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several changes in 'utf8.offset'

This commit is contained in:
Roberto Ierusalimschy 2014-04-03 10:45:09 -03:00
parent 007f66408d
commit 144afa4d47
1 changed files with 27 additions and 22 deletions
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49
lutf8lib.c
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@ -1,5 +1,5 @@
/*
** $Id: lutf8lib.c,v 1.5 2014/04/01 14:39:55 roberto Exp roberto $
** $Id: lutf8lib.c,v 1.6 2014/04/02 17:01:22 roberto Exp roberto $
** Standard library for UTF-8 manipulation
** See Copyright Notice in lua.h
*/
@ -150,41 +150,46 @@ static int utfchar (lua_State *L) {
/*
** offset(s, n, [i]) -> index where n-th character *after*
** offset(s, n, [i]) -> index where n-th character counting from
** position 'i' starts; 0 means character at 'i'.
*/
static int byteoffset (lua_State *L) {
size_t len;
const char *s = luaL_checklstring(L, 1, &len);
int n = luaL_checkint(L, 2);
lua_Integer posi = u_posrelat(luaL_optinteger(L, 3, 1), len) - 1;
luaL_argcheck(L, 0 <= posi && posi <= (lua_Integer)len, 3,
lua_Integer posi = (n >= 0) ? 1 : len + 1;
posi = u_posrelat(luaL_optinteger(L, 3, posi), len);
luaL_argcheck(L, 1 <= posi && --posi <= (lua_Integer)len, 3,
"position out of range");
if (n == 0) {
/* find beginning of current byte sequence */
while (posi > 0 && iscont(s + posi)) posi--;
}
else if (n < 0) {
while (n < 0 && posi > 0) { /* move back */
do { /* find beginning of previous character */
posi--;
} while (posi > 0 && iscont(s + posi));
n++;
}
}
else {
n--; /* do not move for 1st character */
while (n > 0 && posi < (lua_Integer)len) {
do { /* find beginning of next character */
posi++;
} while (iscont(s + posi)); /* ('\0' is not continuation) */
n--;
}
if (iscont(s + posi))
luaL_error(L, "initial position is a continuation byte");
if (n < 0) {
while (n < 0 && posi > 0) { /* move back */
do { /* find beginning of previous character */
posi--;
} while (posi > 0 && iscont(s + posi));
n++;
}
}
else {
n--; /* do not move for 1st character */
while (n > 0 && posi < (lua_Integer)len) {
do { /* find beginning of next character */
posi++;
} while (iscont(s + posi)); /* (cannot pass final '\0') */
n--;
}
}
}
if (n == 0)
if (n == 0) /* did it find given character? */
lua_pushinteger(L, posi + 1);
else
lua_pushnil(L); /* no such position */
else /* no such character */
lua_pushnil(L);
return 1;
}