133 lines
4.1 KiB
Go
133 lines
4.1 KiB
Go
package mangler
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import (
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"encoding/binary"
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"reflect"
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"unsafe"
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"github.com/cespare/xxhash"
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"github.com/cornelk/hashmap"
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)
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var (
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// manglers is a map of runtime type ptrs => Mangler functions.
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manglers = hashmap.New[uintptr, Mangler]()
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// bin is a short-hand for our chosen byteorder encoding.
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bin = binary.LittleEndian
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)
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// Mangled is an interface that allows any type to implement a custom
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// Mangler function to improve performance when mangling this type.
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type Mangled interface {
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Mangle(buf []byte) []byte
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}
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// Mangler is a function that will take an input interface value of known
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// type, and append it in mangled serialized form to the given byte buffer.
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// While the value type is an interface, the Mangler functions are accessed
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// by the value's runtime type pointer, allowing the input value type to be known.
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type Mangler func(buf []byte, value any) []byte
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// rMangler is functionally the same as a Mangler function, but it
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// takes the value input in reflected form. By specifying these differences
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// in mangler function types, it allows us to cut back on new calls to
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// `reflect.ValueOf()` and instead pass by existing reflected values.
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type rMangler func(buf []byte, value reflect.Value) []byte
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// Get will fetch the Mangler function for given runtime type.
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func Get(t reflect.Type) (Mangler, bool) {
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if t == nil {
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return nil, false
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}
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uptr := uintptr(iface_value(t))
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return manglers.Get(uptr)
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}
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// Register will register the given Mangler function for use with vars of given runtime type. This allows
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// registering performant manglers for existing types not implementing Mangled (e.g. std library types).
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// NOTE: panics if there already exists a Mangler function for given type. Register on init().
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func Register(t reflect.Type, m Mangler) {
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if t == nil {
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// Nil interface{} types cannot be searched by, do not accept
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panic("cannot register mangler for nil interface{} type")
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}
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// Get raw runtime type ptr
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uptr := uintptr(iface_value(t))
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// Ensure this is a unique encoder
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if _, ok := manglers.Get(uptr); ok {
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panic("already registered mangler for type: " + t.String())
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}
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// Cache this encoder func
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manglers.Set(uptr, m)
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}
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// Append will append the mangled form of input value 'a' to buffer 'b'.
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// See mangler.String() for more information on mangled output.
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func Append(b []byte, a any) []byte {
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// Get reflect type of 'a'
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t := reflect.TypeOf(a)
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// Get raw runtime type ptr
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uptr := uintptr(iface_value(t))
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// Look for a cached mangler
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mng, ok := manglers.Get(uptr)
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if !ok {
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// Load mangler into cache
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mng = loadMangler(a, t)
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manglers.Set(uptr, mng)
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}
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// First write the type ptr (this adds
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// a unique prefix for each runtime type).
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b = mangle_platform_int(b, uptr)
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// Finally, mangle value
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return mng(b, a)
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}
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// String will return the mangled format of input value 'a'. This
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// mangled output will be unique for all default supported input types
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// during a single runtime instance. Uniqueness cannot be guaranteed
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// between separate runtime instances (whether running concurrently, or
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// the same application running at different times).
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//
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// The exact formatting of the output data should not be relied upon,
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// only that it is unique given the above constraints. Generally though,
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// the mangled output is the binary formatted text of given input data.
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//
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// Uniqueness is guaranteed for similar input data of differing types
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// (e.g. string("hello world") vs. []byte("hello world")) by prefixing
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// mangled output with the input data's runtime type pointer.
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//
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// Default supported types include:
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// - string
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// - bool
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// - int,int8,int16,int32,int64
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// - uint,uint8,uint16,uint32,uint64,uintptr
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// - float32,float64
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// - complex64,complex128
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// - all type aliases of above
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// - time.Time{}, *url.URL{}
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// - mangler.Mangled{}
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// - encoding.BinaryMarshaler{}
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// - all pointers to the above
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// - all slices / arrays of the above
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// - all map keys / values of the above
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func String(a any) string {
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b := Append(make([]byte, 0, 32), a)
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return *(*string)(unsafe.Pointer(&b))
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}
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// Hash returns the xxHash digest of the result of mangler.Append(nil, 'a').
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func Hash(a any) uint64 {
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b := make([]byte, 0, 32)
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b = Append(b, a)
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return xxhash.Sum64(b)
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}
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