Parameter Change Action¶

typedef struct cardano_parameter_change_action_t cardano_parameter_change_action_t¶: Updates one or more updatable protocol parameters, excluding changes to major protocol versions (i.e., “hard forks”).

cardano_error_t cardano_parameter_change_action_new(cardano_protocol_param_update_t *protocol_param_update, cardano_governance_action_id_t *governance_action_id, cardano_blake2b_hash_t *policy_hash, cardano_parameter_change_action_t **parameter_change_action)¶

Creates and initializes a new instance of the Parameter Change Action.

This function allocates and initializes a new instance of a cardano_parameter_change_action_t object, which represents an action to update one or more updatable protocol parameters within the Cardano network. These updates exclude major protocol version changes, which are managed through different actions.

Governance Action ID: The action requires a governance action ID to reference the most recent enacted action of the same type. This is necessary to prevent unintended conflicts between governance actions of the same type. You can retrieve this information from the governance state query:

cardano-cli conway query gov-state | jq .nextRatifyState.nextEnactState.prevGovActionIds

Example output:

{
  "Committee": {
    "govActionIx": 0,
    "txId": "6bff8515060c08e9cae4d4e203a4d8b2e876848aae8c4e896acda7202d3ac679"
  },
  "Constitution": null,
  "HardFork": null,
  "PParamUpdate": {
    "govActionIx": 0,
    "txId": "7e199d036f1e8d725ea8aba30c5f8d0d2ab9dbd45c7f54e7d85c92c022673f0f"
  }
}

Guardrails Script Hash: The policy_hash parameter represents the hash of the guardrails script (also known as the governance action policy script). The guardrails script is a Plutus script that acts as a safeguard by imposing additional constraints on certain types of governance actions, such as protocol parameter updates and treasury withdrawals. When proposing a protocol parameter update, you must provide the guardrails script hash to reference it. This ensures that the proposal is validated against the guardrails script during the transaction processing.

You can obtain the guardrails script hash using the cardano-cli:

cardano-cli hash script --script-file guardrails-script.plutus

Example output:

fa24fb305126805cf2164c161d852a0e7330cf988f1fe558cf7d4a64

Return Value: Usage Example:

// Initialize the protocol parameter updates
cardano_protocol_param_update_t* protocol_param_update = cardano_protocol_param_update_new();
// Set the parameters you wish to update, for example:
cardano_protocol_param_update_set_key_deposit(protocol_param_update, 1000000);

// Retrieve the last enacted governance action ID (if any)
cardano_governance_action_id_t* governance_action_id = cardano_governance_action_id_new(0, "7e199d036f1e8d725ea8aba30c5f8d0d2ab9dbd45c7f54e7d85c92c022673f0f");

// Obtain the guardrails script hash (if required)
cardano_blake2b_hash_t* policy_hash = cardano_blake2b_hash_from_hex("fa24fb305126805cf2164c161d852a0e7330cf988f1fe558cf7d4a64");

cardano_parameter_change_action_t* parameter_change_action = NULL;
cardano_error_t result = cardano_parameter_change_action_new(
  protocol_param_update,
  governance_action_id,
  policy_hash,
  &parameter_change_action);

// Clean up
cardano_protocol_param_update_unref(&protocol_param_update);
cardano_governance_action_id_unref(&governance_action_id);
cardano_blake2b_hash_unref(&policy_hash);

Parameters:¶

cardano_protocol_param_update_t *protocol_param_update¶: [in] A pointer to a cardano_protocol_param_update_t object representing the protocol parameter updates. This object should include the parameters you wish to update.
cardano_governance_action_id_t *governance_action_id¶: [in] An optional pointer to a cardano_governance_action_id_t object representing the last enacted governance action of the same type (Protocol Parameter Update). This parameter can be NULL if no governance action of this type has been enacted.
cardano_blake2b_hash_t *policy_hash¶: [in] An optional pointer to a cardano_blake2b_hash_t object representing the hash of the guardrails script.
cardano_parameter_change_action_t **parameter_change_action¶: [out] On successful initialization, this will point to a newly created cardano_parameter_change_action_t object. This object represents a “strong reference” to the parameter change action, meaning that it is fully initialized and ready for use. The caller is responsible for managing the lifecycle of this object; specifically, once the parameter change action is no longer needed, the caller must release it by calling cardano_parameter_change_action_unref.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the parameter change action was successfully created, or an appropriate error code indicating the failure reason.

cardano_error_t cardano_parameter_change_action_from_cbor(cardano_cbor_reader_t *reader, cardano_parameter_change_action_t **parameter_change_action)¶

Creates a cardano_parameter_change_action_t from a CBOR reader.

This function parses CBOR data using a provided cardano_cbor_reader_t and constructs a cardano_parameter_change_action_t object. It assumes that the CBOR reader is set up correctly and that the CBOR data corresponds to the structure expected for a parameter_change_action.

Usage Example:

cardano_cbor_reader_t* reader = cardano_cbor_reader_new(cbor_data, data_size);
cardano_parameter_change_action_t* parameter_change_action = NULL;

cardano_error_t result = cardano_parameter_change_action_from_cbor(reader, &parameter_change_action);

if (result == CARDANO_SUCCESS)
{
  // Use the parameter_change_action

  // Once done, ensure to clean up and release the parameter_change_action
  cardano_parameter_change_action_unref(&parameter_change_action);
}
else
{
  const char* error = cardano_cbor_reader_get_last_error(reader);
  printf("Failed to decode parameter_change_action: %s\n", error);
}

cardano_cbor_reader_unref(&reader); // Cleanup the CBOR reader

Note

If the function fails, the last error can be retrieved by calling cardano_cbor_reader_get_last_error with the reader. The caller is responsible for freeing the created cardano_parameter_change_action_t object by calling cardano_parameter_change_action_unref when it is no longer needed.

Parameters:¶

cardano_cbor_reader_t *reader¶: [in] A pointer to an initialized cardano_cbor_reader_t that is ready to read the CBOR-encoded data.
cardano_parameter_change_action_t **parameter_change_action¶: [out] A pointer to a pointer of cardano_parameter_change_action_t that will be set to the address of the newly created parameter_change_action object upon successful decoding.

Returns:¶

A cardano_error_t value indicating the outcome of the operation. Returns CARDANO_SUCCESS if the object was successfully created, or an appropriate error code if an error occurred.

cardano_error_t cardano_parameter_change_action_to_cbor(const cardano_parameter_change_action_t *parameter_change_action, cardano_cbor_writer_t *writer)¶

Serializes the certificate into CBOR format using a CBOR writer.

This function serializes the given cardano_parameter_change_action_t object using a cardano_cbor_writer_t.

Usage Example:

cardano_parameter_change_action_t* parameter_change_action = ...;
cardano_cbor_writer_t* writer = cardano_cbor_writer_new();

if (writer)
{
  cardano_error_t result = cardano_parameter_change_action_to_cbor(parameter_change_action, writer);

  if (result == CARDANO_SUCCESS)
  {
    // Use the writer's buffer containing the serialized data
  }
  else
  {
    const char* error_message = cardano_cbor_writer_get_last_error(writer);
    printf("Serialization failed: %s\n", error_message);
  }

  cardano_cbor_writer_unref(&writer);
}

cardano_parameter_change_action_unref(&parameter_change_action);

Parameters:¶

const cardano_parameter_change_action_t *parameter_change_action¶: [in] A constant pointer to the cardano_parameter_change_action_t object that is to be serialized.
cardano_cbor_writer_t *writer¶: [out] A pointer to a cardano_cbor_writer_t where the CBOR serialized data will be written. The writer must already be initialized and ready to accept the data.

Returns:¶

Returns CARDANO_SUCCESS if the serialization is successful. If the parameter_change_action or writer is NULL, returns CARDANO_ERROR_POINTER_IS_NULL.

cardano_error_t cardano_parameter_change_action_to_cip116_json(const cardano_parameter_change_action_t *action, cardano_json_writer_t *writer)¶

Serializes a parameter change action to CIP-116 JSON.

The function writes the full JSON object, including the surrounding braces. Keys are written in the order: “tag”, “gov_action_id”, “protocol_param_update”, “policy_hash”.

Parameters:¶

const cardano_parameter_change_action_t *action¶: [in] Pointer to a valid cardano_parameter_change_action_t.
cardano_json_writer_t *writer¶: [in] Pointer to a valid cardano_json_writer_t.

Returns:¶

CARDANO_SUCCESS On success. CARDANO_ERROR_POINTER_IS_NULL If action or writer is NULL. CARDANO_ERROR_MEMORY_ALLOCATION_FAILED If memory allocation fails. Other Any error propagated from nested writers.

cardano_error_t cardano_parameter_change_action_set_protocol_param_update(cardano_parameter_change_action_t *parameter_change_action, cardano_protocol_param_update_t *protocol_param_update)¶

Sets the protocol parameter update in the parameter change action.

This function updates the protocol parameter update section of a cardano_parameter_change_action_t object. The protocol parameter update is a cardano_protocol_param_update_t object representing the set of changes to the protocol parameters.

Usage Example:

cardano_parameter_change_action_t* parameter_change_action = ...; // Assume parameter_change_action is already initialized
cardano_protocol_param_update_t* protocol_param_update = cardano_protocol_param_update_new(...); // Assume protocol_param_update is already initialized

cardano_error_t result = cardano_parameter_change_action_set_protocol_param_update(parameter_change_action, protocol_param_update);
if (result == CARDANO_SUCCESS)
{
  // The protocol parameter updates are now set for the parameter_change_action
}
else
{
  printf("Failed to set the protocol parameter updates.\n");
}

// Cleanup the parameter_change_action and protocol_param_update after use
cardano_parameter_change_action_unref(&parameter_change_action);
cardano_protocol_param_update_unref(&protocol_param_update);

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [inout] A pointer to an initialized cardano_parameter_change_action_t object to which the protocol parameter update will be set.
cardano_protocol_param_update_t *protocol_param_update¶: [in] A pointer to an initialized cardano_protocol_param_update_t object representing the new protocol parameter updates.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the protocol parameter update was successfully set, or an appropriate error code indicating the failure reason, such as CARDANO_ERROR_POINTER_IS_NULL if the parameter_change_action pointer is NULL.

cardano_protocol_param_update_t *cardano_parameter_change_action_get_protocol_param_update(cardano_parameter_change_action_t *parameter_change_action)¶

Retrieves the protocol parameter updates from a parameter_change_action.

This function retrieves the protocol parameter updates from a given cardano_parameter_change_action_t object. The protocol parameter updates are represented as a cardano_protocol_param_update_t object.

Usage Example:

cardano_parameter_change_action_t* parameter_change_action = ...; // Assume initialized
cardano_protocol_param_update_t* protocol_param_update = cardano_parameter_change_action_get_protocol_param_update(parameter_change_action);

if (protocol_param_update != NULL)
{
  // Use the protocol parameter updates

  // Once done, ensure to clean up and release the protocol parameter updates
  cardano_protocol_param_update_unref(&protocol_param_update);
}

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [in] A pointer to an initialized cardano_parameter_change_action_t object from which the protocol parameter updates are retrieved.

Returns:¶

A pointer to the retrieved cardano_protocol_param_update_t object representing the protocol parameter updates. This will be a new reference, and the caller is responsible for releasing it with cardano_protocol_param_update_unref when it is no longer needed.

cardano_error_t cardano_parameter_change_action_set_policy_hash(cardano_parameter_change_action_t *parameter_change_action, cardano_blake2b_hash_t *policy_hash)¶

Sets the guardrails script hash in the parameter change action.

This function updates the guardrails script hash (also known as the policy hash) of a cardano_parameter_change_action_t object. The guardrails script is an optional Plutus script that imposes additional constraints on certain types of governance actions, such as protocol parameter updates and treasury withdrawals. By setting the guardrails script hash, you reference this script in your parameter change action, ensuring that the proposal adheres to the constraints defined by the script.

Return Value: Usage Example:

// Assume parameter_change_action is already initialized
cardano_parameter_change_action_t* parameter_change_action = ...;

// Obtain the guardrails script hash
cardano_blake2b_hash_t* policy_hash = cardano_blake2b_hash_from_hex("fa24fb305126805cf2164c161d852a0e7330cf988f1fe558cf7d4a64");

// Set the guardrails script hash in the parameter change action
cardano_error_t result = cardano_parameter_change_action_set_policy_hash(parameter_change_action, policy_hash);
if (result == CARDANO_SUCCESS)
{
  // The guardrails script hash is now set for the parameter_change_action
}
else
{
  printf("Failed to set the guardrails script hash: %s\n", cardano_error_to_string(result));
}

// Clean up after use
cardano_parameter_change_action_unref(&parameter_change_action);
cardano_blake2b_hash_unref(&policy_hash);

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [inout] A pointer to an initialized cardano_parameter_change_action_t object to which the guardrails script hash will be set.
cardano_blake2b_hash_t *policy_hash¶: [in] A pointer to an initialized cardano_blake2b_hash_t object representing the new guardrails script hash. This parameter can be NULL if you wish to unset any previously set guardrails script hash.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the guardrails script hash was successfully set, or an appropriate error code indicating the failure reason, such as CARDANO_ERROR_POINTER_IS_NULL if the parameter_change_action pointer is NULL.

cardano_blake2b_hash_t *cardano_parameter_change_action_get_policy_hash(cardano_parameter_change_action_t *parameter_change_action)¶

Retrieves the guardrails script hash from a parameter change action.

This function retrieves the guardrails script hash (also known as the policy hash) from a given cardano_parameter_change_action_t object. The guardrails script is an optional Plutus script that imposes additional constraints on certain types of governance actions, such as protocol parameter updates and treasury withdrawals. By obtaining the guardrails script hash, you can verify whether the parameter change action references a guardrails script, which may be required for the transaction to be valid.

Return Value: Usage Example:

cardano_parameter_change_action_t* parameter_change_action = ...; // Assume initialized
cardano_blake2b_hash_t* guardrails_hash = cardano_parameter_change_action_get_policy_hash(parameter_change_action);

if (guardrails_hash != NULL)
{
  char* hash_str = cardano_blake2b_hash_to_string(guardrails_hash);
  printf("Guardrails Script Hash: %s\n", hash_str);
  // Use the guardrails script hash as needed

  // Clean up
  cardano_blake2b_hash_unref(&guardrails_hash);
  free(hash_str);
}
else
{
  printf("No guardrails script hash set for this parameter change action.\n");
}

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [in] A pointer to an initialized cardano_parameter_change_action_t object from which the guardrails script hash is retrieved.

Returns:¶

A pointer to the retrieved cardano_blake2b_hash_t object representing the guardrails script hash. This will be a new reference, and the caller is responsible for releasing it with cardano_blake2b_hash_unref when it is no longer needed. If the parameter_change_action does not have a guardrails script hash set, NULL is returned.

cardano_error_t cardano_parameter_change_action_set_governance_action_id(cardano_parameter_change_action_t *parameter_change_action, cardano_governance_action_id_t *governance_action_id)¶

Sets the governance action ID in the parameter_change_action.

This function updates the governance action ID of a cardano_parameter_change_action_t object. The governance action ID is a cardano_governance_action_id_t object representing the last enacted action of the same type.

Usage Example:

cardano_parameter_change_action_t* parameter_change_action = ...; // Assume parameter_change_action is already initialized
cardano_governance_action_id_t* governance_action_id = cardano_governance_action_id_new(...); // Optionally initialized

cardano_error_t result = cardano_parameter_change_action_set_governance_action_id(parameter_change_action, governance_action_id);
if (result == CARDANO_SUCCESS)
{
  // The governance action ID is now set for the parameter_change_action
}
else
{
  printf("Failed to set the governance action ID.\n");
}

// Cleanup the parameter_change_action and optionally the governance action ID
cardano_parameter_change_action_unref(&parameter_change_action);

if (governance_action_id)
{
  cardano_governance_action_id_unref(&governance_action_id);
}

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [inout] A pointer to an initialized cardano_parameter_change_action_t object to which the governance action ID will be set.
cardano_governance_action_id_t *governance_action_id¶: [in] A pointer to an initialized cardano_governance_action_id_t object representing the last enacted action of the same type. This parameter can be NULL if the governance action ID is to be unset.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the governance action ID was successfully set, or an appropriate error code indicating the failure reason, such as CARDANO_ERROR_POINTER_IS_NULL if the parameter_change_action pointer is NULL.

cardano_governance_action_id_t *cardano_parameter_change_action_get_governance_action_id(cardano_parameter_change_action_t *parameter_change_action)¶

Retrieves the governance action ID from a parameter_change_action.

This function retrieves the governance action ID from a given cardano_parameter_change_action_t object. The governance action ID is represented as a cardano_governance_action_id_t object.

Usage Example:

cardano_parameter_change_action_t* parameter_change_action = ...; // Assume initialized
cardano_governance_action_id_t* governance_action_id = cardano_parameter_change_action_get_governance_action_id(parameter_change_action);

if (governance_action_id != NULL)
{
  printf("Governance Action ID: %u\n", cardano_governance_action_id_to_uint(governance_action_id));
  // Use the governance action ID

  // Once done, ensure to clean up and release the governance action ID
  cardano_governance_action_id_unref(&governance_action_id);
}

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [in] A pointer to an initialized cardano_parameter_change_action_t object from which the governance action ID is retrieved.

Returns:¶

A pointer to the retrieved cardano_governance_action_id_t object representing the governance action ID. This will be a new reference, and the caller is responsible for releasing it with cardano_governance_action_id_unref when it is no longer needed.

void cardano_parameter_change_action_unref(cardano_parameter_change_action_t **parameter_change_action)¶

Decrements the reference count of a cardano_parameter_change_action_t object.

This function is responsible for managing the lifecycle of a cardano_parameter_change_action_t object by decreasing its reference count. When the reference count reaches zero, the parameter_change_action is finalized; its associated resources are released, and its memory is deallocated.

Usage Example:

cardano_parameter_change_action_t* parameter_change_action = cardano_parameter_change_action_new(major, minor);

// Perform operations with the parameter_change_action...

cardano_parameter_change_action_unref(&parameter_change_action);
// At this point, parameter_change_action is NULL and cannot be used.

Note

After calling cardano_parameter_change_action_unref, the pointer to the cardano_parameter_change_action_t object will be set to NULL to prevent its reuse.

Parameters:¶

cardano_parameter_change_action_t **parameter_change_action¶: [inout] A pointer to the pointer of the parameter_change_action object. This double indirection allows the function to set the caller’s pointer to NULL, avoiding dangling pointer issues after the object has been freed.

void cardano_parameter_change_action_ref(cardano_parameter_change_action_t *parameter_change_action)¶

Increases the reference count of the cardano_parameter_change_action_t object.

This function is used to manually increment the reference count of an cardano_parameter_change_action_t object, indicating that another part of the code has taken ownership of it. This ensures the object remains allocated and valid until all owners have released their reference by calling cardano_parameter_change_action_unref.

Usage Example:

// Assuming parameter_change_action is a previously created parameter_change_action object

cardano_parameter_change_action_ref(parameter_change_action);

// Now parameter_change_action can be safely used elsewhere without worrying about premature deallocation

Note

Always ensure that for every call to cardano_parameter_change_action_ref there is a corresponding call to cardano_parameter_change_action_unref to prevent memory leaks.

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: A pointer to the cardano_parameter_change_action_t object whose reference count is to be incremented.

size_t cardano_parameter_change_action_refcount(const cardano_parameter_change_action_t *parameter_change_action)¶

Retrieves the current reference count of the cardano_parameter_change_action_t object.

This function returns the number of active references to an cardano_parameter_change_action_t object. It’s useful for debugging purposes or managing the lifecycle of the object in complex scenarios.

Usage Example:

// Assuming parameter_change_action is a previously created parameter_change_action object

size_t ref_count = cardano_parameter_change_action_refcount(parameter_change_action);

printf("Reference count: %zu\n", ref_count);

Warning

This function does not account for transitive references. A transitive reference occurs when an object holds a reference to another object, rather than directly to the cardano_parameter_change_action_t. As such, the reported count may not fully represent the total number of conceptual references in cases where such transitive relationships exist.

Parameters:¶

const cardano_parameter_change_action_t *parameter_change_action¶: A pointer to the cardano_parameter_change_action_t object whose reference count is queried. The object must not be NULL.

Returns:¶

The number of active references to the specified cardano_parameter_change_action_t object. If the object is properly managed (i.e., every cardano_parameter_change_action_ref call is matched with a cardano_parameter_change_action_unref call), this count should reach zero right before the object is deallocated.

void cardano_parameter_change_action_set_last_error(cardano_parameter_change_action_t *parameter_change_action, const char *message)¶

Sets the last error message for a given cardano_parameter_change_action_t object.

Records an error message in the parameter_change_action’s last_error buffer, overwriting any existing message. This is useful for storing descriptive error information that can be later retrieved. The message is truncated if it exceeds the buffer’s capacity.

Note

The error message is limited to 1023 characters, including the null terminator, due to the fixed size of the last_error buffer.

Parameters:¶

cardano_parameter_change_action_t *parameter_change_action¶: [in] A pointer to the cardano_parameter_change_action_t instance whose last error message is to be set. If NULL, the function does nothing.
const char *message¶: [in] A null-terminated string containing the error message. If NULL, the parameter_change_action’s last_error is set to an empty string, indicating no error.

const char *cardano_parameter_change_action_get_last_error(const cardano_parameter_change_action_t *parameter_change_action)¶

Retrieves the last error message recorded for a specific parameter_change_action.

This function returns a pointer to the null-terminated string containing the last error message set by cardano_parameter_change_action_set_last_error for the given parameter_change_action. If no error message has been set, or if the last_error buffer was explicitly cleared, an empty string is returned, indicating no error.

Note

The returned string points to internal storage within the object and must not be modified by the caller. The string remains valid until the next call to cardano_parameter_change_action_set_last_error for the same parameter_change_action, or until the parameter_change_action is deallocated.

Parameters:¶

const cardano_parameter_change_action_t *parameter_change_action¶: [in] A pointer to the cardano_parameter_change_action_t instance whose last error message is to be retrieved. If the parameter_change_action is NULL, the function returns a generic error message indicating the null parameter_change_action.

Returns:¶

A pointer to a null-terminated string containing the last error message for the specified parameter_change_action. If the parameter_change_action is NULL, “Object is NULL.” is returned to indicate the error.