Source code of Windows XP (NT5)
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5.2 KiB

/*++
Copyright (C) 1999-2001 Microsoft Corporation
Module Name:
GENLEX.CPP
Abstract:
Generic lexer framework classes.
History:
--*/
#include "precomp.h"
#include <stdio.h>
#include <genlex.h>
//***************************************************************************
//
//***************************************************************************
CGenLexer::CGenLexer(LexEl *pTbl, CGenLexSource *pSrc)
{
m_nCurBufSize = 256;
m_pTokenBuf = (wchar_t *) HeapAlloc(GetProcessHeap(), 0,
m_nCurBufSize * 2);
m_nCurrentLine = 1;
m_pTable = pTbl;
m_pSrc = pSrc;
}
//***************************************************************************
//
//***************************************************************************
void CGenLexer::Reset()
{
m_pSrc->Reset();
m_nCurrentLine = 1;
}
//***************************************************************************
//
//***************************************************************************
CGenLexer::~CGenLexer()
{
HeapFree(GetProcessHeap(), 0, m_pTokenBuf);
}
//***************************************************************************
//
//***************************************************************************
int CGenLexer::NextToken()
{
int nState = 0;
int nCurBufEnd = 0;
BOOL bRead = TRUE;
wchar_t cCurrent = 0;
BOOL bEOF = FALSE;
if (m_pTokenBuf == 0)
return 0;
*m_pTokenBuf = 0;
// Generic DFA driver based on the table specified
// in the constructor.
// ===============================================
while (1)
{
BOOL bMatch = FALSE;
WORD wInstructions = m_pTable[nState].wInstructions;
if (bRead)
{
if(bEOF)
{
// The lexer table allowed us to go past end of string!!!
return 1;
}
cCurrent = m_pSrc->NextChar();
if(cCurrent == 0)
bEOF = TRUE;
}
bRead = FALSE;
// Check here if only the first character is present.
// ==================================================
if (m_pTable[nState].cFirst == GLEX_ANY)
bMatch = TRUE;
else if (m_pTable[nState].cLast == GLEX_EMPTY)
{
if (cCurrent == m_pTable[nState].cFirst)
bMatch = TRUE;
else if ((wInstructions & GLEX_NOT) &&
!(cCurrent == m_pTable[nState].cFirst))
bMatch = TRUE;
}
// If here, both first/last are present and we
// are testing to see if the input is in between.
// ==============================================
else if (m_pTable[nState].cFirst != GLEX_ANY)
{
if ((wInstructions & GLEX_NOT) &&
!(cCurrent >= m_pTable[nState].cFirst &&
cCurrent <= m_pTable[nState].cLast))
bMatch = TRUE;
else if (cCurrent >= m_pTable[nState].cFirst &&
cCurrent <= m_pTable[nState].cLast)
bMatch = TRUE;
}
// Interpret the instruction field to determine
// whether the character is actually to be included
// in the token text.
// ================================================
if (bMatch)
{
if (wInstructions & GLEX_ACCEPT)
{
// Expand the current buffer, if required.
// =======================================
if (nCurBufEnd == m_nCurBufSize - 1)
{
m_nCurBufSize += 256;
m_pTokenBuf = (wchar_t *) HeapReAlloc(GetProcessHeap(), 0, m_pTokenBuf,
m_nCurBufSize * 2);
if (m_pTokenBuf == 0)
return 0; // out of memory
}
m_pTokenBuf[nCurBufEnd] = cCurrent;
m_pTokenBuf[++nCurBufEnd]= 0;
bRead = TRUE;
}
if (wInstructions & GLEX_CONSUME)
bRead = TRUE;
// else GLEX_CONSUME, which means 'skip'
// If the PUSHBACK instruction is present,
// push the char back.
// ======================================
if (wInstructions & GLEX_PUSHBACK)
{
bRead = TRUE;
m_pSrc->Pushback(cCurrent);
}
// If a linefeed instruction.
// ==========================
if (wInstructions & GLEX_LINEFEED)
m_nCurrentLine++;
// If the return field is present and there was
// a match, then return the specified token. Alternately,
// the GLEX_RETURN instruction will force a return
// match, or no match.
// =======================================================
if (m_pTable[nState].wReturnTok ||
(wInstructions & GLEX_RETURN))
return int(m_pTable[nState].wReturnTok);
nState = int(m_pTable[nState].wGotoState);
}
// If here, there was no match.
// ===================================
else
nState++;
}
return 0; // No path to here
}