6257ddba78
The big change is that the GeoJSON package has been completely rewritten to fix a few of geometry calculation bugs, increase performance, and to better follow the GeoJSON spec RFC 7946. GeoJSON updates - A LineString now requires at least two points. - All json members, even foreign, now persist with the object. - The bbox member persists too but is no longer used for geometry calculations. This is change in behavior. Previously Tile38 would treat the bbox as the object's physical rectangle. - Corrections to geometry intersects and within calculations. Faster spatial queries - The performance of Point-in-polygon and object intersect operations are greatly improved for complex polygons and line strings. It went from O(n) to roughly O(log n). - The same for all collection types with many children, including FeatureCollection, GeometryCollection, MultiPoint, MultiLineString, and MultiPolygon. Codebase changes - The pkg directory has been renamed to internal - The GeoJSON internal package has been moved to a seperate repo at https://github.com/tidwall/geojson. It's now vendored. Please look out for higher memory usage for datasets using complex shapes. A complex shape is one that has 64 or more points. For these shapes it's expected that there will be increase of least 54 bytes per point.
125 lines
2.8 KiB
Go
125 lines
2.8 KiB
Go
// Copyright 2016 Apcera Inc. All rights reserved.
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// A unique identifier generator that is high performance, very fast, and tries to be entropy pool friendly.
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package nuid
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import (
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"crypto/rand"
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"fmt"
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"math"
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"math/big"
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"sync"
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"time"
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prand "math/rand"
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)
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// NUID needs to be very fast to generate and truly unique, all while being entropy pool friendly.
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// We will use 12 bytes of crypto generated data (entropy draining), and 10 bytes of sequential data
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// that is started at a pseudo random number and increments with a pseudo-random increment.
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// Total is 22 bytes of base 62 ascii text :)
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// Version of the library
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const Version = "1.0.0"
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const (
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digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
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base = 62
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preLen = 12
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seqLen = 10
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maxSeq = int64(839299365868340224) // base^seqLen == 62^10
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minInc = int64(33)
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maxInc = int64(333)
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totalLen = preLen + seqLen
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)
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type NUID struct {
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pre []byte
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seq int64
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inc int64
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}
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type lockedNUID struct {
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sync.Mutex
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*NUID
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}
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// Global NUID
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var globalNUID *lockedNUID
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// Seed sequential random with crypto or math/random and current time
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// and generate crypto prefix.
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func init() {
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r, err := rand.Int(rand.Reader, big.NewInt(math.MaxInt64))
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if err != nil {
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prand.Seed(time.Now().UnixNano())
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} else {
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prand.Seed(r.Int64())
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}
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globalNUID = &lockedNUID{NUID: New()}
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globalNUID.RandomizePrefix()
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}
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// New will generate a new NUID and properly initialize the prefix, sequential start, and sequential increment.
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func New() *NUID {
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n := &NUID{
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seq: prand.Int63n(maxSeq),
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inc: minInc + prand.Int63n(maxInc-minInc),
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pre: make([]byte, preLen),
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}
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n.RandomizePrefix()
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return n
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}
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// Generate the next NUID string from the global locked NUID instance.
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func Next() string {
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globalNUID.Lock()
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nuid := globalNUID.Next()
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globalNUID.Unlock()
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return nuid
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}
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// Generate the next NUID string.
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func (n *NUID) Next() string {
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// Increment and capture.
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n.seq += n.inc
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if n.seq >= maxSeq {
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n.RandomizePrefix()
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n.resetSequential()
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}
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seq := n.seq
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// Copy prefix
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var b [totalLen]byte
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bs := b[:preLen]
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copy(bs, n.pre)
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// copy in the seq in base36.
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for i, l := len(b), seq; i > preLen; l /= base {
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i -= 1
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b[i] = digits[l%base]
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}
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return string(b[:])
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}
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// Resets the sequential portion of the NUID.
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func (n *NUID) resetSequential() {
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n.seq = prand.Int63n(maxSeq)
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n.inc = minInc + prand.Int63n(maxInc-minInc)
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}
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// Generate a new prefix from crypto/rand.
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// This call *can* drain entropy and will be called automatically when we exhaust the sequential range.
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// Will panic if it gets an error from rand.Int()
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func (n *NUID) RandomizePrefix() {
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var cb [preLen]byte
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cbs := cb[:]
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if nb, err := rand.Read(cbs); nb != preLen || err != nil {
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panic(fmt.Sprintf("nuid: failed generating crypto random number: %v\n", err))
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}
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for i := 0; i < preLen; i++ {
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n.pre[i] = digits[int(cbs[i])%base]
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}
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}
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