diff options
Diffstat (limited to 'vendor/github.com/oschwald/maxminddb-golang/reader.go')
-rw-r--r-- | vendor/github.com/oschwald/maxminddb-golang/reader.go | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/vendor/github.com/oschwald/maxminddb-golang/reader.go b/vendor/github.com/oschwald/maxminddb-golang/reader.go new file mode 100644 index 0000000..97b9607 --- /dev/null +++ b/vendor/github.com/oschwald/maxminddb-golang/reader.go @@ -0,0 +1,259 @@ +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. +type Reader struct { + hasMappedFile bool + buffer []byte + decoder decoder + Metadata Metadata + ipv4Start uint +} + +// Metadata holds the metadata decoded from the MaxMind DB file. In particular +// in 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 { + BinaryFormatMajorVersion uint `maxminddb:"binary_format_major_version"` + BinaryFormatMinorVersion uint `maxminddb:"binary_format_minor_version"` + BuildEpoch uint `maxminddb:"build_epoch"` + DatabaseType string `maxminddb:"database_type"` + Description map[string]string `maxminddb:"description"` + IPVersion uint `maxminddb:"ip_version"` + Languages []string `maxminddb:"languages"` + 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 + + rvMetdata := reflect.ValueOf(&metadata) + _, err := metadataDecoder.decode(0, rvMetdata, 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)], + } + + reader := &Reader{ + buffer: buffer, + decoder: d, + Metadata: metadata, + ipv4Start: 0, + } + + reader.ipv4Start, err = reader.startNode() + + return reader, err +} + +func (r *Reader) startNode() (uint, error) { + if r.Metadata.IPVersion != 6 { + return 0, nil + } + + nodeCount := r.Metadata.NodeCount + + node := uint(0) + var err error + for i := 0; i < 96 && node < nodeCount; i++ { + node, err = r.readNode(node, 0) + if err != nil { + return 0, err + } + } + return node, err +} + +// Lookup takes an IP address as a net.IP structure and a pointer to the +// result value to Decode into. +func (r *Reader) Lookup(ipAddress net.IP, result interface{}) error { + if r.buffer == nil { + return errors.New("cannot call Lookup on a closed database") + } + pointer, err := r.lookupPointer(ipAddress) + if pointer == 0 || err != nil { + return err + } + return 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(ipAddress net.IP) (uintptr, error) { + if r.buffer == nil { + return 0, errors.New("cannot call LookupOffset on a closed database") + } + pointer, err := r.lookupPointer(ipAddress) + if pointer == 0 || err != nil { + return NotFound, err + } + return r.resolveDataPointer(pointer) +} + +// 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 +// data or an empty interface{} 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. +func (r *Reader) Decode(offset uintptr, result interface{}) error { + if r.buffer == nil { + return errors.New("cannot call Decode on a closed database") + } + return r.decode(offset, result) +} + +func (r *Reader) decode(offset uintptr, result interface{}) error { + rv := reflect.ValueOf(result) + if rv.Kind() != reflect.Ptr || rv.IsNil() { + return errors.New("result param must be a pointer") + } + + _, err := r.decoder.decode(uint(offset), reflect.ValueOf(result), 0) + return err +} + +func (r *Reader) lookupPointer(ipAddress net.IP) (uint, error) { + if ipAddress == nil { + return 0, errors.New("ipAddress passed to Lookup cannot be nil") + } + + ipV4Address := ipAddress.To4() + if ipV4Address != nil { + ipAddress = ipV4Address + } + if len(ipAddress) == 16 && r.Metadata.IPVersion == 4 { + return 0, fmt.Errorf("error looking up '%s': you attempted to look up an IPv6 address in an IPv4-only database", ipAddress.String()) + } + + return r.findAddressInTree(ipAddress) +} + +func (r *Reader) findAddressInTree(ipAddress net.IP) (uint, error) { + + bitCount := uint(len(ipAddress) * 8) + + var node uint + if bitCount == 32 { + node = r.ipv4Start + } + + nodeCount := r.Metadata.NodeCount + + for i := uint(0); i < bitCount && node < nodeCount; i++ { + bit := uint(1) & (uint(ipAddress[i>>3]) >> (7 - (i % 8))) + + var err error + node, err = r.readNode(node, bit) + if err != nil { + return 0, err + } + } + if node == nodeCount { + // Record is empty + return 0, nil + } else if node > nodeCount { + return node, nil + } + + return 0, newInvalidDatabaseError("invalid node in search tree") +} + +func (r *Reader) readNode(nodeNumber uint, index uint) (uint, error) { + RecordSize := r.Metadata.RecordSize + + baseOffset := nodeNumber * RecordSize / 4 + + var nodeBytes []byte + var prefix uint + switch RecordSize { + case 24: + offset := baseOffset + index*3 + nodeBytes = r.buffer[offset : offset+3] + case 28: + prefix = uint(r.buffer[baseOffset+3]) + if index != 0 { + prefix &= 0x0F + } else { + prefix = (0xF0 & prefix) >> 4 + } + offset := baseOffset + index*4 + nodeBytes = r.buffer[offset : offset+3] + case 32: + offset := baseOffset + index*4 + nodeBytes = r.buffer[offset : offset+4] + default: + return 0, newInvalidDatabaseError("unknown record size: %d", RecordSize) + } + return uintFromBytes(prefix, nodeBytes), nil +} + +func (r *Reader) retrieveData(pointer uint, result interface{}) error { + offset, err := r.resolveDataPointer(pointer) + if err != nil { + return err + } + return r.decode(offset, result) +} + +func (r *Reader) resolveDataPointer(pointer uint) (uintptr, error) { + var 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 +} |