Fix download diff

index.js

@@ -441,10 +441,10 @@ module.exports = class Hyperdrive extends ReadyResource {
 
     for await (const entry of this.diff(length, folder, opts)) {
       if (!entry.left) continue
-      const b = entry.left.value.blob
-      if (!b) continue
+      const blob = entry.left.value.blob
+      if (!blob) continue
       const blobs = await this.getBlobs()
-      dls.push(blobs.core.download({ start: b.blockOffset, length: b.blockLength }))
+      dls.push(await Download.downloadEntry(blobs, blob))
     }
 
     return new Download(this, null, { downloads: dls })
@@ -484,16 +484,16 @@ module.exports = class Hyperdrive extends ReadyResource {
     const blobs = await this.getBlobs()
     const entry = !path || path.endsWith('/') ? null : await this.entry(path)
     if (entry) {
-      const b = entry.value.blob
-      if (!b) return false
-      return await blobs.core.has(b.blockOffset, b.blockOffset + b.blockLength)
+      const blob = entry.value.blob
+      if (!blob) return false
+      return this._hasEntry(blobs, blob)
     }
     let isDir = false
     for await (const entry of this.list(path)) {
       isDir = true
-      const b = entry.value.blob
-      if (!b) continue
-      const has = await blobs.core.has(b.blockOffset, b.blockOffset + b.blockLength)
+      const blob = entry.value.blob
+      if (!blob) continue
+      const has = await this._hasEntry(blobs, blob)
       if (!has) return false
     }
     return isDir
@@ -659,6 +659,22 @@ module.exports = class Hyperdrive extends ReadyResource {
     }
   }
 
+  async _hasEntry(blobs, blob) {
+    if (blob.blockMap) {
+      const hasMap = await blobs.core.has(blob.blockOffset, blob.blockOffset + blob.blockLength)
+      if (!hasMap) return false
+
+      const map = await blobs.getBlockMap(blob)
+      for (const block of map.blocks) {
+        const has = await blobs.core.has(block.index)
+        if (!has) return false
+      }
+      return true
+    } else {
+      return blobs.core.has(blob.blockOffset, blob.blockOffset + blob.blockLength)
+    }
+  }
+
   static normalizePath(name) {
     return std(name, false)
   }

lib/download.js

@@ -8,25 +8,31 @@ module.exports = class Download extends ReadyResource {
     this.folder = folder
     this.options = options || {}
     this.downloads = this.options.downloads || []
-    this.destroyed = false
+    this._cancelled = new Promise((resolve) => {
+      this._cancel = resolve
+    })
     this.ready().catch(noop)
   }
 
   async _open() {
     const drive = this.drive
+    const blobs = await drive.getBlobs()
+
     const entry =
       !this.folder || this.folder.endsWith('/')
         ? null
         : await drive.entry(this.folder, this.options)
 
     if (entry) {
-      const b = entry.value.blob
-      if (!b) return
-      const blobs = await drive.getBlobs()
-      const download = blobs.core.download({
-        start: b.blockOffset,
-        length: b.blockLength
-      })
+      const blob = entry.value.blob
+      if (!blob) return
+
+      const mapDownload = await this._cancellableDownload(
+        this.constructor.downloadEntryMap(blobs, blob)
+      )
+      if (!mapDownload) return
+
+      const download = await this.constructor.downloadEntry(blobs, blob)
       this.downloads.push(download)
       return
     }
@@ -38,16 +44,61 @@ module.exports = class Download extends ReadyResource {
         // ignore
       }
 
+      const maps = []
+      const entries = []
       for await (const entry of drive.list(this.folder, this.options)) {
-        const b = entry.value.blob
-        if (!b) continue
+        const blob = entry.value.blob
+        if (!blob) continue
+        if (blob.blockMap && blob.blockLength) {
+          maps.push(blobs.core.download({ start: blob.blockOffset, length: blob.blockLength }))
+        }
+        entries.push(entry) // cache entries
+      }
+
+      const results = await Promise.all(maps.map((m) => this._cancellableDownload(m)))
+      if (results.includes(false)) return
 
-        const blobs = await drive.getBlobs()
-        this.downloads.push(blobs.core.download({ start: b.blockOffset, length: b.blockLength }))
+      for (const entry of entries) {
+        const blob = entry.value.blob
+        const download = await this.constructor.downloadEntry(blobs, blob)
+        this.downloads.push(download)
       }
     }
   }
 
+  static downloadEntryMap(blobs, blob) {
+    return blobs.core.download({ start: blob.blockOffset, length: blob.blockLength })
+  }
+
+  static async downloadEntry(blobs, blob) {
+    if (blob.blockMap) {
+      const map = await blobs.getBlockMap(blob)
+      const blocks = []
+      for (const block of map.blocks) blocks.push(block.index)
+
+      const download = blobs.core.download({ blocks })
+      await download.ready()
+      return download
+    } else {
+      const download = blobs.core.download({
+        start: blob.blockOffset,
+        length: blob.blockLength
+      })
+      await download.ready()
+      return download
+    }
+  }
+
+  async _cancellableDownload(download) {
+    return Promise.race([
+      download.done().then(() => true),
+      this._cancelled.then(() => {
+        download.destroy()
+        return false
+      })
+    ])
+  }
+
   _close() {
     for (const d of this.downloads) {
       d.destroy()
@@ -56,6 +107,7 @@ module.exports = class Download extends ReadyResource {
 
   destroy() {
     this.destroyed = true
+    this._cancel()
     this._safeBackgroundDestroy()
   }