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package asm
import (
"testing"
"unsafe"
"github.com/go-quicktest/qt"
)
func TestMetadata(t *testing.T) {
var m Metadata
// Metadata should be the size of a pointer.
qt.Assert(t, qt.Equals(unsafe.Sizeof(m), unsafe.Sizeof(uintptr(0))))
// A lookup in a nil meta should return nil.
qt.Assert(t, qt.IsNil(m.Get(bool(false))))
// We can look up anything we inserted.
m.Set(bool(false), int(0))
m.Set(int(1), int(1))
qt.Assert(t, qt.Equals(m.Get(bool(false)), 0))
qt.Assert(t, qt.Equals(m.Get(1), 1))
// We have copy on write semantics
old := m
m.Set(bool(false), int(1))
qt.Assert(t, qt.Equals(m.Get(bool(false)), 1))
qt.Assert(t, qt.Equals(m.Get(int(1)), 1))
qt.Assert(t, qt.Equals(old.Get(bool(false)), 0))
qt.Assert(t, qt.Equals(old.Get(int(1)), 1))
// Newtypes are handled distinctly.
type b bool
m.Set(b(false), int(42))
qt.Assert(t, qt.Equals(m.Get(bool(false)), 1))
qt.Assert(t, qt.Equals(m.Get(int(1)), 1))
qt.Assert(t, qt.Equals(m.Get(b(false)), 42))
// Setting nil removes a key.
m.Set(bool(false), nil)
qt.Assert(t, qt.IsNil(m.Get(bool(false))))
qt.Assert(t, qt.Equals(m.Get(int(1)), 1))
qt.Assert(t, qt.Equals(m.Get(b(false)), 42))
}
func BenchmarkMetadata(b *testing.B) {
// Assume that three bits of metadata on a single instruction is
// our worst case.
const worstCaseItems = 3
type t struct{}
b.Run("add first", func(b *testing.B) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
var v Metadata
v.Set(t{}, 0)
}
})
b.Run("add last", func(b *testing.B) {
var m Metadata
for i := 0; i < worstCaseItems-1; i++ {
m.Set(i, i)
}
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
v := m
v.Set(t{}, 0)
}
})
b.Run("add existing", func(b *testing.B) {
var m Metadata
for i := 0; i < worstCaseItems-1; i++ {
m.Set(i, i)
}
m.Set(t{}, 0)
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
v := m
v.Set(t{}, 0)
}
})
b.Run("get miss", func(b *testing.B) {
var m Metadata
for i := 0; i < worstCaseItems; i++ {
m.Set(i, i)
}
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
if m.Get(t{}) != nil {
b.Fatal("got result from miss")
}
}
})
}
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