mercurial/changelog.py

revlog.revision: avoid opening the datafile without need.

If there's no inline data, revlog.revision opens the data file every
time it's called.  This is useful if we're going to call chunk many
times, but, if we're going to call it only once, it's better to let
chunk open the file - if we're lucky, all the data we're going to need
is already cached and we won't need to even look at the file.

# changelog.py - changelog class for mercurial
#
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

from revlog import *
from i18n import _
import os, time, util

def _string_escape(text):
    """
    >>> d = {'nl': chr(10), 'bs': chr(92), 'cr': chr(13), 'nul': chr(0)}
    >>> s = "ab%(nl)scd%(bs)s%(bs)sn%(nul)sab%(cr)scd%(bs)s%(nl)s" % d
    >>> s
    'ab\\ncd\\\\\\\\n\\x00ab\\rcd\\\\\\n'
    >>> res = _string_escape(s)
    >>> s == res.decode('string_escape')
    True
    """
    # subset of the string_escape codec
    text = text.replace('\\', '\\\\').replace('\n', '\\n').replace('\r', '\\r')
    return text.replace('\0', '\\0')

class appender:
    '''the changelog index must be update last on disk, so we use this class
    to delay writes to it'''
    def __init__(self, fp, buf):
        self.data = buf
        self.fp = fp
        self.offset = fp.tell()
        self.size = util.fstat(fp).st_size

    def end(self):
        return self.size + len("".join(self.data))
    def tell(self):
        return self.offset
    def flush(self):
        pass
    def close(self):
        self.fp.close()

    def seek(self, offset, whence=0):
        '''virtual file offset spans real file and data'''
        if whence == 0:
            self.offset = offset
        elif whence == 1:
            self.offset += offset
        elif whence == 2:
            self.offset = self.end() + offset
        if self.offset < self.size:
            self.fp.seek(self.offset)

    def read(self, count=-1):
        '''only trick here is reads that span real file and data'''
        ret = ""
        if self.offset < self.size:
            s = self.fp.read(count)
            ret = s
            self.offset += len(s)
            if count > 0:
                count -= len(s)
        if count != 0:
            doff = self.offset - self.size
            self.data.insert(0, "".join(self.data))
            del self.data[1:]
            s = self.data[0][doff:doff+count]
            self.offset += len(s)
            ret += s
        return ret

    def write(self, s):
        self.data.append(str(s))
        self.offset += len(s)

class changelog(revlog):
    def __init__(self, opener):
        revlog.__init__(self, opener, "00changelog.i")

    def delayupdate(self):
        "delay visibility of index updates to other readers"
        self._realopener = self.opener
        self.opener = self._delayopener
        self._delaycount = self.count()
        self._delaybuf = []
        self._delayname = None

    def finalize(self, tr):
        "finalize index updates"
        self.opener = self._realopener
        # move redirected index data back into place
        if self._delayname:
            util.rename(self._delayname + ".a", self._delayname)
        elif self._delaybuf:
            fp = self.opener(self.indexfile, 'a')
            fp.write("".join(self._delaybuf))
            fp.close()
            del self._delaybuf
        # split when we're done
        self.checkinlinesize(tr)

    def _delayopener(self, name, mode='r'):
        fp = self._realopener(name, mode)
        # only divert the index
        if not name == self.indexfile:
            return fp
        # if we're doing an initial clone, divert to another file
        if self._delaycount == 0:
            self._delayname = fp.name
            return self._realopener(name + ".a", mode)
        # otherwise, divert to memory
        return appender(fp, self._delaybuf)

    def checkinlinesize(self, tr, fp=None):
        if self.opener == self._delayopener:
            return
        return revlog.checkinlinesize(self, tr, fp)

    def decode_extra(self, text):
        extra = {}
        for l in text.split('\0'):
            if l:
                k, v = l.decode('string_escape').split(':', 1)
                extra[k] = v
        return extra

    def encode_extra(self, d):
        # keys must be sorted to produce a deterministic changelog entry
        keys = d.keys()
        keys.sort()
        items = [_string_escape('%s:%s' % (k, d[k])) for k in keys]
        return "\0".join(items)

    def read(self, node):
        """
        format used:
        nodeid\n        : manifest node in ascii
        user\n          : user, no \n or \r allowed
        time tz extra\n : date (time is int or float, timezone is int)
                        : extra is metadatas, encoded and separated by '\0'
                        : older versions ignore it
        files\n\n       : files modified by the cset, no \n or \r allowed
        (.*)            : comment (free text, ideally utf-8)

        changelog v0 doesn't use extra
        """
        text = self.revision(node)
        if not text:
            return (nullid, "", (0, 0), [], "", {'branch': 'default'})
        last = text.index("\n\n")
        desc = util.tolocal(text[last + 2:])
        l = text[:last].split('\n')
        manifest = bin(l[0])
        user = util.tolocal(l[1])

        extra_data = l[2].split(' ', 2)
        if len(extra_data) != 3:
            time = float(extra_data.pop(0))
            try:
                # various tools did silly things with the time zone field.
                timezone = int(extra_data[0])
            except:
                timezone = 0
            extra = {}
        else:
            time, timezone, extra = extra_data
            time, timezone = float(time), int(timezone)
            extra = self.decode_extra(extra)
        if not extra.get('branch'):
            extra['branch'] = 'default'
        files = l[3:]
        return (manifest, user, (time, timezone), files, desc, extra)

    def add(self, manifest, list, desc, transaction, p1=None, p2=None,
                  user=None, date=None, extra={}):

        user, desc = util.fromlocal(user), util.fromlocal(desc)

        if date:
            parseddate = "%d %d" % util.parsedate(date)
        else:
            parseddate = "%d %d" % util.makedate()
        if extra and extra.get("branch") in ("default", ""):
            del extra["branch"]
        if extra:
            extra = self.encode_extra(extra)
            parseddate = "%s %s" % (parseddate, extra)
        list.sort()
        l = [hex(manifest), user, parseddate] + list + ["", desc]
        text = "\n".join(l)
        return self.addrevision(text, transaction, self.count(), p1, p2)