ayuda con el compilador scan.c
Publicado por Angel (1 intervención) el 27/05/2017 07:13:17
Quisiera que alguien me explique lo que significa cada línea, que hace, incluyendo las bibliotecas. Los comentarios a veces no se entienden y por eso quiero que me expliquen.
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#include "globals.h"#include "util.h"#include "scan.h"/* states in scanner DFA */typedef enum
{ START,INASSIGN,INCOMMENT,INNUM,INID,DONE }
StateType;
/* lexeme of identifier or reserved word */char tokenString[MAXTOKENLEN+1];
/* BUFLEN = length of the input buffer for
source code lines */#define BUFLEN 256
static char lineBuf[BUFLEN]; /* holds the current line */
static int linepos = 0; /* current position in LineBuf */static int bufsize = 0; /* current size of buffer string */static int EOF_flag = FALSE; /* corrects ungetNextChar behavior on EOF *//* getNextChar fetches the next non-blank character
from lineBuf, reading in a new line if lineBuf is
exhausted */static int getNextChar(void)
{ if (!(linepos < bufsize))
{ lineno++;
if (fgets(lineBuf,BUFLEN-1,source))
{ if (EchoSource) fprintf(listing,"%4d: %s",lineno,lineBuf);
bufsize = strlen(lineBuf);
linepos = 0;return lineBuf[linepos++];
}else
{ EOF_flag = TRUE;
return EOF;
} }else return lineBuf[linepos++];
}/* ungetNextChar backtracks one character
in lineBuf */static void ungetNextChar(void)
{ if (!EOF_flag) linepos-- ;}
/* lookup table of reserved words */static struct
{ char* str;
TokenType tok;
} reservedWords[MAXRESERVED]
= {{"if",IF},{"then",THEN},{"else",ELSE},{"end",END},
{"repeat",REPEAT},{"until",UNTIL},{"read",READ},
{"write",WRITE}};
/* lookup an identifier to see if it is a reserved word *//* uses linear search */static TokenType reservedLookup (char * s)
{ int i;for (i=0;i<MAXRESERVED;i++)
if (!strcmp(s,reservedWords[i].str))
return reservedWords[i].tok;
return ID;
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