commit 12e0b049f96901be321d7797730555f81af2eee8
parent ad9c3eeed6939fd545333482bf951991ab3e1b25
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date: Tue, 11 Mar 2014 15:31:01 +0100
Do a prefetch of 1 token
C is a LR(2) language so it means we need 2 tokens in order to
decide what is the next step. We have solving this problem with
backtracking and a tricky ahead, that was used only to detect that
the proximus token was ':' or not. Since we want to remove the
backtracking we need a real ahead() function, and the better
way is having a prefetch token.
Diffstat:
| M | lex.c | | | 99 | ++++++++++++++++++++++++++++++++++++++++--------------------------------------- |
1 file changed, 50 insertions(+), 49 deletions(-)
diff --git a/lex.c b/lex.c
@@ -9,10 +9,9 @@
#include "symbol.h"
#include "sizes.h"
-#define NR_KEYW_HASH 16
-
unsigned char yytoken;
char yytext[IDENTSIZ + 1];
+static char yybuf[IDENTSIZ + 1];
unsigned linenum;
unsigned columnum;
const char *filename;
@@ -24,7 +23,7 @@ struct keyword {
};
static FILE *yyin;
-
+static struct symbol yysym = {.name = ""}, *yynval = &yysym;
struct symbol *yyval;
struct symbol *
@@ -50,6 +49,7 @@ type: switch (ch = toupper(getc(yyin))) {
v = strtoll(s, NULL, base);
sym = lookup(NULL, NS_IDEN);
+ sym->tok = CONSTANT;
sym->ctype = *tp;
switch (tp->type) {
@@ -72,7 +72,7 @@ type: switch (ch = toupper(getc(yyin))) {
return sym;
}
-static char
+static struct symbol *
number(void)
{
register char *bp, ch;
@@ -90,7 +90,7 @@ number(void)
ungetc(ch, yyin);
}
- for (bp = yytext; bp < &yytext[IDENTSIZ]; *bp++ = ch) {
+ for (bp = yybuf; bp < &yybuf[IDENTSIZ]; *bp++ = ch) {
ch = getc(yyin);
switch (base) {
case 8:
@@ -108,13 +108,11 @@ number(void)
}
}
-end: if (bp == &yytext[IDENTSIZ])
- error("identifier too long %s", yytext);
+end: if (bp == &yybuf[IDENTSIZ])
+ error("identifier too long %s", yybuf);
*bp = '\0';
ungetc(ch, yyin);
- yyval = integer(yytext, base);
-
- return CONSTANT;
+ return integer(yybuf, base);
}
void
@@ -169,35 +167,36 @@ init_keywords(void)
}
}
-static unsigned char
+static struct symbol *
iden(void)
{
register char ch, *bp;
- for (bp = yytext; bp < &yytext[IDENTSIZ]; *bp++ = ch) {
+ for (bp = yybuf; bp < &yybuf[IDENTSIZ]; *bp++ = ch) {
if (!isalnum(ch = getc(yyin)) && ch != '_')
break;
}
- if (bp == &yytext[IDENTSIZ])
- error("identifier too long %s", yytext);
+ if (bp == &yybuf[IDENTSIZ])
+ error("identifier too long %s", yybuf);
*bp = '\0';
ungetc(ch, yyin);
- yyval = lookup(yytext, NS_IDEN);
- return yyval->tok;
+ return lookup(yybuf, NS_IDEN);
}
static unsigned char
skip(void)
{
- register int c;
+ static int c;
extern char parser_out_home;
- while (isspace(c = getc(yyin))) {
- switch (c) {
- case '\n': ++linenum, columnum = 1; break;
- case '\t': columnum += 8; break;
- default: ++columnum; break;
+ if (c != EOF) {
+ while (c != EOF && isspace(c = getc(yyin))) {
+ switch (c) {
+ case '\n': ++linenum, columnum = 1; break;
+ case '\t': columnum += 8; break;
+ default: ++columnum; break;
+ }
}
}
if (c == EOF) {
@@ -214,14 +213,14 @@ follow(unsigned char op, unsigned char eq, unsigned char rep)
{
register char c = getc(yyin);
- yytext[1] = c;
- yytext[2] = '\0';
+ yybuf[1] = c;
+ yybuf[2] = '\0';
if (c == '=')
return eq;
else if (c == op && rep)
return rep;
- yytext[1] = '\0';
+ yybuf[1] = '\0';
ungetc(c, yyin);
return op;
}
@@ -231,23 +230,24 @@ rel_shift(unsigned char op)
{
static char tokens[2][3] = {
{GE, SHL, SHL_EQ},
- {LE, SHR, SHR_EQ}};
+ {LE, SHR, SHR_EQ}
+ };
register char c = getc(yyin);
register char *tp = tokens[op == '>'];
- yytext[1] = c;
- yytext[2] = '\0';
+ yybuf[1] = c;
+ yybuf[2] = '\0';
if (c == '=') {
return tp[0];
} else if (c == op) {
if ((c = getc(yyin)) == '=') {
- yytext[2] = c;
- yytext[3] = '\0';
+ yybuf[2] = c;
+ yybuf[3] = '\0';
return tp[2];
}
op = tp[1];
} else {
- yytext[1] = '\0';
+ yybuf[1] = '\0';
}
ungetc(c, yyin);
return op;
@@ -258,13 +258,13 @@ minus(void)
{
register int c = getc(yyin);
- yytext[1] = c;
+ yybuf[1] = c;
switch (c) {
case '-': return DEC;
case '>': return INDIR;
case '=': return SUB_EQ;
default:
- yytext[1] = '\0';
+ yybuf[1] = '\0';
ungetc(c, yyin);
return '-';
}
@@ -275,8 +275,8 @@ operator(void)
{
register unsigned char c = getc(yyin);
- yytext[0] = c;
- yytext[1] = '\0';
+ yybuf[0] = c;
+ yybuf[1] = '\0';
switch (c) {
case '=': return follow('=', EQ, 0);
case '^': return follow('^', XOR_EQ, 0);
@@ -297,28 +297,28 @@ next(void)
{
register unsigned char c;
+ strcpy(yytext, yybuf);
+ yyval = yynval;
+ yytoken = yynval->tok;
+ yynval = &yysym;
+
if (!skip()) {
- yytoken = EOFTOK;
+ yysym.tok = EOFTOK;
} else {
ungetc(c = getc(yyin), yyin);
if (isalpha(c) || c == '_')
- yytoken = iden();
+ yynval = iden();
else if (isdigit(c))
- yytoken = number();
+ yynval = number();
else
- yytoken = operator();
+ yysym.tok = operator();
}
}
unsigned char
ahead(void)
{
- register char c;
-
- if (!skip())
- return EOFTOK;
- ungetc(c = getc(yyin), yyin);
- return c;
+ return yynval->tok;
}
char
@@ -347,10 +347,11 @@ open_file(register const char *file)
if (file == NULL) {
yyin = stdin;
filename = "(stdin)";
- return;
+ } else {
+ if ((yyin = fopen(file, "r")) == NULL)
+ die("file '%s' not found", file);
+ filename = file;
}
- if ((yyin = fopen(file, "r")) == NULL)
- die("file '%s' not found", file);
- filename = file;
columnum = linenum = 1;
+ next(); /* prefetch first token */
}
