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new way to avoid infinite loops in empty matches: "Python rule" 

("Empty matches for the pattern are replaced only when not
adjacent to a previous match")
This commit is contained in:
Roberto Ierusalimschy 2016-03-31 16:07:42 -03:00
parent 8d4feb504f
commit 783aa8a9da
1 changed files with 8 additions and 8 deletions
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16
lstrlib.c
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@ -1,5 +1,5 @@
/* /*
** $Id: lstrlib.c,v 1.241 2016/03/23 17:12:17 roberto Exp roberto $ ** $Id: lstrlib.c,v 1.242 2016/03/23 18:08:26 roberto Exp roberto $
** Standard library for string operations and pattern-matching ** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -681,6 +681,7 @@ static int str_match (lua_State *L) {
typedef struct GMatchState { typedef struct GMatchState {
const char *src; /* current position */ const char *src; /* current position */
const char *p; /* pattern */ const char *p; /* pattern */
const char *lastmatch; /* end of last match */
MatchState ms; /* match state */ MatchState ms; /* match state */
} GMatchState; } GMatchState;
@ -692,9 +693,8 @@ static int gmatch_aux (lua_State *L) {
for (src = gm->src; src <= gm->ms.src_end; src++) { for (src = gm->src; src <= gm->ms.src_end; src++) {
const char *e; const char *e;
reprepstate(&gm->ms); reprepstate(&gm->ms);
if ((e = match(&gm->ms, src, gm->p)) != NULL) { if ((e = match(&gm->ms, src, gm->p)) != NULL && e != gm->lastmatch) {
/* in empty matches, advance at least one position */ gm->src = gm->lastmatch = e;
gm->src = (e == src) ? src + 1 : e;
return push_captures(&gm->ms, src, e); return push_captures(&gm->ms, src, e);
} }
} }
@ -710,7 +710,7 @@ static int gmatch (lua_State *L) {
lua_settop(L, 2); /* keep them on closure to avoid being collected */ lua_settop(L, 2); /* keep them on closure to avoid being collected */
gm = (GMatchState *)lua_newuserdata(L, sizeof(GMatchState)); gm = (GMatchState *)lua_newuserdata(L, sizeof(GMatchState));
prepstate(&gm->ms, L, s, ls, p, lp); prepstate(&gm->ms, L, s, ls, p, lp);
gm->src = s; gm->p = p; gm->src = s; gm->p = p; gm->lastmatch = NULL;
lua_pushcclosure(L, gmatch_aux, 3); lua_pushcclosure(L, gmatch_aux, 3);
return 1; return 1;
} }
@ -779,6 +779,7 @@ static int str_gsub (lua_State *L) {
size_t srcl, lp; size_t srcl, lp;
const char *src = luaL_checklstring(L, 1, &srcl); /* subject */ const char *src = luaL_checklstring(L, 1, &srcl); /* subject */
const char *p = luaL_checklstring(L, 2, &lp); /* pattern */ const char *p = luaL_checklstring(L, 2, &lp); /* pattern */
const char *lastmatch = NULL; /* end of last match */
int tr = lua_type(L, 3); /* replacement type */ int tr = lua_type(L, 3); /* replacement type */
lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1); /* max replacements */ lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1); /* max replacements */
int anchor = (*p == '^'); int anchor = (*p == '^');
@ -796,12 +797,11 @@ static int str_gsub (lua_State *L) {
while (n < max_s) { while (n < max_s) {
const char *e; const char *e;
reprepstate(&ms); /* (re)prepare state for new match */ reprepstate(&ms); /* (re)prepare state for new match */
if ((e = match(&ms, src, p)) != NULL) { /* match? */ if ((e = match(&ms, src, p)) != NULL && e != lastmatch) { /* match? */
n++; n++;
add_value(&ms, &b, src, e, tr); /* add replacement to buffer */ add_value(&ms, &b, src, e, tr); /* add replacement to buffer */
src = lastmatch = e;
} }
if (e && e>src) /* non empty match? */
src = e; /* skip it */
else if (src < ms.src_end) /* otherwise, skip one character */ else if (src < ms.src_end) /* otherwise, skip one character */
luaL_addchar(&b, *src++); luaL_addchar(&b, *src++);
else break; /* end of subject */ else break; /* end of subject */