Class: OpenC3::JsonAccessor

Inherits:
Accessor show all
Defined in:
lib/openc3/accessors/json_accessor.rb

Direct Known Subclasses

CborAccessor

Class Method Summary collapse

Methods inherited from Accessor

convert_to_type, #read_item, #write_item

Class Method Details

.read_item(item, buffer) ⇒ Object 



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# File 'lib/openc3/accessors/json_accessor.rb', line 22

def self.read_item(item, buffer)
  return nil if item.data_type == :DERIVED
  return JsonPath.on(buffer, item.key).first
end

.read_items(items, buffer) ⇒ Object 



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# File 'lib/openc3/accessors/json_accessor.rb', line 48

def self.read_items(items, buffer)
  # Prevent JsonPath from decoding every call
  if String === buffer
    decoded = JSON.parse(buffer)
  else
    decoded = buffer
  end
  super(items, decoded)
end

.write_item(item, value, buffer) ⇒ Object 



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# File 'lib/openc3/accessors/json_accessor.rb', line 27

def self.write_item(item, value, buffer)
  return nil if item.data_type == :DERIVED

  # Convert to ruby objects
  if String === buffer
    decoded = JSON.parse(buffer, :allow_nan => true)
  else
    decoded = buffer
  end

  # Write the value
  write_item_internal(item, value, decoded)

  # Update buffer
  if String === buffer
    buffer.replace(JSON.generate(decoded, :allow_nan => true))
  end

  return buffer
end

.write_item_internal(item, value, decoded) ⇒ Object 



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# File 'lib/openc3/accessors/json_accessor.rb', line 81

def self.write_item_internal(item, value, decoded)
  return nil if item.data_type == :DERIVED

  # Save traversal state
  parent_node = nil
  parent_key = nil
  node = decoded

  # Parse the JsonPath
  json_path = JsonPath.new(item.key)

  # Handle each token
  json_path.path.each do |token|
    case token
    when '$'
      # Ignore start - it is implied
      next
    when /\[.*\]/
      # Array or Hash Index
      if token.index("'") # Hash index
        key = token[2..-3]
        if not (Hash === node)
          node = {}
          parent_node[parent_key] = node
        end
        parent_node = node
        parent_key = key
        node = node[key]
      else # Array index
        key = token[1..-2].to_i
        if not (Array === node)
          node = []
          parent_node[parent_key] = node
        end
        parent_node = node
        parent_key = key
        node = node[key]
      end
    else
      raise "Unsupported key/token: #{item.key} - #{token}"
    end
  end
  if parent_node
    parent_node[parent_key] = value
  else
    decoded.replace(value)
  end
  return decoded
end

.write_items(items, values, buffer) ⇒ Object 



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# File 'lib/openc3/accessors/json_accessor.rb', line 58

def self.write_items(items, values, buffer)
  # Start with an empty object if no buffer
  buffer.replace("{}") if buffer.length == 0 or buffer[0] == "\x00"

  # Convert to ruby objects
  if String === buffer
    decoded = JSON.parse(buffer, :allow_nan => true)
  else
    decoded = buffer
  end

  items.each_with_index do |item, index|
    write_item_internal(item, values[index], decoded)
  end

  # Update buffer
  if String === buffer
    buffer.replace(JSON.generate(decoded, :allow_nan => true))
  end

  return buffer
end