eat
	// . Eats 'n' characters and updates our position.
	void Stream::eat(int n)
	{
		for(int i=0;i<n;i++)
			get();
	}

	void Stream::AdvanceCurrent()
	{
		if (!m_readahead.empty())
		{
			m_readahead.pop_front();
			m_mark.pos++;
		}

		ReadAheadTo(0);
	}

	bool Stream::_ReadAheadTo(size_t i) const
	{
		while (m_input.good() && (m_readahead.size() <= i))
		{
			switch (m_charSet)
			{
			case utf8: StreamInUtf8(); break;
			case utf16le: StreamInUtf16(); break;
			case utf16be: StreamInUtf16(); break;
			case utf32le: StreamInUtf32(); break;
			case utf32be: StreamInUtf32(); break;
			}
		}
		
		// signal end of stream
		if(!m_input.good())
			m_readahead.push_back(Stream::eof());

		return m_readahead.size() > i;
	}

	void Stream::StreamInUtf8() const
	{
		unsigned char b = GetNextByte();
		if (m_input.good())
		{
			m_readahead.push_back(b);
		}
	}

	void Stream::StreamInUtf16() const
	{
		unsigned long ch = 0;
		unsigned char bytes[2];
		int nBigEnd = (m_charSet == utf16be) ? 0 : 1;

		bytes[0] = GetNextByte();
		bytes[1] = GetNextByte();
		if (!m_input.good())
		{
			return;
		}
		ch = (static_cast<unsigned long>(bytes[nBigEnd]) << 8) |
			static_cast<unsigned long>(bytes[1 ^ nBigEnd]);

		if (ch >= 0xDC00 && ch < 0xE000)
		{
			// Trailing (low) surrogate...ugh, wrong order
			QueueUnicodeCodepoint(m_readahead, CP_REPLACEMENT_CHARACTER);
			return;
		}
		else if (ch >= 0xD800 && ch < 0xDC00)
		{
			// ch is a leading (high) surrogate

			// Four byte UTF-8 code point

			// Read the trailing (low) surrogate
			for (;;)
			{
				bytes[0] = GetNextByte();
				bytes[1] = GetNextByte();
				if (!m_input.good())
				{
					QueueUnicodeCodepoint(m_readahead, CP_REPLACEMENT_CHARACTER);
					return;
				}
				unsigned long chLow = (static_cast<unsigned long>(bytes[nBigEnd]) << 8) |
					static_cast<unsigned long>(bytes[1 ^ nBigEnd]);
				if (chLow < 0xDC00 || ch >= 0xE000)
				{
					// Trouble...not a low surrogate.  Dump a REPLACEMENT CHARACTER into the stream.
					QueueUnicodeCodepoint(m_readahead, CP_REPLACEMENT_CHARACTER);

					// Deal with the next UTF-16 unit
					if (chLow < 0xD800 || ch >= 0xE000)
					{
						// Easiest case: queue the codepoint and return
						QueueUnicodeCodepoint(m_readahead, ch);
						return;
					}
					else
					{
						// Start the loop over with the new high surrogate
						ch = chLow;
						continue;
					}
				}

				// Select the payload bits from the high surrogate
				ch &= 0x3FF;
				ch <<= 10;

				// Include bits from low surrogate
				ch |= (chLow & 0x3FF);

				// Add the surrogacy offset
				ch += 0x10000;
			}
		}

		QueueUnicodeCodepoint(m_readahead, ch);
	}

	inline char* ReadBuffer(unsigned char* pBuffer)
	{
		return reinterpret_cast<char*>(pBuffer);
	}

	unsigned char Stream::GetNextByte() const
	{
		if (m_nPrefetchedUsed >= m_nPrefetchedAvailable)
		{
			std::streambuf *pBuf = m_input.rdbuf();
			m_nPrefetchedAvailable = static_cast<std::size_t>(pBuf->sgetn(ReadBuffer(m_pPrefetched), YAML_PREFETCH_SIZE));
			m_nPrefetchedUsed = 0;
			if (!m_nPrefetchedAvailable)
			{
				m_input.setstate(std::ios_base::eofbit);
			}

			if (0 == m_nPrefetchedAvailable)
			{
				return 0;
			}
		}

		return m_pPrefetched[m_nPrefetchedUsed++];
	}

	void Stream::StreamInUtf32() const
	{
		static int indexes[2][4] = {
			{3, 2, 1, 0},
			{0, 1, 2, 3}
		};

		unsigned long ch = 0;
		unsigned char bytes[4];
		int* pIndexes = (m_charSet == utf32be) ? indexes[1] : indexes[0];

		bytes[0] = GetNextByte();
		bytes[1] = GetNextByte();
		bytes[2] = GetNextByte();
		bytes[3] = GetNextByte();
		if (!m_input.good())
		{
			return;
		}

		for (int i = 0; i < 4; ++i)
		{
			ch <<= 8;
			ch |= bytes[pIndexes[i]];
		}

		QueueUnicodeCodepoint(m_readahead, ch);
	}
}