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using System;
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using Implab.Automaton.RegularExpressions;
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using Implab.Automaton;
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namespace Implab.Formats {
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public struct BufferScanner<TTag> {
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char[] m_buffer;
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int m_offset;
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int m_position;
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int m_hi;
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readonly int m_chunk;
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readonly int m_limit;
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readonly DFAStateDescriptor<TTag>[] m_dfa;
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int m_state;
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public BufferScanner(DFAStateDescriptor<TTag>[] dfa, int initialState, int chunk, int limit) {
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m_dfa = dfa;
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m_state = initialState;
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m_chunk = chunk;
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m_limit = limit;
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m_buffer = null;
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m_offset = 0;
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m_position = 0;
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m_hi = 0;
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}
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public char[] Buffer {
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get {
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return m_buffer;
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}
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}
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public int HiMark {
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get {
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return m_hi;
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}
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}
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public int Position {
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get {
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return m_position;
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}
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}
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public int Length {
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get {
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return m_hi - m_position;
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}
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}
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public int TokenOffset {
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get {
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return m_offset;
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}
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}
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public int TokenLength {
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get {
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return m_position - m_offset;
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}
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}
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public void Init(char[] buffer, int position, int length) {
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m_buffer = buffer;
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m_position = position;
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m_offset = position;
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m_hi = position + length;
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}
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public int Extend() {
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// free space
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var free = m_buffer.Length - m_hi;
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// if the buffer have enough free space
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if (free > 0)
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return free;
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// effective size of the buffer
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var size = m_buffer.Length - m_offset;
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// calculate the new size
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int grow = Math.Min(m_limit - size, m_chunk);
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if (grow <= 0)
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throw new ParserException(String.Format("Input buffer {0} bytes limit exceeded", m_limit));
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var temp = new char[size + grow];
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Array.Copy(m_buffer, m_offset, temp, 0, m_hi - m_offset);
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m_position -= m_offset;
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m_hi -= m_offset;
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m_offset = 0;
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m_buffer = temp;
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return free + grow;
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}
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public void RaiseMark(int size) {
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m_hi += size;
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}
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/// <summary>
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/// Scan this instance.
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/// </summary>
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/// <returns><c>true</c> - additional data required</returns>
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public bool Scan() {
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while (m_position < m_hi) {
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var ch = m_buffer[m_position];
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var next = m_dfa[m_state].transitions[(int)ch];
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if (next == DFAConst.UNREACHABLE_STATE) {
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if (m_dfa[m_state].final)
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return false;
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throw new ParserException(
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String.Format(
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"Unexpected token '{0}'",
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new string(m_buffer, m_offset, m_position - m_offset)
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)
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);
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}
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m_state = next;
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m_position++;
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}
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return true;
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}
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public void Eof() {
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if (!m_dfa[m_state].final)
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throw new ParserException(
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String.Format(
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"Unexpected token '{0}'",
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new string(m_buffer, m_offset, m_position - m_offset)
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)
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);
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}
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public TTag[] GetTokenTags() {
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return m_dfa[m_state].tags;
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}
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}
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}
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