This fixes test_bitcoin failures on openbsd reported by dhill on IRC.
On some systems rand() is a simple LCG over 2^31 and so it produces
an even-odd sequence. ApproximateBestSubset was only using the least
significant bit and so every run of the iterative solver would be the
same for some inputs, resulting in some pretty dumb decisions.
Using something other than the least significant bit would paper over
the issue but who knows what other way a system's rand() might get us
here. Instead we use an internal RNG with a period of something like
2^60 which is well behaved. This also makes it possible to make the
selection deterministic for the tests, if we wanted to implement that.
* During block verification (when parallelism is requested), script
check actions are stored instead of being executed immediately.
* After every processed transactions, its signature actions are
pushed to a CScriptCheckQueue, which maintains a queue and some
synchronization mechanism.
* Two or more threads (if enabled) start processing elements from
this queue,
* When the block connection code is finished processing transactions,
it joins the worker pool until the queue is empty.
As cs_main is held the entire time, and all verification must be
finished before the block continues processing, this does not reach
the best possible performance. It is a less drastic change than
some more advanced mechanisms (like doing verification out-of-band
entirely, and rolling back blocks when a failure is detected).
The -par=N flag controls the number of threads (1-16). 0 means auto,
and is the default.
These flags select features to be enabled/disabled during script
evaluation/checking, instead of several booleans passed along.
Currently these flags are defined:
* SCRIPT_VERIFY_P2SH: enable BIP16-style subscript evaluation
* SCRIPT_VERIFY_STRICTENC: enforce strict adherence to pubkey/sig encoding standards.
Flushes the blktree/ and coins/ databases, and reindexes the
block chain files, as if their contents was loaded via -loadblock.
Based on earlier work by Jeff Garzik.
signrawtransaction was unable to sign pay-to-script-hash inputs
when given the list of private keys to use. With this commit
you can provide the p2sh redemption script in the list of
inputs.
To prevent excessive copying of CCoins in and out of the CCoinsView
implementations, introduce a GetCoins() function in CCoinsViewCache
with returns a direct reference. The block validation and connection
logic is updated to require caching CCoinsViews, and exploits the
GetCoins() function heavily.
This switches bitcoin's transaction/block verification logic to use a
"coin database", which contains all unredeemed transaction output scripts,
amounts and heights.
The name ultraprune comes from the fact that instead of a full transaction
index, we only (need to) keep an index with unspent outputs. For now, the
blocks themselves are kept as usual, although they are only necessary for
serving, rescanning and reorganizing.
The basic datastructures are CCoins (representing the coins of a single
transaction), and CCoinsView (representing a state of the coins database).
There are several implementations for CCoinsView. A dummy, one backed by
the coins database (coins.dat), one backed by the memory pool, and one
that adds a cache on top of it. FetchInputs, ConnectInputs, ConnectBlock,
DisconnectBlock, ... now operate on a generic CCoinsView.
The block switching logic now builds a single cached CCoinsView with
changes to be committed to the database before any changes are made.
This means no uncommitted changes are ever read from the database, and
should ease the transition to another database layer which does not
support transactions (but does support atomic writes), like LevelDB.
For the getrawtransaction() RPC call, access to a txid-to-disk index
would be preferable. As this index is not necessary or even useful
for any other part of the implementation, it is not provided. Instead,
getrawtransaction() uses the coin database to find the block height,
and then scans that block to find the requested transaction. This is
slow, but should suffice for debug purposes.
Special serializer/deserializer for amount values. It is optimized for
values which have few non-zero digits in decimal representation. Most
amounts currently in the txout set take only 1 or 2 bytes to
represent.
Variable-length integers: bytes are a MSB base-128 encoding of the number.
The high bit in each byte signifies whether another digit follows. To make
the encoding is one-to-one, one is subtracted from all but the last digit.
Thus, the byte sequence a[] with length len, where all but the last byte
has bit 128 set, encodes the number:
(a[len-1] & 0x7F) + sum(i=1..len-1, 128^i*((a[len-i-1] & 0x7F)+1))
Properties:
* Very small (0-127: 1 byte, 128-16511: 2 bytes, 16512-2113663: 3 bytes)
* Every integer has exactly one encoding
* Encoding does not depend on size of original integer type
