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Lexer.HC
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Lexer.HC
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// NOTE: This version of the lexer is very slow and isn't currently
// used. See FastLexer.HC for the real one. I may get around to
// writing a proper lexer generator eventually.
#ifndef LEXER_HC
#define LEXER_HC
#include "Array.HC"
#include "PArray.HC"
#include "Regex.HC"
#include "String.HC"
#include "Util.HC"
class Lexer
{
PArray *_regexes; // Array of pointers to Regex terms
PArray *_aux_regexes; // Auxiliary regexes with '.*' appended to the end
};
class Token
{
INT i;
String *s;
};
Token *TokenMk(INT i, String *s)
{
Token *t = MAlloc(sizeof(Token));
t->i = i;
t->s = s;
return t;
}
VOID TokenDelete(Token *t)
{
NullCheck(t, "token");
Free(t);
}
VOID LexerDelete(Lexer *l)
{
NullCheck(l, "lexer");
NullCheck(l->_regexes, "lexer regexes");
INT i;
for (i = 0; i < PArraySize(l->_regexes); ++i) {
RegexDelete(PArrayGet(l->_regexes, i));
}
Free(l);
}
Lexer *LexerEmpty()
{
Lexer *l = MAlloc(sizeof(Lexer));
l->_regexes = PArrayEmpty;
l->_aux_regexes = PArrayEmpty;
return l;
}
// expects [patterns] to be an PArray of Strings
Lexer *LexerMk(PArray *patterns)
{
NullCheck(patterns, "regex patterns");
INT i;
Lexer *l = LexerEmpty;
String *p;
Regex *r;
for (i = 0; i < PArraySize(patterns); ++i) {
p = PArrayGet(patterns, i);
r = RegexParse(p);
PArrayPush(l->_regexes, r);
PArrayPush(l->_aux_regexes, RegexMkPrefix(r));
}
return l;
}
// expects [patterns] to be an Array of c-strings
Lexer *LexerMkC(PArray *patterns)
{
INT i;
PArray *strings = PArrayEmpty;
for (i = 0; i < PArraySize(patterns); ++i) {
PArrayPush(strings, StringMk(PArrayGet(patterns, i)));
}
return LexerMk(strings);
}
INT _greedyMatch(Regex *r, String *s)
{
INT i, match;
INT max_i = 0;
String *sub;
for (i = 1; i <= StringLen(s); ++i) {
sub = StringSubstr(s, 0, i);
match = RegexMatch(r, sub, 0);
if (match)
max_i = i;
}
return max_i;
}
Token *LexerMatch(Lexer *l, String *s)
{
NullCheck(l, "lexer");
NullCheck(s, "input string");
INT i, j;
Regex *r, *r_aux;
for (i = 0; i < PArraySize(l->_regexes); ++i) {
r_aux = PArrayGet(l->_aux_regexes, i);
if (RegexMatch(r_aux, s, 0)) {
r = PArrayGet(l->_regexes, i);
j = _greedyMatch(r, s);
return TokenMk(i, StringSubstr(s, 0, j));
}
}
return NULL;
}
PArray *LexerLex(Lexer *l, String *s)
{
INT i = 0;
NullCheck(l, "lexer");
NullCheck(s, "input string");
s = StringCopy(s);
PArray *a = PArrayEmpty;
Token *t;
while (StringLen(s)) {
t = LexerMatch(l, s);
if (!t) {
for (i = 0; i < PArraySize(a); ++i) {
TokenDelete(PArrayGet(a, i));
}
return NULL;
}
PArrayPush(a, t);
StringErase(s, 0, StringLen(t->s));
}
return a;
}
#endif