131 lines
3.8 KiB
Go
131 lines
3.8 KiB
Go
package mangler
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import (
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"reflect"
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"sync"
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"unsafe"
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)
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// manglers is a map of runtime
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// type ptrs => Mangler functions.
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var manglers sync.Map
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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, ptr unsafe.Pointer) []byte
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// Get will fetch the Mangler function for given runtime type.
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// Note that the returned mangler will be a no-op in the case
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// that an incorrect type is passed as the value argument.
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func Get(t reflect.Type) Mangler {
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var mng Mangler
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// Get raw runtime type ptr
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uptr := uintptr(eface_data(t))
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// Look for a cached mangler
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v, ok := manglers.Load(uptr)
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if !ok {
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// Load mangler function
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mng = loadMangler(t)
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} else {
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// cast cached value
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mng = v.(Mangler)
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}
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return func(buf []byte, ptr unsafe.Pointer) []byte {
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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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buf = append_uint64(buf, uint64(uptr))
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// Finally, mangle value
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return mng(buf, ptr)
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}
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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(eface_data(t))
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// Ensure this is a unique encoder
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if _, ok := manglers.Load(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.Store(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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var mng Mangler
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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(eface_data(t))
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// Look for a cached mangler
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v, ok := manglers.Load(uptr)
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if !ok {
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// Load into cache
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mng = loadMangler(t)
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manglers.Store(uptr, mng)
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} else {
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// cast cached value
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mng = v.(Mangler)
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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 = append_uint64(b, uint64(uptr))
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// Finally, mangle value
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ptr := eface_data(a)
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return mng(b, ptr)
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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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// - arbitrary structs
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// - all type aliases of above
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// - all pointers to the above
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// - all slices / arrays 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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