[RFC PATCH v1 6/6] tools/include/string: Implement `strdup()` and `strndup()`

[Ammar Faizi]

Add strdup and strndup support. These functions are only available on
architectures that have my_syscall6() macro from nolibc.

Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---
 tools/include/nolibc/string.h | 68 +++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index 4554b6fcb400..413c65f7c853 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -9,6 +9,10 @@
 
 #include "std.h"
 
+static void free(void *ptr);
+static void *malloc(size_t len);
+static void *realloc(void *old_ptr, size_t new_size);
+
 /*
  * As much as possible, please keep functions alphabetically sorted.
  */
@@ -127,6 +131,70 @@ size_t nolibc_strlen(const char *str)
 		nolibc_strlen((str));           \
 })
 
+static __attribute__((unused))
+char *strdup(const char *str)
+{
+	size_t allocated = 2048;
+	size_t i;
+	char *ret;
+	char *tmp;
+
+	ret = malloc(allocated);
+	if (__builtin_expect(!ret, 0))
+		return NULL;
+
+	i = 0;
+	for (;;) {
+		char c = *str;
+		if (!c)
+			break;
+
+		if (i == allocated) {
+			allocated += 2048;
+			tmp = realloc(ret, allocated);
+			if (__builtin_expect(!tmp, 0)) {
+				free(ret);
+				return NULL;
+			}
+			ret = tmp;
+		}
+
+		ret[i++] = c;
+		str++;
+	}
+
+	ret[i] = '\0';
+	return ret;
+}
+
+static __attribute__((unused))
+char *strndup(const char *str, size_t maxlen)
+{
+	size_t i;
+	char *ret;
+
+	ret = malloc(maxlen + 1);
+	if (__builtin_expect(!ret, 0))
+		return NULL;
+
+	i = 0;
+	for (;;) {
+		char c = *str;
+		if (!c)
+			break;
+
+		if (i == maxlen)
+			break;
+
+		ret[i++] = c;
+		str++;
+	}
+
+	ret[i] = '\0';
+	return ret;
+}
+
+
 static __attribute__((unused))
 size_t strlcat(char *dst, const char *src, size_t size)
 {
-- 
Ammar Faizi