Replace legacy db_*_i64 intrinsics with KV intrinsics

[heifner]

Summary

This PR replaces the 60 legacy EOSIO db_*_i64 and db_idx* host functions with 22 new KV (key-value) database intrinsics. All contract storage now uses a unified key-value model instead of the legacy multi-table system inherited from EOSIO.

Companion CDT PR: Wire-Network/wire-cdt#41

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Why

The legacy database layer is a complex subsystem inherited from EOSIO:

• 60 host functions (10 primary + 50 secondary index) with intricate iterator caching, table_id indirection, and 6 different chainbase object types
• Every contract operation requires a two-step lookup: find table_id_object → then find key_value_object within it
• Five separate secondary index types (idx64, idx128, idx256, idx_double, idx_long_double), each with 10 host functions and its own chainbase object
• The iterator cache maintains raw pointers into chainbase that can be invalidated by session rollback — a recurring source of upstream security fixes

Wire is a new chain that hasn't launched yet. We have the rare opportunity to replace this before any production state exists.

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What Changed

Chain Library (22 new intrinsics replacing 60)

Category	Old	New
Primary CRUD	db_store/update/remove/get_i64	kv_set, kv_get, kv_erase, kv_contains
Primary iteration	db_find/next/previous/lowerbound/upperbound/end_i64	kv_it_create/destroy/status/next/prev/lower_bound/key/value
Secondary indices	50 functions across 5 types	12 unified kv_idx_* functions

Key Design Decisions

1. SSO (Small String Optimization) — Keys ≤24 bytes stored inline in the chainbase object, avoiding heap allocation. The standard key layout [table:8B][scope:8B][pk:8B] = 24 bytes fits exactly in SSO.

2. Integer fast-path comparator — 8-byte keys compared via bswap64 + integer comparison instead of memcmp. Endian-portable via kv_load_be64 (bswap on LE, identity on BE).

3. Unified secondary index — One kv_index_object type replaces all 5 legacy secondary index types. Secondary keys stored as variable-length bytes with order-preserving encoding.

4. key_format field — Each row has a key_format (0=raw, 1=standard 24-byte). SHiP uses this to deterministically decode keys back to legacy (code, scope, table, pk) format.

5. kv_idx_find_secondary/kv_idx_lower_bound return int32_t — Returns -1 for not-found (no handle allocated), >= 0 for valid handle. kv_idx_lower_bound returns handle in iterator_end state when bound is past all entries but table is non-empty (enables kv_idx_prev for reverse iteration). Saves 1-2 host function calls per secondary lookup.

6. Iterator cached-ID fast path — Iterators cache the chainbase object ID. On next/prev, the fast path does db.find(cached_id) + O(1) iterator_to + O(1) advance, avoiding the expensive composite-key lower_bound re-seek. Falls back to composite key lookup only when the row was erased mid-iteration. The key/value read functions also use the cached ID, eliminating composite index lookups for the common case. Per-step cost drops from 3 composite index lookups to 3 simple integer-key lookups (~3x faster constant factor).

RPC API

• get_table_rows — Fully functional for both primary AND secondary index queries. Supports all key types: i64, i128, sha256/i256, float64, float128. Forward/reverse iteration, pagination with next_key, scope filtering.
• get_kv_rows — New endpoint for querying format=0 (raw_table) entries with composite key decoding. Uses be_key_codec with NUL-escape string encoding.
• get_table_by_scope — Reimplemented with KV prefix scanning.

SHiP Compatibility

• Format=1 rows (standard 24-byte keys) emitted as "contract_row" — backward compatible with Hyperion
• Format=0 rows (raw keys) emitted as "contract_row_kv" — new delta type, clients opt in
• Breaking: contract_table deltas removed (tables are implicit in KV key prefixes). Secondary index deltas consolidated into contract_index_kv (generic bytes instead of typed fields). SHiP consumers that parse secondary index deltas or track table creation/removal events must be updated.

Deep Mind

• Standard keys (format=1) emit DB_OP INS/UPD/REM — same format as legacy for backward compatibility
• Raw keys (format=0) emit KV_OP INS/UPD/REM — new log format with hex-encoded keys
• UPD correctly logs old_payer:new_payer (old payer captured before db.modify)

Snapshot Format

• Snapshot DTOs use std::vector<char> instead of shared_blob — JSON snapshots encode key/value fields as hex (previously base64). Binary snapshot format is unchanged.
• Pre-V7 snapshot loading removed (Wire starts from genesis, no legacy state to migrate)

CDT Changes

• #include <sysio/multi_index.hpp> and sysio::multi_index still work — they forward to the KV implementation
• Same for sysio::singleton
• New sysio::kv::table for zero-copy high-performance contracts
• New sysio::kv::raw_table for ordered key-value store with custom keys
• Post-increment/decrement deleted on all iterators for performance (use ++it / --it)
• be_key_stream supports all types: int8-128 (signed/unsigned), float, double, bool, name, NUL-escaped strings, vector

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Pros

Simplicity

• 60 → 22 host functions — 63% reduction in attack surface
• 6 → 2 chainbase object types — kv_object + kv_index_object replace table_id_object + key_value_object + 5 secondary index types
• No more table_id_object indirection — every lookup is direct
• No more iterator_cache with raw pointers — KV iterators re-seek by key with cached-ID fast path

Security

• Structurally prevents the most critical upstream vulnerability (cross-contract write via iterator reuse) — writes are keyed by receiver
• Iterator re-seek design eliminates use-after-free bugs from session rollback
• 95+ dedicated kv_api_tests + security audit document
• All memcpy/memset calls in SSO assign functions guarded against null pointers with size checks

Performance

• SSO keys avoid heap allocation for the common case
• Eliminates table_id_object lookup on every operation
• kv::table zero-copy path for trivially_copyable structs
• Integer fast-path comparator for 8-byte keys (endian-portable)
• Secondary index lookups save 1-2 host calls via int32_t return encoding
• Cached-ID iterator fast path: next/prev/key/value use O(1) iterator_to instead of composite key re-seek

RAM Efficiency

• sysio.token: 21% less RAM per balance row (184 bytes vs 232 legacy, no secondary index)
• Eliminates per-scope table_id_object overhead (108 bytes per unique scope)

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Cons

Breaking Change

• Not backward compatible with legacy chain state — Wire hasn't launched, so acceptable
• Pre-compiled WASMs with legacy db_* imports must be recompiled
• SHiP schema changes: contract_table removed, secondary index deltas consolidated

Secondary Index Overhead

• Per-row cost with secondary indices is ~7% higher due to SSO buffers in kv_index_object
• Offset by eliminating table_id_object overhead

CDT Dependency

• The CDT must be updated in lockstep — the wire-cdt feature/cdt-db-kv branch is required

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[jglanz]

Considering this is new code, shouldn't we be using GLOB[_RECURSE] file sets?

This applies to all new CMake files in the PR under unittests/test-contracts/*/CMakeLists.txt

[jglanz]

A few changes