[libvirt] [PATCH 1/1] Implement variable length structure allocator
* This patch implements a memory allocator to obtain memory for
structures whose last member is a variable length array. C99 refers
to these variable length objects as structs containing flexible
array members.
---
src/util/memory.c | 40 ++++++++++++++++++++++++++++++++++++++++
src/util/memory.h | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+), 0 deletions(-)
diff --git a/src/util/memory.c b/src/util/memory.c
index b2ee376..dd1216b 100644
--- a/src/util/memory.c
+++ b/src/util/memory.c
@@ -165,6 +165,46 @@ int virReallocN(void *ptrptr, size_t size, size_t count)
}
/**
+ * Vir_Alloc_Var:
+ * @ptrptr: pointer to hold address of allocated memory
+ * @struct_size: size of initial struct
+ * @element_size: size of array elements
+ * @count: number of array elements to allocate
+ *
+ * Allocate struct_size bytes plus an array of 'count' elements, each
+ * of size element_size. This sort of allocation is useful for
+ * receiving the data of certain ioctls and other APIs which return a
+ * struct in which the last element is an array of undefined length.
+ * The caller of this type of API is expected to know the length of
+ * the array that will be returned and allocate a suitable buffer to
+ * contain the returned data. C99 refers to these variable length
+ * objects as structs containing flexible array members.
+ *
+ * Returns -1 on failure, 0 on success
+ */
+int virAllocVar(void *ptrptr, size_t struct_size, size_t element_size, size_t count)
+{
+ size_t alloc_size = 0;
+
+#if TEST_OOM
+ if (virAllocTestFail())
+ return -1;
+#endif
+
+ if (VIR_ALLOC_VAR_OVERSIZED(struct_size, count, element_size)) {
+ errno = ENOMEM;
+ return -1;
+ }
+
+ alloc_size = struct_size + (element_size * count);
+ *(void **)ptrptr = calloc(1, alloc_size);
+ if (*(void **)ptrptr == NULL)
+ return -1;
+ return 0;
+}
+
+
+/**
* virFree:
* @ptrptr: pointer to pointer for address of memory to be freed
*
diff --git a/src/util/memory.h b/src/util/memory.h
index 0228173..c717610 100644
--- a/src/util/memory.h
+++ b/src/util/memory.h
@@ -48,6 +48,10 @@
int virAlloc(void *ptrptr, size_t size) ATTRIBUTE_RETURN_CHECK;
int virAllocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK;
int virReallocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK;
+int virAllocVar(void *ptrptr,
+ size_t struct_size,
+ size_t element_size,
+ size_t count) ATTRIBUTE_RETURN_CHECK;
void virFree(void *ptrptr);
/**
@@ -88,6 +92,37 @@ void virFree(void *ptrptr);
*/
# define VIR_REALLOC_N(ptr, count) virReallocN(&(ptr), sizeof(*(ptr)), (count))
+/*
+ * VIR_ALLOC_VAR_OVERSIZED:
+ * @M: size of base structure
+ * @N: number of array elements in trailing array
+ * @S: size of trailing array elements
+ *
+ * Check to make sure that the requested allocation will not cause
+ * arithmetic overflow in the allocation size. The check is
+ * essentially the same as that in gnulib's xalloc_oversized.
+ */
+#define VIR_ALLOC_VAR_OVERSIZED(M, N, S) ((((size_t)-1) - (M)) / (S) < (N))
+
+/**
+ * VIR_ALLOC_VAR:
+ * @ptr: pointer to hold address of allocated memory
+ * @type: element type of trailing array
+ * @count: number of array elements to allocate
+ *
+ * Allocate sizeof(*ptr) bytes plus an array of 'count' elements, each
+ * sizeof('type'). This sort of allocation is useful for receiving
+ * the data of certain ioctls and other APIs which return a struct in
+ * which the last element is an array of undefined length. The caller
+ * of this type of API is expected to know the length of the array
+ * that will be returned and allocate a suitable buffer to contain the
+ * returned data. C99 refers to these variable length objects as
+ * structs containing flexible array members.
+
+ * Returns -1 on failure, 0 on success
+ */
+#define VIR_ALLOC_VAR(ptr, type, count) virAllocVar(&(ptr), sizeof(*ptr),
sizeof(type), (count))
+
/**
* VIR_FREE:
* @ptr: pointer holding address to be freed
--
1.7.0.1