gotosocial/vendor/codeberg.org/gruf/go-cache/v3/result/key.go

275 lines
6.4 KiB
Go

package result
import (
"fmt"
"reflect"
"strings"
"sync"
"unicode"
"unicode/utf8"
"codeberg.org/gruf/go-byteutil"
"codeberg.org/gruf/go-mangler"
)
// structKeys provides convience methods for a list
// of structKey field combinations used for cache keys.
type structKeys []structKey
// get fetches the structKey info for given lookup name (else, panics).
func (sk structKeys) get(name string) *structKey {
for i := range sk {
if sk[i].name == name {
return &sk[i]
}
}
panic("unknown lookup: \"" + name + "\"")
}
// generate will calculate and produce a slice of cache keys the given value
// can be stored under in the, as determined by receiving struct keys.
func (sk structKeys) generate(a any) []cacheKey {
var keys []cacheKey
// Get reflected value in order
// to access the struct fields
v := reflect.ValueOf(a)
// Iteratively deref pointer value
for v.Kind() == reflect.Pointer {
if v.IsNil() {
panic("nil ptr")
}
v = v.Elem()
}
// Acquire byte buffer
buf := getBuf()
defer putBuf(buf)
outer:
for i := range sk {
// Reset buffer
buf.Reset()
// Append each field value to buffer.
for _, field := range sk[i].fields {
fv := v.Field(field.index)
fi := fv.Interface()
// Mangle this key part into buffer.
ok := field.manglePart(buf, fi)
if !ok {
// don't generate keys
// for zero value parts.
continue outer
}
// Append part separator.
buf.B = append(buf.B, '.')
}
// Drop last '.'
buf.Truncate(1)
// Append new cached key to slice
keys = append(keys, cacheKey{
info: &sk[i],
key: string(buf.B), // copy
})
}
return keys
}
type cacheKeys []cacheKey
// drop will drop the cachedKey with lookup name from receiving cacheKeys slice.
func (ck *cacheKeys) drop(name string) {
_ = *ck // move out of loop
for i := range *ck {
if (*ck)[i].info.name == name {
(*ck) = append((*ck)[:i], (*ck)[i+1:]...)
break
}
}
}
// cacheKey represents an actual cached key.
type cacheKey struct {
// info is a reference to the structKey this
// cacheKey is representing. This is a shared
// reference and as such only the structKey.pkeys
// lookup map is expecting to be modified.
info *structKey
// value is the actual string representing
// this cache key for hashmap lookups.
key string
}
// structKey represents a list of struct fields
// encompassing a single cache key, the string name
// of the lookup, the lookup map to primary cache
// keys, and the key's possible zero value string.
type structKey struct {
// name is the provided cache lookup name for
// this particular struct key, consisting of
// period ('.') separated struct field names.
name string
// unique determines whether this structKey supports
// multiple or just the singular unique result.
unique bool
// fields is a slice of runtime struct field
// indices, of the fields encompassed by this key.
fields []structField
// pkeys is a lookup of stored struct key values
// to the primary cache lookup key (int64).
pkeys map[string][]int64
}
// newStructKey will generate a structKey{} information object for user-given lookup
// key information, and the receiving generic paramter's type information. Panics on error.
func newStructKey(lk Lookup, t reflect.Type) structKey {
var sk structKey
// Set the lookup name
sk.name = lk.Name
// Split dot-separated lookup to get
// the individual struct field names
names := strings.Split(lk.Name, ".")
// Allocate the mangler and field indices slice.
sk.fields = make([]structField, len(names))
for i, name := range names {
// Get field info for given name
ft, ok := t.FieldByName(name)
if !ok {
panic("no field found for name: \"" + name + "\"")
}
// Check field is usable
if !isExported(name) {
panic("field must be exported")
}
// Set the runtime field index
sk.fields[i].index = ft.Index[0]
// Allocate new instance of field
v := reflect.New(ft.Type)
v = v.Elem()
// Fetch mangler for field type.
sk.fields[i].mangle = mangler.Get(ft.Type)
if !lk.AllowZero {
// Append the mangled zero value interface
zero := sk.fields[i].mangle(nil, v.Interface())
sk.fields[i].zero = string(zero)
}
}
// Set unique lookup flag.
sk.unique = !lk.Multi
// Allocate primary lookup map
sk.pkeys = make(map[string][]int64)
return sk
}
// genKey generates a cache key string for given key parts (i.e. serializes them using "go-mangler").
func (sk *structKey) genKey(parts []any) string {
// Check this expected no. key parts.
if len(parts) != len(sk.fields) {
panic(fmt.Sprintf("incorrect no. key parts provided: want=%d received=%d", len(parts), len(sk.fields)))
}
// Acquire byte buffer
buf := getBuf()
defer putBuf(buf)
buf.Reset()
for i, part := range parts {
// Mangle this key part into buffer.
// specifically ignoring whether this
// is returning a zero value key part.
_ = sk.fields[i].manglePart(buf, part)
// Append part separator.
buf.B = append(buf.B, '.')
}
// Drop last '.'
buf.Truncate(1)
// Return string copy
return string(buf.B)
}
type structField struct {
// index is the reflect index of this struct field.
index int
// zero is the possible zero value for this
// key part. if set, this will _always_ be
// non-empty due to how the mangler works.
//
// i.e. zero = "" --> allow zero value keys
// zero != "" --> don't allow zero value keys
zero string
// mangle is the mangler function for
// serializing values of this struct field.
mangle mangler.Mangler
}
// manglePart ...
func (field *structField) manglePart(buf *byteutil.Buffer, part any) bool {
// Start of part bytes.
start := len(buf.B)
// Mangle this key part into buffer.
buf.B = field.mangle(buf.B, part)
// End of part bytes.
end := len(buf.B)
// Return whether this is zero value.
return (field.zero == "" ||
string(buf.B[start:end]) != field.zero)
}
// isExported checks whether function name is exported.
func isExported(fnName string) bool {
r, _ := utf8.DecodeRuneInString(fnName)
return unicode.IsUpper(r)
}
// bufpool provides a memory pool of byte
// buffers use when encoding key types.
var bufPool = sync.Pool{
New: func() any {
return &byteutil.Buffer{B: make([]byte, 0, 512)}
},
}
// getBuf acquires a byte buffer from memory pool.
func getBuf() *byteutil.Buffer {
return bufPool.Get().(*byteutil.Buffer)
}
// putBuf replaces a byte buffer back in memory pool.
func putBuf(buf *byteutil.Buffer) {
if buf.Cap() > int(^uint16(0)) {
return // drop large bufs
}
bufPool.Put(buf)
}