Implement fileOffset in readFile

README.md

@@ -13,7 +13,7 @@
 In order to use this library, we need to add the following line in our `build.sbt` file:
 
 ```scala
-libraryDependencies += "dev.zio" %% "zio-ftp" % "0.4.1" 
+libraryDependencies += "dev.zio" %% "zio-ftp" % "0.4.2" 
 ```
 
 ## How to use it?

zio-ftp/src/main/scala/zio/ftp/FtpAccessors.scala

@@ -27,8 +27,9 @@ trait FtpAccessors[+A] {
    *
    * @param path absolute path of a file
    * @param chunkSize default chunk size is 2048 bytes
+   * @param fileOffset optional initial offset in bytes
    */
-  def readFile(path: String, chunkSize: Int = 2048): ZStream[Any, IOException, Byte]
+  def readFile(path: String, chunkSize: Int = 2048, fileOffset: Long = 0): ZStream[Any, IOException, Byte]
 
   /**
    * Delete a file on a server. If the operation failed, an error will be emitted

zio-ftp/src/main/scala/zio/ftp/SecureFtp.scala

@@ -41,13 +41,13 @@ final private class SecureFtp(unsafeClient: Client) extends FtpAccessors[Client]
   def stat(path: String): ZIO[Any, IOException, Option[FtpResource]] =
     execute(c => Option(c.statExistence(path)).map(FtpResource(path, _)))
 
-  def readFile(path: String, chunkSize: Int): ZStream[Any, IOException, Byte] =
+  def readFile(path: String, chunkSize: Int, fileOffset: Long): ZStream[Any, IOException, Byte] =
     for {
       remoteFile             <- ZStream.fromZIO(
                                   execute(_.open(path, util.EnumSet.of(OpenMode.READ)))
                                 )
 
-      is: java.io.InputStream = new remoteFile.ReadAheadRemoteFileInputStream(64) {
+      is: java.io.InputStream = new remoteFile.ReadAheadRemoteFileInputStream(64, fileOffset) {
 
                                   override def close(): Unit =
                                     try super.close()

zio-ftp/src/main/scala/zio/ftp/TestFtp.scala

@@ -42,14 +42,15 @@ object TestFtp {
           .refineToOrDie[IOException]
       }
 
-      override def readFile(path: String, chunkSize: Int): ZStream[Any, IOException, Byte] =
+      override def readFile(path: String, chunkSize: Int, fileOffset: Long): ZStream[Any, IOException, Byte] =
         ZStream
           .fromZIO(Files.readAllBytes(root / ZPath(path).elements.mkString("/")))
           .catchAll {
             case _: NoSuchFileException => ZStream.fail(InvalidPathError(s"File does not exist $path"))
             case err                    => ZStream.fail(err)
           }
           .flatMap(ZStream.fromChunk(_))
+          .drop(fileOffset.toInt)
 
       override def rm(path: String): ZIO[Any, IOException, Unit] =
         Files

zio-ftp/src/main/scala/zio/ftp/UnsecureFtp.scala

@@ -33,7 +33,9 @@ final private class UnsecureFtp(unsafeClient: Client) extends FtpAccessors[Clien
   def stat(path: String): ZIO[Any, IOException, Option[FtpResource]] =
     execute(c => Option(c.mlistFile(path))).map(_.map(FtpResource.fromFtpFile(_)))
 
-  def readFile(path: String, chunkSize: Int = 2048): ZStream[Any, IOException, Byte] = {
+  def readFile(path: String, chunkSize: Int = 2048, fileOffset: Long): ZStream[Any, IOException, Byte] = {
+    val initialize = execute(_.setRestartOffset(fileOffset))
+
     val terminate = ZIO
       .fail(
         FileTransferIncompleteError(s"Cannot finalize the file transfer and completely read the entire file $path.")
@@ -43,7 +45,8 @@ final private class UnsecureFtp(unsafeClient: Client) extends FtpAccessors[Clien
     val inputStream =
       execute(c => Option(c.retrieveFileStream(path))).someOrFail(InvalidPathError(s"File does not exist $path"))
 
-    ZStream.fromInputStreamZIO(inputStream, chunkSize) ++ ZStream.fromZIO(terminate) *> ZStream.empty
+    (ZStream.fromZIO(initialize) *> ZStream.empty) ++ ZStream.fromInputStreamZIO(inputStream, chunkSize) ++ (ZStream
+      .fromZIO(terminate) *> ZStream.empty)
   }
 
   def rm(path: String): ZIO[Any, IOException, Unit] =

zio-ftp/src/main/scala/zio/ftp/package.scala

@@ -61,8 +61,8 @@ package object ftp {
         _   <- ftp.upload(path, source)
       } yield ()
 
-    def readFile(path: String, chunkSize: Int = 2048): ZStream[Ftp, IOException, Byte] =
-      ZStream.serviceWithStream(_.readFile(path, chunkSize))
+    def readFile(path: String, chunkSize: Int = 2048, fileOffset: Long = 0): ZStream[Ftp, IOException, Byte] =
+      ZStream.serviceWithStream(_.readFile(path, chunkSize, fileOffset))
 
     def rename(oldPath: String, newPath: String): ZIO[Ftp, Exception, Unit] =
       ZIO.serviceWithZIO(_.rename(oldPath, newPath))
@@ -100,8 +100,8 @@ package object ftp {
         _   <- ftp.upload(path, source)
       } yield ()
 
-    def readFile(path: String, chunkSize: Int = 2048): ZStream[SFtp, IOException, Byte] =
-      ZStream.serviceWithStream(_.readFile(path, chunkSize))
+    def readFile(path: String, chunkSize: Int = 2048, fileOffset: Long = 0): ZStream[SFtp, IOException, Byte] =
+      ZStream.serviceWithStream(_.readFile(path, chunkSize, fileOffset))
 
     def rename(oldPath: String, newPath: String): ZIO[SFtp, Exception, Unit] =
       ZIO.serviceWithZIO(_.rename(oldPath, newPath))
@@ -139,8 +139,8 @@ package object ftp {
         _   <- ftp.upload(path, source)
       } yield ()
 
-    def readFile(path: String, chunkSize: Int = 2048): ZStream[StubFtp, IOException, Byte] =
-      ZStream.serviceWithStream(_.readFile(path, chunkSize))
+    def readFile(path: String, chunkSize: Int = 2048, fileOffset: Long = 0): ZStream[StubFtp, IOException, Byte] =
+      ZStream.serviceWithStream(_.readFile(path, chunkSize, fileOffset))
 
     def rename(oldPath: String, newPath: String): ZIO[StubFtp, Exception, Unit] =
       ZIO.serviceWithZIO(_.rename(oldPath, newPath))

zio-ftp/src/test/scala/zio/ftp/SecureFtpSpec.scala

@@ -122,6 +122,11 @@ object SecureFtpSpec extends ZIOSpecDefault {
                |this is a beautiful day""".stripMargin
         )
       },
+      test("readFile with offset") {
+        for {
+          content <- readFile("/notes.txt", fileOffset = 16).via(utf8Decode).runCollect
+        } yield assert(content.mkString)(equalTo("this is a beautiful day"))
+      },
       test("readFile does not exist") {
         for {
           invalid <- readFile("/invalid.txt")

zio-ftp/src/test/scala/zio/ftp/StubFtpSpec.scala

@@ -67,6 +67,11 @@ object StubFtpSpec extends ZIOSpecDefault {
         } yield assert(content.mkString)(equalTo("""|Hello world !!!
                                                     |this is a beautiful day""".stripMargin))
       },
+      test("readFile with offset") {
+        for {
+          content <- readFile("/notes.txt", fileOffset = 16).via(utf8Decode).runCollect
+        } yield assert(content.mkString)(equalTo("this is a beautiful day"))
+      },
       test("readFile does not exist") {
         for {
           invalid <- readFile("/invalid.txt")

zio-ftp/src/test/scala/zio/ftp/UnsecureFtpSpec.scala

@@ -106,6 +106,11 @@ object FtpSuite {
         } yield assert(content.mkString)(equalTo("""|Hello world !!!
                                                     |this is a beautiful day""".stripMargin))
       },
+      test("readFile with offset") {
+        for {
+          content <- readFile("/notes.txt", fileOffset = 16).via(utf8Decode).runCollect
+        } yield assert(content.mkString)(equalTo("this is a beautiful day"))
+      },
       test("readFile does not exist") {
         for {
           invalid <- readFile("/invalid.txt")