source.cpp

表达式分析, 支持算术运算,括号,关系运算,逻辑运算,字符串的like运算等。采用了有限自动机做词法分析, 语法分析用算符优先分析方法

#include "source.h"
#include <string.h>

cSourceString::cSourceString(char * buf, int len)
{
	if(!buf)
	{
		m_buf		= 0;
		m_buf_len	= 0;
	}
	else if(len == 0)
	{
		m_buf		= buf;
		m_buf_len	= strlen(buf);
	}
	else
	{
		m_buf		= buf;
		m_buf_len	= len;
	}
	m_cur_pos = 0;
}

unsigned char cSourceString::GetChar()
{
	
	if(!m_buf_len || m_cur_pos >= m_buf_len || m_cur_pos < 0)
		return (unsigned char)0;
	return (unsigned char)m_buf[m_cur_pos++];
}

void cSourceString::PushBackOne()
{
	if(m_cur_pos > 0 && m_cur_pos <= m_buf_len)
		m_cur_pos--;
}