binary.Read（）在struct中不产生期望值

Question

I'm trying to make a MOBI file parser and I'm running into a bit of an issue with trying to parse some of the binary into a struct with binary.Read().

I'm thinking it's an alignment issue, but I'm at a loss for why I'm not getting expected values. I've run the .mobi file through libmobi to test my code's output against, as well as inspected the binary of the .mobi in order to verify that I'm not crazy and the libmobi code wasn't doing something weird (which it's not).

Here's a stripped-down example:

package main

import (
    "bytes"
    "encoding/binary"
    "fmt"
)

type Header struct {
    Type        [4]byte
    Creator     [4]byte
    Uid         uint32
    Next        uint32
    RecordCount uint16
}

func main() {
    testBytes := []byte{66, 79, 79, 75, 77, 79, 66, 73, 0, 0, 1, 17, 0, 0, 0, 0, 0, 136}

    h := Header{}
    buf := bytes.NewBuffer(testBytes)
    binary.Read(buf, binary.LittleEndian, &h)

    fmt.Printf("%s
", h.Type)    // BOOK, as expected
    fmt.Printf("%s
", h.Creator) // MOBI, as expected
    fmt.Printf("%d
", h.Next)    // 0, as expected

    fmt.Printf("%d
", h.Uid)
    // expecting Uid to be 273, but it's 285278208...
    fmt.Printf("%d
", h.RecordCount)
    // expecting RecordCount to be 136, but it's 34816...
}

Any help would be greatly appreciated!

EDIT: here are the hex bytes from doing a xxd on book.mobi:

424f 4f4b 4d4f 4249 0000 0111 0000 0000 0088

Answer 1

Yes BigEndian works much better

package main

import (
    "bytes"
    "encoding/binary"
    "fmt"
)

type Header struct {
    Type        [4]byte
    Creator     [4]byte
    Uid         uint32
    Next        uint32
    RecordCount uint16
}

func main() {
    testBytes := []byte{66, 79, 79, 75, 77, 79, 66, 73, 0, 0, 1, 17, 0, 0, 0, 0, 0, 136}

    h := Header{}
    buf := bytes.NewBuffer(testBytes)
    binary.Read(buf, binary.BigEndian, &h)

    fmt.Printf("%s
", h.Type)    // BOOK, as expected
    fmt.Printf("%s
", h.Creator) // MOBI, as expected
    fmt.Printf("%d
", h.Next)    // 0, as expected

    fmt.Printf("%d
", h.Uid)
    // expecting Uid to be 273, but it's 285278208...
    fmt.Printf("%d
", h.RecordCount)
    // expecting RecordCount to be 136, but it's 34816...
}