Add support for nested structs

[sinisterchipmunk]

This pull request does a few things. The main goal of the PR is to add support for nested structs and unions containing structs, as discussed in #12. I need this for a non-trivial project and have been using the nested struct code in numerous places within that project for several weeks now, so I am confident it is working properly. The syntax is a little strange, but works quite well, and is easy to learn. One could express the example given in #12 like so:

StudentCollegeDetail = struct [
  'int college_id',
  'char college_name[50]'
]

StudentDetail = struct [
  'int id',
  'char name[20]',
  { clg_data: StudentCollegeDetail }
]

It is also possible to specify the nested struct in-line, by replacing StudentCollegeDetail with struct([...]), like so:

StudentDetail = struct [
  'int id',
  'char name[20]',
  {
    clg_data: struct([
                      'int college_id',
                      'char college_name[50]'
                    ])
  }
]

The hash does not need to appear last. In fact, its position in the list of members dictates the offset into the parent struct at which the nested struct appears, in order to play nicely with C structs. There can be multiple hashes, or a single hash with multiple keys/values, or any combination of these. The following examples are also valid syntax, but will result in the struct members being laid out at different offsets within the outer struct's memory:

# order of members in memory: position, id, dimensions
Rect = struct [ { position: struct(['float x', 'float y']) },
                'int id',
                { dimensions: struct(['float w', 'float h']) }
              ]

# order of members in memory: id, position, dimensions (assuming ordered hash)
Rect = struct [ 'int id',
                {
                  position: struct(['float x', 'float y']),
                  dimensions: struct(['float w', 'float h'])
                }
              ]

Second: when calling Fiddle.malloc, the contents of the resulting memory were not initialized to 0 as they were when calling Fiddle::Pointer.malloc. This inconsistency caused me a few headaches so I decided to fix it.

Third: CStructEntity defines array set and get methods ([] / []=), which is fine except that they override Fiddle::Pointer#[] and Fiddle::Pointer#[]= and do not handle the 3rd argument that the base class allows for. I found that if I wanted to access the underlying memory of a struct directly, instead of working with the struct members, I had no good way to do that. So I modified these methods to check for an additional argument, and if present, delegate that to super so that the underlying memory could be accessed / assigned directly.

Fourth: When a member of a struct is an array, CStructEntity was returning a temporary array containing those values. Assignment to that array became a no-op, which was confusing. I fixed this so that assignment to the returned array correctly updates the member within the struct. (Example: a = struct(['int i[5]']).malloc; a.i[2] = 1; a.i[2] #=> 1)

I am happy to move these changes into multiple pull requests, or back out an undesirable change, if needed.

[sinisterchipmunk]

@nobu Is there anything that I can do to help move this along?

[kematy]

CADDRAW=struct ['long size',
'long dc',
{r:struct(['int left', 'int top','int right','int bottom'])},
'byte drawMode']
d:/Ruby25/lib/ruby/2.5.0/fiddle/cparser.rb:193:in compact': undefined method gsub' for {:r=>#Class:0x02b1b3e0}:Hash (NoMethodError)
from d:/Ruby25/lib/ruby/2.5.0/fiddle/cparser.rb:42:in block in parse_struct_signature' from d:/Ruby25/lib/ruby/2.5.0/fiddle/cparser.rb:41:in each'
from d:/Ruby25/lib/ruby/2.5.0/fiddle/cparser.rb:41:in parse_struct_signature' from d:/Ruby25/lib/ruby/2.5.0/fiddle/import.rb:219:in struct'
from D:/ruby-lab/caddll/caddll2019-11-6/Demos/View/DemoVB/test_fiddle-jh.rb:20:in `

'

Is {r:struct(['int left', 'int top','int right','int bottom'])} need to be added '.inspect'

[nobu]

Please split proposals for each “a few things.”

[kematy]

CADDRAW=struct [
'long size',
'long dc',
{
r: struct([
'int left',
'int top',
'int right',
'int bottom'
])
},
'byte drawMode'
]
get same error msg

[sinisterchipmunk]

@nobu I have split this PR into separate requests, as instructed. Hopefully this helps clarify the purpose of each proposal.

I also used the latest revision in master as the starting point to be sure of compatibility.

Please note that #27 depends on #26 and #26 depends on #25. I hope this is acceptable. #27 in particular would lose a lot of functionality around properly handling arrays if de-coupled from #26.

@kematy I do not fully understand your question, but I have seen that error message when Ruby tried to require the built-in version of Fiddle rather than the development version. Ruby only wants to load the built-in version, no matter what is specified in the project Gemfile. The built-in version lacks the proposed changes and so fails to parse with the error you listed. I am able to test Fiddle itself with no issues using bundle exec rake, but in order to use it from any other project I actually had to locally change fiddle's gem name, run rake install and then use the customized gem name with bundler. This makes Ruby think it's loading some other gem. I do get lots of warnings, however. For example, it correctly warns about constants that are created by fiddle and then replaced by my "fiddle-dev" gem.

[kematy]

hello,I got it.I thought that the  parser has been modefied into the built-in version.

…

------------------&nbsp;原始邮件&nbsp;------------------ 发件人:&nbsp;"sinisterchipmunk"<notifications@github.com&gt;; 发送时间:&nbsp;2020年1月22日(星期三) 中午12:23 收件人:&nbsp;"ruby/fiddle"<fiddle@noreply.github.com&gt;; 抄送:&nbsp;"远寞"<151711064@qq.com&gt;;"Mention"<mention@noreply.github.com&gt;; 主题:&nbsp;Re: [ruby/fiddle] Add support for nested structs (#14) @nobu I have split this PR into separate requests, as instructed. Hopefully this helps clarify the purpose of each proposal. I also used the latest revision in master as the starting point to be sure of compatibility. Please note that #27 depends on #26 and #26 depends on #25. I hope this is acceptable. #27 in particular would lose a lot of functionality around properly handling arrays if de-coupled from #26. @kematy I do not fully understand your question, but I have seen that error message when Ruby tried to require the built-in version of Fiddle rather than the development version. Ruby only wants to load the built-in version, no matter what is specified in the project Gemfile. The built-in version lacks the proposed changes and so fails to parse with the error you listed. I am able to test Fiddle itself with no issues using bundle exec rake, but in order to use it from any other project I actually had to locally change fiddle's gem name, run rake install and then use the customized gem name with bundler. This makes Ruby think it's loading some other gem. I do get lots of warnings, however. For example, it correctly warns about constants that are created by fiddle and then replaced by my "fiddle-dev" gem. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.

[kematy]

Thank you!

…

------------------&nbsp;原始邮件&nbsp;------------------ 发件人:&nbsp;"sinisterchipmunk"<notifications@github.com&gt;; 发送时间:&nbsp;2020年1月22日(星期三) 中午12:23 收件人:&nbsp;"ruby/fiddle"<fiddle@noreply.github.com&gt;; 抄送:&nbsp;"远寞"<151711064@qq.com&gt;;"Mention"<mention@noreply.github.com&gt;; 主题:&nbsp;Re: [ruby/fiddle] Add support for nested structs (#14) @nobu I have split this PR into separate requests, as instructed. Hopefully this helps clarify the purpose of each proposal. I also used the latest revision in master as the starting point to be sure of compatibility. Please note that #27 depends on #26 and #26 depends on #25. I hope this is acceptable. #27 in particular would lose a lot of functionality around properly handling arrays if de-coupled from #26. @kematy I do not fully understand your question, but I have seen that error message when Ruby tried to require the built-in version of Fiddle rather than the development version. Ruby only wants to load the built-in version, no matter what is specified in the project Gemfile. The built-in version lacks the proposed changes and so fails to parse with the error you listed. I am able to test Fiddle itself with no issues using bundle exec rake, but in order to use it from any other project I actually had to locally change fiddle's gem name, run rake install and then use the customized gem name with bundler. This makes Ruby think it's loading some other gem. I do get lots of warnings, however. For example, it correctly warns about constants that are created by fiddle and then replaced by my "fiddle-dev" gem. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.