string.h: Move common string functions into .c file

There's no clear reason why most of coreboot's basic string functions
are static inline. These functions don't particularly benefit from
inlining (at least not notably more than other functions). This patch
moves them to string.c to be more consistent with our usual coding
practices.

Leaving the ctype functions as static inline because they actually seem
small and collapsible enough that inlining seems reasonable.

Also clarified the situation of strdup() and strconcat() a bit more,
optimized strrchr() to be single-pass, fixed a bug with using strchr()
to find '\0' and got rid of unnecessary register keywords.

Change-Id: I88166ba9876e94dfa3cfc06969c78a9e1bc6fc36
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32901
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Alex Thiessen <alex.thiessen.de+coreboot@gmail.com>

src/lib/string.c

@@ -1,9 +1,14 @@
+#include <assert.h>
+#include <rules.h>
 #include <string.h>
 #include <stddef.h>
 #include <stdlib.h>
 
 char *strdup(const char *s)
 {
+	if (!ENV_RAMSTAGE)
+		dead_code();	/* This can't be used without malloc(). */
+
 	size_t sz = strlen(s) + 1;
 	char *d = malloc(sz);
 	if (d)
@@ -13,6 +18,9 @@ char *strdup(const char *s)
 
 char *strconcat(const char *s1, const char *s2)
 {
+	if (!ENV_RAMSTAGE)
+		dead_code();	/* This can't be used without malloc(). */
+
 	size_t sz_1 = strlen(s1);
 	size_t sz_2 = strlen(s2);
 	char *d = malloc(sz_1 + sz_2 + 1);
@@ -22,3 +30,104 @@ char *strconcat(const char *s1, const char *s2)
 	}
 	return d;
 }
+
+size_t strnlen(const char *src, size_t max)
+{
+	size_t i = 0;
+	while ((*src++) && (i < max))
+		i++;
+	return i;
+}
+
+size_t strlen(const char *src)
+{
+	size_t i = 0;
+	while (*src++)
+		i++;
+	return i;
+}
+
+char *strchr(const char *s, int c)
+{
+	do {
+		if (*s == c)
+			return (char *)s;
+	} while (*s++);
+
+	return NULL;
+}
+
+char *strrchr(const char *s, int c)
+{
+	char *p = NULL;
+
+	do {
+		if (*s == c)
+			p = (char *)s;
+	} while (*s++);
+
+	return p;
+}
+
+char *strncpy(char *to, const char *from, int count)
+{
+	char *ret = to;
+	char data;
+
+	while (count > 0) {
+		count--;
+		data = *from++;
+		*to++  = data;
+		if (data == '\0')
+			break;
+	}
+
+	while (count > 0) {
+		count--;
+		*to++ = '\0';
+	}
+	return ret;
+}
+
+char *strcpy(char *dst, const char *src)
+{
+	char *ptr = dst;
+
+	while (*src)
+		*dst++ = *src++;
+	*dst = '\0';
+
+	return ptr;
+}
+
+int strcmp(const char *s1, const char *s2)
+{
+	int r;
+
+	while ((r = (*s1 - *s2)) == 0 && *s1) {
+		s1++;
+		s2++;
+	}
+	return r;
+}
+
+int strncmp(const char *s1, const char *s2, int maxlen)
+{
+	int i;
+
+	for (i = 0; i < maxlen; i++) {
+		if ((s1[i] != s2[i]) || (s1[i] == '\0'))
+			return s1[i] - s2[i];
+	}
+
+	return 0;
+}
+
+unsigned int skip_atoi(char **s)
+{
+	unsigned int i = 0;
+
+	while (isdigit(**s))
+		i = i*10 + *((*s)++) - '0';
+	return i;
+}