[PATCH 4 of 4] revlog: separate methods for deltas and key frames compression/decompression

[Wojciech Lopata]

Siddharth noticed this series is not only going to break the lz4revlog extension, but will also make it pretty difficult to fix.

Let me modify it and resend soon. 

> -----Original Message-----
> From: mercurial-devel-bounces at selenic.com [mailto:mercurial-devel-
> bounces at selenic.com] On Behalf Of Wojciech Lopata
> Sent: Thursday, September 26, 2013 11:15 AM
> To: mercurial-devel at selenic.com
> Subject: [PATCH 4 of 4] revlog: separate methods for deltas and key frames
> compression/decompression
> 
> # HG changeset patch
> # User Wojciech Lopata <lopek at fb.com>
> # Date 1380212200 25200
> #      Thu Sep 26 09:16:40 2013 -0700
> # Node ID b7528dd2041110229810e71245eefa4d70aca648
> # Parent  16ba1a7b494caeb45d24ca81d49bbc866af1e7c5
> revlog: separate methods for deltas and key frames
> compression/decompression
> 
> This change makes possible:
>   1) to use different compression methods in various revlog subclasses
>   2) to use different compression methods for key frames and deltas
> 
> diff --git a/mercurial/revlog.py b/mercurial/revlog.py
> --- a/mercurial/revlog.py
> +++ b/mercurial/revlog.py
> @@ -881,11 +881,23 @@
>          length = end - start
>          return self._getchunk(start, length)
> 
> +    def compressdelta(self, delta):
> +        return compress(delta)
> +
> +    def compresskeyframe(self, text):
> +        return compress(text)
> +
> +    def decompressdelta(self, bin):
> +        return decompress(bin)
> +
> +    def decompresskeyframe(self, bin):
> +        return decompress(bin)
> +
>      def _deltachunk(self, rev):
> -        return decompress(self._chunkraw(rev, rev))
> +        return self.decompressdelta(self._chunkraw(rev, rev))
> 
>      def _keyframechunk(self, rev):
> -        return decompress(self._chunkraw(rev, rev))
> +        return self.decompresskeyframe(self._chunkraw(rev, rev))
> 
>      def _deltachunks(self, revs):
>          '''faster version of [self._deltachunk(rev) for rev in revs] @@ -906,6
> +918,7 @@
>          self._chunkraw(revs[0], revs[-1])
>          offset, data = self._chunkcache
> 
> +        decompress = self.decompressdelta
>          for rev in revs:
>              chunkstart = start(rev)
>              if inline:
> @@ -1112,7 +1125,7 @@
>                  t = buildtext()
>                  ptext = self.revision(self.node(rev))
>                  delta = mdiff.textdiff(ptext, t)
> -            data = compress(delta)
> +            data = self.compressdelta(delta)
>              l = len(data[1]) + len(data[0])
>              if basecache[0] == rev:
>                  chainbase = basecache[1] @@ -1158,7 +1171,7 @@
>              textlen = len(text)
>          if d is None or dist > textlen * 2:
>              text = buildtext()
> -            data = compress(text)
> +            data = self.compresskeyframe(text)
>              l = len(data[1]) + len(data[0])
>              base = chainbase = curr
> 
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