Create utils.py

Start moving Gerber/Excellon number formatting to utility module

gerber/utils.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+gerber.utils
+============
+**Gerber and Excellon file handling utilities**
+
+This module provides utility functions for working with Gerber and Excellon
+files.
+"""
+
+# Author: Hamilton Kibbe <ham@hamiltonkib.be>
+# License: MIT
+
+def parse_gerber_value(value, format=(2, 5), zero_suppression='trailing'):
+    """ Convert gerber/excellon formatted string to floating-point number
+    
+    .. note::
+        Format and zero suppression are configurable. Note that the Excellon 
+        and Gerber formats use opposite terminology with respect to leading 
+        and trailing zeros. The Gerber format specifies which zeros are 
+        suppressed, while the Excellon format specifies which zeros are 
+        included. This function uses the Gerber-file convention, so an 
+        Excellon file in LZ (leading zeros) mode would use 
+        `zero_suppression='trailing'` 
+    
+    
+    Parameters
+    ----------
+    value : string
+        A Gerber/Excellon-formatted string representing a numerical value.
+
+    format :  tuple (int,int)
+        Gerber/Excellon precision format expressed as a tuple containing: 
+        (number of integer-part digits, number of decimal-part digits)
+
+    zero_suppression : string
+        Zero-suppression mode. May be 'leading' or 'trailing'
+
+    Returns
+    -------
+    value : float
+        The specified value as a floating-point number.
+    
+    """
+    # Format precision
+    integer_digits, decimal_digits = format
+    MAX_DIGITS = integer_digits + decimal_digits
+    
+    # Absolute maximum number of digits supported. This will handle up to
+    # 6:7 format, which is somewhat supported, even though the gerber spec
+    # only allows up to 6:6
+    if MAX_DIGITS > 13 or integer_digits > 6 or decimal_digits > 7:
+        raise ValueError('Parser only supports precision up to 6:7 format')
+
+    # Remove extraneous information
+    value = value.strip(' +')
+    negative = '-' in value
+    if negative:
+        value = value.strip(' -')
+        
+    # Handle excellon edge case with explicit decimal. "That was easy!"
+    if '.' in value:
+        return float(value)
+    
+    digits = [digit for digit in '0' * MAX_DIGITS]
+    offset = 0 if zero_suppression == 'trailing' else (MAX_DIGITS - len(value))
+    for i, digit in enumerate(value):
+        digits[i + offset] = digit
+            
+    result = float(''.join(digits[:integer_digits] + ['.'] + digits[integer_digits:]))
+    return -1.0 * result if negative else result
+    
+    
+def write_gerber_value(value, format=(2, 5), zero_suppression='trailing'):
+    """ Convert a floating point number to a Gerber/Excellon-formatted string.
+    
+    .. note::
+        Format and zero suppression are configurable. Note that the Excellon 
+        and Gerber formats use opposite terminology with respect to leading 
+        and trailing zeros. The Gerber format specifies which zeros are 
+        suppressed, while the Excellon format specifies which zeros are 
+        included. This function uses the Gerber-file convention, so an 
+        Excellon file in LZ (leading zeros) mode would use 
+        `zero_suppression='trailing'`
+    
+    Parameters
+    ----------
+    value : float
+        A floating point value.
+
+    format :  tuple (n=2)
+        Gerber/Excellon precision format expressed as a tuple containing: 
+        (number of integer-part digits, number of decimal-part digits)
+
+    zero_suppression : string
+        Zero-suppression mode. May be 'leading' or 'trailing'
+
+    Returns
+    -------
+    value : string
+        The specified value as a Gerber/Excellon-formatted string.
+    """
+    # Format precision
+    integer_digits, decimal_digits = format
+    MAX_DIGITS = integer_digits + decimal_digits
+    
+    if MAX_DIGITS > 13 or integer_digits > 6 or decimal_digits > 7:
+        raise ValueError('Parser only supports precision up to 6:7 format')
+    
+    # negative sign affects padding, so deal with it at the end...
+    negative =  value < 0.0
+    if negative:
+        value = -1.0 * value
+
+    # Format string for padding out in both directions
+    fmtstring = '%%0%d.0%df' % (MAX_DIGITS + 1, decimal_digits)
+
+    digits = [val for val in fmtstring % value if val != '.']
+    
+    # Suppression... 
+    if zero_suppression == 'trailing':
+        while digits[-1] == '0':
+            digits.pop()
+    else:
+        while digits[0] == '0':
+            digits.pop(0)
+        
+    return ''.join(digits) if not negative else ''.join(['-'] + digits)
+