FastInpurScanner.cs
123 lines
| 4.0 KiB
| text/x-csharp
|
CSharpLexer
cin
|
r289 | using Implab.Automaton; | ||
| using System.Diagnostics; | ||||
| using System.Runtime.CompilerServices; | ||||
| namespace Implab.Formats { | ||||
| /// <summary> | ||||
| /// Fast input scanner for max 255 states and 255 input chacters. | ||||
| /// </summary> | ||||
| /// <typeparam name="TTag"></typeparam> | ||||
| /// <remarks> | ||||
| /// <para> | ||||
| /// Creates a one rank array to store automa transition table, each entry in this table is byte, to make this table small enough to fit L1 cache. | ||||
| /// </para> | ||||
| /// <para> | ||||
| /// Each entry is addressed as <c>(state << 8) | input</c> which make this quite fast to get the next state. Each input symbol below 255 is treated as 255. | ||||
| /// </para> | ||||
| /// </remarks> | ||||
| public class FastInputScanner<TTag> { | ||||
| const int StateShift = 8; | ||||
| const int StateMask = ~((1 << StateShift) - 1); | ||||
| const int AlphabetSize = 1 << StateShift; | ||||
| const int UnclassifiedInput = (1 << StateShift) - 1; | ||||
| const byte UnreachableState = byte.MaxValue; | ||||
| readonly TTag[] m_tags; | ||||
| readonly bool[] m_final; | ||||
| readonly byte m_initialState; | ||||
| readonly byte[] m_dfa; | ||||
| int m_position; | ||||
| byte m_state; | ||||
| protected FastInputScanner(byte[] table, bool[] final, TTag[] tags, byte initial) { | ||||
| m_dfa = table; | ||||
| m_final = final; | ||||
| m_tags = tags; | ||||
| m_initialState = initial; | ||||
| } | ||||
| public FastInputScanner(int[,] dfaTable, bool[] finalStates, TTag[] tags, int initialState, int[] inputMap) { | ||||
| var states = dfaTable.GetLength(0); | ||||
| Debug.Assert(states < byte.MaxValue); | ||||
| m_dfa = new byte[states << StateShift]; | ||||
| m_initialState = (byte)initialState; | ||||
| m_tags = tags; | ||||
| m_final = finalStates; | ||||
| // iterate over states | ||||
| for(int si = 0; si < states; si++) { | ||||
| // state offset for the new table | ||||
| var offset = si << StateShift; | ||||
| // iterate over alphabet | ||||
| for(int a = 0; a < AlphabetSize; a++) { | ||||
| var next = dfaTable[si, a < inputMap.Length ? inputMap[a] : AutomatonConst.UnclassifiedInput]; | ||||
| if (next == AutomatonConst.UnreachableState) | ||||
| next = UnreachableState; | ||||
| m_dfa[offset | a] = (byte)next; | ||||
| } | ||||
| } | ||||
| } | ||||
| public TTag Tag { | ||||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||||
| get { | ||||
| return m_tags[m_state]; | ||||
| } | ||||
| } | ||||
| public int Position { | ||||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||||
| get { | ||||
| return m_position; | ||||
| } | ||||
| } | ||||
| public bool IsFinal { | ||||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||||
| get { | ||||
| return m_final[m_state]; | ||||
| } | ||||
| } | ||||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||||
| public void ResetState() { | ||||
| m_state = m_initialState; | ||||
| } | ||||
| public FastInputScanner<TTag> Clone() { | ||||
| var clone = new FastInputScanner<TTag>(m_dfa, m_final, m_tags, m_initialState); | ||||
| clone.m_state = m_state; | ||||
| clone.m_position = m_position; | ||||
| return clone; | ||||
| } | ||||
| public bool Scan(char[] data, int offset, int max) { | ||||
| var next = m_state; | ||||
| m_position = offset; | ||||
| while (m_position < max) { | ||||
| var ch = data[m_position]; | ||||
| next = m_dfa[(ch >= AlphabetSize ? (next << StateShift) | UnclassifiedInput : (next << StateShift) | ch)]; | ||||
| if (next == UnreachableState) | ||||
| // scanner stops at the next position after the last recognized symbol | ||||
| return false; | ||||
| m_state = next; | ||||
| m_position++; | ||||
| } | ||||
| return true; | ||||
| } | ||||
| } | ||||
| } | ||||