Add support for nested structs

README.md

@@ -42,6 +42,57 @@ floor = Fiddle::Function.new(
 puts floor.call(3.14159) #=> 3.0
 ```
 
+### Nested Structs
+
+You can use hashes to create nested structs, where the hash keys are member names and the values are the nested structs:
+
+```ruby
+StudentCollegeDetail = struct [
+  'int college_id',
+  'char college_name[50]'
+]
+
+StudentDetail = struct [
+  'int id',
+  'char name[20]',
+  { clg_data: StudentCollegeDetail }
+]
+```
+
+You can also specify an anonymous nested struct, like so:
+
+```ruby
+StudentDetail = struct [
+  'int id',
+  'char name[20]',
+  {
+    clg_data: struct([
+                      'int college_id',
+                      'char college_name[50]'
+                    ])
+  }
+]
+```
+
+The position of a hash (and the order of the keys in the hash, in the case of a hash with multiple entries), dictate the offsets of the nested struct in memory. The following examples are both syntactically valid but will lay out the structs differently in memory:
+
+```ruby
+# 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
+Rect = struct [ 'int id',
+                {
+                  position: struct(['float x', 'float y']),
+                  dimensions: struct(['float w', 'float h'])
+                }
+              ]
+```
+
+
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

lib/fiddle/cparser.rb

@@ -35,12 +35,37 @@ module CParser
     def parse_struct_signature(signature, tymap=nil)
       if signature.is_a?(String)
         signature = split_arguments(signature, /[,;]/)
+      elsif signature.is_a?(Hash)
+        signature = [signature]
       end
       mems = []
       tys  = []
       signature.each{|msig|
-        msig = compact(msig)
+        msig = compact(msig) if msig.is_a?(String)
         case msig
+        when Hash
+          msig.each do |struct_name, struct_signature|
+            struct_name = struct_name.to_s if struct_name.is_a?(Symbol)
+            struct_name = compact(struct_name)
+            struct_count = nil
+            if struct_name =~ /^([\w\*\s]+)\[(\d+)\]$/
+              struct_count = $2.to_i
+              struct_name = $1
+            end
+            if struct_signature.respond_to?(:entity_class)
+              struct_type = struct_signature
+            else
+              parsed_struct = parse_struct_signature(struct_signature, tymap)
+              struct_type = CStructBuilder.create(CStruct, *parsed_struct)
+            end
+            if struct_count
+              ty = [struct_type, struct_count]
+            else
+              ty = struct_type
+            end
+            mems.push([struct_name, struct_type.members])
+            tys.push(ty)
+          end
         when /^[\w\*\s]+[\*\s](\w+)$/
           mems.push($1)
           tys.push(parse_ctype(msig, tymap))

lib/fiddle/struct.rb

@@ -6,10 +6,67 @@
 module Fiddle
   # A base class for objects representing a C structure
   class CStruct
+    include Enumerable
+
     # accessor to Fiddle::CStructEntity
     def CStruct.entity_class
       CStructEntity
     end
+
+    def each
+      return enum_for(__function__) unless block_given?
+
+      self.class.members.each do |name,|
+        yield(self[name])
+      end
+    end
+
+    def each_pair
+      return enum_for(__function__) unless block_given?
+
+      self.class.members.each do |name,|
+        yield(name, self[name])
+      end
+    end
+
+    def to_h
+      hash = {}
+      each_pair do |name, value|
+        hash[name] = unstruct(value)
+      end
+      hash
+    end
+
+    def replace(another)
+      if another.nil?
+        self.class.members.each do |name,|
+          self[name] = nil
+        end
+      elsif another.respond_to?(:each_pair)
+        another.each_pair do |name, value|
+          self[name] = value
+        end
+      else
+        another.each do |name, value|
+          self[name] = value
+        end
+      end
+      self
+    end
+
+    private
+    def unstruct(value)
+      case value
+      when CStruct
+        value.to_h
+      when Array
+        value.collect do |v|
+          unstruct(v)
+        end
+      else
+        value
+      end
+    end
   end
 
   # A base class for objects representing a C union
@@ -27,10 +84,14 @@ class StructArray < Array
     def initialize(ptr, type, initial_values)
       @ptr = ptr
       @type = type
-      @align = PackInfo::ALIGN_MAP[type]
-      @size = Fiddle::PackInfo::SIZE_MAP[type]
-      @pack_format = Fiddle::PackInfo::PACK_MAP[type]
-      super(initial_values.collect { |v| unsigned_value(v, type) })
+      @is_struct = @type.respond_to?(:entity_class)
+      if @is_struct
+        super(initial_values)
+      else
+        @size = Fiddle::PackInfo::SIZE_MAP[type]
+        @pack_format = Fiddle::PackInfo::PACK_MAP[type]
+        super(initial_values.collect { |v| unsigned_value(v, type) })
+      end
     end
 
     def to_ptr
@@ -42,8 +103,12 @@ def []=(index, value)
         raise IndexError, 'index %d outside of array bounds 0...%d' % [index, size]
       end
 
-      to_ptr[index * @size, @size] = [value].pack(@pack_format)
-      super(index, value)
+      if @is_struct
+        self[index].replace(value)
+      else
+        to_ptr[index * @size, @size] = [value].pack(@pack_format)
+        super(index, value)
+      end
     end
   end
 
@@ -105,16 +170,23 @@ def create(klass, types, members)
         define_method(:[]=) { |*args| @entity.send(:[]=, *args) }
         define_method(:to_ptr){ @entity }
         define_method(:to_i){ @entity.to_i }
+        define_singleton_method(:types) { types }
+        define_singleton_method(:members) { members }
         members.each{|name|
+          name = name[0] if name.is_a?(Array) # name is a nested struct
+          next if method_defined?(name)
           define_method(name){ @entity[name] }
           define_method(name + "="){|val| @entity[name] = val }
         }
-        size = klass.entity_class.size(types)
+        entity_class = klass.entity_class
+        alignment = entity_class.alignment(types)
+        size = entity_class.size(types)
+        define_singleton_method(:alignment) { alignment }
         define_singleton_method(:size) { size }
-        define_singleton_method(:malloc) do |func=nil|
-          if block_given?
+        define_singleton_method(:malloc) do |func=nil, &block|
+          if block
             entity_class.malloc(types, func, size) do |entity|
-              yield new(entity)
+              block.call(new(entity))
             end
           else
             new(entity_class.malloc(types, func, size))
@@ -131,6 +203,19 @@ class CStructEntity < Fiddle::Pointer
     include PackInfo
     include ValueUtil
 
+    def CStructEntity.alignment(types)
+      max = 1
+      types.each do |type, count = 1|
+        if type.respond_to?(:entity_class)
+          n = type.alignment
+        else
+          n = ALIGN_MAP[type]
+        end
+        max = n if n > max
+      end
+      max
+    end
+
     # Allocates a C struct with the +types+ provided.
     #
     # See Fiddle::Pointer.malloc for memory management issues.
@@ -160,9 +245,15 @@ def CStructEntity.size(types)
       max_align = types.map { |type, count = 1|
         last_offset = offset
 
-        align = PackInfo::ALIGN_MAP[type]
+        if type.respond_to?(:entity_class)
+          align = type.alignment
+          type_size = type.size
+        else
+          align = PackInfo::ALIGN_MAP[type]
+          type_size = PackInfo::SIZE_MAP[type]
+        end
         offset = PackInfo.align(last_offset, align) +
-                 (PackInfo::SIZE_MAP[type] * count)
+                 (type_size * count)
 
         align
       }.max
@@ -185,7 +276,28 @@ def initialize(addr, types, func = nil)
 
     # Set the names of the +members+ in this C struct
     def assign_names(members)
-      @members = members
+      @members = []
+      @nested_structs = {}
+      members.each_with_index do |member, index|
+        if member.is_a?(Array) # nested struct
+          member_name = member[0]
+          struct_type, struct_count = @ctypes[index]
+          if struct_count.nil?
+            struct = struct_type.new(to_i + @offset[index])
+          else
+            structs = struct_count.times.map do |i|
+              struct_type.new(to_i + @offset[index] + i * struct_type.size)
+            end
+            struct = StructArray.new(to_i + @offset[index],
+                                     struct_type,
+                                     structs)
+          end
+          @nested_structs[member_name] = struct
+        else
+          member_name = member
+        end
+        @members << member_name
+      end
     end
 
     # Calculates the offsets and sizes for the given +types+ in the struct.
@@ -196,12 +308,18 @@ def set_ctypes(types)
 
       max_align = types.map { |type, count = 1|
         orig_offset = offset
-        align = ALIGN_MAP[type]
+        if type.respond_to?(:entity_class)
+          align = type.alignment
+          type_size = type.size
+        else
+          align = ALIGN_MAP[type]
+          type_size = SIZE_MAP[type]
+        end
         offset = PackInfo.align(orig_offset, align)
 
         @offset << offset
 
-        offset += (SIZE_MAP[type] * count)
+        offset += (type_size * count)
 
         align
       }.max
@@ -230,7 +348,13 @@ def [](*args)
       end
       ty = @ctypes[idx]
       if( ty.is_a?(Array) )
-        r = super(@offset[idx], SIZE_MAP[ty[0]] * ty[1])
+        if ty.first.respond_to?(:entity_class)
+          return @nested_structs[name]
+        else
+          r = super(@offset[idx], SIZE_MAP[ty[0]] * ty[1])
+        end
+      elsif ty.respond_to?(:entity_class)
+        return @nested_structs[name]
       else
         r = super(@offset[idx], SIZE_MAP[ty.abs])
       end
@@ -270,6 +394,24 @@ def [](*args)
     def []=(*args)
       return super(*args) if args.size > 2
       name, val = *args
+      name = name.to_s if name.is_a?(Symbol)
+      nested_struct = @nested_structs[name]
+      if nested_struct
+        if nested_struct.is_a?(StructArray)
+          if val.nil?
+            nested_struct.each do |s|
+              s.replace(nil)
+            end
+          else
+            val.each_with_index do |v, i|
+              nested_struct[i] = v
+            end
+          end
+        else
+          nested_struct.replace(val)
+        end
+        return val
+      end
       idx = @members.index(name)
       if( idx.nil? )
         raise(ArgumentError, "no such member: #{name}")
@@ -307,7 +449,11 @@ class CUnionEntity < CStructEntity
     #       Fiddle::TYPE_VOIDP ]) #=> 8
     def CUnionEntity.size(types)
       types.map { |type, count = 1|
-        PackInfo::SIZE_MAP[type] * count
+        if type.respond_to?(:entity_class)
+          type.size * count
+        else
+          PackInfo::SIZE_MAP[type] * count
+        end
       }.max
     end