feat(fs#write): write buffer at specific position (#4169)

Fixes #4156

@xen-orchestra/fs/src/abstract.js

@@ -410,6 +410,18 @@ export default class RemoteHandlerAbstract {
     await this._unlink(file).catch(ignoreEnoent)
   }
 
+  async write(
+    file: File,
+    buffer: Buffer,
+    position: number
+  ): Promise<{| bytesWritten: number, buffer: Buffer |}> {
+    await this._write(
+      typeof file === 'string' ? normalizePath(file) : file,
+      buffer,
+      position
+    )
+  }
+
   async writeFile(
     file: string,
     data: Data,
@@ -546,6 +558,28 @@ export default class RemoteHandlerAbstract {
     throw new Error('Not implemented')
   }
 
+  async _write(file: File, buffer: Buffer, position: number): Promise<void> {
+    const isPath = typeof file === 'string'
+    if (isPath) {
+      file = await this.openFile(file, 'r+')
+    }
+    try {
+      return await this._writeFd(file, buffer, position)
+    } finally {
+      if (isPath) {
+        await this.closeFile(file)
+      }
+    }
+  }
+
+  async _writeFd(
+    fd: FileDescriptor,
+    buffer: Buffer,
+    position: number
+  ): Promise<void> {
+    throw new Error('Not implemented')
+  }
+
   async _writeFile(
     file: string,
     data: Data,

@xen-orchestra/fs/src/fs.spec.js

@@ -3,9 +3,9 @@
 import 'dotenv/config'
 import asyncIteratorToStream from 'async-iterator-to-stream'
 import getStream from 'get-stream'
+import { forOwn, random } from 'lodash'
 import { fromCallback } from 'promise-toolbox'
 import { pipeline } from 'readable-stream'
-import { random } from 'lodash'
 import { tmpdir } from 'os'
 
 import { getHandler } from '.'
@@ -310,5 +310,45 @@ handlers.forEach(url => {
         await handler.unlink('file')
       })
     })
+
+    describe('#write()', () => {
+      beforeEach(() => handler.outputFile('file', TEST_DATA))
+
+      const PATCH_DATA_LEN = Math.ceil(TEST_DATA_LEN / 2)
+      const PATCH_DATA = unsecureRandomBytes(PATCH_DATA_LEN)
+
+      forOwn(
+        {
+          'dont increase file size': (() => {
+            const offset = random(0, TEST_DATA_LEN - PATCH_DATA_LEN)
+
+            const expected = Buffer.from(TEST_DATA)
+            PATCH_DATA.copy(expected, offset)
+
+            return { offset, expected }
+          })(),
+          'increase file size': (() => {
+            const offset = random(
+              TEST_DATA_LEN - PATCH_DATA_LEN + 1,
+              TEST_DATA_LEN
+            )
+
+            const expected = Buffer.alloc(offset + PATCH_DATA_LEN)
+            TEST_DATA.copy(expected)
+            PATCH_DATA.copy(expected, offset)
+
+            return { offset, expected }
+          })(),
+        },
+        ({ offset, expected }, title) => {
+          describe(title, () => {
+            testWithFileDescriptor('file', 'r+', async ({ file }) => {
+              await handler.write(file, PATCH_DATA, offset)
+              await expect(await handler.readFile('file')).toEqual(expected)
+            })
+          })
+        }
+      )
+    })
   })
 })

@xen-orchestra/fs/src/local.js

@@ -110,6 +110,10 @@ export default class LocalHandler extends RemoteHandlerAbstract {
     return fs.unlink(this._getFilePath(file))
   }
 
+  _writeFd(file, buffer, position) {
+    return fs.write(file.fd, buffer, 0, buffer.length, position)
+  }
+
   _writeFile(file, data, { flags }) {
     return fs.writeFile(this._getFilePath(file), data, { flag: flags })
   }

@xen-orchestra/fs/src/smb.js

@@ -159,6 +159,10 @@ export default class SmbHandler extends RemoteHandlerAbstract {
     return this._client.unlink(this._getFilePath(file)).catch(normalizeError)
   }
 
+  _writeFd(file, buffer, position) {
+    return this._client.write(file.fd, buffer, 0, buffer.length, position)
+  }
+
   _writeFile(file, data, options) {
     return this._client
       .writeFile(this._getFilePath(file), data, options)

CHANGELOG.unreleased.md

@@ -6,5 +6,6 @@
 
 ### Released packages
 
+- @xen-orchestra/fs v0.9.0
 - xo-server v5.41.0
 - xo-web v5.41.0