view mercurial/changelog.py @ 4269:73c918c71300

changelog: optimize delayed updates for clone vs pull

pull index updates get redirected to memory, then appended on finalize
clone index updates get sent to 00changelog.i.a, then renamed on finalize

# changelog.py - changelog class for mercurial
#
# Copyright 2005, 2006 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 == _string_unescape(res)
    True
    """
    # subset of the string_escape codec
    text = text.replace('\\', '\\\\').replace('\n', '\\n').replace('\r', '\\r')
    return text.replace('\0', '\\0')

def _string_unescape(text):
    return text.decode('string_escape')

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):
        close(self.fp)

    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 = ""
        old_offset = self.offset
        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(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 not l:
                continue
            k, v = _string_unescape(l).split(':', 1)
            extra[k] = v
        return extra

    def encode_extra(self, d):
        items = [_string_escape(":".join(t)) for t in d.iteritems()]
        return "\0".join(items)

    def extract(self, text):
        """
        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
        """
        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 read(self, node):
        return self.extract(self.revision(node))

    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)