Host functions

A module can import only these functions. Every SDK wraps them; the raw ABI is listed for reference.

Host import	What it does	Rust	Go	AssemblyScript	JS engine	Python
storage.get	Read a key of this module’s state	storage::get, get_string, get_json	StorageGet, StorageGetString, StorageGetJSON	storage.get(key) ("" if unset)	storage.get, db.get(key, default)	hive.storage.get, hive.db.get(key, default)
storage.set	Write a key (an empty value deletes it)	storage::set, set_json	StorageSet, StorageSetString, StorageSetJSON	storage.set(key, value)	storage.set, db.set	hive.storage.set, hive.db.set
storage.del	Delete a key	storage::del	StorageDel	storage.del	storage.del / db.del	hive.storage.delete / hive.db.delete
hive.emit	Record an event {name, data}	emit(name, &data)	Emit, EmitRaw	hive.emit(name, dataJson)	hive.emit(name, data)	hive.emit(name, data)
hive.call	Call another deployed module synchronously	call, call_json	Call, CallJSON	hive.call, hive.tryCall, hive.tryCallRaw	hive.call, hive.callRaw, hive.tryCall	hive.call, hive.call_raw, hive.try_call
crypto.hash	Keccak-256 of bytes, as 0x + 64 hex	hash(&[u8])	Hash(data)	hive.hash(data)	hive.hash(data)	hive.hash(data)
console.log	Debug log on the node (no consensus effect)	log(&str)	Log, Logf	hive.log(msg)	hive.log(…), console.log(…), ctx.log.info(…)	hive.log(…), ctx.log.info(…)
hive.abort	Fail the call with a message	abort(&str), or return Err	Abort(msg), or return an error	hive.fail(msg)	hive.fail(msg) or throw	hive.fail(msg) or raise

Storage

• State is a key/value map private to the module (namespaced by its address). A module can never read or write another module’s keys; use hive.call to ask the other module.
• Keys are 1–256 bytes, values up to 64 KiB, at most 1 MiB written per top-level call.
• Writes are buffered and committed only if the whole top-level call succeeds. A failed call (error, abort, trap, out of gas) writes nothing and emits nothing.
• Storage exists only for modules run through validator rounds (/v1/execute). Committee workers are stateless. Two ways to run a module

Events

• Name: [A-Za-z0-9_.:-]{1,64}. Data: JSON that canonical JSON accepts: no floats, integers within ±(2^53−1). Use integer minor units (cents, micro-units) or strings.
• Up to 64 events per call, 16 KiB of data each. Events are part of the receipt (events_hash).
• Function outputs are plain UTF-8 text and may contain any JSON, floats included; only events and signed structures are restricted.

hive.call

• The callee runs in a fresh instance with all remaining gas; what it uses is charged to the caller.
• Callee success: its state writes and events merge into the caller’s call. Callee failure: they are discarded and the caller gets an error code it can handle.
• Depth limit 8. The call is synchronous and atomic with the caller.

Code	Meaning
-1	Module not found
-2	Function not found
-3	Callee failed (trap, abort, error)
-4	Reserved: out of gas always fails the whole call
-5	Call depth exceeded
-6	Malformed address

Example of cross-language calls: Cross-module composition.

Inputs and outputs

The input is a byte string, usually JSON. Through the API, a string input is passed byte for byte and any other JSON value is passed as canonical JSON (floats are rejected; send them inside a string). Outputs must be valid UTF-8 and at most 1 MiB.