###--------------------------------------------------------------------------
### External dependencies.
-import ConfigParser as CP
import mLib as M
from optparse import OptionParser
import cdb as CDB
from sys import stdin, stdout, exit, argv
import re as RX
import os as OS
+from cStringIO import StringIO
###--------------------------------------------------------------------------
### Utilities.
def finish(me):
pass
+class ExpectedError (Exception): pass
+
###--------------------------------------------------------------------------
### A bulk DNS resolver.
+class ResolverFailure (ExpectedError):
+ def __init__(me, host, msg):
+ me.host = host
+ me.msg = msg
+ def __str__(me):
+ return "failed to resolve `%s': %s" % (me.host, me.msg)
+
+class ResolvingHost (object):
+ """
+ A host name which is being looked up by a bulk-resolver instance.
+ """
+
+ def __init__(me, name):
+ """Make a new resolving-host object for the host NAME."""
+ me.name = name
+ me.addr = None
+ me.failure = None
+
+ def setaddr(me, addr):
+ """Add the address ADDR."""
+ me.addr = addr
+
+ def failed(me, msg):
+ """
+ Report that resolution of this host failed, with a human-readable MSG.
+ """
+ me.failure = msg
+
+ def get(me):
+ """Return the resolved address."""
+ if me.failure is not None: raise ResolverFailure(me.name, me.failure)
+ return me.addr
+
class BulkResolver (object):
"""
Resolve a number of DNS names in parallel.
def __init__(me):
"""Initialize the resolver."""
- me._resolvers = {}
me._namemap = {}
-
- def prepare(me, host):
- """Prime the resolver to resolve the name HOST."""
- if host not in me._resolvers:
- me._resolvers[host] = M.SelResolveByName \
- (host,
- lambda name, alias, addr:
- me._resolved(host, addr[0]),
- lambda: me._resolved(host, None))
+ me._noutstand = 0
+
+ def prepare(me, name):
+ """Prime the resolver to resolve the given host NAME."""
+ if name not in me._namemap:
+ me._namemap[name] = host = ResolvingHost(name)
+ host._resolv = M.SelResolveByName(
+ name,
+ lambda cname, alias, addr: me._resolved(host, addr[0]),
+ lambda: me._resolved(host, None))
+ me._noutstand += 1
def run(me):
"""Run the background DNS resolver until it's finished."""
- while me._resolvers:
- M.select()
+ while me._noutstand: M.select()
- def lookup(me, host):
- """
- Fetch the address corresponding to HOST.
- """
- addr = me._namemap[host]
- if addr is None:
- raise KeyError(host)
- return addr
+ def lookup(me, name):
+ """Fetch the address corresponding to the host NAME."""
+ return me._namemap[name].get()
def _resolved(me, host, addr):
"""Callback function: remember that ADDR is the address for HOST."""
- me._namemap[host] = addr
- del me._resolvers[host]
+ if addr is None:
+ host.failed('(unknown failure)')
+ else:
+ host.setaddr(addr)
+ host._resolv = None
+ me._noutstand -= 1
###--------------------------------------------------------------------------
### The configuration parser.
+## Match a comment or empty line.
+RX_COMMENT = RX.compile(r'(?x) ^ \s* (?: $ | [;#])')
+
+## Match a section group header.
+RX_GRPHDR = RX.compile(r'(?x) ^ \s* \[ (.*) \] \s* $')
+
+## Match an assignment line.
+RX_ASSGN = RX.compile(r'''(?x) ^
+ ([^\s:=] (?: [^:=]* [^\s:=])?)
+ \s* [:=] \s*
+ (| \S | \S.*\S)
+ \s* $''')
+
+## Match a continuation line.
+RX_CONT = RX.compile(r'''(?x) ^ \s+
+ (| \S | \S.*\S)
+ \s* $''')
+
## Match a $(VAR) configuration variable reference; group 1 is the VAR.
RX_REF = RX.compile(r'(?x) \$ \( ([^)]+) \)')
## Match a $[HOST] name resolution reference; group 1 is the HOST.
RX_RESOLVE = RX.compile(r'(?x) \$ \[ ([^]]+) \]')
+class ConfigSyntaxError (ExpectedError):
+ def __init__(me, fname, lno, msg):
+ me.fname = fname
+ me.lno = lno
+ me.msg = msg
+ def __str__(me):
+ return '%s:%d: %s' % (me.fname, me.lno, me.msg)
+
def _fmt_path(path):
return ' -> '.join(["`%s'" % hop for hop in path])
-class AmbiguousOptionError (Exception):
+class AmbiguousOptionError (ExpectedError):
def __init__(me, key, patha, vala, pathb, valb):
me.key = key
me.patha, me.vala = patha, vala
"path %s yields `%s' but %s yields `%s'" % \
(me.key, _fmt_path(me.patha), me.vala, _fmt_path(me.pathb), me.valb)
-class InheritanceCycleError (Exception):
+class InheritanceCycleError (ExpectedError):
def __init__(me, key, path):
me.key = key
me.path = path
return "Found a cycle %s looking up key `%s'" % \
(_fmt_path(me.path), me.key)
-class MissingKeyException (Exception):
+class MissingSectionException (ExpectedError):
+ def __init__(me, sec):
+ me.sec = sec
+ def __str__(me):
+ return "Section `%s' not found" % (me.sec)
+
+class MissingKeyException (ExpectedError):
def __init__(me, sec, key):
me.sec = sec
me.key = key
def __str__(me):
return "Key `%s' not found in section `%s'" % (me.key, me.sec)
-class MyConfigParser (CP.RawConfigParser):
+class ConfigSection (object):
"""
- A more advanced configuration parser.
+ A section in a configuration parser.
- This has three major enhancements over the standard ConfigParser which are
- relevant to us.
-
- * It recognizes `@inherits' keys and follows them when expanding a
- value.
-
- * It recognizes `$(VAR)' references to configuration variables during
- expansion and processes them correctly.
-
- * It recognizes `$[HOST]' name-resolver requests and handles them
- correctly.
-
- Use:
-
- 1. Call read(FILENAME) and/or read(FP, [FILENAME]) to slurp in the
- configuration data.
-
- 2. Call resolve() to collect the hostnames which need to be resolved and
- actually do the name resolution.
-
- 3. Call get(SECTION, ITEM) to collect the results, or items(SECTION) to
- iterate over them.
+ This is where a lot of the nitty-gritty stuff actually happens. The
+ `MyConfigParser' knows a lot about the internals of this class, which saves
+ on building a complicated interface.
"""
- def __init__(me):
- """
- Initialize a new, empty configuration parser.
- """
- CP.RawConfigParser.__init__(me)
- me._resolver = BulkResolver()
-
- def resolve(me):
- """
- Works out all of the hostnames which need resolving and resolves them.
-
- Until you call this, attempts to fetch configuration items which need to
- resolve hostnames will fail!
- """
- for sec in me.sections():
- for key, value in me.items(sec, resolvep = False):
- for match in RX_RESOLVE.finditer(value):
- me._resolver.prepare(match.group(1))
- me._resolver.run()
-
- def _expand(me, sec, string, resolvep):
+ def __init__(me, name, cp):
+ """Initialize a new, empty section with a given NAME and parent CP."""
+
+ ## The cache maps item keys to entries, which consist of a pair of
+ ## objects. There are four possible states for a cache entry:
+ ##
+ ## * missing -- there is no entry at all with this key, so we must
+ ## search for it;
+ ##
+ ## * None, None -- we are actively trying to resolve this key, so if we
+ ## encounter this state, we have found a cycle in the inheritance
+ ## graph;
+ ##
+ ## * None, [] -- we know that this key isn't reachable through any of
+ ## our parents;
+ ##
+ ## * VALUE, PATH -- we know that the key resolves to VALUE, along the
+ ## PATH from us (exclusive) to the defining parent (inclusive).
+ me.name = name
+ me._itemmap = dict()
+ me._cache = dict()
+ me._cp = cp
+
+ def _expand(me, string, resolvep):
"""
Expands $(...) and (optionally) $[...] placeholders in STRING.
- The SEC is the configuration section from which to satisfy $(...)
- requests. RESOLVEP is a boolean switch: do we bother to tax the resolver
- or not? This is turned off by the resolve() method while it's collecting
- hostnames to be resolved.
+ RESOLVEP is a boolean switch: do we bother to tax the resolver or not?
+ This is turned off by MyConfigParser's resolve() method while it's
+ collecting hostnames to be resolved.
"""
string = RX_REF.sub \
- (lambda m: me.get(sec, m.group(1), resolvep), string)
+ (lambda m: me.get(m.group(1), resolvep), string)
if resolvep:
- string = RX_RESOLVE.sub(lambda m: me._resolver.lookup(m.group(1)),
+ string = RX_RESOLVE.sub(lambda m: me._cp._resolver.lookup(m.group(1)),
string)
return string
- def has_option(me, sec, key):
- """
- Decide whether section SEC has a configuration key KEY.
-
- This version of the method properly handles the @inherit key.
- """
- return key == 'name' or me._get(sec, key)[0] is not None
+ def _parents(me):
+ """Yield this section's parents."""
+ try: names = me._itemmap['@inherit']
+ except KeyError: return
+ for name in names.replace(',', ' ').split():
+ yield me._cp.section(name)
- def _get(me, sec, key, map = None, path = None):
+ def _get(me, key, path = None):
"""
Low-level option-fetching method.
- Fetch the value for the named KEY from section SEC, or maybe
- (recursively) a section which SEC inherits from.
+ Fetch the value for the named KEY in this section, or maybe (recursively)
+ a section which it inherits from.
Returns a pair VALUE, PATH. The value is not expanded; nor do we check
for the special `name' key. The caller is expected to do these things.
Returns None if no value could be found.
"""
- ## If we weren't given a memoization map or path, then we'd better make
- ## one.
- if map is None: map = {}
+ ## If we weren't given a path, then we'd better make one.
if path is None: path = []
- ## Extend the path to cover the lookup section, but remember to remove us
- ## again when we've finished. If we need to pass the current path back
- ## upwards, then remember to take a copy.
- path.append(sec)
+ ## Extend the path to cover us, but remember to remove us again when
+ ## we've finished. If we need to pass the current path back upwards,
+ ## then remember to take a copy.
+ path.append(me.name)
try:
- ## If we've been this way before on another pass through then return
- ## the value we found then. If we're still thinking about it then
- ## we've found a cycle.
- try: threadp, value = map[sec]
+ ## If we've been this way before on another pass through then return the
+ ## value we found then. If we're still thinking about it then we've
+ ## found a cycle.
+ try: v, p = me._cache[key]
except KeyError: pass
else:
- if threadp: raise InheritanceCycleError(key, path[:])
+ if p is None: raise InheritanceCycleError(key, path[:])
+ else: return v, path + p
## See whether the answer is ready waiting for us.
- try: v = CP.RawConfigParser.get(me, sec, key)
- except CP.NoOptionError: pass
- else: return v, path[:]
-
- ## No, apparently, not. Find out our list of parents.
- try:
- parents = CP.RawConfigParser.get(me, sec, '@inherit').\
- replace(',', ' ').split()
- except CP.NoOptionError:
- parents = []
+ try: v = me._itemmap[key]
+ except KeyError: pass
+ else:
+ p = path[:]
+ me._cache[key] = v, []
+ return v, p
## Initially we have no idea.
value = None
- winner = None
+ winner = []
## Go through our parents and ask them what they think.
- map[sec] = True, None
- for p in parents:
+ me._cache[key] = None, None
+ for p in me._parents():
## See whether we get an answer. If not, keep on going.
- v, pp = me._get(p, key, map, path)
+ v, pp = p._get(key, path)
if v is None: continue
## If we got an answer, check that it matches any previous ones.
raise AmbiguousOptionError(key, winner, value, pp, v)
## That's the best we could manage.
- map[sec] = False, value
+ me._cache[key] = value, winner[len(path):]
return value, winner
finally:
## Remove us from the path again.
path.pop()
- def get(me, sec, key, resolvep = True):
+ def get(me, key, resolvep = True):
"""
- Retrieve the value of KEY from section SEC.
+ Retrieve the value of KEY from this section.
"""
## Special handling for the `name' key.
if key == 'name':
- try: value = CP.RawConfigParser.get(me, sec, key)
- except CP.NoOptionError: value = sec
+ value = me._itemmap.get('name', me.name)
+ elif key == '@inherits':
+ try: return me._itemmap['@inherits']
+ except KeyError: raise MissingKeyException(me.name, key)
else:
- value, _ = me._get(sec, key)
+ value, _ = me._get(key)
if value is None:
- raise MissingKeyException(sec, key)
+ raise MissingKeyException(me.name, key)
## Expand the value and return it.
- return me._expand(sec, value, resolvep)
+ return me._expand(value, resolvep)
- def items(me, sec, resolvep = True):
+ def items(me, resolvep = True):
"""
- Return a list of (NAME, VALUE) items in section SEC.
-
- This extends the default method by handling the inheritance chain.
+ Yield a list of item names in the section.
"""
## Initialize for a depth-first walk of the inheritance graph.
- d = {}
- visited = {}
- basesec = sec
- stack = [sec]
+ seen = { 'name': True }
+ visiting = { me.name: True }
+ stack = [me]
## Visit nodes, collecting their keys. Don't believe the values:
## resolving inheritance is too hard to do like this.
while stack:
sec = stack.pop()
- if sec in visited: continue
- visited[sec] = True
+ for p in sec._parents():
+ if p.name not in visiting:
+ stack.append(p); visiting[p.name] = True
- for key, value in CP.RawConfigParser.items(me, sec):
- if key == '@inherit': stack += value.replace(',', ' ').split()
- else: d[key] = None
-
- ## Now collect the values for the known keys, one by one.
- items = []
- for key in d: items.append((key, me.get(basesec, key, resolvep)))
+ for key in sec._itemmap.iterkeys(): seen[key] = None
## And we're done.
- return items
+ return seen.iterkeys()
+
+class MyConfigParser (object):
+ """
+ A more advanced configuration parser.
+
+ This has four major enhancements over the standard ConfigParser which are
+ relevant to us.
+
+ * It recognizes `@inherits' keys and follows them when expanding a
+ value.
+
+ * It recognizes `$(VAR)' references to configuration variables during
+ expansion and processes them correctly.
+
+ * It recognizes `$[HOST]' name-resolver requests and handles them
+ correctly.
+
+ * Its parsing behaviour is well-defined.
+
+ Use:
+
+ 1. Call parse(FILENAME) to slurp in the configuration data.
+
+ 2. Call resolve() to collect the hostnames which need to be resolved and
+ actually do the name resolution.
+
+ 3. Call sections() to get a list of the configuration sections, or
+ section(NAME) to find a named section.
+
+ 4. Call get(ITEM) on a section to collect the results, or items() to
+ iterate over them.
+ """
+
+ def __init__(me):
+ """
+ Initialize a new, empty configuration parser.
+ """
+ me._sectmap = dict()
+ me._resolver = BulkResolver()
+
+ def parse(me, f):
+ """
+ Parse configuration from a file F.
+ """
+
+ ## Initial parser state.
+ sect = None
+ key = None
+ val = None
+ lno = 0
+
+ ## An unpleasant hack. Python makes it hard to capture a value in a
+ ## variable and examine it in a single action, and this is the best that
+ ## I came up with.
+ m = [None]
+ def match(rx): m[0] = rx.match(line); return m[0]
+
+ ## Commit a key's value when we've determined that there are no further
+ ## continuation lines.
+ def flush():
+ if key is not None: sect._itemmap[key] = val.getvalue()
+
+ ## Work through all of the input lines.
+ for line in f:
+ lno += 1
+
+ if match(RX_COMMENT):
+ ## A comment or a blank line. Nothing doing. (This means that we
+ ## leave out blank lines which look like they might be continuation
+ ## lines.)
+
+ pass
+
+ elif match(RX_GRPHDR):
+ ## A section header. Flush out any previous value and set up the new
+ ## group.
+
+ flush()
+ name = m[0].group(1)
+ try: sect = me._sectmap[name]
+ except KeyError: sect = me._sectmap[name] = ConfigSection(name, me)
+ key = None
+
+ elif match(RX_ASSGN):
+ ## A new assignment. Flush out the old one, and set up to store this
+ ## one.
+
+ if sect is None:
+ raise ConfigSyntaxError(f.name, lno, 'no active section to update')
+ flush()
+ key = m[0].group(1)
+ val = StringIO(); val.write(m[0].group(2))
+
+ elif match(RX_CONT):
+ ## A continuation line. Accumulate the value.
+
+ if key is None:
+ raise ConfigSyntaxError(f.name, lno, 'no config value to continue')
+ val.write('\n'); val.write(m[0].group(1))
+
+ else:
+ ## Something else.
+
+ raise ConfigSyntaxError(f.name, lno, 'incomprehensible line')
+
+ ## Don't forget to commit any final value material.
+ flush()
+
+ def section(me, name):
+ """Return a ConfigSection with the given NAME."""
+ try: return me._sectmap[name]
+ except KeyError: raise MissingSectionException(name)
+
+ def sections(me):
+ """Yield the known sections."""
+ return me._sectmap.itervalues()
+
+ def resolve(me):
+ """
+ Works out all of the hostnames which need resolving and resolves them.
+
+ Until you call this, attempts to fetch configuration items which need to
+ resolve hostnames will fail!
+ """
+ for sec in me.sections():
+ for key in sec.items():
+ value = sec.get(key, resolvep = False)
+ for match in RX_RESOLVE.finditer(value):
+ me._resolver.prepare(match.group(1))
+ me._resolver.run()
###--------------------------------------------------------------------------
### Command-line handling.
"""
conf = MyConfigParser()
for f in inputiter(args):
- conf.readfp(f)
+ conf.parse(f)
conf.resolve()
return conf
This is where the special `user' and `auto' database entries get set.
"""
auto = []
- for sec in sorted(conf.sections()):
- if sec.startswith('@'):
+ for sec in sorted(conf.sections(), key = lambda sec: sec.name):
+ if sec.name.startswith('@'):
continue
- elif sec.startswith('$'):
- label = sec
+ elif sec.name.startswith('$'):
+ label = sec.name
else:
- label = 'P%s' % sec
- if conf.has_option(sec, 'auto') and \
- conf.get(sec, 'auto') in ('y', 'yes', 't', 'true', '1', 'on'):
- auto.append(sec)
- if conf.has_option(sec, 'user'):
- cdb.add('U%s' % conf.get(sec, 'user'), sec)
- url = M.URLEncode(laxp = True, semip = True)
- for key, value in sorted(conf.items(sec), key = lambda (k, v): k):
+ label = 'P%s' % sec.name
+ try: a = sec.get('auto')
+ except MissingKeyException: pass
+ else:
+ if a in ('y', 'yes', 't', 'true', '1', 'on'): auto.append(sec.name)
+ try: u = sec.get('user')
+ except MissingKeyException: pass
+ else: cdb.add('U%s' % u)
+ url = M.URLEncode(semip = True)
+ for key in sorted(sec.items()):
if not key.startswith('@'):
- url.encode(key, ' '.join(M.split(value)[0]))
+ url.encode(key, sec.get(key))
cdb.add(label, url.result)
cdb.add('%AUTO', ' '.join(auto))
cdb.finish()
cdb = CDB.cdbmake(opts.cdbfile, opts.cdbfile + '.new')
else:
cdb = CDBFake()
- conf = getconf(args[1:])
- output(conf, cdb)
+ try:
+ conf = getconf(args[1:])
+ output(conf, cdb)
+ except ExpectedError, e:
+ M.moan(str(e))
+ exit(2)
if __name__ == '__main__':
main()
~mdw / tripe / blobdiff