This commit implements a new type, named scriptNum, for handling all
numeric values used in scripts and converts the code over to make use of
it. This is being done for a few of reasons.
First, the consensus rules for handling numeric values in the scripts
require special handling with subtle semantics. By encapsulating those
details into a type specifically dedicated to that purpose, it
simplifies the code and generally helps prevent improper usage.
Second, the new type is quite a bit more efficient than big.Ints which
are designed to be arbitrarily large and thus involve a lot of heap
allocations and additional multi-precision bookkeeping. Because this
new type is based on an int64, it allows the numbers to be stack
allocated thereby eliminating a lot of GC and also eliminates the extra
multi-precision arithmetic bookkeeping.
The use of an int64 is possible because the consensus rules dictate that
when data is interpreted as a number, it is limited to an int32 even
though results outside of this range are allowed so long as they are not
interpreted as integers again themselves. Thus, the maximum possible
result comes from multiplying a max int32 by itself which safely fits
into an int64 and can then still appropriately provide the serialization
of the larger number as required by consensus.
Finally, it more closely resembles the implementation used by Bitcoin
Core and thus makes is easier to compare the behavior between the two
implementations.
This commit also includes a full suite of tests with 100% coverage of
the semantics of the new type.
- Remove all redundant opcode tests in favor of the JSON-based tests
in the data directory.
- Remove duplicate stack nip test
- Add new tests to data/script_invalid.json to exercise additional
negative error paths
- Remove old unneeded pubkey trace code from opcodeCheckSig
- Simplify and improve the disassembly print function
- Add new tests to directly test all individual opcode disassembly
- Add new tests to directly test opcode disabled function which does not
get invoked during ordinary execution
- Improve test coverage of opcode.go
This commit unexports the Stack type since it is only intended to be
used internally during script execution. Further, the engine exposes
the {G,S}etStack and {G,S}etAltStack functions which return the items as
a slice of byte slices ([][]byte) for caller access while stepping.
This commit contains the entire btcscript repository along with several
changes needed to move all of the files into the txscript directory in
order to prepare it for merging. This does NOT update btcd or any of the
other packages to use the new location as that will be done separately.
- All import paths in the old btcscript test files have been changed to the
new location
- All references to btcscript as the package name have been chagned to
txscript
This is ongoing work toward #214.
