Blobs

Discussion

The SSM allocator allows programs to allocate contiguous chunks of reference-counted memory whose contents are of arbitrary layout. This object type provides users the flexibility to extend runtime with objects that the runtime does not natively support, so long as they commit to managing stored resources themselves, because the garbage collector will not scan the payload for other managed heap pointers.

Blobs use size-flavored ssm_mm headers, where the size field determines the size of blob payload. To support even larger blob sizes, the actual size is divided by SSM_BLOB_SIZE_SCALE while stored in size.

The heap memory layout for blobs are described by ssm_blob1.

Data Structures
struct	ssm_blob1
	The struct template of a heap-allocated blob. More...

Macros
#define	SSM_BLOB_SIZE_SCALE   4
	The size resolution for heap-allocated blobs. More...
#define	ssm_blob_size(size)    (sizeof(struct ssm_blob1) - SSM_BLOB_SIZE_SCALE + (size))
	Compute the size of a blob with its header. More...
#define	ssm_blob_heap_size(v)    ssm_blob_size(((v).heap_ptr->info.size) * SSM_BLOB_SIZE_SCALE)
	Compute the size a blob in the heap. More...
#define	ssm_blob_payload(v)    (&*(container_of((v).heap_ptr, struct ssm_blob1, mm)->payload))
	Obtain pointer to the payload of a blob from an ssm_value_t. More...
#define	ssm_new_blob(s)

Functions
ssm_value_t	ssm_new_blob_int (uint16_t size)
	Allocate a blob on the heap. More...

Macro Definition Documentation

SSM_BLOB_SIZE_SCALE

#define SSM_BLOB_SIZE_SCALE   4

The size resolution for heap-allocated blobs.

Definition at line 1067 of file ssm.h.

ssm_blob_size

#define ssm_blob_size

(

size

)

(sizeof(struct ssm_blob1) - SSM_BLOB_SIZE_SCALE + (size))

Compute the size of a blob with its header.

The size parameter should already be scaled, i.e., already multiplied by SSM_BLOB_SIZE_SCALE, before being passed into this macro.

Parameters

size	scaled size of the blob's payload.

Returns

size that a blob of size payload occupies in the heap.

Definition at line 1106 of file ssm.h.

ssm_blob_heap_size

#define ssm_blob_heap_size

(

v

)

ssm_blob_size(((v).heap_ptr->info.size) * SSM_BLOB_SIZE_SCALE)

Compute the size a blob in the heap.

Parameters

v	ssm_value_t pointing to some blob in the heap.

Returns

size of the blob that v points to.

Definition at line 1114 of file ssm.h.

ssm_blob_payload

#define ssm_blob_payload

(

v

)

(&*(container_of((v).heap_ptr, struct ssm_blob1, mm)->payload))

Obtain pointer to the payload of a blob from an ssm_value_t.

Definition at line 1118 of file ssm.h.

ssm_new_blob

#define ssm_new_blob

(

s

)

Value:

  (fprintf(stderr, "%s:%d:ssm_new_blob(%lu)\n", __FILE__, __LINE__, (size)),   \
   ssm_new_blob_int(size))

Definition at line 1128 of file ssm.h.

Function Documentation

ssm_new_blob_int()

ssm_value_t ssm_new_blob_int

(

uint16_t

size

)

Allocate a blob on the heap.

Parameters

size	size of the payload to the allocated.

Returns

ssm_value_t pointing to heap-allocated blob.

Definition at line 313 of file ssm-mem.c.