在 () golang 中读取二进制数据

Question

I need to read a specific binary data format ( https://www.usna.edu/Users/oceano/pguth/md_help/html/BT_file_format.htm ). Go seems to be able to do so quite nicely:

// ...

    f, _ := os.Open(filename)
    var data struct {
        Indicator         [10]byte
        Columns           [4]byte
        Rows              [4]byte
        DataSize          [4]byte
        UTMFlag           [2]byte
        UTMZone           [2]byte
        LeftExtend        [4]byte
        RightExtend       [4]byte
        BottomExtend      [4]byte
        TopExtend         [4]byte
        FloatingPointFlag [2]byte
    }
    _ = binary.Read(f, binary.LittleEndian, &data)
// ...

That seems to work since spew.dump(data.Indicator) for example return the correct data. What I do not understand is how to cast fixed slices like [2]byte to an integer I can actually work with. Any suggestions?

Answer 1

Declare the fields with fixed size numeric types:

var data struct {
    Indicator         [10]byte
    Columns           uint32
    Rows              uint32
    DataSize          uint32
    UTMFlag           uint16
    UTMZone           uint16
    LeftExtend        uint32
    RightExtend       uint32
    BottomExtend      uint32
    TopExtend         uint32
    FloatingPointFlag uint16
}

I used unsigned integers here, but it's also OK to use signed integers. Use the type that matches the data.

https://play.golang.org/p/95yqMAYsWVR