Can I create from a Bitmap an a specification ?

[camilotorres]

Can I create a specification from a Bitmap ?

[alovak]

@camilotorres can you please be more specific with your question?

[camilotorres]

@alovak , sure, thanks; if we have a structure into the database for MTI transactions for example 0100 with BITMAP "F0040000200000000000000000000000" then I could create the specification of the message with this fields from this bitmap.

[alovak]

Having a bitmap you can see which fields of the spec are present in the message. Here is the test code that you can use to see set bits in your bitmap:

package iso8583_test

import (
	"fmt"
	"testing"

	"github.com/moov-io/iso8583/encoding"
	"github.com/moov-io/iso8583/field"
	"github.com/moov-io/iso8583/prefix"
)

func TestBitmap(t *testing.T) {
	bitmapSpec := &field.Spec{
		Length:      8,
		Description: "Bitmap",
		Enc:         encoding.BytesToASCIIHex,
		Pref:        prefix.Hex.Fixed,
	}

	bitmap := field.NewBitmap(bitmapSpec)

	_, err := bitmap.Unpack([]byte("F0040000200000000000000000000000"))
	if err != nil {
		t.Fatal(err)
	}

	bits, _ := bitmap.String()

	fmt.Printf("bits of the bitmap: %s\n", bits)

	for i := 1; i <= bitmap.Len(); i++ {
		if bitmap.IsSet(i) {
			fmt.Printf("bit %d is set\n", i)
		}
	}
}

The output is:

bits of the bitmap: 11110000 00000100 00000000 00000000 00100000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bit 1 is set
bit 2 is set
bit 3 is set
bit 4 is set
bit 14 is set
bit 35 is set

So, you can see that the message for this bitmap has the following fields: 1,2,3,4,14,35.

But that's all you can get having only the bitmap.

You need a full message spec (at least you need to describe fields that are in the message) to properly decode the message.

If you don't have a document that in details describes the field formats, then I would suggest you try this one: https://github.com/moov-io/iso8583/blob/master/specs/spec87ascii.go#L12 as you may see I copied bitmap spec from that file.

If you can provide more details about the data you have, together we may try to guess what the spec is. I'll also better understand what you want to achieve using the iso8583 package.

[adamdecaf]

Would a CLI command to unpack and describe the set bits be helpful?

[camilotorres]

Excelent thanks !!