Module hdk::prelude

source ·
Expand description

Exports common types and functions according to the Rust prelude pattern.


pub use crate::capability::create_cap_claim;
pub use crate::capability::create_cap_grant;
pub use crate::capability::delete_cap_grant;
pub use crate::capability::generate_cap_secret;
pub use crate::capability::update_cap_grant;
pub use crate::chain::get_agent_activity;
pub use crate::chain::query;
pub use crate::countersigning::accept_countersigning_preflight_request;
pub use crate::countersigning::session_times_from_millis;
pub use crate::ed25519::sign;
pub use crate::ed25519::sign_ephemeral;
pub use crate::ed25519::sign_ephemeral_raw;
pub use crate::ed25519::sign_raw;
pub use crate::entry::create;
pub use crate::entry::create_entry;
pub use crate::entry::delete;
pub use crate::entry::delete_entry;
pub use crate::entry::get;
pub use crate::entry::get_details;
pub use crate::entry::update;
pub use crate::entry::update_entry;
pub use crate::hash_path::anchor::anchor;
pub use crate::hash_path::anchor::list_anchor_addresses;
pub use crate::hash_path::anchor::list_anchor_tags;
pub use crate::hash_path::anchor::list_anchor_type_addresses;
pub use crate::hash_path::anchor::Anchor;
pub use crate::hash_path::path::Path;
pub use crate::hash_path::path::TypedPath;
pub use crate::info::agent_info;
pub use crate::info::call_info;
pub use crate::map_extern;
pub use crate::p2p::call;
pub use crate::p2p::call_remote;
pub use crate::p2p::emit_signal;
pub use crate::p2p::remote_signal;
pub use crate::time::schedule;
pub use crate::time::sleep;
pub use crate::time::sys_time;
pub use crate::x_salsa20_poly1305::create_x25519_keypair;
pub use crate::x_salsa20_poly1305::x_25519_x_salsa20_poly1305_encrypt;
pub use crate::x_salsa20_poly1305::x_salsa20_poly1305_encrypt;
pub use crate::x_salsa20_poly1305::x_salsa20_poly1305_shared_secret_create_random;
pub use crate::x_salsa20_poly1305::x_salsa20_poly1305_shared_secret_export;
pub use crate::x_salsa20_poly1305::x_salsa20_poly1305_shared_secret_ingest;
pub use hdi;
pub use hdk_derive;
pub use holo_hash;
pub use tracing;
pub use crate::hash::*;
pub use crate::hdk::*;
pub use crate::random::*;
pub use crate::time::*;


represent arbitrary bytes (not serialized) e.g. totally random crypto bytes from random_bytes
Capability Grants and Claims
A “Cell” represents a DNA/AgentId pair - a space where one dna/agent can track its source chain and service network requests / responses.
Countersigned entries involve preflights between many agents to build a session that is part of the entry.
Re-exported dependencies
Defines DnaDef struct
An Entry is a unit of data in a Holochain Source Chain.
Items related to the DNA initialization callback.
Attach a span to a std::future::Future.
Wrapper type to indicate some data which has a ValidationStatus associated with it.
Metadata types for use in wasm
Types for source chain queries
Types for rate limiting
Defines a Record, the basic unit of Holochain data.
Types for requesting metadata
Schedule functions to run outside a direct zome call.
Wrapper types to enable optimized handling of &[u8] and Vec<u8>.
App-defined signals
Signature for authenticity of data
A microsecond-precision UTC timestamp for use in Holochain’s actions.
Types related to the debug host function
Tracking versions between the WASM host and guests and other interfaces.
Types for warrants
A Zome is a module of app-defined code which can be run by Holochain. A group of Zomes are composed to form a DnaDef.


Implements conversion traits to allow a struct to be handled as an app entry. If you have some need to implement custom serialization logic or metadata injection you can do so by implementing these traits manually instead.
Constructs an event at the debug level.
Implements a whole lot of sane defaults for a struct or enum that should behave as an entry. All the entry def fields are available as dedicated methods on the type and matching From impls are provided for each. This allows for both Foo::entry_def() and EntryDef::from(Foo::new()) style logic which are both useful in different scenarios.
Constructs an event at the error level.
Serialization for fixed arrays is generally not available in a way that can be derived. Being able to wrap fixed size arrays is important e.g. for crypto safety etc. so this is a simple way to implement serialization so that we can send these types between the host/guest.
unidiomatic way to derive default trait implementations of TryFrom in/out of SerializedBytes
Helper macro for implementing ToSql, when using rusqlite as a dependency
Helper macro for implementing ToSql, when using rusqlite as a dependency
Constructs an event at the info level.
Hides away the gross bit where we hook up integer pointers to length-prefixed guest memory to serialization and deserialization, and returning things to the host, and memory allocation and deallocation.
Cryptographic secrets are fiddly at the best of times.
Constructs an event at the trace level.
A simple macro to wrap return_err_ptr in an analogy to the native rust ?.
Constructs an event at the warn level.
Helper macro for returning an error from a WASM.


An agents chain records returned from a agent_activity_query
The struct containing all information about the executing agent’s identity.
Action for an agent validation package, used to determine whether an agent is allowed to participate in this DNA
Newtype for the bytes comprising an App entry
The location of an app entry definition.
Identifier for an entry definition. This may be removed.
Information about a class of Entries provided by the DNA
A signal emitted by an app via emit_signal
An ordered set based on a B-Tree.
System entry to hold a capability token claim for use as a caller. Stored by a claimant so they can remember what’s necessary to exercise this capability by sending the secret to the grantor.
A CapSecret is used by a caller to prove to a callee access to a committed CapGrant.
The unique identifier for a Cell. Cells are uniquely determined by this pair - this pair is necessary and sufficient to refer to a cell in a conductor
Filter source chain items. Starting from some chain position given as an ActionHash the chain is walked backwards to genesis. The filter can stop early by specifying the number of chain items to take and / or an ActionHash to consume until.
The chain has been forked by these two actions
The action at the head of the complete chain. This is as far as this authority can see a chain with no gaps.
Specifies arguments to a query of the source chain, including ordering and filtering.
Identifier of a clone cell, composed of the DNA’s role id and the index of the clone, starting at 0.
When migrating to a new version of a DNA, this action is committed to the old chain to declare the migration path taken. Currently unused
Every countersigning agent must sign against their chain state. The chain must be frozen until each agent decides to sign or exit the session.
All the data required for a countersigning session.
Every countersigning session must complete a full set of actions between the start and end times to be valid.
A action which “speaks” Entry content into being. The same content can be referenced by multiple such actions.
Base data for Create actions.
Zome input to create an entry.
Declares that a metadata Link should be made between two EntryHashes
Zome IO inner type for link creation.
@todo Ability to forcibly curry payloads into functions that are called with a claim.
Declare that a previously published Action should be nullified and considered deleted.
Placeholder for future when we want to have deletes on actions Not currently in use.
Zome input for all delete operations.
Declares that a previously made Link should be nullified and considered removed.
Query arguments for the deterministic version of GetAgentActivity
The Dna Action is always the first action in a source chain
The definition of a DNA: the hash of this data is what produces the DnaHash.
Information about the current DNA.
Modifiers of this DNA - the network seed, properties and origin time - as opposed to the actual DNA code. These modifiers are included in the DNA hash computation.
DnaModifiers options of which all are optional.
All definitions for all entry types in an integrity zome.
An Entry with all its metadata.
A newtype for a collection of EntryHashes, needed for some wasm return types.
Combination of the three main rate limiting data types, for convenience
The output of ephemeral signing. The private key for this public key has been discarded by this point. The signatures match the public key provided but cannot be reproduced or forged because the private key no longer exists. The signatures match the input items positionally in the vector, it is up to the caller to reconstruct/align/zip them back together.
A single function name.
Data passed into the genesis_self_check callback for verifying the initial chain entries
Zome input for get and get_details calls.
Options for controlling how get works
Parameters for granting a zome call capability.
256 Bit generic hash.
512 Bit generic hash.
A hash set implemented as a HashMap where the value is ().
The highest action sequence observed by this authority. This also includes the actions at this sequence. If there is more then one then there is a fork.
A HoloHash contains a vector of 36 bytes representing a 32-byte blake2b hash plus 4 bytes representing a DHT location. It also contains a zero-sized type which specifies what it is a hash of.
Represents some piece of content along with its hash representation, so that hashes need not be calculated multiple times. Provides an easy constructor which consumes the content.
A action which declares that all zome init functions have successfully completed, and the chain is ready for commits. Contains no explicit data.
Data with an optional validation status.
CreateLinks with and DeleteLinks on them [CreateLink, [DeleteLink]]
Opaque tag for the link applied at the app layer, used to differentiate between different semantics and validation rules for different links
Metadata that can be requested on a basis
Zome input for must_get_action.
Input to the must_get_agent_activity call.
Zome input for must_get_entry.
Zome input for must_get_valid_record.
When migrating to a new version of a DNA, this action is committed to the new chain to declare the migration path taken. Currently unused
Every preflight request can have optional arbitrary bytes that can be agreed to.
The same PreflightRequest is sent to every agent. Each agent signs this data as part of their PreflightResponse. Every preflight must be identical and signed by every agent for a session to be valid.
Every agent must send back a preflight response. All the preflight response data is signed by each agent and included in the session data.
Specifies arguments to a query of the source chain, including ordering and filtering.
Combination of two rate limiting data types, for convenience
a chain record containing the signed action along with the entry if the action type has one.
A specific Record with any deletes This is all the metadata available for a record.
Registers a new Action on an agent source chain. This is the act of creating any Action and publishing it to the DHT.
Registers a link between two Entrys. This is the act of creating a Action::CreateLink and publishing it to the DHT. The authority is the entry authority for the base Entry.
Registers a deletion of an instance of an Entry in the DHT. This is the act of creating a Action::Delete and publishing it to the DHT.
Deletes a link between two Entrys. This is the act of creating a Action::DeleteLink and publishing it to the DHT. The delete always references a specific Action::CreateLink.
Registers an update from an instance of an Entry in the DHT. This is the act of creating a Action::Update and publishing it to the DHT. Note that the Action::Update stores an new instance of an Entry and registers it as an update to the original Entry. This operation is only concerned with registering the update.
Remote signal many agents without waiting for responses.
The number of validations required for an entry to be considered published.
Agents can have a role specific to each countersigning session. The role is app defined and opaque to the subconscious.
A fully qualified scheduled function.
A type with the zome that it is defined in.
zome types that are in scope for the calling zome.
The set of EntryDefIndex and LinkTypes in scope for the calling zome.
A Canonical Serialized Bytes representation for data If you have a data structure that needs a canonical byte representation use this Always round-trip through SerializedBytes via. a single TryFrom implementation. This ensures that the internal bytes of SerializedBytes are indeed canonical. The corrolary is that if bytes are NOT wrapped in SerializedBytes we can assume they are NOT canonical. Typically we need a canonical serialization when data is to be handled at the byte level by independently implemented and maintained systems.
Input structure for creating a signature.
Ephemerally sign a vector of bytes (i.e. a Vec<Vec>) Each of the items of the outer vector represents something to sign and will have a corresponding Signature in the output. The public key for the ephemeral operation will be returned in the output. Structurally mirrors/complements the Signature struct as a new type. There we know the key on the input side, here we receive the key on the output.
The raw bytes of a signature.
A combination of an action and its signature.
Any content that has been hashed and signed.
Stores a new Entry in the DHT. This is the act of creating a either a Action::Create or a Action::Update and publishing it to the DHT. These actions create a new instance of an Entry.
Stores a new Record in the DHT. This is the act of creating a new Action and publishing it to the DHT. Note that not all Actions contain an Entry.
A microsecond-precision UTC timestamp for use in Holochain’s actions.
Representation of message to be logged via the debug host function
UnsafeBytes the only way to implement a custom round trip through bytes for SerializedBytes It is intended to be an internal implementation in TryFrom implementations The assumption is that any code using UnsafeBytes is NOT valid messagepack data This allows us to enforce that all data round-tripping through SerializedBytes is via TryFrom and also allow for custom non-messagepack canonical representations of data types.
A action which specifies that some new Entry content is intended to be an update to some old Entry.
Placeholder for future when we want to have updates on actions Not currently in use.
Base data for Update actions.
Zome input type for all update operations.
Mirror struct for Sign that includes a signature to verify against a key and data.
Placeholder for warrant type
Wraps a WasmErrorInner with a file and line number. The easiest way to generate this is with the wasm_error! macro that will insert the correct file/line and can create strings by forwarding args to the format! macro.
A zome defined by Wasm bytecode
Data that can be encrypted with secretbox.
Key refs represent shared secrets stored in the keystore. They can either be user-specified, or auto-generated at time of secret creation, or ingestion.
A Holochain Zome. Includes the ZomeDef as well as the name of the Zome.
The entry for the ZomeCall capability grant. This data is committed to the callee’s source chain as a private entry. The remote calling agent must provide a secret and we source their pubkey from the active network connection. This must match the strictness of the CapAccess.
The index into the ZomeId vec.
this id is an internal reference, which also serves as a canonical ordering for zome initialization. The value should be auto-generated from the Zome Bundle def
The properties of the current dna/zome being called.
ZomeName as a String.
A key to the ScopedZomeTypes container.


Action contains variants for each type of action.
Enum to mirror Action for all the shared data required to build session actions. Does NOT hold any agent specific information.
A unit enum which just maps onto the different Action variants, without containing any extra data
Get either the full activity or just the status of the chain
Represents access requirements for capability grants.
Represents a potentially valid access grant to a zome call. Zome call response will be Unauthorized without a valid grant.
Specify which Actions to allow through this filter.
Defines several ways that queries can be restricted to a range. Notably hash bounded ranges disambiguate forks whereas sequence indexes do not as the same position can be found in many forks. The reason that this does NOT use native rust range traits is that the hash bounded queries MUST be inclusive otherwise the integrity and fork disambiguation logic is impossible. An exclusive range bound that does not include the final action tells us nothing about which fork to select between N forks of equal length that proceed it. With an inclusive hash bounded range the final action always points unambiguously at the “correct” fork that the range is over. Start hashes are not needed to provide this property so ranges can be hash terminated with a length of preceeding records to return only. Technically the seq bounded ranges do not imply any fork disambiguation and so could be a range but for simplicity we left the API symmetrical in boundedness across all enum variants. @TODO It may be possible to provide/implement RangeBounds in the case that a full sequence of records/actions is provided but it would need to be handled as inclusive first, to enforce the integrity of the query, then the exclusiveness achieved by simply removing the final record after the fact.
Status of the agent activity chain
Errors during conversion from AppRoleId to CloneId.
Errors related to the secure primitive macro.
Return type for get_details calls. ActionHash returns a Record. EntryHash returns an Entry.
Structure holding the entry portion of a chain record.
Either a Action::Create or a Action::Update. These actions both create a new instance of an Entry.
Either an EntryDefIndex or one of:
The status of an Entry in the Dht
Errors involving app entry creation
Allows Actions which reference Entries to know what type of Entry it is referencing. Useful for examining Actions without needing to fetch the corresponding Entries.
Describes the get call and what information the caller is concerned about. This helps the subconscious avoid unnecessary network calls.
Input to holochain hash function.
Output from the holochain hashing host function.
Anything that can go wrong while calling a HostFnApi method
A human-readable timestamp which is represented/serialized as an RFC3339 when possible, and a microsecond integer count otherwise. Both representations can be deserialized to this type.
The result of the DNA initialization callback.
Maps directly to the tracing Levels but here to define the interface. See
Filter on a set of LinkTypes.
These are the operations that can be applied to Holochain data. Every Action produces a set of operations. These operations are each sent to an authority for validation.
Data specific to the Op::RegisterAgentActivity operation.
Data specific to the Op::RegisterDelete operation.
Data specific to the Op::StoreEntry operation.
Data specific to the Op::StoreRecord operation.
A convenience type for validation Ops.
Data specific to the Op::RegisterUpdate operation.
A preflight request can be accepted, or invalid, or valid but the local agent cannot accept it.
Represents the different ways the entry_address reference within an action can be intepreted
The level of validation package required by an entry.
Defines either a persisted or ephemeral schedule for a schedule function. Persisted schedules survive a conductor reboot, ephemeral will not. Persisted schedules continue beyond irrecoverable errors, ephemeral do not.
Scheduling errors.
Errors related to the secure primitive macro.
Unresolved dependencies that are either a set of hashes or an agent activity query.
The validation status for an op or record much of this happens in the subconscious an entry missing validation dependencies may cycle through Pending many times before finally reaching a final validation state or being abandoned
Enum of all possible ERROR states that wasm can encounter.
Input to the weigh callback. Includes an “unweighed” action, and Entry if applicable.
Response to a zome call.
Just the definition of a Zome, without the name included. This exists mainly for use in HashMaps where ZomeDefs are keyed by ZomeName.
Anything that can go wrong while calling a HostFnApi method


The number of bits we want for a comfy secret.
The number of bytes we want for a comfy secret.
Delimiter in a clone id that separates the base cell’s role id from the clone index.
Entries larger than this number of bytes cannot be created
8 seems like a reasonable limit of agents to countersign.
Need at least two to countersign.
One million
Expire persisted schedules after this long.
Any action with a action_seq less than this value is part of a record created during genesis. Anything with this seq or higher was created after genesis.
Tick the scheduler every this many millis.
The timestamps on actions for a session use this offset relative to the session start time. This makes it easier for agents to accept a preflight request with actions that are after their current chain top, after network latency.
Maximum time in the future the session start can be in the opinion of the participating agent. As the action will be SESSION_ACTION_TIME_OFFSET after the session start we include that here.
Ed25519 signatures are always the same length, 64 bytes.


Builder for non-genesis Actions
A trait to unify the “inner” parts of an Action, i.e. the structs inside the Action enum’s variants. This trait is used for the “unweighed” version of each struct, i.e. the version with weight information erased.
A trait to unify the “inner” parts of an Action, i.e. the structs inside the Action enum’s variants. This trait is used for the “weighed” version of each struct, i.e. the version without weight information erased.
A data structure that can be deserialized from any data format supported by Serde.
Trait for binding static EntryDef property access for a type. This trait maps a type to its corresponding EntryDef property at compile time.
Helper trait for deserializing Entrys to the correct type.
Anything which has an owned HoloHashOf.
Data that requires a validation status.
An extension to obtain a link type filter.
A helper trait for finding the app defined link type from a ZomeId and LinkType.
This trait provides a conversion to a convenience type OpType for use in the validation call back.
A data structure that can be serialized into any data format supported by Serde.
Simple and safe type conversions that may fail in a controlled way under some circumstances. It is the reciprocal of TryInto.
An attempted conversion that consumes self, which may or may not be expensive.
Helper trait for types that are internally represented as u8 but need to be used as indicies into containers.
A utility trait for associating a data enum with a unit enum that has the same variants.


Get the DNA information. There are no inputs to dna_info .
Helpful pattern for debug formatting many bytes. If the size is > 32 bytes, only the first 8 and last 8 bytes will be displayed.
Receive arguments from the host. The guest sets the type O that the host needs to match. If deserialization fails then a GuestPtr to a WasmError::Deserialize is returned. The guest should immediately return an Err back to the host. The WasmError::Deserialize enum contains the bytes that failed to deserialize so the host can unambiguously provide debug information.
Given an extern that we expect the host to provide:
Given a pointer and a length, return a u64 merged GuestPtrLen. Works via a simple bitwise shift to move the pointer to high bits then OR the length into the low bits.
MUST get a SignedActionHashed at a given ActionHash.
The chain this filter produces on the given agents chain must be fetched before the validation can be completed. This allows for deterministic validation of chain activity by making a hash bounded range of an agents chain into a dependency for something that is being validated.
MUST get an EntryHashed at a given EntryHash.
MUST get a VALID Record at a given ActionHash.
Convert a WasmError to a GuestPtrLen as best we can. This is not necessarily straightforward as the serialization process can error recursively. In the worst case we can’t even serialize an enum variant, in which case we panic. The casts from usize to u32 are safe as long as the guest code is compiled for wasm32-unknown-unknown target.
Convert any serializable value into a GuestPtr that can be returned to the host. The host is expected to know how to consume and deserialize it.
Given a merged GuestPtrLen, split out a u32 pointer and length. Performs the inverse of merge_u64. Takes the low u32 bits as the length then shifts the 32 high bits down and takes those as the pointer.
Verify the passed signature and public key against the passed serializable input.
Verify the passed signature and public key against the literal bytes input.
Libsodium keypair based authenticated encryption: box_open
Libsodium secret-key authenticated encryption: secretbox_open
Get the zome information. There are no inputs to zome_info .

Type Definitions

The hash of an action
An Agent public signing key. Not really a hash, more of an “identity hash”.
The hash of anything referrable in the DHT. This is a composite of either an EntryHash or a ActionHash
The hash of anything linkable.
Identifier for an App Role, a foundational concept in the App manifest.
simply alias whatever serde bytes is already doing for Vec
The data type written to the source chain to denote a capability claim
The data type written to the source chain when explicitly granting a capability. NB: this is not simply CapGrant, because the CapGrant::ChainAuthor grant is already implied by Entry::Agent, so that should not be committed to a chain. This is a type alias because if we add other capability types in the future, we may want to include them
A fixed size array of bytes that a secret must be.
Ordered list of coordinator zomes in this DNA.
Alias for a list of agents and their roles.
The hash of an Entry.
An Entry paired with its EntryHash
Every extern must return a WasmError in the case of failure.
The hash of some external data that can’t or doesn’t exist on the DHT.
a single zome/function pair
A collection of zome/function pairs
A WasmSize that points to a position in wasm linear memory that the host and guest are sharing to communicate across function calls.
Enough bits to fit a pointer and length into so we can return it. The externs defined as “C” don’t support multiple return values (unlike wasm). The native Rust support for wasm externs is not stable at the time of writing.
Ordered list of integrity zomes in this DNA.
A WasmSize integer that represents the size of bytes to read/write to memory.
App-specific payload for proving membership in the membrane of the app
Placeholder for a real network seed type. See DnaDef.
The amount that a bucket is “filled”
A bucket ID, for rate limiting
The normalized total size of this action, for rate limiting
The weight of this action, for rate limiting
An EntryDefIndex within the scope of the zome where it’s defined.
A LinkType within the scope of the zome where it’s defined.
The hashed action and the signature that signed it
Something like usize for wasm. Wasm has a memory limit of 4GB so offsets and lengths fit in u32.

Attribute Macros

Declares the integrity zome’s entry types.
Helper for entry data types.
Implements all the required types needed for a LinkTypes enum.
Instruments a function to create and enter a tracing span every time the function is called.

Derive Macros