Although it is possible to get the command name for each msg type by
creating an instances of the type and calling the Command method against
it, it's slightly more efficient to simply allows callers to have direct
access to the exported constants.
This is currently really useful for the reject message since callers need
to be able to examine the command type to determine whether or not the
hash field needs to be included.
This commit adds a new function named SerializeSize to the public API for
MsgBlock which can be used to determine how many bytes the serialized data would
take without having to actually serialize it. In addition, it makes the
exported BlockVersion an untyped constant as well as changes the block and
tx versions to a signed integer to more closely match the protocol.
Finally, this commit also adds tests for the new function.
The following benchmark shows the difference between using the new
function to get the serialize size for a typical block and serializing
into a temporary buffer and taking the length of it:
Bufffer: BenchmarkBlockSerializeSizeBuffer 200000 27050 ns/op
New: BenchmarkBlockSerializeSizeNew 100000000 34 ns/op
Closes#19.
* Introduced common methods readVarBytes, writeVarBytes.
* Added type Alert which knows how to deserialize
the serialized payload and also serialize itself back.
* Updated MsgAlert BtcEncode/BtcDecode methods to handle the
new Alert.
* Sane limits are placed on variable length fields like SetCancel
and SetSubVer
serialization buffer in MsgTx's TxSha().
Benchmarking shows this is slightly faster due to avoiding the extra
garbage collection in addition to less peak memory usage.
Before: BenchmarkTxShaOld 500000 5626 ns/op
After: BenchmarkTxShaNew 500000 5457 ns/op
This commit exports the VarIntSerializeSize function to provide callers
with an easy method to determine how many bytes it would take to serialize
the passed value as a variable length integer.
The benchmark results for the current commit:
Before: BenchmarkDeserializeTx 500000 4018 ns/op
After: BenchmarkDeserializeTx 500000 3780 ns/op
The cumulative benchmark results since commit b7b700fd5a:
Before: BenchmarkDeserializeTx 200000 10665 ns/op
After: BenchmarkDeserializeTx 500000 3780 ns/op
This is part of the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
The benchmark results for the current commit:
Before: BenchmarkSerializeTx 1000000 1233 ns/op
After: BenchmarkSerializeTx 1000000 1083 ns/op
The cumulative benchmark results since commit b7b700fd5a:
Before: BenchmarkSerializeTx 1000000 5437 ns/op
After: BenchmarkSerializeTx 1000000 1083 ns/op
This is part of the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Before: BenchmarkWriteTxIn 5000000 422 ns/op
After: BenchmarkWriteTxIn 5000000 389 ns/op
This is part of the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Before: BenchmarkReadTxIn 1000000 2435 ns/op
After: BenchmarkReadTxIn 1000000 1427 ns/op
This is part of the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Before: BenchmarkReadTxOut 500000 4576 ns/op
After: BenchmarkReadTxOut 2000000 871 ns/op
This is part ef the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Before: BenchmarkWriteTxOut 500000 4050 ns/op
After: BenchmarkWriteTxOut 10000000 248 ns/op
This is part ef the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Before: BenchmarkReadOutPoint 500000 2946 ns/op
After: BenchmarkReadOutPoint 5000000 582 ns/op
This is part ef the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Before: BenchmarkWriteOutPoint 500000 2664 ns/op
After: BenchmarkWriteOutPoint 10000000 151 ns/op
This is part ef the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
This commit adds a new function named SerializeSize to the public API for
MsgTx, TxOut, and TxIn which can be used to determine how many bytes the
serialized data would take without having to actually serialize it.
The following benchmark shows the difference between using the new
function to get the serialize size for a typical transaction and
serializing into a temporary buffer and taking the length of it:
Bufffer: BenchmarkTxSerializeSizeBuffer 200000 7050 ns/op
New: BenchmarkTxSerializeSizeNew 100000000 18 ns/op
This is part of the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
Several of the bitcoin data structures contain variable length entries,
many of which have well-defined maximum limits. However, there are still
a few cases, such as variable length strings and number of transactions
which don't have clearly defined maximum limits. Instead they are only
limited by the maximum size of a message.
In order to efficiently decode messages, space is pre-allocated for the
slices which hold these variable length pieces as to avoid needing to
dynamically grow the backing arrays. Due to this however, it was
previously possible to claim extremely high slice lengths which exceed
available memory (or maximum allowed slice lengths).
This commit imposes limits to all of these cases based on calculating
the maximum possible number of elements that could fit into a message
and using those as sane upper limits.
The variable length string case was found (and tests added to hit it) by
drahn@ which prompted an audit to find all cases.
Several of the messages store the parts that have a variable number of
elements as slices. This commit modifies the code to choose sane defaults
for the backing arrays for the slices so when the entries are actually
appended, a lot of the overhead of growing the backing arrays and copying
the data multiple times is avoided.
Along the same lines, when decoding messages, the actual size is known and
now is pre-allocated instead of dynamically growing the backing array
thereby avoiding some overhead.
Both of these depend on the serialized bytes which are dependent on the
version field in the block/transaction. They must be independent of the
protocol version so there is no need to require it.
This commit introduces two new functions for MsgBlock and MsgTx named
Serialize and Deserialize. The functions provide a stable mechanism for
serializing and deserializing blocks and transactions to and from disk
without having to worry about the protocol version. Instead these
functions use the Version fields in the blocks and transactions.
These new functions differ from BtcEncode and BtcDecode in that the latter
functions are intended to encode/decode blocks and transaction from the
wire which technically can differ depending on the protocol version and
don't even really need to use the same format as the stored data.
Currently, there is no difference between the two, and due to how
intertwined they are in the reference implementaiton, they may not ever
diverge, but there is a difference and the goal for btcwire is to provide
a stable API that is flexible enough to deal with encoding changes.
The functions for generating transaction and block hashes contained a few
error checks for conditions which could never fail without run-time
panics. This commit removes those superfluous checks and adds explanatory
comments.
