Specify sourceLength when calling Core.copyFrom (#487)

* add copyFrom test with additional from past

* copyFrom start option used to place additional block

* rename start to sourceLength

* fix standard

---------

Co-authored-by: Mathias Buus <[email protected]>

Author: chm-diederichs

lib/core.js

@@ -226,7 +226,7 @@ module.exports = class Core {
     return false
   }
 
-  async copyFrom (src, signature, { length = src.tree.length, fork = src.tree.fork, additional = [] } = {}) {
+  async copyFrom (src, signature, { length = src.tree.length, sourceLength = src.tree.length, fork = src.tree.fork, additional = [] } = {}) {
     await this._mutex.lock()
 
     try {
@@ -288,8 +288,9 @@ module.exports = class Core {
       // add additional blocks
       if (length > src.tree.length) {
         const missing = length - src.tree.length
+        const offset = src.tree.length - sourceLength
 
-        if (additional.length < missing) {
+        if (additional.length < missing + offset) {
           throw INVALID_OPERATION('Insufficient additional nodes were passed')
         }
 
@@ -299,7 +300,7 @@ module.exports = class Core {
         batch.length = source.length
         batch.byteLength = source.byteLength
 
-        const blocks = additional.length === missing ? additional : additional.slice(0, missing)
+        const blocks = additional.length === missing ? additional : additional.slice(offset, offset + missing)
 
         await this.blocks.putBatch(source.length, blocks, source.byteLength)
         this.bitfield.setRange(source.length, missing, true)

test/core.js

@@ -608,6 +608,45 @@ test('core - clone with different fork', async function (t) {
   t.alike(await clone2.blocks.get(2), b4a.from('c'))
 })
 
+test('core - copyFrom with partially out of date additional', async function (t) {
+  const { core } = await create()
+  const { core: copy } = await create({ keyPair: core.header.keyPair })
+  const { core: clone } = await create({ keyPair: { publicKey: core.header.keyPair.publicKey } })
+
+  await core.append([b4a.from('a'), b4a.from('b')])
+  await copy.copyFrom(core, core.tree.signature)
+
+  t.is(copy.header.keyPair.publicKey, core.header.keyPair.publicKey)
+  t.is(copy.header.keyPair.publicKey, clone.header.keyPair.publicKey)
+
+  await core.append([b4a.from('c')])
+  await core.append([b4a.from('d')])
+
+  // copy is independent
+  await copy.append([b4a.from('c')])
+
+  await clone.copyFrom(copy, core.tree.signature, {
+    length: 4,
+    sourceLength: 2,
+    additional: [
+      b4a.from('c'),
+      b4a.from('d')
+    ]
+  })
+
+  t.is(clone.header.tree.length, 4)
+  t.alike(clone.header.tree.signature, core.header.tree.signature)
+
+  t.is(clone.tree.length, core.tree.length)
+  t.is(clone.tree.byteLength, core.tree.byteLength)
+  t.alike(clone.roots, core.roots)
+
+  t.alike(await clone.blocks.get(0), b4a.from('a'))
+  t.alike(await clone.blocks.get(1), b4a.from('b'))
+  t.alike(await clone.blocks.get(2), b4a.from('c'))
+  t.alike(await clone.blocks.get(3), b4a.from('d'))
+})
+
 async function create (opts) {
   const storage = new Map()