Graft pcb-tools upstream onto gerbonara tree

1 files changed, 979 insertions, 0 deletions

diff --git a/gerber/excellon_statements.py b/gerber/excellon_statements.py
new file mode 100644
index 0000000..2c50ef9
--- /dev/null
+++ b/gerber/excellon_statements.py
@@ -0,0 +1,979 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# copyright 2014 Hamilton Kibbe <ham@hamiltonkib.be>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Excellon Statements
+====================
+**Excellon file statement classes**
+
+"""
+
+import re
+import uuid
+import itertools
+from .utils import (parse_gerber_value, write_gerber_value, decimal_string,
+                    inch, metric)
+
+
+__all__ = ['ExcellonTool', 'ToolSelectionStmt', 'CoordinateStmt',
+           'CommentStmt', 'HeaderBeginStmt', 'HeaderEndStmt',
+           'RewindStopStmt', 'EndOfProgramStmt', 'UnitStmt',
+           'IncrementalModeStmt', 'VersionStmt', 'FormatStmt', 'LinkToolStmt',
+           'MeasuringModeStmt', 'RouteModeStmt', 'LinearModeStmt', 'DrillModeStmt',
+           'AbsoluteModeStmt', 'RepeatHoleStmt', 'UnknownStmt',
+           'ExcellonStatement', 'ZAxisRoutPositionStmt',
+           'RetractWithClampingStmt', 'RetractWithoutClampingStmt',
+           'CutterCompensationOffStmt', 'CutterCompensationLeftStmt',
+           'CutterCompensationRightStmt', 'ZAxisInfeedRateStmt',
+           'NextToolSelectionStmt', 'SlotStmt']
+
+
+class ExcellonStatement(object):
+    """ Excellon Statement abstract base class
+    """
+
+    @classmethod
+    def from_excellon(cls, line):
+        raise NotImplementedError('from_excellon must be implemented in a '
+                                  'subclass')
+
+    def __init__(self, unit='inch', id=None):
+        self.units = unit
+        self.id = uuid.uuid4().int if id is None else id
+
+    def to_excellon(self, settings=None):
+        raise NotImplementedError('to_excellon must be implemented in a '
+                                  'subclass')
+
+    def to_inch(self):
+        self.units = 'inch'
+
+    def to_metric(self):
+        self.units = 'metric'
+
+    def offset(self, x_offset=0, y_offset=0):
+        pass
+
+    def __eq__(self, other):
+        return self.__dict__ == other.__dict__
+
+
+class ExcellonTool(ExcellonStatement):
+    """ Excellon Tool class
+
+    Parameters
+    ----------
+    settings : FileSettings (dict-like)
+        File-wide settings.
+
+    kwargs : dict-like
+        Tool settings from the excellon statement. Valid keys are:
+            - `diameter` : Tool diameter [expressed in file units]
+            - `rpm` : Tool RPM
+            - `feed_rate` : Z-axis tool feed rate
+            - `retract_rate` : Z-axis tool retraction rate
+            - `max_hit_count` : Number of hits allowed before a tool change
+            - `depth_offset` : Offset of tool depth from tip of tool.
+
+    Attributes
+    ----------
+    number : integer
+        Tool number from the excellon file
+
+    diameter : float
+        Tool diameter in file units
+
+    rpm : float
+        Tool RPM
+
+    feed_rate : float
+        Tool Z-axis feed rate.
+
+    retract_rate : float
+        Tool Z-axis retract rate
+
+    depth_offset : float
+        Offset of depth measurement from tip of tool
+
+    max_hit_count : integer
+        Maximum number of tool hits allowed before a tool change
+
+    hit_count : integer
+        Number of tool hits in excellon file.
+    """
+
+    PLATED_UNKNOWN = None
+    PLATED_YES = 'plated'
+    PLATED_NO = 'nonplated'
+    PLATED_OPTIONAL = 'optional'
+
+    @classmethod
+    def from_tool(cls, tool):
+        args = {}
+
+        args['depth_offset'] = tool.depth_offset
+        args['diameter'] = tool.diameter
+        args['feed_rate'] = tool.feed_rate
+        args['max_hit_count'] = tool.max_hit_count
+        args['number'] = tool.number
+        args['plated'] = tool.plated
+        args['retract_rate'] = tool.retract_rate
+        args['rpm'] = tool.rpm
+
+        return cls(None, **args)
+
+    @classmethod
+    def from_excellon(cls, line, settings, id=None, plated=None):
+        """ Create a Tool from an excellon file tool definition line.
+
+        Parameters
+        ----------
+        line : string
+            Tool definition line from an excellon file.
+
+        settings : FileSettings (dict-like)
+            Excellon file-wide settings
+
+        Returns
+        -------
+        tool : Tool
+            An ExcellonTool representing the tool defined in `line`
+        """
+        commands = pairwise(re.split('([BCFHSTZ])', line)[1:])
+        args = {}
+        args['id'] = id
+        nformat = settings.format
+        zero_suppression = settings.zero_suppression
+        for cmd, val in commands:
+            if cmd == 'B':
+                args['retract_rate'] = parse_gerber_value(val, nformat, zero_suppression)
+            elif cmd == 'C':
+                args['diameter'] = parse_gerber_value(val, nformat, zero_suppression)
+            elif cmd == 'F':
+                args['feed_rate'] = parse_gerber_value(val, nformat, zero_suppression)
+            elif cmd == 'H':
+                args['max_hit_count'] = parse_gerber_value(val, nformat, zero_suppression)
+            elif cmd == 'S':
+                args['rpm'] = 1000 * parse_gerber_value(val, nformat, zero_suppression)
+            elif cmd == 'T':
+                args['number'] = int(val)
+            elif cmd == 'Z':
+                args['depth_offset'] = parse_gerber_value(val, nformat, zero_suppression)
+
+        if plated != ExcellonTool.PLATED_UNKNOWN:
+            # Sometimees we can can parse the plating status
+            args['plated'] = plated
+        return cls(settings, **args)
+
+    @classmethod
+    def from_dict(cls, settings, tool_dict):
+        """ Create an ExcellonTool from a dict.
+
+        Parameters
+        ----------
+        settings : FileSettings (dict-like)
+            Excellon File-wide settings
+
+        tool_dict : dict
+            Excellon tool parameters as a dict
+
+        Returns
+        -------
+        tool : ExcellonTool
+            An ExcellonTool initialized with the parameters in tool_dict.
+        """
+        return cls(settings, **tool_dict)
+
+    def __init__(self, settings, **kwargs):
+        if kwargs.get('id') is not None:
+            super(ExcellonTool, self).__init__(id=kwargs.get('id'))
+        self.settings = settings
+        self.number = kwargs.get('number')
+        self.feed_rate = kwargs.get('feed_rate')
+        self.retract_rate = kwargs.get('retract_rate')
+        self.rpm = kwargs.get('rpm')
+        self.diameter = kwargs.get('diameter')
+        self.max_hit_count = kwargs.get('max_hit_count')
+        self.depth_offset = kwargs.get('depth_offset')
+        self.plated = kwargs.get('plated')
+
+        self.hit_count = 0
+
+    def to_excellon(self, settings=None):
+        if self.settings and not settings:
+            settings = self.settings
+        fmt = settings.format
+        zs = settings.zero_suppression
+        stmt = 'T%02d' % self.number
+        if self.retract_rate is not None:
+            stmt += 'B%s' % write_gerber_value(self.retract_rate, fmt, zs)
+        if self.feed_rate is not None:
+            stmt += 'F%s' % write_gerber_value(self.feed_rate, fmt, zs)
+        if self.max_hit_count is not None:
+            stmt += 'H%s' % write_gerber_value(self.max_hit_count, fmt, zs)
+        if self.rpm is not None:
+            if self.rpm < 100000.:
+                stmt += 'S%s' % write_gerber_value(self.rpm / 1000., fmt, zs)
+            else:
+                stmt += 'S%g' % (self.rpm / 1000.)
+        if self.diameter is not None:
+            stmt += 'C%s' % decimal_string(self.diameter, fmt[1], True)
+        if self.depth_offset is not None:
+            stmt += 'Z%s' % write_gerber_value(self.depth_offset, fmt, zs)
+        return stmt
+
+    def to_inch(self):
+        if self.settings.units != 'inch':
+            self.settings.units = 'inch'
+            if self.diameter is not None:
+                self.diameter = inch(self.diameter)
+
+    def to_metric(self):
+        if self.settings.units != 'metric':
+            self.settings.units = 'metric'
+            if self.diameter is not None:
+                self.diameter = metric(self.diameter)
+
+    def _hit(self):
+        self.hit_count += 1
+
+    def equivalent(self, other):
+        """
+        Is the other tool equal to this, ignoring the tool number, and other file specified properties
+        """
+
+        if type(self) != type(other):
+            return False
+
+        return (self.diameter == other.diameter
+            and self.feed_rate == other.feed_rate
+            and self.retract_rate == other.retract_rate
+            and self.rpm == other.rpm
+            and self.depth_offset == other.depth_offset
+            and self.max_hit_count == other.max_hit_count
+            and self.plated == other.plated
+            and self.settings.units == other.settings.units)
+
+    def __repr__(self):
+        unit = 'in.' if self.settings.units == 'inch' else 'mm'
+        fmtstr = '<ExcellonTool %%02d: %%%d.%dg%%s dia.>' % self.settings.format
+        return fmtstr % (self.number, self.diameter, unit)
+
+
+class ToolSelectionStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        """ Create a ToolSelectionStmt from an excellon file line.
+
+        Parameters
+        ----------
+        line : string
+            Line from an Excellon file
+
+        Returns
+        -------
+        tool_statement : ToolSelectionStmt
+            ToolSelectionStmt representation of `line.`
+        """
+        line = line[1:]
+        compensation_index = None
+
+        # up to 3 characters for tool number (Frizting uses that)
+        if len(line) <= 3:
+            tool = int(line)
+        else:
+            tool = int(line[:2])
+            compensation_index = int(line[2:])
+
+        return cls(tool, compensation_index, **kwargs)
+
+    def __init__(self, tool, compensation_index=None, **kwargs):
+        super(ToolSelectionStmt, self).__init__(**kwargs)
+        tool = int(tool)
+        compensation_index = (int(compensation_index) if compensation_index
+                              is not None else None)
+        self.tool = tool
+        self.compensation_index = compensation_index
+
+    def to_excellon(self, settings=None):
+        stmt = 'T%02d' % self.tool
+        if self.compensation_index is not None:
+            stmt += '%02d' % self.compensation_index
+        return stmt
+
+class NextToolSelectionStmt(ExcellonStatement):
+
+    # TODO the statement exists outside of the context of the file,
+    # so it is imposible to know that it is really the next tool
+
+    def __init__(self, cur_tool, next_tool, **kwargs):
+        """
+        Select the next tool in the wheel.
+        Parameters
+        ----------
+        cur_tool : the tool that is currently selected
+        next_tool : the that that is now selected
+        """
+        super(NextToolSelectionStmt, self).__init__(**kwargs)
+
+        self.cur_tool = cur_tool
+        self.next_tool = next_tool
+
+    def to_excellon(self, settings=None):
+        stmt = 'M00'
+        return stmt
+
+class ZAxisInfeedRateStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        """ Create a ZAxisInfeedRate from an excellon file line.
+
+        Parameters
+        ----------
+        line : string
+            Line from an Excellon file
+
+        Returns
+        -------
+        z_axis_infeed_rate : ToolSelectionStmt
+            ToolSelectionStmt representation of `line.`
+        """
+        rate = int(line[1:])
+
+        return cls(rate, **kwargs)
+
+    def __init__(self, rate, **kwargs):
+        super(ZAxisInfeedRateStmt, self).__init__(**kwargs)
+        self.rate = rate
+
+    def to_excellon(self, settings=None):
+        return 'F%02d' % self.rate
+
+
+class CoordinateStmt(ExcellonStatement):
+
+    @classmethod
+    def from_point(cls, point, mode=None):
+
+        stmt = cls(point[0], point[1])
+        if mode:
+            stmt.mode = mode
+        return stmt
+
+    @classmethod
+    def from_excellon(cls, line, settings, **kwargs):
+        x_coord = None
+        y_coord = None
+        if line[0] == 'X':
+            splitline = line.strip('X').split('Y')
+            x_coord = parse_gerber_value(splitline[0], settings.format,
+                                         settings.zero_suppression)
+            if len(splitline) == 2:
+                y_coord = parse_gerber_value(splitline[1], settings.format,
+                                             settings.zero_suppression)
+        else:
+            y_coord = parse_gerber_value(line.strip(' Y'), settings.format,
+                                         settings.zero_suppression)
+        c = cls(x_coord, y_coord, **kwargs)
+        c.units = settings.units
+        return c
+
+    def __init__(self, x=None, y=None, **kwargs):
+        super(CoordinateStmt, self).__init__(**kwargs)
+        self.x = x
+        self.y = y
+        self.mode = None
+
+    def to_excellon(self, settings):
+        stmt = ''
+        if self.mode == "ROUT":
+            stmt += "G00"
+        if self.mode == "LINEAR":
+            stmt += "G01"
+        if self.x is not None:
+            stmt += 'X%s' % write_gerber_value(self.x, settings.format,
+                                               settings.zero_suppression)
+        if self.y is not None:
+            stmt += 'Y%s' % write_gerber_value(self.y, settings.format,
+                                               settings.zero_suppression)
+        return stmt
+
+    def to_inch(self):
+        if self.units == 'metric':
+            self.units = 'inch'
+            if self.x is not None:
+                self.x = inch(self.x)
+            if self.y is not None:
+                self.y = inch(self.y)
+
+    def to_metric(self):
+        if self.units == 'inch':
+            self.units = 'metric'
+            if self.x is not None:
+                self.x = metric(self.x)
+            if self.y is not None:
+                self.y = metric(self.y)
+
+    def offset(self, x_offset=0, y_offset=0):
+        if self.x is not None:
+            self.x += x_offset
+        if self.y is not None:
+            self.y += y_offset
+
+    def __str__(self):
+        coord_str = ''
+        if self.x is not None:
+            coord_str += 'X: %g ' % self.x
+        if self.y is not None:
+            coord_str += 'Y: %g ' % self.y
+
+        return '<Coordinate Statement: %s>' % coord_str
+
+
+class RepeatHoleStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, settings, **kwargs):
+        match = re.compile(r'R(?P<rcount>[0-9]*)X?(?P<xdelta>[+\-]?\d*\.?\d*)?Y?'
+                           '(?P<ydelta>[+\-]?\d*\.?\d*)?').match(line)
+        stmt = match.groupdict()
+        count = int(stmt['rcount'])
+        xdelta = (parse_gerber_value(stmt['xdelta'], settings.format,
+                                     settings.zero_suppression)
+                  if stmt['xdelta'] is not '' else None)
+        ydelta = (parse_gerber_value(stmt['ydelta'], settings.format,
+                                     settings.zero_suppression)
+                  if stmt['ydelta'] is not '' else None)
+        c = cls(count, xdelta, ydelta, **kwargs)
+        c.units = settings.units
+        return c
+
+    def __init__(self, count, xdelta=0.0, ydelta=0.0, **kwargs):
+        super(RepeatHoleStmt, self).__init__(**kwargs)
+        self.count = count
+        self.xdelta = xdelta
+        self.ydelta = ydelta
+
+    def to_excellon(self, settings):
+        stmt = 'R%d' % self.count
+        if self.xdelta is not None and self.xdelta != 0.0:
+            stmt += 'X%s' % write_gerber_value(self.xdelta, settings.format,
+                                               settings.zero_suppression)
+        if self.ydelta is not None and self.ydelta != 0.0:
+            stmt += 'Y%s' % write_gerber_value(self.ydelta, settings.format,
+                                               settings.zero_suppression)
+        return stmt
+
+    def to_inch(self):
+        if self.units == 'metric':
+            self.units = 'inch'
+            if self.xdelta is not None:
+                self.xdelta = inch(self.xdelta)
+            if self.ydelta is not None:
+                self.ydelta = inch(self.ydelta)
+
+    def to_metric(self):
+        if self.units == 'inch':
+            self.units = 'metric'
+            if self.xdelta is not None:
+                self.xdelta = metric(self.xdelta)
+            if self.ydelta is not None:
+                self.ydelta = metric(self.ydelta)
+
+    def __str__(self):
+        return '<Repeat Hole: %d times, offset X: %g Y: %g>' % (
+            self.count,
+            self.xdelta if self.xdelta is not None else 0,
+            self.ydelta if self.ydelta is not None else 0)
+
+
+class CommentStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        return cls(line.lstrip(';'))
+
+    def __init__(self, comment, **kwargs):
+        super(CommentStmt, self).__init__(**kwargs)
+        self.comment = comment
+
+    def to_excellon(self, settings=None):
+        return ';%s' % self.comment
+
+
+class HeaderBeginStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(HeaderBeginStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'M48'
+
+
+class HeaderEndStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(HeaderEndStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'M95'
+
+
+class RewindStopStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(RewindStopStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return '%'
+
+
+class ZAxisRoutPositionStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(ZAxisRoutPositionStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'M15'
+
+
+class RetractWithClampingStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(RetractWithClampingStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'M16'
+
+
+class RetractWithoutClampingStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(RetractWithoutClampingStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'M17'
+
+
+class CutterCompensationOffStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(CutterCompensationOffStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G40'
+
+
+class CutterCompensationLeftStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(CutterCompensationLeftStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G41'
+
+
+class CutterCompensationRightStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(CutterCompensationRightStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G42'
+
+
+class EndOfProgramStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, settings, **kwargs):
+        match = re.compile(r'M30X?(?P<x>\d*\.?\d*)?Y?'
+                           '(?P<y>\d*\.?\d*)?').match(line)
+        stmt = match.groupdict()
+        x = (parse_gerber_value(stmt['x'], settings.format,
+                                settings.zero_suppression)
+             if stmt['x'] is not '' else None)
+        y = (parse_gerber_value(stmt['y'], settings.format,
+                                settings.zero_suppression)
+             if stmt['y'] is not '' else None)
+        c = cls(x, y, **kwargs)
+        c.units = settings.units
+        return c
+
+    def __init__(self, x=None, y=None, **kwargs):
+        super(EndOfProgramStmt, self).__init__(**kwargs)
+        self.x = x
+        self.y = y
+
+    def to_excellon(self, settings=None):
+        stmt = 'M30'
+        if self.x is not None:
+            stmt += 'X%s' % write_gerber_value(self.x)
+        if self.y is not None:
+            stmt += 'Y%s' % write_gerber_value(self.y)
+        return stmt
+
+    def to_inch(self):
+        if self.units == 'metric':
+            self.units = 'inch'
+            if self.x is not None:
+                self.x = inch(self.x)
+            if self.y is not None:
+                self.y = inch(self.y)
+
+    def to_metric(self):
+        if self.units == 'inch':
+            self.units = 'metric'
+            if self.x is not None:
+                self.x = metric(self.x)
+            if self.y is not None:
+                self.y = metric(self.y)
+
+    def offset(self, x_offset=0, y_offset=0):
+        if self.x is not None:
+            self.x += x_offset
+        if self.y is not None:
+            self.y += y_offset
+
+
+class UnitStmt(ExcellonStatement):
+
+    @classmethod
+    def from_settings(cls, settings):
+        """Create the unit statement from the FileSettings"""
+
+        return cls(settings.units, settings.zeros)
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        units = 'inch' if 'INCH' in line else 'metric'
+        zeros = 'leading' if 'LZ' in line else 'trailing'
+        if '0000.00' in line:
+            format = (4, 2)
+        elif '000.000' in line:
+            format = (3, 3)
+        elif '00.0000' in line:
+            format = (2, 4)
+        else:
+            format = None
+        return cls(units, zeros, format, **kwargs)
+
+    def __init__(self, units='inch', zeros='leading', format=None, **kwargs):
+        super(UnitStmt, self).__init__(**kwargs)
+        self.units = units.lower()
+        self.zeros = zeros
+        self.format = format
+
+    def to_excellon(self, settings=None):
+        # TODO This won't export the invalid format statement if it exists
+        stmt = '%s,%s' % ('INCH' if self.units == 'inch' else 'METRIC',
+                          'LZ' if self.zeros == 'leading'
+                          else 'TZ')
+        return stmt
+
+    def to_inch(self):
+        self.units = 'inch'
+
+    def to_metric(self):
+        self.units = 'metric'
+
+
+class IncrementalModeStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        return cls('off', **kwargs) if 'OFF' in line else cls('on', **kwargs)
+
+    def __init__(self, mode='off', **kwargs):
+        super(IncrementalModeStmt, self).__init__(**kwargs)
+        if mode.lower() not in ['on', 'off']:
+            raise ValueError('Mode may be "on" or "off"')
+        self.mode = mode
+
+    def to_excellon(self, settings=None):
+        return 'ICI,%s' % ('OFF' if self.mode == 'off' else 'ON')
+
+
+class VersionStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        version = int(line.split(',')[1])
+        return cls(version, **kwargs)
+
+    def __init__(self, version=1, **kwargs):
+        super(VersionStmt, self).__init__(**kwargs)
+        version = int(version)
+        if version not in [1, 2]:
+            raise ValueError('Valid versions are  1 or 2')
+        self.version = version
+
+    def to_excellon(self, settings=None):
+        return 'VER,%d' % self.version
+
+
+class FormatStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        fmt = int(line.split(',')[1])
+        return cls(fmt, **kwargs)
+
+    def __init__(self, format=1, **kwargs):
+        super(FormatStmt, self).__init__(**kwargs)
+        format = int(format)
+        if format not in [1, 2]:
+            raise ValueError('Valid formats are 1 or 2')
+        self.format = format
+
+    def to_excellon(self, settings=None):
+        return 'FMAT,%d' % self.format
+
+    @property
+    def format_tuple(self):
+        return (self.format, 6 - self.format)
+
+
+class LinkToolStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        linked = [int(tool) for tool in line.split('/')]
+        return cls(linked, **kwargs)
+
+    def __init__(self, linked_tools, **kwargs):
+        super(LinkToolStmt, self).__init__(**kwargs)
+        self.linked_tools = [int(x) for x in linked_tools]
+
+    def to_excellon(self, settings=None):
+        return '/'.join([str(x) for x in self.linked_tools])
+
+
+class MeasuringModeStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        if not ('M71' in line or 'M72' in line):
+            raise ValueError('Not a measuring mode statement')
+        return cls('inch', **kwargs) if 'M72' in line else cls('metric', **kwargs)
+
+    def __init__(self, units='inch', **kwargs):
+        super(MeasuringModeStmt, self).__init__(**kwargs)
+        units = units.lower()
+        if units not in ['inch', 'metric']:
+            raise ValueError('units must be "inch" or "metric"')
+        self.units = units
+
+    def to_excellon(self, settings=None):
+        return 'M72' if self.units == 'inch' else 'M71'
+
+    def to_inch(self):
+        self.units = 'inch'
+
+    def to_metric(self):
+        self.units = 'metric'
+
+
+class RouteModeStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(RouteModeStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G00'
+
+
+class LinearModeStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(LinearModeStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G01'
+
+
+class DrillModeStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(DrillModeStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G05'
+
+
+class AbsoluteModeStmt(ExcellonStatement):
+
+    def __init__(self, **kwargs):
+        super(AbsoluteModeStmt, self).__init__(**kwargs)
+
+    def to_excellon(self, settings=None):
+        return 'G90'
+
+
+class UnknownStmt(ExcellonStatement):
+
+    @classmethod
+    def from_excellon(cls, line, **kwargs):
+        return cls(line, **kwargs)
+
+    def __init__(self, stmt, **kwargs):
+        super(UnknownStmt, self).__init__(**kwargs)
+        self.stmt = stmt
+
+    def to_excellon(self, settings=None):
+        return self.stmt
+
+    def __str__(self):
+        return "<Unknown Statement: %s>" % self.stmt
+
+
+class SlotStmt(ExcellonStatement):
+    """
+    G85 statement.  Defines a slot created by multiple drills between two specified points.
+
+    Format is two coordinates, split by G85in the middle, for example, XnY0nG85XnYn
+    """
+
+    @classmethod
+    def from_points(cls, start, end):
+
+        return cls(start[0], start[1], end[0], end[1])
+
+    @classmethod
+    def from_excellon(cls, line, settings, **kwargs):
+        # Split the line based on the G85 separator
+        sub_coords = line.split('G85')
+        (x_start_coord, y_start_coord) = SlotStmt.parse_sub_coords(sub_coords[0], settings)
+        (x_end_coord, y_end_coord) = SlotStmt.parse_sub_coords(sub_coords[1], settings)
+
+        # Some files seem to specify only one of the coordinates
+        if x_end_coord == None:
+            x_end_coord = x_start_coord
+        if y_end_coord == None:
+            y_end_coord = y_start_coord
+
+        c = cls(x_start_coord, y_start_coord, x_end_coord, y_end_coord, **kwargs)
+        c.units = settings.units
+        return c
+
+    @staticmethod
+    def parse_sub_coords(line, settings):
+
+        x_coord = None
+        y_coord = None
+
+        if line[0] == 'X':
+            splitline = line.strip('X').split('Y')
+            x_coord = parse_gerber_value(splitline[0], settings.format,
+                                         settings.zero_suppression)
+            if len(splitline) == 2:
+                y_coord = parse_gerber_value(splitline[1], settings.format,
+                                             settings.zero_suppression)
+        else:
+            y_coord = parse_gerber_value(line.strip(' Y'), settings.format,
+                                         settings.zero_suppression)
+
+        return (x_coord, y_coord)
+
+
+    def __init__(self, x_start=None, y_start=None, x_end=None, y_end=None, **kwargs):
+        super(SlotStmt, self).__init__(**kwargs)
+        self.x_start = x_start
+        self.y_start = y_start
+        self.x_end = x_end
+        self.y_end = y_end
+        self.mode = None
+
+    def to_excellon(self, settings):
+        stmt = ''
+
+        if self.x_start is not None:
+            stmt += 'X%s' % write_gerber_value(self.x_start, settings.format,
+                                               settings.zero_suppression)
+        if self.y_start is not None:
+            stmt += 'Y%s' % write_gerber_value(self.y_start, settings.format,
+                                               settings.zero_suppression)
+
+        stmt += 'G85'
+
+        if self.x_end is not None:
+            stmt += 'X%s' % write_gerber_value(self.x_end, settings.format,
+                                               settings.zero_suppression)
+        if self.y_end is not None:
+            stmt += 'Y%s' % write_gerber_value(self.y_end, settings.format,
+                                               settings.zero_suppression)
+
+        return stmt
+
+    def to_inch(self):
+        if self.units == 'metric':
+            self.units = 'inch'
+            if self.x_start is not None:
+                self.x_start = inch(self.x_start)
+            if self.y_start is not None:
+                self.y_start = inch(self.y_start)
+            if self.x_end is not None:
+                self.x_end = inch(self.x_end)
+            if self.y_end is not None:
+                self.y_end = inch(self.y_end)
+
+    def to_metric(self):
+        if self.units == 'inch':
+            self.units = 'metric'
+            if self.x_start is not None:
+                self.x_start = metric(self.x_start)
+            if self.y_start is not None:
+                self.y_start = metric(self.y_start)
+            if self.x_end is not None:
+                self.x_end = metric(self.x_end)
+            if self.y_end is not None:
+                self.y_end = metric(self.y_end)
+
+    def offset(self, x_offset=0, y_offset=0):
+        if self.x_start is not None:
+            self.x_start += x_offset
+        if self.y_start is not None:
+            self.y_start += y_offset
+        if self.x_end is not None:
+            self.x_end += x_offset
+        if self.y_end is not None:
+            self.y_end += y_offset
+
+    def __str__(self):
+        start_str = ''
+        if self.x_start is not None:
+            start_str += 'X: %g ' % self.x_start
+        if self.y_start is not None:
+            start_str += 'Y: %g ' % self.y_start
+
+        end_str = ''
+        if self.x_end is not None:
+            end_str += 'X: %g ' % self.x_end
+        if self.y_end is not None:
+            end_str += 'Y: %g ' % self.y_end
+
+        return '<Slot Statement: %s to %s>' % (start_str, end_str)
+
+def pairwise(iterator):
+    """ Iterate over list taking two elements at a time.
+
+    e.g. [1, 2, 3, 4, 5, 6] ==> [(1, 2), (3, 4), (5, 6)]
+    """
+    a, b = itertools.tee(iterator)
+    itr = zip(itertools.islice(a, 0, None, 2), itertools.islice(b, 1, None, 2))
+    for elem in itr:
+        yield elem