fs.FS does not support positional reads. It is always the entire file.
You can create a wrapper struct that implements the Seek() (trivial - just keep
a position and adjust Read() accordingly).
> On Sep 21, 2022, at 6:58 PM, Rory Campbell-Lange <r...@campbell-lange.net>
> wrote:
>
> I have a program that needs to work equally for a directory of files or for
> the contents of a zip file, so I'm using an fs.FS to abstract the two.
>
> Some of the files need to be provided to a PDF importer that accepts an
> io.ReadSeeker (#1).
>
> Generally this is working fine except when trying to convert a zip file to an
> io.ReadSeeker. Concisely:
>
> 1 package main
> 2
> 3 import (
> 4 "archive/zip"
> 5 "fmt"
> 6 "io"
> 7 )
> 8
> 9 func main() {
> 10 z, _ := zip.OpenReader("a.zip")
> 11 a, _ := z.Open("a") // a is a file in a.zip
> 12 f, _ := a.Stat()
> 13 fmt.Println(f.Name() == "a") // true
> 14 fmt.Println(a.(io.ReadSeeker))
> 15 }
>
> Fails on line 14 with
>
> interface conversion: *zip.checksumReader is not io.ReadSeeker: missing
> method Seek
>
> Advice on how to rectify this would be gratefully received.
>
> #1
> https://github.com/phpdave11/gofpdf/blob/b09d9214a2296c8ea10312d9c5a520e27f2148c9/contrib/gofpdi/gofpdi.go#L52
>
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