xmalloc: add xmemdup and xarraydup utility functions

There are multiple instances of using pair of x*alloc and memcpy calls
to duplicate an entity;  sometimes they even utilise xcalloc and perform
unnecessary zeroing of the memory.  Implement a separate routine
that allows more compact code.

* src/xmalloc.h (xmemdup, xarraydup): New declarations.
(xobjdup): New macro, a wrapper for xmemdup.
* src/xmalloc.c (xmemdup, xarraydup): New functions.

2 files changed, 29 insertions, 1 deletions

diff --git a/src/xmalloc.c b/src/xmalloc.c
index be5e601e1..527e7c56e 100644
--- a/src/xmalloc.c
+++ b/src/xmalloc.c
@@ -150,6 +150,25 @@ xstrndup(const char *str, size_t n)
 	return p;
 }
 
+void *
+xmemdup(const void *src, size_t size)
+{
+	if (!src)
+		return NULL;
+
+	return memcpy(xmalloc(size), src, size);
+}
+
+void *
+xarraydup(const void *src, size_t nmemb, size_t memb_size)
+{
+	if (!src)
+		return NULL;
+
+	/* (nmemb * memb_size) checks are already done inside xallocarray */
+	return memcpy(xallocarray(nmemb, memb_size), src, nmemb * memb_size);
+}
+
 char *
 xasprintf(const char *fmt, ...)
 {
diff --git a/src/xmalloc.h b/src/xmalloc.h
index 505c64739..94d2689b0 100644
--- a/src/xmalloc.h
+++ b/src/xmalloc.h
@@ -69,7 +69,7 @@ void *xreallocarray(void *ptr, size_t nmemb, size_t size)
 void *xgrowarray(void *ptr, size_t *nmemb, size_t memb_size);
 
 /*
- * Note that the following two functions return NULL when NULL is specified
+ * Note that the following four functions return NULL when NULL is specified
  * and not when allocation is failed, since, as the "x" prefix implies,
  * the allocation failure leads to program termination, so we may re-purpose
  * this return value and simplify the idiom "str ? xstrdup(str) : NULL".
@@ -77,6 +77,15 @@ void *xgrowarray(void *ptr, size_t *nmemb, size_t memb_size);
 char *xstrdup(const char *str) ATTRIBUTE_MALLOC;
 char *xstrndup(const char *str, size_t n) ATTRIBUTE_MALLOC;
 
+/** Implements xmalloc + memcpy idiom. */
+void *xmemdup(const void *src, size_t size)
+	ATTRIBUTE_MALLOC ATTRIBUTE_ALLOC_SIZE((2));
+/** Implements xallocarray + memcpy idiom. */
+void *xarraydup(const void *src, size_t nmemb, size_t memb_size)
+	ATTRIBUTE_MALLOC ATTRIBUTE_ALLOC_SIZE((2, 3));
+
+#define xobjdup(src_) xmemdup(src_, sizeof(*(src_)))
+
 /**
  * Analogous to asprintf, die in case of an error.
  */