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54f22ed30b
who writes: Here is batch 2, as a big collection of CVS context diffs. Along with moving comments into docstrings, i've added a couple of missing docstrings and attempted to make sure more module docstrings begin with a one-line summary. I did not add docstrings to the methods in profile.py for fear of upsetting any careful optimizations there, though i did move class documentation into class docstrings. The convention i'm using is to leave credits/version/copyright type of stuff in # comments, and move the rest of the descriptive stuff about module usage into module docstrings. Hope this is okay.
298 lines
8.5 KiB
Python
298 lines
8.5 KiB
Python
"""Conversion pipeline templates.
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The problem:
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------------
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Suppose you have some data that you want to convert to another format
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(e.g. from GIF image format to PPM image format). Maybe the
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conversion involves several steps (e.g. piping it through compress or
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uuencode). Some of the conversion steps may require that their input
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is a disk file, others may be able to read standard input; similar for
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their output. The input to the entire conversion may also be read
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from a disk file or from an open file, and similar for its output.
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The module lets you construct a pipeline template by sticking one or
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more conversion steps together. It will take care of creating and
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removing temporary files if they are necessary to hold intermediate
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data. You can then use the template to do conversions from many
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different sources to many different destinations. The temporary
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file names used are different each time the template is used.
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The templates are objects so you can create templates for many
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different conversion steps and store them in a dictionary, for
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instance.
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Directions:
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-----------
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To create a template:
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t = Template()
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To add a conversion step to a template:
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t.append(command, kind)
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where kind is a string of two characters: the first is '-' if the
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command reads its standard input or 'f' if it requires a file; the
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second likewise for the output. The command must be valid /bin/sh
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syntax. If input or output files are required, they are passed as
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$IN and $OUT; otherwise, it must be possible to use the command in
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a pipeline.
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To add a conversion step at the beginning:
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t.prepend(command, kind)
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To convert a file to another file using a template:
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sts = t.copy(infile, outfile)
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If infile or outfile are the empty string, standard input is read or
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standard output is written, respectively. The return value is the
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exit status of the conversion pipeline.
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To open a file for reading or writing through a conversion pipeline:
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fp = t.open(file, mode)
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where mode is 'r' to read the file, or 'w' to write it -- just like
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for the built-in function open() or for os.popen().
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To create a new template object initialized to a given one:
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t2 = t.clone()
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For an example, see the function test() at the end of the file.
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"""
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import sys
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import re
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import os
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import tempfile
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import string
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# Conversion step kinds
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FILEIN_FILEOUT = 'ff' # Must read & write real files
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STDIN_FILEOUT = '-f' # Must write a real file
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FILEIN_STDOUT = 'f-' # Must read a real file
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STDIN_STDOUT = '--' # Normal pipeline element
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SOURCE = '.-' # Must be first, writes stdout
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SINK = '-.' # Must be last, reads stdin
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stepkinds = [FILEIN_FILEOUT, STDIN_FILEOUT, FILEIN_STDOUT, STDIN_STDOUT, \
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SOURCE, SINK]
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class Template:
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"""Class representing a pipeline template."""
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def __init__(self):
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"""Template() returns a fresh pipeline template."""
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self.debugging = 0
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self.reset()
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def __repr__(self):
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"""t.__repr__() implements `t`."""
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return '<Template instance, steps=' + `self.steps` + '>'
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def reset(self):
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"""t.reset() restores a pipeline template to its initial state."""
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self.steps = []
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def clone(self):
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"""t.clone() returns a new pipeline template with identical
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initial state as the current one."""
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t = Template()
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t.steps = self.steps[:]
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t.debugging = self.debugging
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return t
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def debug(self, flag):
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"""t.debug(flag) turns debugging on or off."""
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self.debugging = flag
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def append(self, cmd, kind):
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"""t.append(cmd, kind) adds a new step at the end."""
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if type(cmd) <> type(''):
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raise TypeError, \
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'Template.append: cmd must be a string'
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if kind not in stepkinds:
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raise ValueError, \
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'Template.append: bad kind ' + `kind`
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if kind == SOURCE:
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raise ValueError, \
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'Template.append: SOURCE can only be prepended'
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if self.steps <> [] and self.steps[-1][1] == SINK:
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raise ValueError, \
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'Template.append: already ends with SINK'
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if kind[0] == 'f' and not re.search('\$IN\b', cmd):
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raise ValueError, \
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'Template.append: missing $IN in cmd'
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if kind[1] == 'f' and not re.search('\$OUT\b', cmd):
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raise ValueError, \
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'Template.append: missing $OUT in cmd'
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self.steps.append((cmd, kind))
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def prepend(self, cmd, kind):
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"""t.prepend(cmd, kind) adds a new step at the front."""
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if type(cmd) <> type(''):
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raise TypeError, \
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'Template.prepend: cmd must be a string'
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if kind not in stepkinds:
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raise ValueError, \
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'Template.prepend: bad kind ' + `kind`
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if kind == SINK:
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raise ValueError, \
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'Template.prepend: SINK can only be appended'
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if self.steps <> [] and self.steps[0][1] == SOURCE:
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raise ValueError, \
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'Template.prepend: already begins with SOURCE'
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if kind[0] == 'f' and not re.search('\$IN\b', cmd):
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raise ValueError, \
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'Template.prepend: missing $IN in cmd'
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if kind[1] == 'f' and not re.search('\$OUT\b', cmd):
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raise ValueError, \
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'Template.prepend: missing $OUT in cmd'
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self.steps.insert(0, (cmd, kind))
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def open(self, file, rw):
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"""t.open(file, rw) returns a pipe or file object open for
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reading or writing; the file is the other end of the pipeline."""
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if rw == 'r':
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return self.open_r(file)
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if rw == 'w':
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return self.open_w(file)
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raise ValueError, \
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'Template.open: rw must be \'r\' or \'w\', not ' + `rw`
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def open_r(self, file):
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"""t.open_r(file) and t.open_w(file) implement
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t.open(file, 'r') and t.open(file, 'w') respectively."""
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if self.steps == []:
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return open(file, 'r')
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if self.steps[-1][1] == SINK:
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raise ValueError, \
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'Template.open_r: pipeline ends width SINK'
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cmd = self.makepipeline(file, '')
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return os.popen(cmd, 'r')
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def open_w(self, file):
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if self.steps == []:
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return open(file, 'w')
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if self.steps[0][1] == SOURCE:
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raise ValueError, \
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'Template.open_w: pipeline begins with SOURCE'
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cmd = self.makepipeline('', file)
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return os.popen(cmd, 'w')
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def copy(self, infile, outfile):
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return os.system(self.makepipeline(infile, outfile))
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def makepipeline(self, infile, outfile):
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cmd = makepipeline(infile, self.steps, outfile)
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if self.debugging:
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print cmd
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cmd = 'set -x; ' + cmd
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return cmd
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def makepipeline(infile, steps, outfile):
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# Build a list with for each command:
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# [input filename or '', command string, kind, output filename or '']
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list = []
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for cmd, kind in steps:
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list.append(['', cmd, kind, ''])
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#
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# Make sure there is at least one step
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#
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if list == []:
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list.append(['', 'cat', '--', ''])
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#
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# Take care of the input and output ends
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#
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[cmd, kind] = list[0][1:3]
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if kind[0] == 'f' and not infile:
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list.insert(0, ['', 'cat', '--', ''])
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list[0][0] = infile
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#
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[cmd, kind] = list[-1][1:3]
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if kind[1] == 'f' and not outfile:
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list.append(['', 'cat', '--', ''])
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list[-1][-1] = outfile
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#
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# Invent temporary files to connect stages that need files
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#
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garbage = []
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for i in range(1, len(list)):
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lkind = list[i-1][2]
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rkind = list[i][2]
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if lkind[1] == 'f' or rkind[0] == 'f':
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temp = tempfile.mktemp()
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garbage.append(temp)
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list[i-1][-1] = list[i][0] = temp
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#
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for item in list:
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[inf, cmd, kind, outf] = item
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if kind[1] == 'f':
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cmd = 'OUT=' + quote(outf) + '; ' + cmd
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if kind[0] == 'f':
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cmd = 'IN=' + quote(inf) + '; ' + cmd
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if kind[0] == '-' and inf:
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cmd = cmd + ' <' + quote(inf)
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if kind[1] == '-' and outf:
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cmd = cmd + ' >' + quote(outf)
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item[1] = cmd
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#
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cmdlist = list[0][1]
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for item in list[1:]:
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[cmd, kind] = item[1:3]
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if item[0] == '':
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if 'f' in kind:
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cmd = '{ ' + cmd + '; }'
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cmdlist = cmdlist + ' |\n' + cmd
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else:
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cmdlist = cmdlist + '\n' + cmd
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#
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if garbage:
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rmcmd = 'rm -f'
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for file in garbage:
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rmcmd = rmcmd + ' ' + quote(file)
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trapcmd = 'trap ' + quote(rmcmd + '; exit') + ' 1 2 3 13 14 15'
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cmdlist = trapcmd + '\n' + cmdlist + '\n' + rmcmd
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#
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return cmdlist
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# Reliably quote a string as a single argument for /bin/sh
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_safechars = string.letters + string.digits + '!@%_-+=:,./' # Safe unquoted
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_funnychars = '"`$\\' # Unsafe inside "double quotes"
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def quote(file):
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for c in file:
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if c not in _safechars:
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break
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else:
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return file
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if '\'' not in file:
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return '\'' + file + '\''
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res = ''
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for c in file:
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if c in _funnychars:
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c = '\\' + c
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res = res + c
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return '"' + res + '"'
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# Small test program and example
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def test():
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print 'Testing...'
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t = Template()
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t.append('togif $IN $OUT', 'ff')
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t.append('giftoppm', '--')
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t.append('ppmtogif >$OUT', '-f')
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t.append('fromgif $IN $OUT', 'ff')
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t.debug(1)
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FILE = '/usr/local/images/rgb/rogues/guido.rgb'
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t.copy(FILE, '@temp')
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print 'Done.'
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