2.0.0-beta.8

2.0.0-beta.8

• Fixed "no next offset available" error that occurred when using custom
  unmarshalers that decode container types (maps, slices) in struct fields.
  The reflection decoder now correctly calculates field positions when
  advancing to the next field after custom unmarshaling.

v2.0.0-beta.7

2.0.0-beta.7

• Update capitalization of "uint" in ReadUInt* to match KindUint* as well
  as the Go standard library.

2.0.0-beta.6

2.0.0-beta.6

• Update capitalization of "uint" in ReadUInt* to match KindUint* as well
  as the Go standard library.

2.0.0-beta.5

2.0.0-beta.5

• Added Offset() method to Decoder to get the current database offset. This
  enables custom unmarshalers to implement caching for improved performance when
  loading databases with duplicate data structures.
• Fixed infinite recursion in pointer-to-pointer data structures, which are
  invalid per the MaxMind DB specification.

2.0.0-beta-4

• BREAKING CHANGE: Removed experimental deserializer interface and
  supporting code. Applications using this interface should migrate to the
  Unmarshaler interface by implementing UnmarshalMaxMindDB(d *Decoder) error
  instead.
• Open and FromBytes now accept options.
• BREAKING CHANGE: IncludeNetworksWithoutData and IncludeAliasedNetworks
  now return a NetworksOption rather than being one themselves. These must now
  be called as functions: Networks(IncludeAliasedNetworks()) instead of
  Networks(IncludeAliasedNetworks). This was done to improve the documentation
  organization.
• Added Unmarshaler interface to allow custom decoding implementations for
  performance-critical applications. Types implementing
  UnmarshalMaxMindDB(d *Decoder) error will automatically use custom decoding
  logic instead of reflection, following the same pattern as
  json.Unmarshaler.
• Added public Decoder type and Kind constants in mmdbdata package for
  manual decoding. Decoder provides methods like ReadMap(), ReadSlice(),
  ReadString(), ReadUInt32(), PeekKind(), etc. Kind type includes
  helper methods String(), IsContainer(), and IsScalar() for type
  introspection. The main maxminddb package re-exports these types for
  backward compatibility. NewDecoder() supports an options pattern for
  future extensibility.
• Enhanced UnmarshalMaxMindDB to work with nested struct fields, slice
  elements, and map values. The custom unmarshaler is now called recursively
  for any type that implements the Unmarshaler interface, similar to
  encoding/json.
• Improved error messages to include byte offset information and, for the
  reflection-based API, path information for nested structures using JSON
  Pointer format. For example, errors may now show "at offset 1234, path
  /city/names/en" or "at offset 1234, path /list/0/name" instead of just the
  underlying error message.
• PERFORMANCE: Added string interning optimization that reduces allocations
  while maintaining thread safety. Reduces allocation count from 33 to 10 per
  operation in downstream libraries. Uses a fixed 512-entry cache with per-entry
  mutexes for bounded memory usage (~8KB) while minimizing lock contention.

2.0.0-beta.3

• Open will now fall back to loading the database in memory if the file-system does not support mmap. Pull request by database64128. GitHub #163.
• Made significant improvements to the Windows memory-map handling. . GitHub #162.
• Fix an integer overflow on large databases when using a 32-bit architecture. See ipinfo/mmdbctl#33.

2.0.0-beta.2

• Allow negative indexes for arrays when using DecodePath. #152
• Add IncludeNetworksWithoutData option for Networks and NetworksWithin. #155 and #156

2.0.0-beta.1

This is the first beta of the v2 releases. Go 1.23 is required. I don't expect to do a final release until Go 1.24 is available. See #141 for the v2 roadmap.

Notable changes:

• (*Reader).Lookup now takes only the IP address and returns a Result. Lookup(ip, &rec) would now become Lookup(ip).Decode(&rec).
• (*Reader).LookupNetwork has been removed. To get the network for a result, use (Result).Prefix().
• (*Reader).LookupOffset now takes an offset and returns a Result. Result has an Offset() method that returns the offset value. (*Reader).Decode has been removed.
• Use of net.IP and *net.IPNet have been replaced with netip.Addr and netip.Prefix.
• You may now decode a particular path within a database record using (Result).DecodePath. For instance, to decode just the country code in GeoLite2 Country to a string called code, you might do something like Lookup(ip).DecodePath(&code, "country", "iso_code"). Strings should be used for map keys and ints for array indexes.
• (*Reader).Networks and (*Reader).NetworksWithin now return a Go 1.23 iterator of Result values. Aliased networks are now skipped by default. If you wish to include them, use the IncludeAliasedNetworks option.

1.13.1

• Return the *net.IPNet in canonical form when using NetworksWithin to look up a network more specific than the one in the database. Previously, the IP field on the *net.IPNet would be set to the IP from the lookup network rather than the first IP of the network.
• NetworksWithin will now correctly handle an *net.IPNet parameter that is not in canonical form. This issue would only occur if the *net.IPNet was manually constructed, as net.ParseCIDR returns the value in canonical form even if the input string is not.

1.13.0

• Go 1.21 or greater is now required.
• The error messages when decoding have been improved. #119