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pcb-rnd hacking - how importers work

+ +

Introduction

+This document describes the common aspects of import code, be it an +import_ plugin or the load part of an io_plugin, importing a footprint, +loading a board or a netlist. + +

Data structures

+ +The board is stored in PCBType *. Some import code, like the one +that loads a design (an io plugin's ->parse_pcb function), gets the +target in an argument. (Other, non-import code usually operate on +the global variable that represents the current board: +PCBType *PCB.). +

+In either case, PCBType's most important field is PCBDataType *data, +which holds lists and vectors to store all objects on the board. When +the target is a buffer (e.g. io plugin's ->parse_element function), it's +a DataType *buf which also have a PCBDataType *data containing +the same data a board could. +

+A PCBDataType struct in turn has three sets of important fields: +

lists for layer-independent objects (e.g. rat lines, vias, elements) +
number of layers in use (LayerN) and an array of layers (see later) +
rtree structures - these are used for looking up objects for locations +

+Each layer is a LayerType structure. A layer has the following fields: +

lists for lines, texts, arcs, polygons +
some generic layer attributes (colors, flags, key-value pairs) +
an rtree struct for each object type. +

+Any code that needs to create objects should use the functions in create.[ch]. +The functions that operate layer-independently usually get a destination as +PCBDataType, so they can operate both on boards and buffers. A typical +example is PinTypePtr CreateNewVia(DataTypePtr Data, ...) that returns +NULL or the pointer to the new via that is already added to the corresponding list +of Data and in the rtree. +

+Layer object creation is done referencing the layer as LayerType *. A +typical example is LineTypePtr CreateDrawnLineOnLayer(LayerTypePtr Layer, ...) +which returns NULL on error or a pointer to the new line object created (inserted +in the layer's line list, added to the rtree). +

+Code should avoid manipulating the lists and rtree structures directly. + +
+
+Figure 1. simplified map of object related data structures +
+diamond: variable; rectangle: struct; round: struct field +
+ + +

Extra steps around creating a new board

+TODO: postproc, post*, other setup + + + +