CORD CORD_substr(CORD x, size_t i, size_t n)
{
size_t len = CORD_len(x);
if (i >= len || n == 0) return(0);
if (i + n > len) n = len - i;
return(CORD_substr_checked(x, i, n));
}
CORD CORD_substr(CORD x, size_t i, size_t n)
{
register size_t len = CORD_len(x);
if (i >= len || n <= 0) return(0);
/* n < 0 is impossible in a correct C implementation, but */
/* quite possible under SunOS 4.X. */
if (i + n > len) n = len - i;
return(CORD_substr_checked(x, i, n));
}
/* A version of CORD_substr that assumes i >= 0, n > 0, and i + n < length(x).*/
CORD CORD_substr_checked(CORD x, size_t i, size_t n)
{
if (CORD_IS_STRING(x)) {
if (n > SUBSTR_LIMIT) {
return(CORD_substr_closure(x, i, n, CORD_index_access_fn));
} else {
char * result = (char *)GC_MALLOC_ATOMIC(n + 1);
if (result == 0) OUT_OF_MEMORY;
strncpy(result, x+i, n);
result[n] = '\0';
return(result);
}
} else if (IS_CONCATENATION(x)) {
struct Concatenation * conc = &(((CordRep *)x) -> concatenation);
size_t left_len = LEFT_LEN(conc);
size_t right_len = conc -> len - left_len;
if (i >= left_len) {
if (n == right_len) return(conc -> right);
return(CORD_substr_checked(conc -> right, i - left_len, n));
} else if (i+n <= left_len) {
if (n == left_len) return(conc -> left);
return(CORD_substr_checked(conc -> left, i, n));
} else {
/* Need at least one character from each side. */
CORD left_part;
CORD right_part;
size_t left_part_len = left_len - i;
if (i == 0) {
left_part = conc -> left;
} else {
left_part = CORD_substr_checked(conc -> left, i, left_part_len);
}
if (i + n == right_len + left_len) {
right_part = conc -> right;
} else {
right_part = CORD_substr_checked(conc -> right, 0,
n - left_part_len);
}
return(CORD_cat(left_part, right_part));
}
} else /* function */ {
if (n > SUBSTR_LIMIT) {
if (IS_SUBSTR(x)) {
/* Avoid nesting substring nodes. */
struct Function * f = &(((CordRep *)x) -> function);
struct substr_args *descr =
(struct substr_args *)(f -> client_data);
return(CORD_substr_closure((CORD)descr->sa_cord,
i + descr->sa_index,
n, f -> fn));
} else {
return(CORD_substr_closure(x, i, n, CORD_apply_access_fn));
}
} else {
char * result;
struct Function * f = &(((CordRep *)x) -> function);
char buf[SUBSTR_LIMIT+1];
char * p = buf;
size_t j;
size_t lim = i + n;
for (j = i; j < lim; j++) {
char c = (*(f -> fn))(j, f -> client_data);
if (c == '\0') {
return(CORD_substr_closure(x, i, n, CORD_apply_access_fn));
}
*p++ = c;
}
result = (char *)GC_MALLOC_ATOMIC(n + 1);
if (result == 0) OUT_OF_MEMORY;
memcpy(result, buf, n);
result[n] = '\0';
return(result);
}
}
}
