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/*
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright © 2024, Synopsys Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
#include <stdbool.h>
#include "string_private.h"
__errno_t
strncat_s(char * __restrict s1, rsize_t s1max, const char * __restrict s2, rsize_t n)
{
const char *msg = "";
size_t s1_len = 0;
bool write_null = true;
s1_len = strnlen_s(s1, s1max);
if (s1 == NULL) {
msg = "strncat_s: dest is NULL";
write_null = false;
goto handle_error;
} else if ((s1max == 0u) || (CHECK_RSIZE(s1max))) {
msg = "strncat_s: dest buffer size is 0 or exceeds RSIZE_MAX";
write_null = false;
goto handle_error;
} else if (s2 == NULL) {
msg = "strncat_s: source is NULL";
goto handle_error;
} else if (CHECK_RSIZE(n)) {
msg = "strncat_s: copy count exceeds RSIZE_MAX";
goto handle_error;
}
/* It is a constraint violation if s1max is not large enough to contain
* the concatenation of s2.
* It is also a constraint violation if the string pointed to by s2
* overlaps s1 in any way.
* The C11 Rationale says we are permitted to proceed with the copy and
* detect dest buffer overrun and overlapping memory blocks as a byproduct
* of performing the copy operation. This is to avoid calling strlen on
* s2 to detect these violations prior to attempting the copy.
*/
// compute chars available in s1
else if (s1_len == s1max) {
msg = "strncat_s: string 1 length exceeds buffer size";
goto handle_error;
} else {
// compute chars available in s1
uint32_t m = (s1max - s1_len);
uint32_t i = 0;
char *s1cp = s1;
for (i = 0u; i < s1_len; i++) {
s1cp++;
}
// Question; at this point should we just return
// strncpy_s(s1cp, m, s2, n) ?
// perhaps not since overlap check needs to be over entire s1 vs. s2?
const char *overlap_point;
bool check_s1_for_overlap;
const char *s2cp = s2;
if (s1 <= s2) {
// if we ever reach s2 when storing to s1 we have overlap
overlap_point = s2;
check_s1_for_overlap = true;
// make sure source does not lie within initial dest string.
if (s2 <= s1cp) {
msg = "strncat_s: overlapping copy";
goto handle_error;
}
} else {
// if we ever reach s1 when reading from s2 we have overlap
overlap_point = s1;
check_s1_for_overlap = false;
}
uint32_t written = 0;
char c = '.';
while ((written < m) && (written < n)) {
if (check_s1_for_overlap == true) {
if (s1cp == overlap_point) {
msg = "strncat_s: overlapping copy";
goto handle_error;
}
} else if (s2cp == overlap_point) {
msg = "strncat_s: overlapping copy";
goto handle_error;
} else {
/* Normal case*/
}
c = *s2cp;
s2cp++;
*s1cp = c;
s1cp++;
written++;
if (c == '\0') {
break;
}
}
if ((c != '\0') && (written == n) && (written < m)) {
// we copied n chars from s2 and there is room for null char in s1
if ((check_s1_for_overlap == true) && (s1cp == overlap_point)) {
msg = "strncat_s: overlapping copy";
goto handle_error;
} else {
c = '\0';
*s1cp = '\0';
}
}
if (c != '\0') {
msg = "strncat_s: dest buffer size insufficent to copy string";
goto handle_error;
}
}
// Normal return path
return 0;
handle_error:
if (write_null && s1 != NULL) {
*s1 = '\0';
}
if (__cur_handler != NULL) {
__cur_handler(msg, NULL, -1);
}
return -1;
}
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