前往：zlib解压缩字节片

Question

I am trying to parse a file that annoying consists of many separately zipped segments. I have parsed these segments one at a time into a slice of bytes and I want to uncompress them as I go.

Here is my current code that does the decompressing, which doesn't work. from and to are just set at the top as an example, in reality they are set by the code. data is the byte array containing the entire file. I don't want to seek it while it's on disk because its location on another server, so it's only realistic for me to load the entire file to []byte first and then parse it.

from, to := 0, 1000;
b := bytes.NewReader(data[from:from+to])
z, err := zlib.NewReader(b)
CheckErr(err)
defer z.Close()
p := make([]byte,0,1024)
z.Read(p)
fmt.Println(string(p))

So how is it so massively difficult just to unzip a slice of bytes? Anyway...

The problem appears to with how I am reading it out. Where it says z.Read, that doesn't seem to do anything.

How can I read the entire thing in one go into a slice of bytes?

Answer 1

Here's an outline for you. Note: In Go, CHECK FOR ERRORS!

package main

import (
    "bytes"
    "compress/zlib"
    "fmt"
    "io/ioutil"
)

func readSegment(data []byte, from, to int) ([]byte, error) {
    b := bytes.NewReader(data[from : from+to])
    z, err := zlib.NewReader(b)
    if err != nil {
        return nil, err
    }
    defer z.Close()
    p, err := ioutil.ReadAll(z)
    if err != nil {
        return nil, err
    }
    return p, nil
}

func main() {
    from, to := 0, 1000
    data := make([]byte, from+to)
    // ** parse input segments into data **
    p, err := readSegment(data, from, to)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(p))
}