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Merge pull request #1268 from JeremyRubin/patch-1

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Fix BIP-119 Typo + Clarify the reasons for 32 bit lengths
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Luke Dashjr 2022-01-15 23:14:23 +00:00 • committed by GitHub
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@ -356,13 +356,15 @@ spent. In general, using CHECKTEMPLATEVERIFY with more than one input is difficu
and exposes subtle issues, so multiple inputs should not be used except in
specific applications.
In principal, committing to the Sequences Hash (below) implicitly commits to the number of inputs,
In principle, committing to the Sequences Hash (below) implicitly commits to the number of inputs,
making this field strictly redundant. However, separately committing to this number makes it easier
to construct DefaultCheckTemplateVerifyHash from script.
We treat the number of inputs as a `uint32_t` because signature checking code expects nIn to be an
`unsigned int`, even though in principal a transaction can encode more than a `uint32_t`'s worth of
inputs.
We treat the number of inputs as a `uint32_t` because Bitcoin's consensus decoding logic limits vectors
to `MAX_SIZE=33554432` and that is larger than `uint16_t` and smaller than `uint32_t`. 32 bits is also
friendly for manipulation using Bitcoin's current math opcodes, should `OP_CAT` be added. Note that
the max inputs in a block is further restricted by the block size to around 25,000, which would fit
into a `uint16_t`, but that is an uneccessary abstraction leak.
=====Committing to the Sequences Hash=====
@ -378,12 +380,14 @@ script.
=====Committing to the Number of Outputs=====
In principal, committing to the Outputs Hash (below) implicitly commits to the number of outputs,
In principle, committing to the Outputs Hash (below) implicitly commits to the number of outputs,
making this field strictly redundant. However, separately committing to this number makes it easier
to construct DefaultCheckTemplateVerifyHash from script.
We treat the number of outputs as a `uint32_t` because a `COutpoint` index is a `uint32_t`, even
though in principal a transaction could encode more outputs.
We treat the number of outputs as a `uint32_t` because a `COutpoint` index is a `uint32_t`.
Further, Bitcoin's consensus decoding logic limits vectors to `MAX_SIZE=33554432` and that is
larger than `uint16_t` and smaller than `uint32_t`. 32 bits is also friendly for manipulation using
Bitcoin's current math opcodes, should `OP_CAT` be added.
=====Committing to the outputs hash=====