Sorry, per docs, the client should call the Flush method to guarantee all data
has been forwarded to the underlying io.Writer.
Not sure why the Write doesn’t implement Closer. That’s fairly non standard way
of doing buffered io...
> On May 21, 2019, at 8:42 AM, Subramanian Sridharan <clawsonfir...@gmail.com>
> wrote:
>
> I don't think so.
>
> When I close the file and don't explicitly flush:
>
> package main
>
> import (
> "bufio"
> "fmt"
> "io"
> "os"
> )
>
> func main() {
> sourceFilename := "MozillaFirefox-66.0.5-741.4.x86_64.rpm"
> sourcef, err := os.Open(sourceFilename)
> if err != nil {
> fmt.Println("Error while opening source file:", err)
> return
> }
> defer sourcef.Close()
>
> destinationFilename := "CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm"
> os.Create(destinationFilename)
> destf, err := os.OpenFile(destinationFilename, os.O_APPEND|os.O_WRONLY,
> os.ModeAppend)
> if err != nil {
> fmt.Println("Error while opening destination file:", err)
> return
> }
> defer func() {
> fmt.Println("Closing file.")
> destf.Close()
> }()
>
> fReader := bufio.NewReader(sourcef)
> fWriter := bufio.NewWriter(destf)
>
> n, err := io.Copy(fWriter, fReader)
> if err != nil {
> fmt.Println("Error while copying:", err)
> return
> }
>
> fmt.Println("Copied", n, "bytes.")
> }
>
>
> Output:
>
> ➜ throttle-and-resume-download go run copyTest.go
>
> Copied 46061104 bytes.
> Closing file.
> ➜ throttle-and-resume-download diff MozillaFirefox-66.0.5-741.4.x86_64.rpm
> CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm
> Binary files MozillaFirefox-66.0.5-741.4.x86_64.rpm and
> CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm differ
> ➜ throttle-and-resume-download echo $?
> 1
>
>
> When I explicitly flush:
>
> package main
>
> import (
> "bufio"
> "fmt"
> "io"
> "os"
> )
>
> func main() {
> sourceFilename := "MozillaFirefox-66.0.5-741.4.x86_64.rpm"
> sourcef, err := os.Open(sourceFilename)
> if err != nil {
> fmt.Println("Error while opening source file:", err)
> return
> }
> defer sourcef.Close()
>
> destinationFilename := "CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm"
> os.Create(destinationFilename)
> destf, err := os.OpenFile(destinationFilename, os.O_APPEND|os.O_WRONLY,
> os.ModeAppend)
> if err != nil {
> fmt.Println("Error while opening destination file:", err)
> return
> }
> defer func() {
> fmt.Println("Closing file.")
> destf.Close()
> }()
>
> fReader := bufio.NewReader(sourcef)
> fWriter := bufio.NewWriter(destf)
>
> n, err := io.Copy(fWriter, fReader)
> if err != nil {
> fmt.Println("Error while copying:", err)
> return
> }
>
> // Flush writer to ensure all contents are written to file
> err = fWriter.Flush()
> if err != nil {
> fmt.Println("Error while flushing writer:", err)
> return
> } else {
> fmt.Println("Flushed writer.")
> }
>
> fmt.Println("Copied", n, "bytes.")
> }
>
>
> Output:
>
> ➜ throttle-and-resume-download go run copyTest.go
>
> Flushed writer.
> Copied 46061104 bytes.
> Closing file.
> ➜ throttle-and-resume-download diff MozillaFirefox-66.0.5-741.4.x86_64.rpm
> CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm
> ➜ throttle-and-resume-download echo $?
>
> 0
>
>
>
>
>
>
>> On Tuesday, May 21, 2019 at 6:39:08 PM UTC+5:30, Robert Engels wrote:
>> You do not need to flush if you call close. Close will flush. There is some
>> other bug in your code I believe.
>>
>> > On May 21, 2019, at 3:01 AM, Jan Mercl <0xj...@gmail.com> wrote:
>> >
>> >> On Tue, May 21, 2019 at 9:44 AM <pierr...@gmail.com> wrote:
>> >>
>> >> Usually though, you do not need to buffer the input or output at all.
>> >
>> > If I/O is performed in chunks comparable in size to what
>> > bufio.{Reader,Writer} uses then ok. When I/O is done in small chunks,
>> > then using bufio should improve performance.
>> >
>> > The question left is what the "usual" scenario is.
>> >
>> > --
>> > You received this message because you are subscribed to the Google Groups
>> > "golang-nuts" group.
>> > To unsubscribe from this group and stop receiving emails from it, send an
>> > email to golan...@googlegroups.com.
>> > To view this discussion on the web visit
>> > https://groups.google.com/d/msgid/golang-nuts/CAA40n-WsWkLtnP19DUwHNSrjDNBncbVepqNxVj%3DUF6MFV8ARLA%40mail.gmail.com.
>> >
>> > For more options, visit https://groups.google.com/d/optout.
>>
>
> --
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