map_size_test.go

// Copyright (c) 2024 The Go Authors. All rights reserved.
// Modified by kpango.

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package gache

import (
	"sync/atomic"
	"testing"
	"unsafe"
)

// TestGache_MapSize verifies that gache's total memory size footprint is calculated correctly encompassing active entries and internal structures.
func TestGache_MapSize(t *testing.T) {
	gacheMap := new(Map[int, int])
	gacheMap.Store(1, 1)

	size := gacheMap.Size()
	if size <= 0 {
		t.Errorf("gacheMap.Size() should be positive, got %d", size)
	}

	m := make(map[int]*entry[int])
	m[1] = newEntryPointer(new(int), new(atomic.Int64))

	expectedSize := unsafe.Sizeof(gacheMap.mu) +
		unsafe.Sizeof(gacheMap.read) +
		unsafe.Sizeof(gacheMap.misses) +
		mapSize(gacheMap.dirty)

	// Allow for some slack due to readOnly struct and entry sizes

	if size < expectedSize {
		t.Errorf("gacheMap.Size() %d is smaller than expected lower bound %d", size, expectedSize)
	}
}

// TestGache_MapSizeWithExpungedEntries ensures that entries actively expunged from the map do not falsely inflate the reported byte size.
func TestGache_MapSizeWithExpungedEntries(t *testing.T) {
	m := new(Map[int, int])
	m.Store(1, 100)
	m.Delete(1)

	m.Store(2, 200)

	sizeBefore := m.Size()

	m.Store(3, 300)
	sizeAfter := m.Size()

	if sizeAfter <= sizeBefore {
		t.Errorf("Size() should increase after adding an entry: before=%d after=%d", sizeBefore, sizeAfter)
	}

	if sizeBefore == 0 {
		t.Errorf("Size() returned 0 unexpectedly")
	}
}