Every LightClient copied the Sapling spend and output parameters, which
rust-embed already compiles into the binary, onto the heap: 51,551,256
bytes (49.2 MiB) of private memory per live client, whether or not it
ever sent anything.
LightClient::sapling_output and sapling_spend are now Cow<'static, [u8]>
and borrow the embedded image. set_sapling_params still stores an owned
copy, with its is-empty guard, hash checks and disk write unchanged. The
prover receives the same bytes.
Behaviour changes:
- about 49 MiB less anonymous memory per live LightClient; the wallet
file and JSON are unchanged;
- the first send or shield pages the 51.5 MB of embedded params in from
the binary, where client creation used to copy them (an estimated
0.3-1 s from the AppImage);
- the public fields sapling_output and sapling_spend change type from
Vec<u8> to Cow<'static, [u8]>: a Rust API change, with no C ABI or
exported-symbol change.
tests/sapling_params.rs checks that a restored, a new and a reloaded
client all borrow the embedded image (same pointer, pinned lengths and
SHA-256), that set_sapling_params keeps its guard and hash checks, and
that the borrowed params parse like a heap copy. An ignored test
measures 576 KiB of RssAnon growth for a second client, against 46.5 MiB
with the old heap copy.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
DanSandClaude Opus 5.5
6de9b5cc90