feat: support create_external_arraybuffer#30
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ported from ChainSafe/lodestar-z#356 External array buffers have their lifetimes managed by V8's garbage collector, but their backing memory is still managed by the native implementation. We need to call `adjustExternalMemory` to let V8 know about the native allocations; and we need a finalizer to cleanup such allocations (which we add in this PR, and use in lodestar-z) More details from that PR: > This is one of possible likely causes for increased GC pressure on experiments to swap out blst-ts for lodestar-z/bls, as observed on feat2 and feat3 deployments in [this PR](ChainSafe/lodestar#9342). > > With external array buffers, V8 is only aware of the pointer to the backing memory, instead of having to track both the pointer and the backing memory. This means that during marking phase the GC does not have to walk the backing memory to mark it as 'live' - the frequency of the GC firing off is still the same, but each cycle does less work. > > This of course comes with a tradeoff, we need a **finalizer** to let V8 know how much external memory is in native heap so that the GC tells the native impl to free the useless memory. > > Though, regardless of the effect, we should still probably do this anyway, since [napi-rs does the same](https://github.com/napi-rs/napi-rs/blob/159395b365c583a6642ad481edc5708d9f36a24b/crates/napi/src/bindgen_runtime/js_values/arraybuffer.rs#L175), and only defaults to V8 managed array buffers if it is disallowed (like in Electron).
wemeetagain
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May 13, 2026
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lgtm, will wait for review from @nazarhussain
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LGTM. A plus would be to add some example in this file https://github.com/ChainSafe/zapi/blob/main/examples/js_dsl/mod.zig
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wemeetagain
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May 14, 2026
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ported from ChainSafe/lodestar-z#356
External array buffers have their lifetimes managed by V8's garbage collector, but their backing memory is still managed by the native implementation.
We need to call
adjustExternalMemoryto let V8 know about the native allocations; and we need a finalizer to cleanup such allocations (which we add in this PR, and use in lodestar-z)More details from that PR: