1/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
  2/*
  3 * string function definitions for NOLIBC
  4 * Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
  5 */
  6
  7#ifndef _NOLIBC_STRING_H
  8#define _NOLIBC_STRING_H
  9
 10#include "std.h"
 11
 12static void *malloc(size_t len);
 13
 14/*
 15 * As much as possible, please keep functions alphabetically sorted.
 16 */
 17
 18static __attribute__((unused))
 19int memcmp(const void *s1, const void *s2, size_t n)
 20{
 21	size_t ofs = 0;
 22	int c1 = 0;
 23
 24	while (ofs < n && !(c1 = ((unsigned char *)s1)[ofs] - ((unsigned char *)s2)[ofs])) {
 25		ofs++;
 26	}
 27	return c1;
 28}
 29
 30static __attribute__((unused))
 31void *_nolibc_memcpy_up(void *dst, const void *src, size_t len)
 32{
 33	size_t pos = 0;
 34
 35	while (pos < len) {
 36		((char *)dst)[pos] = ((const char *)src)[pos];
 37		pos++;
 38	}
 39	return dst;
 40}
 41
 42static __attribute__((unused))
 43void *_nolibc_memcpy_down(void *dst, const void *src, size_t len)
 44{
 45	while (len) {
 46		len--;
 47		((char *)dst)[len] = ((const char *)src)[len];
 48	}
 49	return dst;
 50}
 51
 52/* might be ignored by the compiler without -ffreestanding, then found as
 53 * missing.
 54 */
 55__attribute__((weak,unused,section(".text.nolibc_memmove")))
 56void *memmove(void *dst, const void *src, size_t len)
 57{
 58	size_t dir, pos;
 59
 60	pos = len;
 61	dir = -1;
 62
 63	if (dst < src) {
 64		pos = -1;
 65		dir = 1;
 66	}
 67
 68	while (len) {
 69		pos += dir;
 70		((char *)dst)[pos] = ((const char *)src)[pos];
 71		len--;
 72	}
 73	return dst;
 74}
 75
 76/* must be exported, as it's used by libgcc on ARM */
 77__attribute__((weak,unused,section(".text.nolibc_memcpy")))
 78void *memcpy(void *dst, const void *src, size_t len)
 79{
 80	return _nolibc_memcpy_up(dst, src, len);
 81}
 82
 83/* might be ignored by the compiler without -ffreestanding, then found as
 84 * missing.
 85 */
 86__attribute__((weak,unused,section(".text.nolibc_memset")))
 87void *memset(void *dst, int b, size_t len)
 88{
 89	char *p = dst;
 90
 91	while (len--) {
 92		/* prevent gcc from recognizing memset() here */
 93		asm volatile("");
 94		*(p++) = b;
 95	}
 96	return dst;
 97}
 98
 99static __attribute__((unused))
100char *strchr(const char *s, int c)
101{
102	while (*s) {
103		if (*s == (char)c)
104			return (char *)s;
105		s++;
106	}
107	return NULL;
108}
109
110static __attribute__((unused))
111int strcmp(const char *a, const char *b)
112{
113	unsigned int c;
114	int diff;
115
116	while (!(diff = (unsigned char)*a++ - (c = (unsigned char)*b++)) && c)
117		;
118	return diff;
119}
120
121static __attribute__((unused))
122char *strcpy(char *dst, const char *src)
123{
124	char *ret = dst;
125
126	while ((*dst++ = *src++));
127	return ret;
128}
129
130/* this function is only used with arguments that are not constants or when
131 * it's not known because optimizations are disabled. Note that gcc 12
132 * recognizes an strlen() pattern and replaces it with a jump to strlen(),
133 * thus itself, hence the asm() statement below that's meant to disable this
134 * confusing practice.
135 */
136static __attribute__((unused))
137size_t strlen(const char *str)
138{
139	size_t len;
140
141	for (len = 0; str[len]; len++)
142		asm("");
143	return len;
144}
145
146/* do not trust __builtin_constant_p() at -O0, as clang will emit a test and
147 * the two branches, then will rely on an external definition of strlen().
148 */
149#if defined(__OPTIMIZE__)
150#define nolibc_strlen(x) strlen(x)
151#define strlen(str) ({                          \
152	__builtin_constant_p((str)) ?           \
153		__builtin_strlen((str)) :       \
154		nolibc_strlen((str));           \
155})
156#endif
157
158static __attribute__((unused))
159size_t strnlen(const char *str, size_t maxlen)
160{
161	size_t len;
162
163	for (len = 0; (len < maxlen) && str[len]; len++);
164	return len;
165}
166
167static __attribute__((unused))
168char *strdup(const char *str)
169{
170	size_t len;
171	char *ret;
172
173	len = strlen(str);
174	ret = malloc(len + 1);
175	if (__builtin_expect(ret != NULL, 1))
176		memcpy(ret, str, len + 1);
177
178	return ret;
179}
180
181static __attribute__((unused))
182char *strndup(const char *str, size_t maxlen)
183{
184	size_t len;
185	char *ret;
186
187	len = strnlen(str, maxlen);
188	ret = malloc(len + 1);
189	if (__builtin_expect(ret != NULL, 1)) {
190		memcpy(ret, str, len);
191		ret[len] = '\0';
192	}
193
194	return ret;
195}
196
197static __attribute__((unused))
198size_t strlcat(char *dst, const char *src, size_t size)
199{
200	size_t len;
201	char c;
202
203	for (len = 0; dst[len];	len++)
204		;
205
206	for (;;) {
207		c = *src;
208		if (len < size)
209			dst[len] = c;
210		if (!c)
211			break;
212		len++;
213		src++;
214	}
215
216	return len;
217}
218
219static __attribute__((unused))
220size_t strlcpy(char *dst, const char *src, size_t size)
221{
222	size_t len;
223	char c;
224
225	for (len = 0;;) {
226		c = src[len];
227		if (len < size)
228			dst[len] = c;
229		if (!c)
230			break;
231		len++;
232	}
233	return len;
234}
235
236static __attribute__((unused))
237char *strncat(char *dst, const char *src, size_t size)
238{
239	char *orig = dst;
240
241	while (*dst)
242		dst++;
243
244	while (size && (*dst = *src)) {
245		src++;
246		dst++;
247		size--;
248	}
249
250	*dst = 0;
251	return orig;
252}
253
254static __attribute__((unused))
255int strncmp(const char *a, const char *b, size_t size)
256{
257	unsigned int c;
258	int diff = 0;
259
260	while (size-- &&
261	       !(diff = (unsigned char)*a++ - (c = (unsigned char)*b++)) && c)
262		;
263
264	return diff;
265}
266
267static __attribute__((unused))
268char *strncpy(char *dst, const char *src, size_t size)
269{
270	size_t len;
271
272	for (len = 0; len < size; len++)
273		if ((dst[len] = *src))
274			src++;
275	return dst;
276}
277
278static __attribute__((unused))
279char *strrchr(const char *s, int c)
280{
281	const char *ret = NULL;
282
283	while (*s) {
284		if (*s == (char)c)
285			ret = s;
286		s++;
287	}
288	return (char *)ret;
289}
290
291/* make sure to include all global symbols */
292#include "nolibc.h"
293
294#endif /* _NOLIBC_STRING_H */