mmdbdata

Documentation

Overview

Package mmdbdata provides low-level types and interfaces for custom MaxMind DB decoding.

This package allows custom decoding logic for applications that need fine-grained control over how MaxMind DB data is processed. For most use cases, the high-level maxminddb.Reader API is recommended instead.

Manual Decoding Example

Custom types can implement the Unmarshaler interface for custom decoding:

type City struct {
	Names     map[string]string `maxminddb:"names"`
	GeoNameID uint              `maxminddb:"geoname_id"`
}

func (c *City) UnmarshalMaxMindDB(d *mmdbdata.Decoder) error {
	mapIter, _, err := d.ReadMap()
	if err != nil { return err }
	for key, err := range mapIter {
		if err != nil { return err }
		switch string(key) {
		case "names":
			nameIter, size, err := d.ReadMap()
			if err != nil { return err }
			names := make(map[string]string, size) // Pre-allocate with size
			for nameKey, nameErr := range nameIter {
				if nameErr != nil { return nameErr }
				value, valueErr := d.ReadString()
				if valueErr != nil { return valueErr }
				names[string(nameKey)] = value
			}
			c.Names = names
		case "geoname_id":
			geoID, err := d.ReadUint32()
			if err != nil { return err }
			c.GeoNameID = uint(geoID)
		default:
			if err := d.SkipValue(); err != nil { return err }
		}
	}
	return nil
}

Types implementing Unmarshaler will automatically use custom decoding logic instead of reflection when used with maxminddb.Reader.Lookup, similar to how json.Unmarshaler works with encoding/json.

Direct Decoder Usage

For even more control, you can use the Decoder directly:

decoder := mmdbdata.NewDecoder(buffer, offset)
value, err := decoder.ReadString()
if err != nil {
	return err
}

Package mmdbdata provides types and interfaces for working with MaxMind DB data.

Index

• Constants
• type Decoder
  • func NewDecoder(buffer []byte, offset uint, options ...DecoderOption) *Decoder
• type DecoderOption
• type Kind
• type Unmarshaler

Constants

const (
	KindExtended  = decoder.KindExtended
	KindPointer   = decoder.KindPointer
	KindString    = decoder.KindString
	KindFloat64   = decoder.KindFloat64
	KindBytes     = decoder.KindBytes
	KindUint16    = decoder.KindUint16
	KindUint32    = decoder.KindUint32
	KindMap       = decoder.KindMap
	KindInt32     = decoder.KindInt32
	KindUint64    = decoder.KindUint64
	KindUint128   = decoder.KindUint128
	KindSlice     = decoder.KindSlice
	KindContainer = decoder.KindContainer
	KindEndMarker = decoder.KindEndMarker
	KindBool      = decoder.KindBool
	KindFloat32   = decoder.KindFloat32
)

Kind constants for MMDB data.

Types

type Decoder

type Decoder = decoder.Decoder

Decoder provides methods for decoding MMDB data.

func NewDecoder

func NewDecoder(buffer []byte, offset uint, options ...DecoderOption) *Decoder

NewDecoder creates a new Decoder with the given buffer, offset, and options. Error messages automatically include contextual information like offset and path (e.g., "/city/names/en") with zero impact on successful operations.

type DecoderOption

type DecoderOption = decoder.DecoderOption

DecoderOption configures a Decoder.

type Kind

type Kind = decoder.Kind

Kind represents MMDB data kinds.

type Unmarshaler

type Unmarshaler interface {
	UnmarshalMaxMindDB(d *Decoder) error
}

Unmarshaler is implemented by types that can unmarshal MaxMind DB data. This follows the same pattern as json.Unmarshaler and other Go standard library interfaces.