Reading Zip into Slice with offset

[Mathews]

Hi,

i have the following problem.

I want to read the contents of a .zip into an array/slice.

For small data this works fine, however, as soon as i want to read more than 32769 bytes,

it doesn't work the way i want to.

The read() only reads up to a maximum of ~32kbyte and i can't pass the old slice to a new call

of read, without the old data getting overriden, since i don't find how to add an offset.

Of course i could read into multiple slices and then copy their contents into a bigger slice, however,

this feels kinda unnecessary copy-work.

Is there a better way around it?

The way i do it now:

var data_hash map[string]*zip.File

func GetData(name string) *[]byte {

    file, ok := data_hash[name]

    if !ok {

        log.Panic("File not found: \"" + name + "\"")

    }

    zip.NewReader()

    reader, err := file.Open()

    if err != nil {

        log.Panicf("Could not read file \"%s\": %v", name, err)

    }

    defer reader.Close()

    size := file.UncompressedSize

    buffer := make([]byte, size)

    n, err := reader.Read(buffer)

    if err != nil {

        log.Panicf("Failed to read file \"%s\": %v", name, err)

    }

    if n != int(size) {
        //This is what happens if the file is too big
        //I want to do something like: reader.Read(buffer + n)

        log.Panicf("Failed to read file \"%s\": File has wrong size.", name)

    }

    return &buffer

}

 

[Peter]

Which version of go or what zip package is this?

archive/zip.NewReader has this signature

 func NewReader(r io.ReaderAt, size int64) (*Reader, error)

[Mathews]

Am Donnerstag, 22. November 2012 16:26:46 UTC+1 schrieb Peter:

Which version of go or what zip package is this?

archive/zip.NewReader has this signature

 func NewReader(r io.ReaderAt, size int64) (*Reader, error)

The latest version (1.0.3)

The function zip.NewReader() is available, however i need to pass

it a ReaderAt() and i don't have one.

(Obviously i cant use a self-implemented, since i'm having problems with getting

read() to work the way i want to.)

[Mathews]

I solved it.

You can call Read(buffer[a:b)]), to pass a part of a slice.

Alternatively there is already the class bytes.buffer, which provides 

buffer.ReadFrom(reader)

[Niklas Schnelle]

I think you might want to have a look at ReadFull, I stumbled into that one twice. Read(buffer[a:b])
might not read the whole range but only as much as available. Especially bufio tends to do that