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Diffstat (limited to 'python_modules/demarshal.py')
| -rw-r--r-- | python_modules/demarshal.py | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/python_modules/demarshal.py b/python_modules/demarshal.py index 57095675..cf6fefd4 100644 --- a/python_modules/demarshal.py +++ b/python_modules/demarshal.py @@ -1,6 +1,35 @@ import ptypes import codegen +# The handling of sizes is somewhat complex, as there are several types of size: +# * nw_size +# This is the network size, i.e. the number of bytes on the network +# +# * mem_size +# The total amount of memory used for the representation of something inside +# spice. This is generally sizeof(C struct), but can be larger if for instance +# the type has a variable size array at the end or has a pointer in it that +# points to another data chunk (which will be allocated after the main +# data chunk). This is essentially how much memory you need to allocate to +# contain the data type. +# +# * extra_size +# This is the size of anything that is not part of the containing structure. +# For instance, a primitive (say uint32_t) member has no extra size, because +# when allocating its part of the sizeof(MessageStructType) struct. However +# a variable array can be places at the end of a structure (@end) and its +# size is then extra_size. Note that this extra_size is included in the +# mem_size of the enclosing struct, and even if you request the mem_size +# of the array itself. However, extra_size is typically not requested +# when the full mem_size is also requested. +# +# extra sizes come in two flavours. contains_extra_size means that the item +# has a normal presence in the parent container, but has some additional +# extra_size it references. For instance via a pointer somewhere in it. +# There is also is_extra_size(). This indicates that the whole elements +# "normal" mem size should be considered extra size for the container, so +# when computing the parent mem_size you should add the mem_size of this +# part as extra_size def write_parser_helpers(writer): if writer.is_generated("helper", "demarshaller"): |