BIP0062 defines specific rules and canonical encodings for data pushes.
The existing script builder code already conformed to all but one of the
canonical data push rules that was added after it was originally
implemented (adding a single byte of 0x81 must be converted to
OP_1NEGATE). This commit implements that case and expands the existing
tests to explicitly cover all cases mentioned in BIP0062.
In addition, as a part of this change, the AddData function has been
modified so that any attempt to push more than the maximum script element
size bytes (520) in one push or any pushes the would cause the script to
exceed the maximum script bytes allowed by the script engine (10000) will
result in the final call to the Script function to only return the script
up to the point of the first error along with the error. This change
should have little effect on existing callers since they are almost
positively not creating scripts which violate these rules as they could
never be executed, however it does mean they need to check the new error
return.
Since the regression tests intentionally need to be able to exceed that
limit, a new function named AddFullData has been added which does not
enforce the limits, but still provides canonical encoding of the pushed
data.
Note that this commit does not affect consensus rules nor modify the
script engine.
Also, the tests have been marked so they can run in parallel.
This commit adds a new ScriptBuilder interface that can be used to build
custom scripts. It currently is fairly basic, but it allows you to push
raw opcodes, ints, and data while respecting canonical encoding. These
primitives are sufficient to build any script.
This could be improved upon with quite a few things. One example would be
functions for certain opcodes that take properly typed parameters to make
it harder to create invalid scripts.
For now though, it is already quite useful since it handles all of the
opcode selection for canonical data pushes and integer encoding.
The initial discussion took place in #5.
