Oracle

This class is one of several convenience collections built on top of the Storage class It implements a map -- a persistent unordered map.

To create a map

let map = new PersistentMap<string, string>("m")  // choose a unique prefix per account

To use the map

map.set(key, value)
map.get(key)

IMPORTANT NOTES:

(1) The Map doesn't store keys, so if you need to retrieve them, include keys in the values.

(2) Since all data stored on the blockchain is kept in a single key-value store under the contract account, you must always use a unique storage prefix for different collections to avoid data collision.

Hierarchy

• PersistentMap<u64, Sample>

  ↳ Oracle

Table of contents

Constructors

• constructor

Methods

• _decreaseSize
• _increaseSize
• before
• binarySearch
• contains
• delete
• get
• getSampleAt
• getSome
• initialize
• set
• size
• update

Constructors

constructor

• new Oracle(prefix): Oracle

Creates or restores a persistent map with a given storage prefix. Always use a unique storage prefix for different collections.

Example

let map = new PersistentMap<string, string>("m") // note the prefix must be unique (per MASSA account)

Parameters

Name	Type	Description
prefix	string	A prefix to use for every key of this map.

Returns

Oracle

Inherited from

PersistentMap.constructor

Defined in

assembly/libraries/PersistentMap.ts:65

Methods

_decreaseSize

▸ _decreaseSize(): void

Decreases the internal map size counter

Returns

void

Inherited from

PersistentMap._decreaseSize

Defined in

assembly/libraries/PersistentMap.ts:144

---

_increaseSize

▸ _increaseSize(key): void

Increases the internal map size counter

Parameters

Name	Type	Description
key	u64	Key to remove.

Returns

void

Inherited from

PersistentMap._increaseSize

Defined in

assembly/libraries/PersistentMap.ts:135

---

before

▸ before(x, n): u64

Parameters

Name	Type	Description
x	u64	The value
n	u64	The modulo value

Returns

u64

result The result

Notice

Internal function to do positive (x - 1) % n

Dev

This function is used to get the previous index of the oracle

Defined in

assembly/structs/Oracle.ts:207

---

binarySearch

▸ binarySearch(_index, _activeSize, _lookUpTimestamp): Sample[]

Parameters

Name	Type	Description
_index	u64	The current index of the oracle
_activeSize	u64	The size of the oracle (without empty data)
_lookUpTimestamp	u64	The looked up timestamp

Returns

Sample[]

Sample[] The last sample with a timestamp lower than the lookUpTimestamp and the first sample with a timestamp greater than the lookUpTimestamp

Notice

Binary search on oracle samples and return the 2 samples (as bytes32) that surrounds the lookUpTimestamp

Dev

The oracle needs to be in increasing order {_index + 1, _index + 2 ..., _index + _activeSize} % _activeSize. The sample that aren't initialized yet will be skipped as _activeSize only contains the samples that are initialized. This function works only if timestamp(_oracle[_index + 1 % _activeSize] <= _lookUpTimestamp <= timestamp(_oracle[_index]. The edge cases needs to be handled before

Defined in

assembly/structs/Oracle.ts:169

---

contains

▸ contains(key): bool

Checks whether the map contains a given key

let map = new PersistentMap<string, string>("m")

map.contains("hello")      // false
map.set("hello", "world")
map.contains("hello")      // true

Parameters

Name	Type	Description
key	u64	Key to check.

Returns

bool

True if the given key present in the map.

Inherited from

PersistentMap.[contains]../libraries/(PersistentMap.md#contains)

Defined in

assembly/libraries/PersistentMap.ts:94

---

delete

▸ delete(key): void

Removes the given key and related value from the map

let map = new PersistentMap<string, string>("m")

map.set("hello", "world")
map.delete("hello")

Removes value and the key from the map.

Parameters

Name	Type	Description
key	u64	Key to remove.

Returns

void

Inherited from

PersistentMap.delete

Defined in

assembly/libraries/PersistentMap.ts:126

---

get

▸ get(key, defaultValue): Sample

Retrieves the related value for a given key, or uses the defaultValue if not key is found

let map = new PersistentMap<string, string>("m")

map.set("hello", "world")
let found = map.get("hello")
let notFound = map.get("goodbye", "cruel world")

assert(found == "world")
assert(notFound == "cruel world")

Parameters

Name	Type	Description
key	u64	Key of the element.
defaultValue	Sample	The default value if the key is not present.

Returns

Sample

Value for the given key or the default value.

Inherited from

PersistentMap.get

Defined in

assembly/libraries/PersistentMap.ts:168

---

getSampleAt

▸ getSampleAt(_activeSize, _activeId, _lookUpTimestamp): GetSampleAtReturn

Parameters

Name	Type	Description
_activeSize	u64	The size of the oracle (without empty data)
_activeId	u64	The active index of the oracle
_lookUpTimestamp	u64	The looked up date

Returns

GetSampleAtReturn

GetSampleAtReturn: timestamp, cumulativeId, cumulativeVolatilityAccumulated, cumulativeBinCrossed

Notice

View function to get the oracle's sample at _ago seconds

Dev

Return a linearized sample, the weighted average of 2 neighboring samples

Defined in

assembly/structs/Oracle.ts:22

---

getSome

▸ getSome(key, msg?): Sample

Retrieves a related value for a given key or fails assertion with "key not found"

let map = new PersistentMap<string, string>("m")

map.set("hello", "world")
let result = map.getSome("hello")
// map.getSome("goodbye")  // will throw with failed assertion

assert(result == "world")

Parameters

Name	Type	Default value	Description
key	u64	undefined	Key of the element.
msg	string	'key not found'	-

Returns

Sample

Value for the given key or the default value.

Inherited from

PersistentMap.getSome

Defined in

assembly/libraries/PersistentMap.ts:230

---

initialize

▸ initialize(_id): void

Parameters

Name	Type	Description
_id	u64	The index to initialize

Returns

void

Notice

Initialize the sample

Defined in

assembly/structs/Oracle.ts:154

---

set

▸ set(key, value): void

let map = new PersistentMap<string, string>("m")

map.set("hello", "world")

Sets the new value for the given key.

Parameters

Name	Type	Description
key	u64	Key of the element.
value	Sample	The new value of the element.

Returns

void

Inherited from

PersistentMap.set

Defined in

assembly/libraries/PersistentMap.ts:273

---

size

▸ size(): usize

Returns the map size

Returns

usize

the map size

Example

let map = new PersistentMap<string, string> ("m")

map.size()

Inherited from

PersistentMap.size

Defined in

assembly/libraries/PersistentMap.ts:109

---

update

▸ update(_size, _sampleLifetime, _lastTimestamp, _lastIndex, _activeId, _volatilityAccumulated, _binCrossed): u64

Parameters

Name	Type	Description
_size	u64	The size of the oracle (last ids can be empty)
_sampleLifetime	u64	The lifetime of a sample, it accumulates information for up to this timestamp
_lastTimestamp	u64	The timestamp of the creation of the oracle's latest sample
_lastIndex	u64	The index of the oracle's latest sample
_activeId	u64	The active index of the pair during the latest swap
_volatilityAccumulated	u64	The volatility accumulated of the pair during the latest swap
_binCrossed	u64	The bin crossed during the latest swap

Returns

u64

updatedIndex The oracle updated index, it is either the same as before, or the next one

Notice

Function to update a sample

Defined in

assembly/structs/Oracle.ts:125