dip/vendor/github.com/oschwald/maxminddb-golang/reader.go

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// Package maxminddb provides a reader for the MaxMind DB file format.
package maxminddb
import (
"bytes"
"errors"
"fmt"
"net"
"reflect"
)
const (
// NotFound is returned by LookupOffset when a matched root record offset
// cannot be found.
NotFound = ^uintptr(0)
dataSectionSeparatorSize = 16
)
var metadataStartMarker = []byte("\xAB\xCD\xEFMaxMind.com")
// Reader holds the data corresponding to the MaxMind DB file. Its only public
// field is Metadata, which contains the metadata from the MaxMind DB file.
//
// All of the methods on Reader are thread-safe. The struct may be safely
// shared across goroutines.
type Reader struct {
nodeReader nodeReader
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buffer []byte
decoder decoder
Metadata Metadata
ipv4Start uint
ipv4StartBitDepth int
nodeOffsetMult uint
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hasMappedFile bool
}
// Metadata holds the metadata decoded from the MaxMind DB file. In particular
// it has the format version, the build time as Unix epoch time, the database
// type and description, the IP version supported, and a slice of the natural
// languages included.
type Metadata struct {
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Description map[string]string `maxminddb:"description"`
DatabaseType string `maxminddb:"database_type"`
Languages []string `maxminddb:"languages"`
BinaryFormatMajorVersion uint `maxminddb:"binary_format_major_version"`
BinaryFormatMinorVersion uint `maxminddb:"binary_format_minor_version"`
BuildEpoch uint `maxminddb:"build_epoch"`
IPVersion uint `maxminddb:"ip_version"`
NodeCount uint `maxminddb:"node_count"`
RecordSize uint `maxminddb:"record_size"`
}
// FromBytes takes a byte slice corresponding to a MaxMind DB file and returns
// a Reader structure or an error.
func FromBytes(buffer []byte) (*Reader, error) {
metadataStart := bytes.LastIndex(buffer, metadataStartMarker)
if metadataStart == -1 {
return nil, newInvalidDatabaseError("error opening database: invalid MaxMind DB file")
}
metadataStart += len(metadataStartMarker)
metadataDecoder := decoder{buffer[metadataStart:]}
var metadata Metadata
rvMetadata := reflect.ValueOf(&metadata)
_, err := metadataDecoder.decode(0, rvMetadata, 0)
if err != nil {
return nil, err
}
searchTreeSize := metadata.NodeCount * metadata.RecordSize / 4
dataSectionStart := searchTreeSize + dataSectionSeparatorSize
dataSectionEnd := uint(metadataStart - len(metadataStartMarker))
if dataSectionStart > dataSectionEnd {
return nil, newInvalidDatabaseError("the MaxMind DB contains invalid metadata")
}
d := decoder{
buffer[searchTreeSize+dataSectionSeparatorSize : metadataStart-len(metadataStartMarker)],
}
nodeBuffer := buffer[:searchTreeSize]
var nodeReader nodeReader
switch metadata.RecordSize {
case 24:
nodeReader = nodeReader24{buffer: nodeBuffer}
case 28:
nodeReader = nodeReader28{buffer: nodeBuffer}
case 32:
nodeReader = nodeReader32{buffer: nodeBuffer}
default:
return nil, newInvalidDatabaseError("unknown record size: %d", metadata.RecordSize)
}
reader := &Reader{
buffer: buffer,
nodeReader: nodeReader,
decoder: d,
Metadata: metadata,
ipv4Start: 0,
nodeOffsetMult: metadata.RecordSize / 4,
}
reader.setIPv4Start()
return reader, err
}
func (r *Reader) setIPv4Start() {
if r.Metadata.IPVersion != 6 {
return
}
nodeCount := r.Metadata.NodeCount
node := uint(0)
i := 0
for ; i < 96 && node < nodeCount; i++ {
node = r.nodeReader.readLeft(node * r.nodeOffsetMult)
}
r.ipv4Start = node
r.ipv4StartBitDepth = i
}
// Lookup retrieves the database record for ip and stores it in the value
// pointed to by result. If result is nil or not a pointer, an error is
// returned. If the data in the database record cannot be stored in result
// because of type differences, an UnmarshalTypeError is returned. If the
// database is invalid or otherwise cannot be read, an InvalidDatabaseError
// is returned.
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func (r *Reader) Lookup(ip net.IP, result any) error {
if r.buffer == nil {
return errors.New("cannot call Lookup on a closed database")
}
pointer, _, _, err := r.lookupPointer(ip)
if pointer == 0 || err != nil {
return err
}
return r.retrieveData(pointer, result)
}
// LookupNetwork retrieves the database record for ip and stores it in the
// value pointed to by result. The network returned is the network associated
// with the data record in the database. The ok return value indicates whether
// the database contained a record for the ip.
//
// If result is nil or not a pointer, an error is returned. If the data in the
// database record cannot be stored in result because of type differences, an
// UnmarshalTypeError is returned. If the database is invalid or otherwise
// cannot be read, an InvalidDatabaseError is returned.
func (r *Reader) LookupNetwork(
ip net.IP,
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result any,
) (network *net.IPNet, ok bool, err error) {
if r.buffer == nil {
return nil, false, errors.New("cannot call Lookup on a closed database")
}
pointer, prefixLength, ip, err := r.lookupPointer(ip)
network = r.cidr(ip, prefixLength)
if pointer == 0 || err != nil {
return network, false, err
}
return network, true, r.retrieveData(pointer, result)
}
// LookupOffset maps an argument net.IP to a corresponding record offset in the
// database. NotFound is returned if no such record is found, and a record may
// otherwise be extracted by passing the returned offset to Decode. LookupOffset
// is an advanced API, which exists to provide clients with a means to cache
// previously-decoded records.
func (r *Reader) LookupOffset(ip net.IP) (uintptr, error) {
if r.buffer == nil {
return 0, errors.New("cannot call LookupOffset on a closed database")
}
pointer, _, _, err := r.lookupPointer(ip)
if pointer == 0 || err != nil {
return NotFound, err
}
return r.resolveDataPointer(pointer)
}
func (r *Reader) cidr(ip net.IP, prefixLength int) *net.IPNet {
// This is necessary as the node that the IPv4 start is at may
// be at a bit depth that is less that 96, i.e., ipv4Start points
// to a leaf node. For instance, if a record was inserted at ::/8,
// the ipv4Start would point directly at the leaf node for the
// record and would have a bit depth of 8. This would not happen
// with databases currently distributed by MaxMind as all of them
// have an IPv4 subtree that is greater than a single node.
if r.Metadata.IPVersion == 6 &&
len(ip) == net.IPv4len &&
r.ipv4StartBitDepth != 96 {
return &net.IPNet{IP: net.ParseIP("::"), Mask: net.CIDRMask(r.ipv4StartBitDepth, 128)}
}
mask := net.CIDRMask(prefixLength, len(ip)*8)
return &net.IPNet{IP: ip.Mask(mask), Mask: mask}
}
// Decode the record at |offset| into |result|. The result value pointed to
// must be a data value that corresponds to a record in the database. This may
// include a struct representation of the data, a map capable of holding the
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// data or an empty any value.
//
// If result is a pointer to a struct, the struct need not include a field
// for every value that may be in the database. If a field is not present in
// the structure, the decoder will not decode that field, reducing the time
// required to decode the record.
//
// As a special case, a struct field of type uintptr will be used to capture
// the offset of the value. Decode may later be used to extract the stored
// value from the offset. MaxMind DBs are highly normalized: for example in
// the City database, all records of the same country will reference a
// single representative record for that country. This uintptr behavior allows
// clients to leverage this normalization in their own sub-record caching.
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func (r *Reader) Decode(offset uintptr, result any) error {
if r.buffer == nil {
return errors.New("cannot call Decode on a closed database")
}
return r.decode(offset, result)
}
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func (r *Reader) decode(offset uintptr, result any) error {
rv := reflect.ValueOf(result)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
return errors.New("result param must be a pointer")
}
if dser, ok := result.(deserializer); ok {
_, err := r.decoder.decodeToDeserializer(uint(offset), dser, 0, false)
return err
}
_, err := r.decoder.decode(uint(offset), rv, 0)
return err
}
func (r *Reader) lookupPointer(ip net.IP) (uint, int, net.IP, error) {
if ip == nil {
return 0, 0, nil, errors.New("IP passed to Lookup cannot be nil")
}
ipV4Address := ip.To4()
if ipV4Address != nil {
ip = ipV4Address
}
if len(ip) == 16 && r.Metadata.IPVersion == 4 {
return 0, 0, ip, fmt.Errorf(
"error looking up '%s': you attempted to look up an IPv6 address in an IPv4-only database",
ip.String(),
)
}
bitCount := uint(len(ip) * 8)
var node uint
if bitCount == 32 {
node = r.ipv4Start
}
node, prefixLength := r.traverseTree(ip, node, bitCount)
nodeCount := r.Metadata.NodeCount
if node == nodeCount {
// Record is empty
return 0, prefixLength, ip, nil
} else if node > nodeCount {
return node, prefixLength, ip, nil
}
return 0, prefixLength, ip, newInvalidDatabaseError("invalid node in search tree")
}
func (r *Reader) traverseTree(ip net.IP, node, bitCount uint) (uint, int) {
nodeCount := r.Metadata.NodeCount
i := uint(0)
for ; i < bitCount && node < nodeCount; i++ {
bit := uint(1) & (uint(ip[i>>3]) >> (7 - (i % 8)))
offset := node * r.nodeOffsetMult
if bit == 0 {
node = r.nodeReader.readLeft(offset)
} else {
node = r.nodeReader.readRight(offset)
}
}
return node, int(i)
}
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func (r *Reader) retrieveData(pointer uint, result any) error {
offset, err := r.resolveDataPointer(pointer)
if err != nil {
return err
}
return r.decode(offset, result)
}
func (r *Reader) resolveDataPointer(pointer uint) (uintptr, error) {
resolved := uintptr(pointer - r.Metadata.NodeCount - dataSectionSeparatorSize)
if resolved >= uintptr(len(r.buffer)) {
return 0, newInvalidDatabaseError("the MaxMind DB file's search tree is corrupt")
}
return resolved, nil
}