lib: Add memdup()

Add a function to duplicate a memory region, a little like strdup().

Signed-off-by: Simon Glass <sjg@chromium.org>

include/linux/string.h

@@ -129,6 +129,19 @@ extern void * memchr(const void *,int,__kernel_size_t);
 void *memchr_inv(const void *, int, size_t);
 #endif
 
+/**
+ * memdup() - allocate a buffer and copy in the contents
+ *
+ * Note that this returns a valid pointer even if @len is 0
+ *
+ * @src: data to copy in
+ * @len: number of bytes to copy
+ * @return allocated buffer with the copied contents, or NULL if not enough
+ *	memory is available
+ *
+ */
+char *memdup(const void *src, size_t len);
+
 unsigned long ustrtoul(const char *cp, char **endp, unsigned int base);
 unsigned long long ustrtoull(const char *cp, char **endp, unsigned int base);
 

lib/string.c

@@ -659,6 +659,19 @@ void * memscan(void * addr, int c, size_t size)
 }
 #endif
 
+char *memdup(const void *src, size_t len)
+{
+	char *p;
+
+	p = malloc(len);
+	if (!p)
+		return NULL;
+
+	memcpy(p, src, len);
+
+	return p;
+}
+
 #ifndef __HAVE_ARCH_STRSTR
 /**
  * strstr - Find the first substring in a %NUL terminated string

test/lib/string.c

@@ -23,6 +23,8 @@
 /* Allow for copying up to 32 bytes */
 #define BUFLEN (SWEEP + 33)
 
+#define TEST_STR	"hello"
+
 /**
  * init_buffer() - initialize buffer
  *
@@ -193,3 +195,33 @@ static int lib_memmove(struct unit_test_state *uts)
 }
 
 LIB_TEST(lib_memmove, 0);
+
+/** lib_memdup() - unit test for memdup() */
+static int lib_memdup(struct unit_test_state *uts)
+{
+	char buf[BUFLEN];
+	size_t len;
+	char *p, *q;
+
+	/* Zero size should do nothing */
+	p = memdup(NULL, 0);
+	ut_assertnonnull(p);
+	free(p);
+
+	p = memdup(buf, 0);
+	ut_assertnonnull(p);
+	free(p);
+
+	strcpy(buf, TEST_STR);
+	len = sizeof(TEST_STR);
+	p = memdup(buf, len);
+	ut_asserteq_mem(p, buf, len);
+
+	q = memdup(p, len);
+	ut_asserteq_mem(q, buf, len);
+	free(q);
+	free(p);
+
+	return 0;
+}
+LIB_TEST(lib_memdup, 0);