add userData API (#11)

* add user data api

* use correct pointer

* pointer typo

* userData key is a string

* add userData iterator

* do not use slab for key encoding

* user data iterator yields objects

index.js

@@ -53,7 +53,7 @@ const DATA = {
   TREE: 4,
   BITFIELD: 5,
   BLOCK: 6,
-  USERDATA: 7
+  USER_DATA: 7
 }
 
 const SLAB = {
@@ -88,7 +88,11 @@ class WriteBatch {
 
   setDataInfo (info) {
     if (info.version !== 0) throw new Error('Version > 0 is not supported')
-    this.write.tryPut(encodeDataIndex(this.dataPointer, DATA.INFO), encode(m.DataInfo, info))
+    this.write.tryPut(encodeDataIndex(this.storage.dataPointer, DATA.INFO), encode(m.DataInfo, info))
+  }
+
+  setUserData (key, value) {
+    this.write.tryPut(encodeUserDataIndex(this.storage.dataPointer, DATA.USER_DATA, key), value)
   }
 
   putBlock (index, data) {
@@ -158,7 +162,11 @@ class ReadBatch {
   }
 
   getDataInfo (info) {
-    return this._get(encodeDataIndex(this.dataPointer, DATA.INFO), m.DataInfo)
+    return this._get(encodeDataIndex(this.storage.dataPointer, DATA.INFO), m.DataInfo)
+  }
+
+  getUserData (key) {
+    return this._get(encodeUserDataIndex(this.storage.dataPointer, DATA.USER_DATA, key), null)
   }
 
   async hasBlock (index) {
@@ -345,6 +353,13 @@ class HypercoreStorage {
     return new WriteBatch(this, this.db.write())
   }
 
+  createUserDataStream (opts = {}) {
+    const r = encodeIndexRange(this.dataPointer, DATA.USER_DATA, opts)
+    const s = this.db.iterator(r)
+    s._readableState.map = mapStreamUserData
+    return s
+  }
+
   createTreeNodeStream (opts = {}) {
     const r = encodeIndexRange(this.dataPointer, DATA.TREE, opts)
     const s = this.db.iterator(r)
@@ -387,6 +402,13 @@ class HypercoreStorage {
     return p
   }
 
+  getUserData (key) {
+    const b = this.createReadBatch()
+    const p = b.getUserData(key)
+    b.tryFlush()
+    return p
+  }
+
   getLocalKeyPair () {
     const b = this.createReadBatch()
     const p = b.getLocalKeyPair()
@@ -432,6 +454,18 @@ class HypercoreStorage {
   }
 }
 
+function mapStreamUserData (data) {
+  const state = { start: 0, end: data.key.byteLength, buffer: data.key }
+
+  UINT.decode(state) // TL.DATA
+  UINT.decode(state) // pointer
+  UINT.decode(state) // DATA.USER_DATA
+
+  const key = c.string.decode(state)
+
+  return { key, value: data.value }
+}
+
 function mapStreamTreeNode (data) {
   return c.decode(m.TreeNode, data.value)
 }
@@ -513,6 +547,18 @@ function encodeDataIndex (pointer, type, index) {
   return state.buffer.subarray(start, state.start)
 }
 
+function encodeUserDataIndex (pointer, type, key) {
+  const end = 128 + key.length
+  const state = { start: 0, end, buffer: Buffer.alloc(end) }
+  const start = state.start
+  UINT.encode(state, TL.DATA)
+  UINT.encode(state, pointer)
+  UINT.encode(state, type)
+  c.string.encode(state, key)
+
+  return state.buffer.subarray(start, state.start)
+}
+
 function encodeDiscoveryKey (discoveryKey) {
   const state = ensureSlab(128)
   const start = state.start

test/basic.js

@@ -549,6 +549,53 @@ test('header', async function (t) {
   t.alike(await c2.getCoreHead(), head)
 })
 
+test('user data', async function (t) {
+  const c = await getCore(t)
+
+  {
+    const b = c.createWriteBatch()
+
+    b.setUserData('hello', Buffer.from('world'))
+    b.setUserData('hej', Buffer.from('verden'))
+
+    await b.flush()
+  }
+
+  {
+    const b = c.createReadBatch()
+    const data1 = b.getUserData('hello')
+    const data2 = b.getUserData('hej')
+    b.tryFlush()
+
+    t.alike(await data1, Buffer.from('world'))
+    t.alike(await data2, Buffer.from('verden'))
+  }
+
+  const exp = [
+    { key: 'hej', value: Buffer.from('verden') },
+    { key: 'hello', value: Buffer.from('world') }
+  ]
+
+  const userData = []
+  for await (const e of c.createUserDataStream()) {
+    userData.push(e)
+  }
+
+  t.alike(userData, exp)
+
+  {
+    const b = c.createWriteBatch()
+
+    b.setUserData('hello', null)
+    b.setUserData('hej', Buffer.from('verden'))
+
+    await b.flush()
+  }
+
+  t.alike(await c.getUserData('hello'), null)
+  t.alike(await c.getUserData('hej'), Buffer.from('verden'))
+})
+
 async function getStorage (t, dir) {
   if (!dir) dir = await tmp(t)
   const s = new CoreStorage(dir)