view mercurial/filelog.py @ 14252:19067884c5f5

revlog: calculate base revisions iteratively

This is in preparation for generaldelta, where the revlog entry base field is
reinterpreted as the deltaparent. For that reason we also rename the base
function to chainbase.

Without generaldelta, performance is unaffected, but generaldelta will suffer
from this in _addrevision, since delta chains will be walked repeatedly.
A cache has been added to eliminate this problem completely.

# filelog.py - file history 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 version 2 or any later version.

import revlog
import re

_mdre = re.compile('\1\n')
def _parsemeta(text):
    """return (metadatadict, keylist, metadatasize)"""
    # text can be buffer, so we can't use .startswith or .index
    if text[:2] != '\1\n':
        return None, None, None
    s = _mdre.search(text, 2).start()
    mtext = text[2:s]
    meta = {}
    keys = []
    for l in mtext.splitlines():
        k, v = l.split(": ", 1)
        meta[k] = v
        keys.append(k)
    return meta, keys, (s + 2)

def _packmeta(meta, keys=None):
    if not keys:
        keys = sorted(meta.iterkeys())
    return "".join("%s: %s\n" % (k, meta[k]) for k in keys)

class filelog(revlog.revlog):
    def __init__(self, opener, path):
        revlog.revlog.__init__(self, opener,
                        "/".join(("data", path + ".i")))

    def read(self, node):
        t = self.revision(node)
        if not t.startswith('\1\n'):
            return t
        s = t.index('\1\n', 2)
        return t[s + 2:]

    def add(self, text, meta, transaction, link, p1=None, p2=None):
        if meta or text.startswith('\1\n'):
            text = "\1\n%s\1\n%s" % (_packmeta(meta), text)
        return self.addrevision(text, transaction, link, p1, p2)

    def renamed(self, node):
        if self.parents(node)[0] != revlog.nullid:
            return False
        t = self.revision(node)
        m = _parsemeta(t)[0]
        if m and "copy" in m:
            return (m["copy"], revlog.bin(m["copyrev"]))
        return False

    def size(self, rev):
        """return the size of a given revision"""

        # for revisions with renames, we have to go the slow way
        node = self.node(rev)
        if self.renamed(node):
            return len(self.read(node))

        # XXX if self.read(node).startswith("\1\n"), this returns (size+4)
        return revlog.revlog.size(self, rev)

    def cmp(self, node, text):
        """compare text with a given file revision

        returns True if text is different than what is stored.
        """

        t = text
        if text.startswith('\1\n'):
            t = '\1\n\1\n' + text

        samehashes = not revlog.revlog.cmp(self, node, t)
        if samehashes:
            return False

        # renaming a file produces a different hash, even if the data
        # remains unchanged. Check if it's the case (slow):
        if self.renamed(node):
            t2 = self.read(node)
            return t2 != text

        return True