[PATCH 1 of 2] verify: document corner cases
Jun Wu
quark at fb.com
Wed Mar 29 17:56:11 EDT 2017
Excerpts from Jun Wu's message of 2017-03-29 14:51:59 -0700:
> # HG changeset patch
> # User Jun Wu <quark at fb.com>
> # Date 1490823901 25200
> # Wed Mar 29 14:45:01 2017 -0700
> # Node ID 1f7890370b5437466534cbd0a313d21671dade03
> # Parent e9fda3b8614a8b701bd48041afa8b709e1227f27
> # Available At https://bitbucket.org/quark-zju/hg-draft
> # hg pull https://bitbucket.org/quark-zju/hg-draft -r 1f7890370b54
> verify: document corner cases
>
> It seems a good idea to list all kinds of "surprises" and expected behavior
> to make the upcoming changes easier to understand.
>
> Note: the comment added do not reflect the actual behavior of the current
> code.
>
> diff --git a/mercurial/verify.py b/mercurial/verify.py
> --- a/mercurial/verify.py
> +++ b/mercurial/verify.py
> @@ -381,4 +381,44 @@ class verifier(object):
>
> # verify contents
> + #
> + # Define 4 cases to help understand corner cases:
> + #
> + # | common | rename | meta | ext
> + # -------------------------------------------------------
> + # flags() | 0 | 0 | 0 | not 0
> + # renamed() | False | True | False | ?
> + # rawtext[0:2]=='\1\n'| False | True | True | ?
> + #
> + # "rawtext" means the raw text stored in revlog data, which
> + # could be retrieved by "revision(rev, raw=True)". "text"
> + # mentioned below is "revision(rev, raw=False)".
> + #
> + # There are 3 different lengths stored physically:
> + # 1. L1: rawsize, stored in revlog index
> + # 2. L2: len(rawtext), stored in revlog data
> + # 3. L3: len(text), stored in revlog data if flags=0, or
> + # possibly somewhere else if flags!=0
> + #
> + # L1 should be equal to L2. L3 is unrelated to L1 or L2. But
> + # text may or may not affect commit hash depending on flag
> + # processors (see revlog.addflagprocessor).
> + #
> + # | common | rename | meta | ext
> + # -------------------------------------------------
> + # rawsize() | L1 | L1 | L1 | L1
> + # size() | L1 | L2-LM | L1(*) | L1 (?)
> + # len(rawtext) | L2 | L2 | L2 | L2
> + # len(text) | L2 | L2 | L2 | L3
> + # len(read()) | L2 | L2-LM | L2-LM | L3
^^^^
This should be "L3 (?)"
If that does not get fixed in flight. I'll send a follow up.
> + #
> + # LM: length of metadata, depending on rawtext
> + # (*): not ideal, see comment in filelog.size
> + # (?): could be "- len(meta)" if the resolved content has
> + # rename metadata
> + #
> + # Checks needed to be done:
> + # 1. length check: L1 == L2, in all cases.
> + # 2. hash check: depending on flag processor, we may need to
> + # use either "text" (external), or "rawtext" (in revlog).
> try:
> l = len(fl.read(n))
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