Reworked LFSR_ATTR macros to support extensions better

Generally the more creative you get with C macros, the more
unmaintainable your codebase becomes, but in this case I think a small
bit of macro sugar for the attribute lists in littlefs goes a long way
for making the internals flexible and readable.

Attribute lists generally look like this:

  LFSR_ATTRS(
      LFSR_ATTR(id, TAG, delta, DATA(data)),
      LFSR_ATTR(id, TAG, delta, DATA(data)),
        ...
      LFSR_ATTR(id, TAG, delta, DATA(data)))

Which more-or-less gets expanded to this:

  ((const lfsr_attr_t[]){
      ((lfsr_attr_t){id, LFSR_TAG_TAG, delta, LFSR_DATA_DATA(data)}),
      ((lfsr_attr_t){id, LFSR_TAG_TAG, delta, LFSR_DATA_DATA(data)}),
        ...
      ((lfsr_attr_t){id, LFSR_TAG_TAG, delta, LFSR_DATA_DATA(data)}),}),
  attr_count

Note the use of preprocessor concatenation to put the TAG and DATA
identifiers in their respective namespaces. These can end up invoking
other macros, which allows attrs to be rather extensible.

Previously there were also LFSR_ATTR_ (note the trailing underscore)
macros to allow passing of variable tags/datas. This is replaced with
redundant macros which sort of "unwrap" themselves as a part of macro
expansion. This avoids a bunch of duplicate macro definitions.

  #define LFSR_TAG_TAG(tag) (tag)
  #define LFSR_DATA_DATA(data) (data)

So:

  LFSR_ATTR(id, TAG(tag), delta, DATA(data))

Becomes:

  ((lfsr_attr_t){id, LFSR_TAG_TAG(tag), delta, LFSR_DATA_DATA(data)})

Becomes:

  ((lfsr_attr_t){id, tag, delta, data})

This commit is contained in:

Christopher Haster

2023-08-08 01:01:35 -05:00

parent d2f2b53262

commit 78a199b59b

6 changed files with 1150 additions and 1147 deletions

tests/test_mtree.toml

+198 -193

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