We lose the histograms, but this prepares it for upstream merge.

One free record is not "uncoalesced".

Remove code duplication, and allow unit tests (which #include both).

Test compiled with warnings:
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c: In function ‘main’:
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:18:2: warning: taking address of expression of type ‘void’
/home/rusty/devel/cvs/ccan/ccan/typesafe_cb/test/compile_ok-typesafe_cb-NULL.c:19:2: warning: taking address of expression of type ‘void’

If they specify valgrind options in their _info, we should use them when
running with --db-attach=yes, too.

This is complicated by valgrind's limited options, and our desire not to run
valgrind twice (it's already the slowest part of the tests).

Ideally I'd like a different error code for each kind of error.  I
could parse and pretty-print the XML output, but instead I just parse
the human-readable (which is fragile).

It requires that we build the objects first.

trbt_delete32() was broken and caused SEGV as soon as you tried to
delete an object from a tree.

Rework trbt_delete32() to instead just call talloc_free() instread of trying
to call delete_node() directly.
This makes the "from_destructor" argument to delete_node() redundant
so that parameter is removed too.
Signed-off-by: Ronnie Sahlberg <sahlberg@lenovo-laptop.(none)>

Unfortunately, gcc only warns if it sees an unknown attribute (in this case, gcc 4.1 vs "cold").

cc -g -Wall -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations -I. -MD -Werror   -c -o tools/ccanlint/tests/examples_run.o tools/ccanlint/tests/examples_run.c
cc1: warnings being treated as errors
tools/ccanlint/tests/examples_run.c: In function ‘scan_forv’:
tools/ccanlint/tests/examples_run.c:37: warning: passing argument 2 of ‘__builtin_va_copy’ discards qualifiers from pointer target type
tools/ccanlint/tests/examples_run.c:43: warning: passing argument 4 of ‘scan_forv’ from incompatible pointer type
tools/ccanlint/tests/examples_run.c:52: warning: passing argument 4 of ‘scan_forv’ from incompatible pointer type
tools/ccanlint/tests/examples_run.c:60: warning: passing argument 4 of ‘scan_forv’ from incompatible pointer type
tools/ccanlint/tests/examples_run.c: In function ‘scan_for’:
tools/ccanlint/tests/examples_run.c:78: warning: passing argument 4 of ‘scan_forv’ from incompatible pointer type
make: *** [tools/ccanlint/tests/examples_run.o] Error 1

It really doesn't like constifying a va_arg, so remove the const declaration.

Chris Cowan tracked down a SEGV in sub_alloc: idp->level can actually
be equal to 7 (MAX_LEVEL) there, as it can be in sub_remove.

(Imported from SAMBA commit 2db1987f5a3a)

Right-shifting signed integers in undefined; indeed it seems that on
AIX with their compiler, doing a 30-bit shift on (INT_MAX-200) gives
0, not 1 as we might expect (THIS WAS WRONG, REAL FIX LATER).

The obvious fix is to make id and oid unsigned: l (level count) is also
logically unsigned.

(Note: Samba doesn't generally get to ids > 1 billion, but ctdb does)
Reported-by: Chris Cowan <cc@us.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

(Imported from b53f8c187de8)

Author: Rusty Russell <rusty@rustorp.com.au>
Date:   Thu Jun 10 13:27:51 2010 -0700

Since idtree assigns sequentially, it rarely reaches high numbers.
But such numbers can be forced with idr_get_new_above(), and that
reveals two bugs:

1) Crash in sub_remove() caused by pa array being too short.
2) Shift by more than 32 in _idr_find(), which is undefined, causing
   the "outside the current tree" optimization to misfire and return NULL.

This causes a SEGV on my laptop.

We insert comments when we massage or combine examples; don't let these
throw off our analysis (as happened for idtree.h).

We might as well use the compiled .o rather than all the little .o files.

Out-by-one error had us using character prior to declaration, eg, in
"static int *foo" we use "*foo".  This seems to compile, but is weird.

Commit da72623a added a typo; ccanlint caught it, but doesn't consider
test compile failing to be fatal (it should!).

Specifically the linked free tables, and reflect on the status of each
point of the design document.

Rather than overloading TDB_USED_MAGIC and the hash value as we do now.
We also rename "free list" to the more-accurate "free table" everywhere.

Currently we fall back to copying data during a transaction, but we don't
need to in many cases.  Grant direct access in those cases.

Before:
$ ./speed --transaction 1000000
Adding 1000000 records:  2409 ns (59916680 bytes)
Finding 1000000 records:  1156 ns (59916680 bytes)
Missing 1000000 records:  604 ns (59916680 bytes)
Missing 1000000 records:  604 ns (59916680 bytes)
Traversing 1000000 records:  1226 ns (59916680 bytes)
Deleting 1000000 records:  1556 ns (119361928 bytes)
Re-adding 1000000 records:  2326 ns (119361928 bytes)
Appending 1000000 records:  3269 ns (246656880 bytes)
Churning 1000000 records:  5613 ns (338235248 bytes)

After:
$ ./speed --transaction 1000000
Adding 1000000 records:  1902 ns (59916680 bytes)
Finding 1000000 records:  1032 ns (59916680 bytes)
Missing 1000000 records:  606 ns (59916680 bytes)
Missing 1000000 records:  606 ns (59916680 bytes)
Traversing 1000000 records:  741 ns (59916680 bytes)
Deleting 1000000 records:  1347 ns (119361928 bytes)
Re-adding 1000000 records:  1727 ns (119361928 bytes)
Appending 1000000 records:  2561 ns (246656880 bytes)
Churning 1000000 records:  4403 ns (338235248 bytes)

This is a precursor to direct access during transactions: they care about
whether we are going to read or write to the file.

If we get enough hash collisions, we can run out of hash bits; this almost
certainly is caused by a deliberate attempt to break the tdb (hash bombing).

Implement chained records for this case; they're slow but will keep the
rest of the database functioning.

We have to unlock during coalescing, so we mark records specially to indicate
to tdb_check that they're not on any list, and to prevent other coalescers
from grabbing them.

Use a special free list number, rather than a new magic.

We already have 10 hash bits encoded in the offset itself; we only get
here incorrectly about 1 time in 1000, so it's a pretty minor
optimization at best.

Nonetheless, we have the information, so let's check it before
accessing the key.  This reduces the probability of a false keycmp by
another factor of 2000.

Logged errors should always set tdb->ecode before they are called, and
there's little reason to have a sprintf-style logging function since
we can do the formatting internally.

Change the tdb_log attribute to just take a "const char *", and create
a new tdb_logerr() helper which sets ecode and calls it.  As a bonus,
mark it COLD so the compiler can optimize appropriately knowing that
it's unlikely to be invoked.

There was an idea that we would use a bit to indicate that we didn't have
the full hash value; this would allow us to move records down when we
expanded a hash without rehashing them.

There's little evidence that rehashing in this case is particularly
expensive, so remove the bit.  We use that bit simply to indicate that
an offset refers to a subhash instead.

This is one case where getting rid of tdb_get() cost us.  Also, we
add more read-only checks.

Before we removed tdb_get:
Adding 1000000 records:  6480 ns (59900296 bytes)
Finding 1000000 records:  2839 ns (59900296 bytes)
Missing 1000000 records:  2485 ns (59900296 bytes)
Traversing 1000000 records:  2598 ns (59900296 bytes)
Deleting 1000000 records:  5342 ns (59900296 bytes)
Re-adding 1000000 records:  5613 ns (59900296 bytes)
Appending 1000000 records:  12194 ns (93594224 bytes)
Churning 1000000 records:  14549 ns (93594224 bytes)

Now:
Adding 1000000 records:  6307 ns (59900296 bytes)
Finding 1000000 records:  2801 ns (59900296 bytes)
Missing 1000000 records:  2515 ns (59900296 bytes)
Traversing 1000000 records:  2579 ns (59900296 bytes)
Deleting 1000000 records:  5225 ns (59900296 bytes)
Re-adding 1000000 records:  5878 ns (59900296 bytes)
Appending 1000000 records:  12665 ns (93594224 bytes)
Churning 1000000 records:  16090 ns (93594224 bytes)

We have four internal helpers for reading data from the database:
1) tdb_read_convert() - read (and convert) into a buffer.
2) tdb_read_off() - read (and convert) and offset.
3) tdb_access_read() - malloc or direct access to the database.
4) tdb_get() - copy into a buffer or direct access to the database.

The last one doesn't really buy us anything, so remove it (except for
tdb_read_off/tdb_write_off, see next patch).

Before:
Adding 1000000 records:  6480 ns (59900296 bytes)
Finding 1000000 records:  2839 ns (59900296 bytes)
Missing 1000000 records:  2485 ns (59900296 bytes)
Traversing 1000000 records:  2598 ns (59900296 bytes)
Deleting 1000000 records:  5342 ns (59900296 bytes)
Re-adding 1000000 records:  5613 ns (59900296 bytes)
Appending 1000000 records:  12194 ns (93594224 bytes)
Churning 1000000 records:  14549 ns (93594224 bytes)

After:
Adding 1000000 records:  6497 ns (59900296 bytes)
Finding 1000000 records:  2854 ns (59900296 bytes)
Missing 1000000 records:  2563 ns (59900296 bytes)
Traversing 1000000 records:  2735 ns (59900296 bytes)
Deleting 1000000 records:  11357 ns (59900296 bytes)
Re-adding 1000000 records:  8145 ns (59900296 bytes)
Appending 1000000 records:  10939 ns (93594224 bytes)
Churning 1000000 records:  18479 ns (93594224 bytes)

Now it will build copies of other ccan deps if it can't find them.

We currently only have one, so shortcut the case where we want our current
one.