chore(kotlin-sdk): tx-decode follow-up — blob hardening, net_from_ord hoist, prevVout docs (#4187 review)

[bfoss765]

Small follow-up promised on #4187, addressing @shumkov's three post-approval review notes on the Kotlin tx-decode JNI binding:

1. Blob hardening (rs-unified-sdk-jni/src/tx_decode.rs) — the output encoder wrote script_pubkey_len unconditionally but the script bytes only when the pointer was non-null, so a defensively-null pointer with a nonzero length field could shift every subsequent field in the blob. Length and bytes are now written together: a null (or empty) script encodes as length 0, never a nonzero length without its bytes. Pinned by a new unit test with a hand-built null-script fixture whose length field deliberately lies. The cross-pinned Kotlin/Rust fixture blob is unchanged.
2. net_from_ord deduplication — tx_decode.rs had added the third private copy (after transactions.rs and identity.rs). There is now a single shared support::net_from_ord; rs_sdk_ffi::FFINetwork and platform_wallet_ffi::FFINetwork are both re-exports of dash_network::ffi::FFINetwork, so the one helper serves every module. A fourth identical copy in persistence.rs was consolidated too. The exhaustive ordinal test moved to support.rs.
3. prevVout signedness — documented rather than retyped: DecodedTransaction.Input.prevVout stays a signed Int carrying the raw u32 bits (the coinbase sentinel 0xFFFFFFFF reads as -1; Swift's UInt32 shows 4294967295), with KDoc spelling that out and a new prevVoutUnsigned: Long convenience view for the numeric u32 / Swift-parity rendering. The existing pinned -1 test is untouched; assertions for the unsigned view were added alongside it.

Verified: cargo test -p rs-unified-sdk-jni (37 pass), cargo clippy -p rs-unified-sdk-jni --all-targets clean, and kotlin-sdk :sdk:compileDebugKotlin + :sdk:testDebugUnitTest green (TransactionDecoderTest 4/4). Each commit builds and tests green standalone.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added an unsigned view of transaction input output indexes, supporting the full 32-bit range and clearly representing coinbase inputs.

• Bug Fixes

  • Improved transaction encoding when input or output data is unavailable or contains inconsistent lengths, preventing malformed data from causing decoding issues.
  • Standardized network handling across SDK operations, including safe fallback behavior for unknown network values.

• Documentation

  • Clarified how signed and unsigned transaction output indexes are represented.

[thepastaclaw]

🕓 Ready for review — 30 ahead in queue (commit d6d0313)
Queue position: 31/72 · 2 reviews active
ETA: start ~02:55 UTC · complete ~03:23 UTC (median 28m across 30 recent reviews; 2 slots)
Queued 22h 42m ago · Last checked: 2026-07-22 19:40 UTC

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: dd9b927a-50c7-47a5-b870-947ae49a8e90

📥 Commits

Reviewing files that changed from the base of the PR and between 5b8dbf4 and d6d0313.

📒 Files selected for processing (7)

• packages/kotlin-sdk/sdk/src/main/kotlin/org/dashfoundation/dashsdk/keywallet/TransactionDecoder.kt
• packages/kotlin-sdk/sdk/src/test/kotlin/org/dashfoundation/dashsdk/keywallet/TransactionDecoderTest.kt
• packages/rs-unified-sdk-jni/src/identity.rs
• packages/rs-unified-sdk-jni/src/persistence.rs
• packages/rs-unified-sdk-jni/src/support.rs
• packages/rs-unified-sdk-jni/src/transactions.rs
• packages/rs-unified-sdk-jni/src/tx_decode.rs

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📝 Walkthrough

Walkthrough

The JNI SDK centralizes network ordinal conversion and hardens packed transaction encoding for null pointers. The Kotlin SDK documents signed prevVout preservation and adds an unsigned 32-bit accessor with fixture and coinbase coverage.

Changes

JNI transaction updates

Layer / File(s)	Summary
Shared JNI network mapping packages/rs-unified-sdk-jni/src/support.rs, packages/rs-unified-sdk-jni/src/{identity,persistence,transactions,tx_decode}.rs	Adds shared ordinal-to-FFINetwork conversion with a Testnet fallback, updates JNI imports and removes duplicated local helpers, and validates the mappings.
Defensive transaction encoding packages/rs-unified-sdk-jni/src/tx_decode.rs	Encodes zero counts or script lengths when decoded pointers or script data are absent, updates the packed-layout documentation, and adds null-pointer encoding tests.

Kotlin unsigned transaction index

Layer / File(s)	Summary
Unsigned previous-output index contract packages/kotlin-sdk/sdk/src/main/kotlin/org/dashfoundation/dashsdk/keywallet/TransactionDecoder.kt, packages/kotlin-sdk/sdk/src/test/kotlin/org/dashfoundation/dashsdk/keywallet/TransactionDecoderTest.kt	Documents bit-preserving signed prevVout behavior, adds prevVoutUnsigned, and tests regular and coinbase representations.

Estimated code review effort: 2 (Simple) | ~15 minutes

Suggested labels: Client Only

Suggested reviewers: quantumexplorer, bezibalazs, shumkov

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main follow-up changes: blob hardening, shared net_from_ord, and prevVout documentation/unsigned view.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[shumkov]

Reviewed (two independent passes) — all three #4187 follow-up items are done completely and correctly: the null-pointer/length-lie hazards are guarded at both the script and array levels with tests that hand-build lying FFI structs, the net_from_ord hoist actually removed a fourth private copy (persistence.rs) beyond the three flagged, with ordinal semantics preserved and test-pinned, and prevVoutUnsigned documents and widens the signed-bits contract properly. The fixture cross-pin is untouched, which is correct — real decode output can never produce the null-with-nonzero-length state. Nothing to add; ready.