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package format
import (
"sync/atomic"
"unsafe"
"codeberg.org/gruf/go-xunsafe"
)
// cache is a concurrency-safe map[xunsafe.TypeInfo]FormatFunc
// cache, designed for heavy reads but with unfortunately expensive
// writes. it is designed such that after some initial load period
// in which functions are cached by types, all future ops are reads.
type cache struct{ p unsafe.Pointer }
// Get will check cache for format func under key.
func (c *cache) Get(t xunsafe.TypeInfo) FormatFunc {
if p := c.load(); p != nil {
return (*p)[t]
}
return nil
}
// Put will place given format func in cache under key, if not already exists.
func (c *cache) Put(t xunsafe.TypeInfo, fn FormatFunc) {
for {
p := c.load()
var cache map[xunsafe.TypeInfo]FormatFunc
if p != nil {
if _, ok := (*p)[t]; ok {
return
}
cache = make(map[xunsafe.TypeInfo]FormatFunc, len(*p)+1)
for key, value := range *p {
cache[key] = value
}
} else {
cache = make(map[xunsafe.TypeInfo]FormatFunc, 1)
}
cache[t] = fn
if c.cas(p, &cache) {
return
}
}
}
// load is a typed wrapper around atomic.LoadPointer().
func (c *cache) load() *map[xunsafe.TypeInfo]FormatFunc {
return (*map[xunsafe.TypeInfo]FormatFunc)(atomic.LoadPointer(&c.p))
}
// cas is a typed wrapper around atomic.CompareAndSwapPointer().
func (c *cache) cas(old, new *map[xunsafe.TypeInfo]FormatFunc) bool {
return atomic.CompareAndSwapPointer(&c.p, unsafe.Pointer(old), unsafe.Pointer(new))
}
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