Internal helper get_type_size() now accept the "list" type

DESCRIPTION

@@ -8,7 +8,7 @@ Description: Wrapping an array-like object (typically an on-disk object) in
 	also works on in-memory array-like objects like DataFrame objects
 	(typically with Rle columns), Matrix objects, and ordinary arrays and
 	data frames.
-Version: 0.7.28
+Version: 0.7.29
 Encoding: UTF-8
 Author: Hervé Pagès <hpages@fredhutch.org>, with contributions from
 	Peter Hickey <peter.hickey@gmail.com>

R/RealizationSink-class.R

@@ -7,7 +7,7 @@
 ### of DelayedArray backends. Concrete subclasses must implement:
 ###   1) A constructor function that takes argument 'dim', 'dimnames', and
 ###      'type'.
-###   2) "dim" and "dimnames" methods.
+###   2) "dim", "dimnames", and "type" methods.
 ###   3) A "write_block" method.
 ###   4) A "close" method (optional).
 ###   5) Coercion to DelayedArray.

R/blockGrid.R

@@ -41,6 +41,15 @@ setDefaultBlockSize <- function(size=1e8)
 ### getDefaultBlockLength()
 ###
 
+### The elements of a character vector or a list have a variable size.
+### For a character vector: the minimum size of an element is 8 bytes which
+### is the overhead of a CHARSXP object. This doesn't account for the string
+### data itself.
+### For a list: the minimum size of a list element is 8 bytes and is obtained
+### when the element is a NULL. However, assuming that a list will typically
+### contain more non-NULL than NULL elements and that the non-NULL elements
+### will typically be atomic vectors, the average element size is more likely
+### to be >= the overhead of an atomic vector which is 56 bytes.
 get_type_size <- function(type)
 {
     ### Atomic type sizes in bytes.
@@ -50,9 +59,9 @@ get_type_size <- function(type)
         numeric=8L,
         double=8L,
         complex=16L,
-        character=8L,  # just the overhead of a CHARSXP; doesn't account for
-                       # the string data itself
-        raw=1L
+        character=8L,  # overhead of a CHARSXP object
+        raw=1L,
+        list=56L       # overhead of an atomic vector
     )
     if (missing(type))
         return(TYPE_SIZES)