add getBlobsLength and truncate

index.js

@@ -9,7 +9,7 @@ const ReadyResource = require('ready-resource')
 const safetyCatch = require('safety-catch')
 const crypto = require('hypercore-crypto')
 const Hypercore = require('hypercore')
-const { BLOCK_NOT_AVAILABLE } = require('hypercore-errors')
+const { BLOCK_NOT_AVAILABLE, BAD_ARGUMENT } = require('hypercore-errors')
 
 const keyEncoding = new SubEncoder('files', 'utf-8')
 
@@ -94,6 +94,31 @@ module.exports = class Hyperdrive extends ReadyResource {
     return this.corestore.findingPeers()
   }
 
+  async truncate (version, { blobs = -1 } = {}) {
+    const blobsVersion = blobs === -1 ? await this.getBlobsLength(version) : blobs
+    const bl = await this.getBlobs()
+
+    if (version > this.core.length || blobsVersion > bl.core.length) {
+      throw BAD_ARGUMENT('Bad truncation length')
+    }
+
+    await this.core.truncate(version)
+    await bl.core.truncate(blobsVersion)
+  }
+
+  async getBlobsLength (checkout) {
+    await this.ready()
+    if (!checkout) checkout = this.version
+
+    const c = this.db.checkout(checkout)
+
+    try {
+      return await getBlobsLength(c)
+    } finally {
+      await c.close()
+    }
+  }
+
   replicate (isInitiator, opts) {
     return this.corestore.replicate(isInitiator, opts)
   }
@@ -645,3 +670,16 @@ function generateContentManifest (m, key) {
     prologue: null // TODO: could be configurable through the header still...
   }
 }
+
+async function getBlobsLength (db) {
+  let length = 0
+
+  for await (const { value } of db.createReadStream()) {
+    const b = value && value.blob
+    if (!b) continue
+    const len = b.blockOffset + b.blockLength
+    if (len > length) length = len
+  }
+
+  return length
+}

test.js

@@ -1402,6 +1402,77 @@ test('non-compat making of cores', async (t) => {
   t.absent(drive.blobs.core.core.compat)
 })
 
+test('getBlobsLength happy paths', async t => {
+  const corestore = new Corestore(RAM.reusable())
+  const drive = new Hyperdrive(corestore.session())
+
+  await drive.put('./file', 'here')
+  t.is(await drive.getBlobsLength(), 1, 'Correct blobs length 1')
+
+  await drive.put('./file', 'here')
+  t.is(await drive.getBlobsLength(), 2, 'Correct blobs length 2')
+
+  t.is(drive.version, 3, 'sanity check')
+  t.is(await drive.getBlobsLength(2), 1, 'Correct blobs length on explicit checkout')
+  t.is(await drive.getBlobsLength(3), 2, 'Correct blobs length on explicit checkout to latest')
+})
+
+test('getBlobsLength when not ready', async t => {
+  const corestore = new Corestore(RAM.reusable())
+  {
+    const drive = new Hyperdrive(corestore.session())
+    await drive.put('./file', 'here')
+    await drive.put('./more', 'here')
+    await drive.close()
+  }
+
+  {
+    const drive = new Hyperdrive(corestore)
+    const length = await drive.getBlobsLength()
+    t.is(length, 2, 'correct blobs length')
+    await drive.close()
+  }
+})
+
+test('getBlobsLength of empty drive', async t => {
+  const corestore = new Corestore(RAM.reusable())
+  const drive = new Hyperdrive(corestore.session())
+  const length = await drive.getBlobsLength()
+  t.is(length, 0, 'empty drive has blobsLength 0')
+})
+
+test('truncate happy path', async t => {
+  const corestore = new Corestore(RAM.reusable())
+  const drive = new Hyperdrive(corestore.session())
+  await drive.ready()
+
+  t.is(drive.db.core.fork, 0, 'sanity check')
+  t.is(drive.blobs.core.fork, 0, 'sanity check')
+
+  await drive.put('file1', 'here1')
+  await drive.put('file2', 'here2')
+  await drive.put('file3', 'here3')
+
+  t.is(drive.version, 4, 'sanity check')
+  t.is(await drive.getBlobsLength(), 3, 'sanity check')
+
+  await drive.truncate(3)
+  t.is(drive.version, 3, 'truncated db correctly')
+  t.is(await drive.getBlobsLength(), 2, 'truncated blobs correctly')
+
+  await drive.put('file3', 'here file 3 post truncation')
+  t.is(drive.version, 4, 'correct version when putting after truncate')
+  t.is(await drive.getBlobsLength(), 3, 'correct blobsLength when putting after truncate')
+  t.is(
+    b4a.toString(await drive.get('file3')),
+    'here file 3 post truncation',
+    'Sanity check'
+  )
+
+  t.is(drive.db.core.fork, 1, 'sanity check on db fork')
+  t.is(drive.blobs.core.fork, 1, 'sanity check on blobs fork')
+})
+
 async function testenv (teardown) {
   const corestore = new Corestore(RAM)
   await corestore.ready()