view mercurial/revlog.py @ 94:7daef883134f

Refactor merge code Delete old code Fix calculation of newer nodes on server Fix branch recursion on client Fix manifest merge problems Add more debugging and note messages to merge
author mpm@selenic.com
date Wed, 18 May 2005 16:29:39 -0800
parents 1b945e8ba67b
children 7a2abee6b0c2
line wrap: on
line source

# revlog.py - storage back-end for mercurial
#
# This provides efficient delta storage with O(1) retrieve and append
# and O(changes) merge between branches
#
# Copyright 2005 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import zlib, struct, sha, os, tempfile, binascii
from mercurial import mdiff

def hex(node): return binascii.hexlify(node)
def bin(node): return binascii.unhexlify(node)
def short(node): return hex(node[:4])

def compress(text):
    return zlib.compress(text)

def decompress(bin):
    return zlib.decompress(bin)

def hash(text, p1, p2):
    l = [p1, p2]
    l.sort()
    return sha.sha(l[0] + l[1] + text).digest()

nullid = "\0" * 20
indexformat = ">4l20s20s20s"

class lazyparser:
    def __init__(self, data):
        self.data = data
        self.s = struct.calcsize(indexformat)
        self.l = len(data)/self.s
        self.index = [None] * self.l
        self.map = {nullid: -1}

        if 0:
            n = 0
            i = self.data
            s = struct.calcsize(indexformat)
            for f in xrange(0, len(i), s):
                # offset, size, base, linkrev, p1, p2, nodeid
                e = struct.unpack(indexformat, i[f:f + s])
                self.map[e[6]] = n
                self.index.append(e)
                n += 1

    def load(self, pos):
        block = pos / 1000
        i = block * 1000
        end = min(self.l, i + 1000)
        while i < end:
            d = self.data[i * self.s: (i + 1) * self.s]
            e = struct.unpack(indexformat, d)
            self.index[i] = e
            self.map[e[6]] = i
            i += 1
        
class lazyindex:
    def __init__(self, parser):
        self.p = parser
    def __len__(self):
        return len(self.p.index)
    def __getitem__(self, pos):
        i = self.p.index[pos]
        if not i:
            self.p.load(pos)
            return self.p.index[pos]
        return i
    def append(self, e):
        self.p.index.append(e)
        
class lazymap:
    def __init__(self, parser):
        self.p = parser
    def load(self, key):
        n = self.p.data.find(key)
        if n < 0: raise KeyError("node " + hex(key))
        pos = n / self.p.s
        self.p.load(pos)
    def __contains__(self, key):
        try:
            self[key]
            return True
        except KeyError:
            return False
    def __getitem__(self, key):
        try:
            return self.p.map[key]
        except KeyError:
            try:
                self.load(key)
                return self.p.map[key]
            except KeyError:
                raise KeyError("node " + hex(key))
    def __setitem__(self, key, val):
        self.p.map[key] = val

class revlog:
    def __init__(self, opener, indexfile, datafile):
        self.indexfile = indexfile
        self.datafile = datafile
        self.opener = opener
        self.cache = None
        # read the whole index for now, handle on-demand later
        try:
            i = self.opener(self.indexfile).read()
        except IOError:
            i = ""
        parser = lazyparser(i)
        self.index = lazyindex(parser)
        self.nodemap = lazymap(parser)

    def tip(self): return self.node(len(self.index) - 1)
    def count(self): return len(self.index)
    def node(self, rev): return (rev < 0) and nullid or self.index[rev][6]
    def rev(self, node): return self.nodemap[node]
    def linkrev(self, node): return self.index[self.nodemap[node]][3]
    def parents(self, node):
        if node == nullid: return (nullid, nullid)
        return self.index[self.nodemap[node]][4:6]

    def start(self, rev): return self.index[rev][0]
    def length(self, rev): return self.index[rev][1]
    def end(self, rev): return self.start(rev) + self.length(rev)
    def base(self, rev): return self.index[rev][2]

    def lookup(self, id):
        try:
            rev = int(id)
            return self.node(rev)
        except ValueError:
            c = []
            for n in self.nodemap:
                if id in hex(n):
                    c.append(n)
            if len(c) > 1: raise KeyError("Ambiguous identifier")
            if len(c) < 1: raise KeyError("No match found")
            return c[0]
                
        return None

    def diff(self, a, b):
        return mdiff.textdiff(a, b)

    def patches(self, t, pl):
        return mdiff.patches(t, pl)

    def revision(self, node):
        if node == nullid: return ""
        if self.cache and self.cache[0] == node: return self.cache[2]

        text = None
        rev = self.rev(node)
        base = self.base(rev)
        start = self.start(base)
        end = self.end(rev)

        if self.cache and self.cache[1] >= base and self.cache[1] < rev:
            base = self.cache[1]
            start = self.start(base + 1)
            text = self.cache[2]
            last = 0

        f = self.opener(self.datafile)
        f.seek(start)
        data = f.read(end - start)

        if not text:
            last = self.length(base)
            text = decompress(data[:last])

        bins = []
        for r in xrange(base + 1, rev + 1):
            s = self.length(r)
            bins.append(decompress(data[last:last + s]))
            last = last + s

        text = mdiff.patches(text, bins)

        (p1, p2) = self.parents(node)
        if node != hash(text, p1, p2):
            raise "integrity check failed on %s:%d" % (self.datafile, rev)

        self.cache = (node, rev, text)
        return text  

    def addrevision(self, text, transaction, link, p1=None, p2=None):
        if text is None: text = ""
        if p1 is None: p1 = self.tip()
        if p2 is None: p2 = nullid

        node = hash(text, p1, p2)

        n = self.count()
        t = n - 1

        if n:
            base = self.base(t)
            start = self.start(base)
            end = self.end(t)
            prev = self.revision(self.tip())
            data = compress(self.diff(prev, text))
            dist = end - start + len(data)

        # full versions are inserted when the needed deltas
        # become comparable to the uncompressed text
        if not n or dist > len(text) * 2:
            data = compress(text)
            base = n
        else:
            base = self.base(t)

        offset = 0
        if t >= 0:
            offset = self.end(t)

        e = (offset, len(data), base, link, p1, p2, node)
        
        self.index.append(e)
        self.nodemap[node] = n
        entry = struct.pack(indexformat, *e)

        transaction.add(self.datafile, e[0])
        self.opener(self.datafile, "a").write(data)
        transaction.add(self.indexfile, n * len(entry))
        self.opener(self.indexfile, "a").write(entry)

        self.cache = (node, n, text)
        return node

    def ancestor(self, a, b):
        def expand(list, map):
            a = []
            while list:
                n = list.pop(0)
                map[n] = 1
                yield n
                for p in self.parents(n):
                    if p != nullid and p not in map:
                        list.append(p)
            yield nullid

        amap = {}
        bmap = {}
        ag = expand([a], amap)
        bg = expand([b], bmap)
        adone = bdone = 0

        while not adone or not bdone:
            if not adone:
                an = ag.next()
                if an == nullid:
                    adone = 1
                elif an in bmap:
                    return an
            if not bdone:
                bn = bg.next()
                if bn == nullid:
                    bdone = 1
                elif bn in amap:
                    return bn

        return nullid

    def group(self, linkmap):
        # given a list of changeset revs, return a set of deltas and
        # metadata corresponding to nodes. the first delta is
        # parent(nodes[0]) -> nodes[0] the receiver is guaranteed to
        # have this parent as it has all history before these
        # changesets. parent is parent[0]

        revs = []
        needed = {}

        # find file nodes/revs that match changeset revs
        for i in xrange(0, self.count()):
            if self.index[i][3] in linkmap:
                revs.append(i)
                needed[i] = 1

        # if we don't have any revisions touched by these changesets, bail
        if not revs: return struct.pack(">l", 0)

        # add the parent of the first rev
        p = self.parents(self.node(revs[0]))[0]
        revs.insert(0, self.rev(p))

        # for each delta that isn't contiguous in the log, we need to
        # reconstruct the base, reconstruct the result, and then
        # calculate the delta. We also need to do this where we've
        # stored a full version and not a delta
        for i in xrange(0, len(revs) - 1):
            a, b = revs[i], revs[i + 1]
            if a + 1 != b or self.base(b) == b:
                for j in xrange(self.base(a), a + 1):
                    needed[j] = 1
                for j in xrange(self.base(b), b + 1):
                    needed[j] = 1

        # calculate spans to retrieve from datafile
        needed = needed.keys()
        needed.sort()
        spans = []
        for n in needed:
            if n < 0: continue
            o = self.start(n)
            l = self.length(n)
            spans.append((o, l, [(n, l)]))

        # merge spans
        merge = [spans.pop(0)]
        while spans:
            e = spans.pop(0)
            f = merge[-1]
            if e[0] == f[0] + f[1]:
                merge[-1] = (f[0], f[1] + e[1], f[2] + e[2])
            else:
                merge.append(e)

        # read spans in, divide up chunks
        chunks = {}
        for span in merge:
            # we reopen the file for each span to make http happy for now
            f = self.opener(self.datafile)
            f.seek(span[0])
            data = f.read(span[1])

            # divide up the span
            pos = 0
            for r, l in span[2]:
                chunks[r] = data[pos: pos + l]
                pos += l

        # helper to reconstruct intermediate versions
        def construct(text, base, rev):
            bins = [decompress(chunks[r]) for r in xrange(base + 1, rev + 1)]
            return mdiff.patches(text, bins)

        # build deltas
        deltas = []
        for d in xrange(0, len(revs) - 1):
            a, b = revs[d], revs[d + 1]
            n = self.node(b)
            
            if a + 1 != b or self.base(b) == b:
                if a >= 0:
                    base = self.base(a)
                    ta = decompress(chunks[self.base(a)])
                    ta = construct(ta, base, a)
                else:
                    ta = ""
                    
                base = self.base(b)
                if a > base:
                    base = a
                    tb = ta
                else:
                    tb = decompress(chunks[self.base(b)])
                tb = construct(tb, base, b)
                d = self.diff(ta, tb)
            else:
                d = decompress(chunks[b])

            p = self.parents(n)
            meta = n + p[0] + p[1] + linkmap[self.linkrev(n)]
            l = struct.pack(">l", len(meta) + len(d) + 4)
            deltas.append(l + meta + d)

        l = struct.pack(">l", sum(map(len, deltas)) + 4)
        deltas.insert(0, l)
        return "".join(deltas)
        
    def addgroup(self, data, linkmapper, transaction):
        # given a set of deltas, add them to the revision log. the
        # first delta is against its parent, which should be in our
        # log, the rest are against the previous delta.

        if not data: return self.tip()

        # retrieve the parent revision of the delta chain
        chain = data[24:44]
        if not chain in self.nodemap:
            raise "unknown base %s" % short(chain[:4])

        # track the base of the current delta log
        r = self.count()
        t = r - 1
        
        base = prev = -1
        start = end = 0
        if r:
            start = self.start(self.base(t))
            end = self.end(t)
            measure = self.length(self.base(t))
            base = self.base(t)
            prev = self.tip()

        transaction.add(self.datafile, end)
        transaction.add(self.indexfile, r * struct.calcsize(indexformat))
        dfh = self.opener(self.datafile, "a")
        ifh = self.opener(self.indexfile, "a")

        # loop through our set of deltas
        pos = 0
        while pos < len(data):
            l, node, p1, p2, cs = struct.unpack(">l20s20s20s20s",
                                                data[pos:pos+84])
            link = linkmapper(cs)
            if node in self.nodemap:
                raise "already have %s" % hex(node[:4])
            delta = data[pos + 84:pos + l]
            pos += l

            # full versions are inserted when the needed deltas become
            # comparable to the uncompressed text or when the previous
            # version is not the one we have a delta against. We use
            # the size of the previous full rev as a proxy for the
            # current size.

            if chain == prev:
                cdelta = compress(delta)

            if chain != prev or (end - start + len(cdelta)) > measure * 2:
                # flush our writes here so we can read it in revision
                dfh.flush()
                ifh.flush()
                text = self.revision(chain)
                text = self.patches(text, [delta])
                chk = self.addrevision(text, transaction, link, p1, p2)
                if chk != node:
                    raise "consistency error adding group"
                measure = len(text)
            else:
                e = (end, len(cdelta), self.base(t), link, p1, p2, node)
                self.index.append(e)
                self.nodemap[node] = r
                dfh.write(cdelta)
                ifh.write(struct.pack(indexformat, *e))

            t, r, chain, prev = r, r + 1, node, node
            start = self.start(self.base(t))
            end = self.end(t)

        dfh.close()
        ifh.close()
        return node