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using System;
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using Implab.Components;
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using System.Diagnostics;
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using Implab.Automaton;
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using System.Text;
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namespace Implab.Formats {
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public abstract class TextScanner : Disposable {
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readonly int m_bufferMax;
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readonly int m_chunkSize;
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char[] m_buffer;
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int m_bufferOffset;
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int m_bufferSize;
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int m_tokenOffset;
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int m_tokenLength;
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/// <summary>
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/// Initializes a new instance of the <see cref="Implab.Formats.TextScanner"/> class.
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/// </summary>
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/// <param name="bufferMax">Buffer max.</param>
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/// <param name="chunkSize">Chunk size.</param>
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protected TextScanner(int bufferMax, int chunkSize) {
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Debug.Assert(m_chunkSize <= m_bufferMax);
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m_bufferMax = bufferMax;
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m_chunkSize = chunkSize;
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="Implab.Formats.TextScanner"/> class.
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/// </summary>
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/// <param name="buffer">Buffer.</param>
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protected TextScanner(char[] buffer) {
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if (buffer != null) {
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m_buffer = buffer;
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m_bufferSize = buffer.Length;
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}
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}
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/// <summary>
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/// (hungry) Reads the next token.
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/// </summary>
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/// <returns><c>true</c>, if token internal was read, <c>false</c> if there is no more tokens in the stream.</returns>
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/// <param name="dfa">The transition map for the automaton</param>
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/// <param name="final">Final states of the automaton.</param>
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/// <param name="tags">Tags.</param>
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/// <param name="state">The initial state for the automaton.</param>
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/// <param name="alphabet"></param>
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/// <param name = "tag"></param>
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internal bool ReadToken<TTag>(int[,] dfa, bool[] final, TTag[][] tags, int state, int[] alphabet, out TTag[] tag) {
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Safe.ArgumentNotNull();
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m_tokenLength = 0;
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var maxSymbol = alphabet.Length - 1;
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do {
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// after the next chunk is read the offset in the buffer may change
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int pos = m_bufferOffset + m_tokenLength;
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while (pos < m_bufferSize) {
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var ch = m_buffer[pos];
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state = dfa[state, ch > maxSymbol ? DFAConst.UNCLASSIFIED_INPUT : alphabet[ch]];
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if (state == DFAConst.UNREACHABLE_STATE)
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break;
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pos++;
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}
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m_tokenLength = pos - m_bufferOffset;
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} while (state != DFAConst.UNREACHABLE_STATE && Feed());
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m_tokenOffset = m_bufferOffset;
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m_bufferOffset += m_tokenLength;
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if (final[state]) {
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tag = tags[state];
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return true;
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}
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if (m_bufferOffset == m_bufferSize) {
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if (m_tokenLength == 0) //EOF
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return false;
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throw new ParserException();
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}
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throw new ParserException(String.Format("Unexpected symbol '{0}'", m_buffer[m_bufferOffset]));
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}
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protected void Feed(char[] buffer, int offset, int length) {
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m_buffer = buffer;
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m_bufferOffset = offset;
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m_bufferSize = offset + length;
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}
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protected bool Feed() {
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if (m_chunkSize <= 0)
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return false;
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if (m_buffer != null) {
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var free = m_buffer.Length - m_bufferSize;
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if (free < m_chunkSize) {
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free += m_chunkSize;
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var used = m_bufferSize - m_bufferOffset;
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var size = used + free;
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if (size > m_bufferMax)
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throw new ParserException(String.Format("The buffer limit ({0} Kb) is reached", m_bufferMax/1024));
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var temp = new char[size];
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var read = Read(temp, used, m_chunkSize);
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if (read == 0)
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return false;
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Array.Copy(m_buffer, m_bufferOffset, temp, 0, used);
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m_bufferOffset = 0;
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m_bufferSize = used + read;
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m_buffer = temp;
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}
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} else {
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Debug.Assert(m_bufferOffset == 0);
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m_buffer = new char[m_chunkSize];
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m_bufferSize = Read(m_buffer, 0, m_chunkSize);
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return (m_bufferSize != 0);
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}
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}
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protected abstract int Read(char[] buffer, int offset, int size);
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public string GetTokenValue() {
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return new String(m_buffer, m_tokenOffset, m_tokenLength);
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}
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public void CopyTokenTo(char[] buffer, int offset) {
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m_buffer.CopyTo(buffer, offset);
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}
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public void CopyTokenTo(StringBuilder sb) {
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sb.Append(m_buffer, m_tokenOffset, m_tokenLength);
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}
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}
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}
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