Add comments for register SP parser API call.

Signed-off-by: Sergey Minaev <[email protected]>

Author: jovfer

libindy/src/api/ledger.rs

@@ -1618,9 +1618,36 @@ pub extern fn indy_parse_get_revoc_reg_delta_response(command_handle: i32,
     res
 }
 
+/// Callback type for parsing Reply from Node to specific StateProof format
+///
+/// # params
+/// reply_from_node: string representation of node's reply ("as is")
+/// parsed_sp: out param to return serialized as string JSON with array of ParsedSP
+///
+/// # return
+/// result ErrorCode
+///
+/// Note: this method allocate memory for result string `CustomFree` should be called to deallocate it
 pub type CustomTransactionParser = extern fn(reply_from_node: *const c_char, parsed_sp: *mut *const c_char) -> ErrorCode;
+
+/// Callback type to deallocate result buffer `parsed_sp` from `CustomTransactionParser`
 pub type CustomFree = extern fn(data: *const c_char) -> ErrorCode;
 
+
+/// Register callbacks (see type description for `CustomTransactionParser` and `CustomFree`
+///
+/// # params
+/// command_handle: command handle to map callback to caller context.
+/// txn_type: type of transaction to apply `parse` callback.
+/// parse: required callback to parse reply for state proof.
+/// free: required callback to deallocate memory.
+/// cb: Callback that takes command result as parameter.
+///
+/// # returns
+/// Status of callbacks registration.
+///
+/// # errors
+/// Common*
 #[no_mangle]
 pub extern fn indy_register_transaction_parser_for_sp(command_handle: i32,
                                                       txn_type: *const c_char,