string.h

  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/* make sure to include all global symbols */
  8#include "nolibc.h"
  9
 10#ifndef _NOLIBC_STRING_H
 11#define _NOLIBC_STRING_H
 12
 13#include "arch.h"
 14#include "std.h"
 15
 16static void *malloc(size_t len);
 17
 18/*
 19 * As much as possible, please keep functions alphabetically sorted.
 20 */
 21
 22static __attribute__((unused))
 23int memcmp(const void *s1, const void *s2, size_t n)
 24{
 25	size_t ofs = 0;
 26	int c1 = 0;
 27
 28	while (ofs < n && !(c1 = ((unsigned char *)s1)[ofs] - ((unsigned char *)s2)[ofs])) {
 29		ofs++;
 30	}
 31	return c1;
 32}
 33
 34#ifndef NOLIBC_ARCH_HAS_MEMMOVE
 35/* might be ignored by the compiler without -ffreestanding, then found as
 36 * missing.
 37 */
 38void *memmove(void *dst, const void *src, size_t len);
 39__attribute__((weak,unused,section(".text.nolibc_memmove")))
 40void *memmove(void *dst, const void *src, size_t len)
 41{
 42	size_t dir, pos;
 43
 44	pos = len;
 45	dir = -1;
 46
 47	if (dst < src) {
 48		pos = -1;
 49		dir = 1;
 50	}
 51
 52	while (len) {
 53		pos += dir;
 54		((char *)dst)[pos] = ((const char *)src)[pos];
 55		len--;
 56	}
 57	return dst;
 58}
 59#endif /* #ifndef NOLIBC_ARCH_HAS_MEMMOVE */
 60
 61#ifndef NOLIBC_ARCH_HAS_MEMCPY
 62/* must be exported, as it's used by libgcc on ARM */
 63void *memcpy(void *dst, const void *src, size_t len);
 64__attribute__((weak,unused,section(".text.nolibc_memcpy")))
 65void *memcpy(void *dst, const void *src, size_t len)
 66{
 67	size_t pos = 0;
 68
 69	while (pos < len) {
 70		((char *)dst)[pos] = ((const char *)src)[pos];
 71		pos++;
 72	}
 73	return dst;
 74}
 75#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCPY */
 76
 77#ifndef NOLIBC_ARCH_HAS_MEMSET
 78/* might be ignored by the compiler without -ffreestanding, then found as
 79 * missing.
 80 */
 81void *memset(void *dst, int b, size_t len);
 82__attribute__((weak,unused,section(".text.nolibc_memset")))
 83void *memset(void *dst, int b, size_t len)
 84{
 85	char *p = dst;
 86
 87	while (len--) {
 88		/* prevent gcc from recognizing memset() here */
 89		__asm__ volatile("");
 90		*(p++) = b;
 91	}
 92	return dst;
 93}
 94#endif /* #ifndef NOLIBC_ARCH_HAS_MEMSET */
 95
 96#ifndef NOLIBC_ARCH_HAS_MEMCHR
 97static __attribute__((unused))
 98void *memchr(const void *s, int c, size_t len)
 99{
100	char *p = (char *)s;
101
102	while (len--) {
103		if (*p == (char)c)
104			return p;
105		p++;
106	}
107	return NULL;
108}
109#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCHR */
110
111static __attribute__((unused))
112char *strchr(const char *s, int c)
113{
114	while (*s) {
115		if (*s == (char)c)
116			return (char *)s;
117		s++;
118	}
119	return NULL;
120}
121
122static __attribute__((unused))
123int strcmp(const char *a, const char *b)
124{
125	unsigned int c;
126	int diff;
127
128	while (!(diff = (unsigned char)*a++ - (c = (unsigned char)*b++)) && c)
129		;
130	return diff;
131}
132
133static __attribute__((unused))
134char *strcpy(char *dst, const char *src)
135{
136	char *ret = dst;
137
138	while ((*dst++ = *src++));
139	return ret;
140}
141
142/* this function is only used with arguments that are not constants or when
143 * it's not known because optimizations are disabled. Note that gcc 12
144 * recognizes an strlen() pattern and replaces it with a jump to strlen(),
145 * thus itself, hence the asm() statement below that's meant to disable this
146 * confusing practice.
147 */
148size_t strlen(const char *str);
149__attribute__((weak,unused,section(".text.nolibc_strlen")))
150size_t strlen(const char *str)
151{
152	size_t len;
153
154	for (len = 0; str[len]; len++)
155		__asm__("");
156	return len;
157}
158
159/* do not trust __builtin_constant_p() at -O0, as clang will emit a test and
160 * the two branches, then will rely on an external definition of strlen().
161 */
162#if defined(__OPTIMIZE__)
163#define nolibc_strlen(x) strlen(x)
164#define strlen(str) ({                          \
165	__builtin_constant_p((str)) ?           \
166		__builtin_strlen((str)) :       \
167		nolibc_strlen((str));           \
168})
169#endif
170
171static __attribute__((unused))
172size_t strnlen(const char *str, size_t maxlen)
173{
174	size_t len;
175
176	for (len = 0; (len < maxlen) && str[len]; len++);
177	return len;
178}
179
180static __attribute__((unused))
181char *strdup(const char *str)
182{
183	size_t len;
184	char *ret;
185
186	len = strlen(str);
187	ret = malloc(len + 1);
188	if (__builtin_expect(ret != NULL, 1))
189		memcpy(ret, str, len + 1);
190
191	return ret;
192}
193
194static __attribute__((unused))
195char *strndup(const char *str, size_t maxlen)
196{
197	size_t len;
198	char *ret;
199
200	len = strnlen(str, maxlen);
201	ret = malloc(len + 1);
202	if (__builtin_expect(ret != NULL, 1)) {
203		memcpy(ret, str, len);
204		ret[len] = '\0';
205	}
206
207	return ret;
208}
209
210static __attribute__((unused))
211size_t strlcat(char *dst, const char *src, size_t size)
212{
213	size_t len = strnlen(dst, size);
214
215	/*
216	 * We want len < size-1. But as size is unsigned and can wrap
217	 * around, we use len + 1 instead.
218	 */
219	while (len + 1 < size) {
220		dst[len] = *src;
221		if (*src == '\0')
222			break;
223		len++;
224		src++;
225	}
226
227	if (len < size)
228		dst[len] = '\0';
229
230	while (*src++)
231		len++;
232
233	return len;
234}
235
236static __attribute__((unused))
237size_t strlcpy(char *dst, const char *src, size_t size)
238{
239	size_t len;
240
241	for (len = 0; len < size; len++) {
242		dst[len] = src[len];
243		if (!dst[len])
244			return len;
245	}
246	if (size)
247		dst[size-1] = '\0';
248
249	while (src[len])
250		len++;
251
252	return len;
253}
254
255static __attribute__((unused))
256char *strncat(char *dst, const char *src, size_t size)
257{
258	char *orig = dst;
259
260	while (*dst)
261		dst++;
262
263	while (size && (*dst = *src)) {
264		src++;
265		dst++;
266		size--;
267	}
268
269	*dst = 0;
270	return orig;
271}
272
273static __attribute__((unused))
274int strncmp(const char *a, const char *b, size_t size)
275{
276	unsigned int c;
277	int diff = 0;
278
279	while (size-- &&
280	       !(diff = (unsigned char)*a++ - (c = (unsigned char)*b++)) && c)
281		;
282
283	return diff;
284}
285
286static __attribute__((unused))
287char *strncpy(char *dst, const char *src, size_t size)
288{
289	size_t len;
290
291	for (len = 0; len < size; len++)
292		if ((dst[len] = *src))
293			src++;
294	return dst;
295}
296
297static __attribute__((unused))
298char *strrchr(const char *s, int c)
299{
300	const char *ret = NULL;
301
302	while (*s) {
303		if (*s == (char)c)
304			ret = s;
305		s++;
306	}
307	return (char *)ret;
308}
309
310static __attribute__((unused))
311char *strstr(const char *haystack, const char *needle)
312{
313	size_t len_haystack, len_needle;
314
315	len_needle = strlen(needle);
316	if (!len_needle)
317		return NULL;
318
319	len_haystack = strlen(haystack);
320	while (len_haystack >= len_needle) {
321		if (!memcmp(haystack, needle, len_needle))
322			return (char *)haystack;
323		haystack++;
324		len_haystack--;
325	}
326
327	return NULL;
328}
329
330static __attribute__((unused))
331int tolower(int c)
332{
333	if (c >= 'A' && c <= 'Z')
334		return c - 'A' + 'a';
335	return c;
336}
337
338static __attribute__((unused))
339int toupper(int c)
340{
341	if (c >= 'a' && c <= 'z')
342		return c - 'a' + 'A';
343	return c;
344}
345
346#endif /* _NOLIBC_STRING_H */