Convert lookup_tag to take a pointer to struct object_id.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert the lookup_tree function to take a pointer to struct object_id.
The commit was created with manual changes to tree.c, tree.h, and
object.c, plus the following semantic patch:
@@
@@
- lookup_tree(EMPTY_TREE_SHA1_BIN)
+ lookup_tree(&empty_tree_oid)
@@
expression E1;
@@
- lookup_tree(E1.hash)
+ lookup_tree(&E1)
@@
expression E1;
@@
- lookup_tree(E1->hash)
+ lookup_tree(E1)
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert lookup_blob to take a pointer to struct object_id.
The commit was created with manual changes to blob.c and blob.h, plus
the following semantic patch:
@@
expression E1;
@@
- lookup_blob(E1.hash)
+ lookup_blob(&E1)
@@
expression E1;
@@
- lookup_blob(E1->hash)
+ lookup_blob(E1)
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
All but a few callers of lookup_blob have been converted to struct
object_id. Introduce a temporary, which will be removed later, into
parse_object to ease the transition, and convert the remaining callers
so that we can update lookup_blob to take struct object_id *.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert lookup_commit, lookup_commit_or_die,
lookup_commit_reference, and lookup_commit_reference_gently to take
struct object_id arguments.
Introduce a temporary in parse_object buffer in order to convert this
function. This is required since in order to convert parse_object and
parse_object_buffer, lookup_commit_reference_gently and
lookup_commit_or_die would need to be converted. Not introducing a
temporary would therefore require that lookup_commit_or_die take a
struct object_id *, but lookup_commit would take unsigned char *,
leaving a confusing and hard-to-use interface.
parse_object_buffer will lose this temporary in a later patch.
This commit was created with manual changes to commit.c, commit.h, and
object.c, plus the following semantic patch:
@@
expression E1, E2;
@@
- lookup_commit_reference_gently(E1.hash, E2)
+ lookup_commit_reference_gently(&E1, E2)
@@
expression E1, E2;
@@
- lookup_commit_reference_gently(E1->hash, E2)
+ lookup_commit_reference_gently(E1, E2)
@@
expression E1;
@@
- lookup_commit_reference(E1.hash)
+ lookup_commit_reference(&E1)
@@
expression E1;
@@
- lookup_commit_reference(E1->hash)
+ lookup_commit_reference(E1)
@@
expression E1;
@@
- lookup_commit(E1.hash)
+ lookup_commit(&E1)
@@
expression E1;
@@
- lookup_commit(E1->hash)
+ lookup_commit(E1)
@@
expression E1, E2;
@@
- lookup_commit_or_die(E1.hash, E2)
+ lookup_commit_or_die(&E1, E2)
@@
expression E1, E2;
@@
- lookup_commit_or_die(E1->hash, E2)
+ lookup_commit_or_die(E1, E2)
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Apply the semantic patch swap.cocci to convert hand-rolled swaps to use
the macro SWAP. The resulting code is shorter and easier to read, the
object code is effectively unchanged.
The patch for object.c had to be hand-edited in order to preserve the
comment before the change; Coccinelle tried to eat it for some reason.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert all instances of get_object_hash to use an appropriate reference
to the hash member of the oid member of struct object. This provides no
functional change, as it is essentially a macro substitution.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>
struct object is one of the major data structures dealing with object
IDs. Convert it to use struct object_id instead of an unsigned char
array. Convert get_object_hash to refer to the new member as well.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>
Convert most instances where the sha1 member of struct object is
dereferenced to use get_object_hash. Most instances that are passed to
functions that have versions taking struct object_id, such as
get_sha1_hex/get_oid_hex, or instances that can be trivially converted
to use struct object_id instead, are not converted.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>
"git cat-file bl $blob" failed to barf even though there is no
object type that is "bl".
* jk/type-from-string-gently:
type_from_string_gently: make sure length matches
When commit fe8e3b7 refactored type_from_string to allow
input that was not NUL-terminated, it switched to using
strncmp instead of strcmp. But this means we check only the
first "len" bytes of the strings, and ignore any remaining
bytes in the object_type_string. We should make sure that it
is also "len" bytes, or else we would accept "comm" as
"commit", and so forth.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is a thin compatibility wrapper around
add_pending_object_with_path. But the only caller is
add_object_array, which is itself just a thin compatibility
wrapper. There are no external callers, so we can just
remove this middle wrapper.
Noticed-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When you resolve a sha1, you can optionally keep any context
found during the resolution, including the path and mode of
a tree entry (e.g., when looking up "HEAD:subdir/file.c").
The add_object_array_with_context function lets you then
attach that context to an entry in a list. Unfortunately,
the interface for doing so is horrible. The object_context
structure is large and most object_array users do not use
it. Therefore we keep a pointer to the structure to avoid
burdening other users too much. But that means when we do
use it that we must allocate the struct ourselves. And the
struct contains a fixed PATH_MAX-sized buffer, which makes
this wholly unsuitable for any large arrays.
We can observe that there is only a single user of the
"with_context" variant: builtin/grep.c. And in that use
case, the only element we care about is the path. We can
therefore store only the path as a pointer (the context's
mode field was redundant with the object_array_entry itself,
and nobody actually cared about the surrounding tree). This
still requires a strdup of the pathname, but at least we are
only consuming the minimum amount of memory for each string.
We can also handle the copying ourselves in
add_object_array_*, and free it as appropriate in
object_array_release_entry.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There's currently no easy way to free the memory associated
with an object_array (and in most cases, we simply leak the
memory in a rev_info's pending array). Let's provide a
helper to make this easier to handle.
We can make use of it in list-objects.c, which does the same
thing by hand (but fails to free the "name" field of each
entry, potentially leaking memory).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is not a lot of code, but it's a logical construct that
should not need to be repeated (and we are about to add a
third repetition).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the next commits, we will enhance the fsck_tag() function to check
tag objects more thoroughly. To this end, we need a function to verify
that a given string is a valid object type, but that does not die() in
the negative case.
While at it, prepare type_from_string() for counted strings, i.e. strings
with an explicitly specified length rather than a NUL termination.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make sure all in-core commit objects are assigned a unique number
so that they can be annotated using the commit-slab API.
* jk/alloc-commit-id:
diff-tree: avoid lookup_unknown_object
object_as_type: set commit index
alloc: factor out commit index
add object_as_type helper for casting objects
parse_object_buffer: do not set object type
move setting of object->type to alloc_* functions
alloc: write out allocator definitions
alloc.c: remove the alloc_raw_commit_node() function
The point of the "index" field of struct commit is that
every allocated commit would have one. It is supposed to be
an invariant that whenever object->type is set to
OBJ_COMMIT, we have a unique index.
Commit 969eba6 (commit: push commit_index update into
alloc_commit_node, 2014-06-10) covered this case for
newly-allocated commits. However, we may also allocate an
"unknown" object via lookup_unknown_object, and only later
convert it to a commit. We must make sure that we set the
commit index when we switch the type field.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When we call lookup_commit, lookup_tree, etc, the logic goes
something like:
1. Look for an existing object struct. If we don't have
one, allocate and return a new one.
2. Double check that any object we have is the expected
type (and complain and return NULL otherwise).
3. Convert an object with type OBJ_NONE (from a prior
call to lookup_unknown_object) to the expected type.
We can encapsulate steps 2 and 3 in a helper function which
checks whether we have the expected object type, converts
OBJ_NONE as appropriate, and returns the object.
Not only does this shorten the code, but it also provides
one central location for converting OBJ_NONE objects into
objects of other types. Future patches will use that to
enforce type-specific invariants.
Since this is a refactoring, we would want it to behave
exactly as the current code. It takes a little reasoning to
see that this is the case:
- for lookup_{commit,tree,etc} functions, we are just
pulling steps 2 and 3 into a function that does the same
thing.
- for the call in peel_object, we currently only do step 3
(but we want to consolidate it with the others, as
mentioned above). However, step 2 is a noop here, as the
surrounding conditional makes sure we have OBJ_NONE
(which we want to keep to avoid an extraneous call to
sha1_object_info).
- for the call in lookup_commit_reference_gently, we are
currently doing step 2 but not step 3. However, step 3
is a noop here. The object we got will have just come
from deref_tag, which must have figured out the type for
each object in order to know when to stop peeling.
Therefore the type will never be OBJ_NONE.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The only way that "obj" can be non-NULL is if it came from
one of the lookup_* functions. These functions always ensure
that the object has the expected type (and return NULL
otherwise), so there is no need for us to set the type.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "struct object" type implements basic object
polymorphism. Individual instances are allocated as
concrete types (or as a union type that can store any
object), and a "struct object *" can be cast into its real
type after examining its "type" enum. This means it is
dangerous to have a type field that does not match the
allocation (e.g., setting the type field of a "struct blob"
to "OBJ_COMMIT" would mean that a reader might read past the
allocated memory).
In most of the current code this is not a problem; the first
thing we do after allocating an object is usually to set its
type field by passing it to create_object. However, the
virtual commits we create in merge-recursive.c do not ever
get their type set. This does not seem to have caused
problems in practice, though (presumably because we always
pass around a "struct commit" pointer and never even look at
the type).
We can fix this oversight and also make it harder for future
code to get it wrong by setting the type directly in the
object allocation functions.
This will also make it easier to fix problems with commit
index allocation, as we know that any object allocated by
alloc_commit_node will meet the invariant that an object
with an OBJ_COMMIT type field will have a unique index
number.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Copying the first bytes of a SHA1 is duplicated in six places,
however, the implications (the actual value would depend on the
endianness of the platform) is documented only once.
Add a properly documented API for this.
Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Most callsites which use the commit buffer try to use the
cached version attached to the commit, rather than
re-reading from disk. Unfortunately, that interface provides
only a pointer to the NUL-terminated buffer, with no
indication of the original length.
For the most part, this doesn't matter. People do not put
NULs in their commit messages, and the log code is happy to
treat it all as a NUL-terminated string. However, some code
paths do care. For example, when checking signatures, we
want to be very careful that we verify all the bytes to
avoid malicious trickery.
This patch just adds an optional "size" out-pointer to
get_commit_buffer and friends. The existing callers all pass
NULL (there did not seem to be any obvious sites where we
could avoid an immediate strlen() call, though perhaps with
some further refactoring we could).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Some call sites check commit->buffer to see whether we have
a cached buffer, and if so, do some work with it. In the
long run we may want to switch these code paths to make
their decision on a different boolean flag (because checking
the cache may get a little more expensive in the future).
But for now, we can easily support them by converting the
calls to use get_cached_commit_buffer.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Right now this is just a one-liner, but abstracting it will
make it easier to change later.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make "git grep" and "git show" pay attention to --textconv when
dealing with blob objects.
* mg/more-textconv:
grep: honor --textconv for the case rev:path
grep: allow to use textconv filters
t7008: demonstrate behavior of grep with textconv
cat-file: do not die on --textconv without textconv filters
show: honor --textconv for blobs
diff_opt: track whether flags have been set explicitly
t4030: demonstrate behavior of show with textconv
hashtable_index() appears to be a close duplicate of hash_obj().
Keep only the later and make it usable for all cases.
Also remove the modulus as this is an expensive operation.
The size argument is always a power of 2 anyway, so a simple
mask operation provides the same result.
On a 'git rev-list --all --objects' run this decreased the time spent
in lookup_object from 27.5% to 24.1%.
[jc: with a few comments on "modulus turned into mask" by Peff]
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If we exit early in the function parse_object_buffer, we did not
write to *eaten_p. Then the calling function parse_object, which looks
like the following with respect to the eaten variable, cannot rely on a
proper value set in eaten, hence the freeing of the buffer depends
on random values in memory.
struct object *parse_object(const unsigned char *sha1)
{
int eaten;
...
obj = parse_object_buffer(sha1, type, size, buffer, &eaten);
if (!eaten)
free(buffer);
}
This change makes sure, the buffer freeing condition is deterministic.
Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Define memory ownership and lifetime rules for what for-each-ref
feeds to its callbacks (in short, "you do not own it, so make a
copy if you want to keep it").
* mh/reflife: (25 commits)
refs: document the lifetime of the args passed to each_ref_fn
register_ref(): make a copy of the bad reference SHA-1
exclude_existing(): set existing_refs.strdup_strings
string_list_add_refs_by_glob(): add a comment about memory management
string_list_add_one_ref(): rename first parameter to "refname"
show_head_ref(): rename first parameter to "refname"
show_head_ref(): do not shadow name of argument
add_existing(): do not retain a reference to sha1
do_fetch(): clean up existing_refs before exiting
do_fetch(): reduce scope of peer_item
object_array_entry: fix memory handling of the name field
find_first_merges(): remove unnecessary code
find_first_merges(): initialize merges variable using initializer
fsck: don't put a void*-shaped peg in a char*-shaped hole
object_array_remove_duplicates(): rewrite to reduce copying
revision: use object_array_filter() in implementation of gc_boundary()
object_array: add function object_array_filter()
revision: split some overly-long lines
cmd_diff(): make it obvious which cases are exclusive of each other
cmd_diff(): rename local variable "list" -> "entry"
...
Previously, the memory management of the object_array_entry::name
field was inconsistent and undocumented. object_array_entries are
ultimately created by a single function, add_object_array_with_mode(),
which has an argument "const char *name". This function used to
simply set the name field to reference the string pointed to by the
name parameter, and nobody on the object_array side ever freed the
memory. Thus, it assumed that the memory for the name field would be
managed by the caller, and that the lifetime of that string would be
at least as long as the lifetime of the object_array_entry. But
callers were inconsistent:
* Some passed pointers to constant strings or argv entries, which was
OK.
* Some passed pointers to newly-allocated memory, but didn't arrange
for the memory ever to be freed.
* Some passed the return value of sha1_to_hex(), which is a pointer to
a statically-allocated buffer that can be overwritten at any time.
* Some passed pointers to refnames that they received from a
for_each_ref()-type iteration, but the lifetimes of such refnames is
not guaranteed by the refs API.
Bring consistency to this mess by changing object_array to make its
own copy for the object_array_entry::name field and free this memory
when an object_array_entry is deleted from the array.
Many callers were passing the empty string as the name parameter, so
as a performance optimization, treat the empty string specially.
Instead of making a copy, store a pointer to a statically-allocated
empty string to object_array_entry::name. When deleting such an
entry, skip the free().
Change the callers that were already passing copies to
add_object_array_with_mode() to either skip the copy, or (if the
memory needed to be allocated anyway) freeing the memory itself.
A part of this commit effectively reverts
70d26c6e76 read_revisions_from_stdin: make copies for handle_revision_arg
because the copying introduced by that commit (which is still
necessary) is now done at a deeper level.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Optimizes object lookup when the object hashtable starts to become
crowded.
* jk/lookup-object-prefer-latest:
lookup_object: prioritize recently found objects
The old version copied one entry to its destination position, then
deleted any matching entries from the tail of the array. This
required the tail of the array to be copied multiple times. It didn't
affect the complexity of the algorithm because the whole tail has to
be searched through anyway. But all the copying was unnecessary.
Instead, check for the existence of an entry with the same name in the
*head* of the list before copying an entry to its final position.
This way each entry has to be copied at most one time.
Extract a helper function contains_name() to do a bit of the work.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a function that allows unwanted entries in an object_array to be
removed. This encapsulation is a step towards giving object_array
ownership of its entries' name memory.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make "grep" honor the "--textconv" option also for the object case, i.e.
when used with an argument "rev:path".
Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The lookup_object function is backed by a hash table of all
objects we have seen in the program. We manage collisions
with a linear walk over the colliding entries, checking each
with hashcmp(). The main cost of lookup is in these
hashcmp() calls; finding our item in the first slot is
cheaper than finding it in the second slot, which is cheaper
than the third, and so on.
If we assume that there is some locality to the object
lookups (e.g., if X and Y collide, and we have just looked
up X, the next lookup is more likely to be for X than for
Y), then we can improve our average lookup speed by checking
X before Y.
This patch does so by swapping a found item to the front of
the collision chain. The p0001 perf test reveals that this
does indeed exploit locality in the case of "rev-list --all
--objects":
Test origin this tree
-------------------------------------------------------------------------
0001.1: rev-list --all 0.40(0.38+0.02) 0.40(0.36+0.03) +0.0%
0001.2: rev-list --all --objects 2.24(2.17+0.05) 1.86(1.79+0.05) -17.0%
This is not surprising, as the full object traversal will
hit the same tree entries over and over (e.g., for every
commit that doesn't change "Documentation/", we will have to
look up the same sha1 just to find out that we already
processed it).
The reason why this technique works (and does not violate
any properties of the hash table) is subtle and bears some
explanation. Let's imagine we get a lookup for sha1 `X`, and
it hashes to bucket `i` in our table. That stretch of the
table may look like:
index | i-1 | i | i+1 | i+2 |
-----------------------------------
entry ... | A | B | C | X | ...
-----------------------------------
We start our probe at i, see that B does not match, nor does
C, and finally find X. There may be multiple C's in the
middle, but we know that there are no empty slots (or else
we would not find X at all).
We do not know the original index of B; it may be `i`, or it
may be less than i (e.g., if it were `i-1`, it would collide
with A and spill over into the `i` bucket). So it is
acceptable for us to move it to the right of a contiguous
stretch of entries (because we will find it from a linear
walk starting anywhere at `i` or before), but never to the
left (if we moved it to `i-1`, we would miss it when
starting our walk at `i`).
We do know the original index of X; it is `i`, so it is safe
to place it anywhere in the contiguous stretch between `i`
and where we found it (`i+2` in the this case).
This patch does a pure swap; after finding X in the
situation above, we would end with:
index | i-1 | i | i+1 | i+2 |
-----------------------------------
entry ... | A | X | C | B | ...
-----------------------------------
We could instead bump X into the `i` slot, and then shift
the whole contiguous chain down by one, resulting in:
index | i-1 | i | i+1 | i+2 |
-----------------------------------
entry ... | A | X | B | C | ...
-----------------------------------
That puts our chain in true most-recently-used order.
However, experiments show that it is not any faster (and in
fact, is slightly slower due to the extra manipulation).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Many call-sites of parse_object assume that they will get a
non-NULL return value; this is not the case if we encounter
an error while parsing the object.
This patch adds a wrapper function around parse_object that
handles dying automatically, and uses it anywhere we
immediately try to access the return value as a non-NULL
pointer (i.e., anywhere that we would currently segfault).
This wrapper may also be useful in other places. The most
obvious one is code like:
o = parse_object(sha1);
if (!o)
die(...);
However, these should not be mechanically converted to
parse_object_or_die, as the die message is sometimes
customized. Later patches can address these sites on a
case-by-case basis.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The error handling routines add a newline. Remove
the duplicate ones in error messages.
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git push --recurse-submodules" learns to optionally look into the
histories of submodules bound to the superproject and push them out.
By Heiko Voigt
* hv/submodule-recurse-push:
push: teach --recurse-submodules the on-demand option
Refactor submodule push check to use string list instead of integer
Teach revision walking machinery to walk multiple times sequencially
Previously it was not possible to iterate revisions twice using the
revision walking api. We add a reset_revision_walk() which clears the
used flags. This allows us to do multiple sequencial revision walks.
We add the appropriate calls to the existing submodule machinery doing
revision walks. This is done to avoid surprises if future code wants to
call these functions more than once during the processes lifetime.
Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Traditionally, all the callers of check_sha1_signature() first
called read_sha1_file() to prepare the whole object data in core,
and called this function. The function is used to revalidate what
we read from the object database actually matches the object name we
used to ask for the data from the object database.
Update the API to allow callers to pass NULL as the object data, and
have the function read and hash the object data using streaming API
to recompute the object name, without having to hold everything in
core at the same time. This is most useful in parse_object() that
parses a blob object, because this caller does not have to keep the
actual blob data around in memory after a "struct blob" is returned.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When parse_object is called, we do the following:
1. read the object data into a buffer via read_sha1_file
2. call parse_object_buffer, which then:
a. calls the appropriate lookup_{commit,tree,blob,tag}
to either create a new "struct object", or to find
an existing one. We know the appropriate type from
the lookup in step 1.
b. calls the appropriate parse_{commit,tree,blob,tag}
to parse the buffer for the new (or existing) object
In step 2b, all of the called functions are no-ops for
object "X" if "X->object.parsed" is set. I.e., when we have
already parsed an object, we end up going to a lot of work
just to find out at a low level that there is nothing left
for us to do (and we throw away the data from read_sha1_file
unread).
We can optimize this by moving the check for "do we have an
in-memory object" from 2a before the expensive call to
read_sha1_file in step 1.
This might seem circular, since step 2a uses the type
information determined in step 1 to call the appropriate
lookup function. However, we can notice that all of the
lookup_* functions are backed by lookup_object. In other
words, all of the objects are kept in a master hash table,
and we don't actually need the type to do the "do we have
it" part of the lookup, only to do the "and create it if it
doesn't exist" part.
This can save time whenever we call parse_object on the same
sha1 twice in a single program. Some code paths already
perform this optimization manually, with either:
if (!obj->parsed)
obj = parse_object(obj->sha1);
if you already have a "struct object", or:
struct object *obj = lookup_unknown_object(sha1);
if (!obj || !obj->parsed)
obj = parse_object(sha1);
if you don't. This patch moves the optimization into
parse_object itself.
Most git operations won't notice any impact. Either they
don't parse a lot of duplicate sha1s, or the calling code
takes special care not to re-parse objects. I timed two
code paths that do benefit (there may be more, but these two
were immediately obvious and easy to time).
The first is fast-export, which calls parse_object on each
object it outputs, like this:
object = parse_object(sha1);
if (!object)
die(...);
if (object->flags & SHOWN)
return;
which means that just to realize we have already shown an
object, we will read the whole object from disk!
With this patch, my best-of-five time for "fast-export --all" on
git.git dropped from 26.3s to 21.3s.
The second case is upload-pack, which will call parse_object
for each advertised ref (because it needs to peel tags to
show "^{}" entries). This doesn't matter for most
repositories, because they don't have a lot of refs pointing
to the same objects. However, if you have a big alternates
repository with a shared object db for a number of child
repositories, then the alternates repository will have
duplicated refs representing each of its children.
For example, GitHub's alternates repository for git.git has
~120,000 refs, of which only ~3200 are unique. The time for
upload-pack to print its list of advertised refs dropped
from 3.4s to 0.76s.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When receive-pack & fetch-pack are run and store the pack obtained over
the wire to a local repository, they internally run the index-pack command
with the --strict option. Make sure that we reject incoming packfile that
records objects twice to avoid spreading such a damage.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Most callers want to silently get a replacement object, and they do not
care what the real name of the replacement object is. Worse yet, no sane
interface to return the underlying object without replacement is provided.
Remove the function and make only the few callers that want the name of
the replacement object find it themselves.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change some expanded tabs (spaces) to tabs in object.c.
Signed-off-by: Jared Hance <jaredhance@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
