1 files changed, 391 insertions, 0 deletions

diff --git a/vendor/github.com/rs/xid/id.go b/vendor/github.com/rs/xid/id.go
new file mode 100644
index 0000000..fcd7a04
--- /dev/null
+++ b/vendor/github.com/rs/xid/id.go
@@ -0,0 +1,391 @@
+// Package xid is a globally unique id generator suited for web scale
+//
+// Xid is using Mongo Object ID algorithm to generate globally unique ids:
+// https://docs.mongodb.org/manual/reference/object-id/
+//
+//   - 4-byte value representing the seconds since the Unix epoch,
+//   - 3-byte machine identifier,
+//   - 2-byte process id, and
+//   - 3-byte counter, starting with a random value.
+//
+// The binary representation of the id is compatible with Mongo 12 bytes Object IDs.
+// The string representation is using base32 hex (w/o padding) for better space efficiency
+// when stored in that form (20 bytes). The hex variant of base32 is used to retain the
+// sortable property of the id.
+//
+// Xid doesn't use base64 because case sensitivity and the 2 non alphanum chars may be an
+// issue when transported as a string between various systems. Base36 wasn't retained either
+// because 1/ it's not standard 2/ the resulting size is not predictable (not bit aligned)
+// and 3/ it would not remain sortable. To validate a base32 `xid`, expect a 20 chars long,
+// all lowercase sequence of `a` to `v` letters and `0` to `9` numbers (`[0-9a-v]{20}`).
+//
+// UUID is 16 bytes (128 bits), snowflake is 8 bytes (64 bits), xid stands in between
+// with 12 bytes with a more compact string representation ready for the web and no
+// required configuration or central generation server.
+//
+// Features:
+//
+//   - Size: 12 bytes (96 bits), smaller than UUID, larger than snowflake
+//   - Base32 hex encoded by default (16 bytes storage when transported as printable string)
+//   - Non configured, you don't need set a unique machine and/or data center id
+//   - K-ordered
+//   - Embedded time with 1 second precision
+//   - Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process
+//
+// Best used with xlog's RequestIDHandler (https://godoc.org/github.com/rs/xlog#RequestIDHandler).
+//
+// References:
+//
+//   - http://www.slideshare.net/davegardnerisme/unique-id-generation-in-distributed-systems
+//   - https://en.wikipedia.org/wiki/Universally_unique_identifier
+//   - https://blog.twitter.com/2010/announcing-snowflake
+package xid
+
+import (
+        "bytes"
+        "crypto/sha256"
+        "crypto/rand"
+        "database/sql/driver"
+        "encoding/binary"
+        "fmt"
+        "hash/crc32"
+        "io/ioutil"
+        "os"
+        "sort"
+        "sync/atomic"
+        "time"
+        "unsafe"
+)
+
+// Code inspired from mgo/bson ObjectId
+
+// ID represents a unique request id
+type ID [rawLen]byte
+
+const (
+        encodedLen = 20 // string encoded len
+        rawLen     = 12 // binary raw len
+
+        // encoding stores a custom version of the base32 encoding with lower case
+        // letters.
+        encoding = "0123456789abcdefghijklmnopqrstuv"
+)
+
+var (
+        // objectIDCounter is atomically incremented when generating a new ObjectId. It's
+        // used as the counter part of an id. This id is initialized with a random value.
+        objectIDCounter = randInt()
+
+        // machineID is generated once and used in subsequent calls to the New* functions.
+        machineID = readMachineID()
+
+        // pid stores the current process id
+        pid = os.Getpid()
+
+        nilID ID
+
+        // dec is the decoding map for base32 encoding
+        dec [256]byte
+)
+
+func init() {
+        for i := 0; i < len(dec); i++ {
+                dec[i] = 0xFF
+        }
+        for i := 0; i < len(encoding); i++ {
+                dec[encoding[i]] = byte(i)
+        }
+
+        // If /proc/self/cpuset exists and is not /, we can assume that we are in a
+        // form of container and use the content of cpuset xor-ed with the PID in
+        // order get a reasonable machine global unique PID.
+        b, err := ioutil.ReadFile("/proc/self/cpuset")
+        if err == nil && len(b) > 1 {
+                pid ^= int(crc32.ChecksumIEEE(b))
+        }
+}
+
+// readMachineID generates a machine ID, derived from a platform-specific machine ID
+// value, or else the machine's hostname, or else a randomly-generated number.
+// It panics if all of these methods fail.
+func readMachineID() []byte {
+        id := make([]byte, 3)
+        hid, err := readPlatformMachineID()
+        if err != nil || len(hid) == 0 {
+                hid, err = os.Hostname()
+        }
+        if err == nil && len(hid) != 0 {
+                hw := sha256.New()
+                hw.Write([]byte(hid))
+                copy(id, hw.Sum(nil))
+        } else {
+                // Fallback to rand number if machine id can't be gathered
+                if _, randErr := rand.Reader.Read(id); randErr != nil {
+                        panic(fmt.Errorf("xid: cannot get hostname nor generate a random number: %v; %v", err, randErr))
+                }
+        }
+        return id
+}
+
+// randInt generates a random uint32
+func randInt() uint32 {
+        b := make([]byte, 3)
+        if _, err := rand.Reader.Read(b); err != nil {
+                panic(fmt.Errorf("xid: cannot generate random number: %v;", err))
+        }
+        return uint32(b[0])<<16 | uint32(b[1])<<8 | uint32(b[2])
+}
+
+// New generates a globally unique ID
+func New() ID {
+        return NewWithTime(time.Now())
+}
+
+// NewWithTime generates a globally unique ID with the passed in time
+func NewWithTime(t time.Time) ID {
+        var id ID
+        // Timestamp, 4 bytes, big endian
+        binary.BigEndian.PutUint32(id[:], uint32(t.Unix()))
+        // Machine ID, 3 bytes
+        id[4] = machineID[0]
+        id[5] = machineID[1]
+        id[6] = machineID[2]
+        // Pid, 2 bytes, specs don't specify endianness, but we use big endian.
+        id[7] = byte(pid >> 8)
+        id[8] = byte(pid)
+        // Increment, 3 bytes, big endian
+        i := atomic.AddUint32(&objectIDCounter, 1)
+        id[9] = byte(i >> 16)
+        id[10] = byte(i >> 8)
+        id[11] = byte(i)
+        return id
+}
+
+// FromString reads an ID from its string representation
+func FromString(id string) (ID, error) {
+        i := &ID{}
+        err := i.UnmarshalText([]byte(id))
+        return *i, err
+}
+
+// String returns a base32 hex lowercased with no padding representation of the id (char set is 0-9, a-v).
+func (id ID) String() string {
+        text := make([]byte, encodedLen)
+        encode(text, id[:])
+        return *(*string)(unsafe.Pointer(&text))
+}
+
+// Encode encodes the id using base32 encoding, writing 20 bytes to dst and return it.
+func (id ID) Encode(dst []byte) []byte {
+        encode(dst, id[:])
+        return dst
+}
+
+// MarshalText implements encoding/text TextMarshaler interface
+func (id ID) MarshalText() ([]byte, error) {
+        text := make([]byte, encodedLen)
+        encode(text, id[:])
+        return text, nil
+}
+
+// MarshalJSON implements encoding/json Marshaler interface
+func (id ID) MarshalJSON() ([]byte, error) {
+        if id.IsNil() {
+                return []byte("null"), nil
+        }
+        text := make([]byte, encodedLen+2)
+        encode(text[1:encodedLen+1], id[:])
+        text[0], text[encodedLen+1] = '"', '"'
+        return text, nil
+}
+
+// encode by unrolling the stdlib base32 algorithm + removing all safe checks
+func encode(dst, id []byte) {
+        _ = dst[19]
+        _ = id[11]
+
+        dst[19] = encoding[(id[11]<<4)&0x1F]
+        dst[18] = encoding[(id[11]>>1)&0x1F]
+        dst[17] = encoding[(id[11]>>6)&0x1F|(id[10]<<2)&0x1F]
+        dst[16] = encoding[id[10]>>3]
+        dst[15] = encoding[id[9]&0x1F]
+        dst[14] = encoding[(id[9]>>5)|(id[8]<<3)&0x1F]
+        dst[13] = encoding[(id[8]>>2)&0x1F]
+        dst[12] = encoding[id[8]>>7|(id[7]<<1)&0x1F]
+        dst[11] = encoding[(id[7]>>4)&0x1F|(id[6]<<4)&0x1F]
+        dst[10] = encoding[(id[6]>>1)&0x1F]
+        dst[9] = encoding[(id[6]>>6)&0x1F|(id[5]<<2)&0x1F]
+        dst[8] = encoding[id[5]>>3]
+        dst[7] = encoding[id[4]&0x1F]
+        dst[6] = encoding[id[4]>>5|(id[3]<<3)&0x1F]
+        dst[5] = encoding[(id[3]>>2)&0x1F]
+        dst[4] = encoding[id[3]>>7|(id[2]<<1)&0x1F]
+        dst[3] = encoding[(id[2]>>4)&0x1F|(id[1]<<4)&0x1F]
+        dst[2] = encoding[(id[1]>>1)&0x1F]
+        dst[1] = encoding[(id[1]>>6)&0x1F|(id[0]<<2)&0x1F]
+        dst[0] = encoding[id[0]>>3]
+}
+
+// UnmarshalText implements encoding/text TextUnmarshaler interface
+func (id *ID) UnmarshalText(text []byte) error {
+        if len(text) != encodedLen {
+                return ErrInvalidID
+        }
+        for _, c := range text {
+                if dec[c] == 0xFF {
+                        return ErrInvalidID
+                }
+        }
+        if !decode(id, text) {
+                *id = nilID
+                return ErrInvalidID
+        }
+        return nil
+}
+
+// UnmarshalJSON implements encoding/json Unmarshaler interface
+func (id *ID) UnmarshalJSON(b []byte) error {
+        s := string(b)
+        if s == "null" {
+                *id = nilID
+                return nil
+        }
+        // Check the slice length to prevent panic on passing it to UnmarshalText()
+        if len(b) < 2 {
+                return ErrInvalidID
+        }
+        return id.UnmarshalText(b[1 : len(b)-1])
+}
+
+// decode by unrolling the stdlib base32 algorithm + customized safe check.
+func decode(id *ID, src []byte) bool {
+        _ = src[19]
+        _ = id[11]
+
+        id[11] = dec[src[17]]<<6 | dec[src[18]]<<1 | dec[src[19]]>>4
+        // check the last byte
+        if encoding[(id[11]<<4)&0x1F] != src[19] {
+                return false
+        }
+        id[10] = dec[src[16]]<<3 | dec[src[17]]>>2
+        id[9] = dec[src[14]]<<5 | dec[src[15]]
+        id[8] = dec[src[12]]<<7 | dec[src[13]]<<2 | dec[src[14]]>>3
+        id[7] = dec[src[11]]<<4 | dec[src[12]]>>1
+        id[6] = dec[src[9]]<<6 | dec[src[10]]<<1 | dec[src[11]]>>4
+        id[5] = dec[src[8]]<<3 | dec[src[9]]>>2
+        id[4] = dec[src[6]]<<5 | dec[src[7]]
+        id[3] = dec[src[4]]<<7 | dec[src[5]]<<2 | dec[src[6]]>>3
+        id[2] = dec[src[3]]<<4 | dec[src[4]]>>1
+        id[1] = dec[src[1]]<<6 | dec[src[2]]<<1 | dec[src[3]]>>4
+        id[0] = dec[src[0]]<<3 | dec[src[1]]>>2
+        return true
+}
+
+// Time returns the timestamp part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ID) Time() time.Time {
+        // First 4 bytes of ObjectId is 32-bit big-endian seconds from epoch.
+        secs := int64(binary.BigEndian.Uint32(id[0:4]))
+        return time.Unix(secs, 0)
+}
+
+// Machine returns the 3-byte machine id part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ID) Machine() []byte {
+        return id[4:7]
+}
+
+// Pid returns the process id part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ID) Pid() uint16 {
+        return binary.BigEndian.Uint16(id[7:9])
+}
+
+// Counter returns the incrementing value part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ID) Counter() int32 {
+        b := id[9:12]
+        // Counter is stored as big-endian 3-byte value
+        return int32(uint32(b[0])<<16 | uint32(b[1])<<8 | uint32(b[2]))
+}
+
+// Value implements the driver.Valuer interface.
+func (id ID) Value() (driver.Value, error) {
+        if id.IsNil() {
+                return nil, nil
+        }
+        b, err := id.MarshalText()
+        return string(b), err
+}
+
+// Scan implements the sql.Scanner interface.
+func (id *ID) Scan(value interface{}) (err error) {
+        switch val := value.(type) {
+        case string:
+                return id.UnmarshalText([]byte(val))
+        case []byte:
+                return id.UnmarshalText(val)
+        case nil:
+                *id = nilID
+                return nil
+        default:
+                return fmt.Errorf("xid: scanning unsupported type: %T", value)
+        }
+}
+
+// IsNil Returns true if this is a "nil" ID
+func (id ID) IsNil() bool {
+        return id == nilID
+}
+
+// Alias of IsNil
+func (id ID) IsZero() bool {
+        return id.IsNil()
+}
+
+// NilID returns a zero value for `xid.ID`.
+func NilID() ID {
+        return nilID
+}
+
+// Bytes returns the byte array representation of `ID`
+func (id ID) Bytes() []byte {
+        return id[:]
+}
+
+// FromBytes convert the byte array representation of `ID` back to `ID`
+func FromBytes(b []byte) (ID, error) {
+        var id ID
+        if len(b) != rawLen {
+                return id, ErrInvalidID
+        }
+        copy(id[:], b)
+        return id, nil
+}
+
+// Compare returns an integer comparing two IDs. It behaves just like `bytes.Compare`.
+// The result will be 0 if two IDs are identical, -1 if current id is less than the other one,
+// and 1 if current id is greater than the other.
+func (id ID) Compare(other ID) int {
+        return bytes.Compare(id[:], other[:])
+}
+
+type sorter []ID
+
+func (s sorter) Len() int {
+        return len(s)
+}
+
+func (s sorter) Less(i, j int) bool {
+        return s[i].Compare(s[j]) < 0
+}
+
+func (s sorter) Swap(i, j int) {
+        s[i], s[j] = s[j], s[i]
+}
+
+// Sort sorts an array of IDs inplace.
+// It works by wrapping `[]ID` and use `sort.Sort`.
+func Sort(ids []ID) {
+        sort.Sort(sorter(ids))
+}