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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
package purego_test
import (
"fmt"
"os"
"path/filepath"
"testing"
"github.com/ebitengine/purego"
"github.com/ebitengine/purego/internal/load"
)
// BenchmarkCallingMethods compares RegisterFunc, SyscallN, and Callback methods
func BenchmarkCallingMethods(b *testing.B) {
testCases := []struct {
n int
goFn any
goFnPtr uintptr
cFnPtr uintptr
cFnName string
cCallbackPtr uintptr
cCallbackName string
args []int64
expectedSum int64
}{
{1, goSum1, 0, 0, "sum1_c", 0, "call_callback1", []int64{1}, 1},
{2, goSum2, 0, 0, "sum2_c", 0, "call_callback2", []int64{1, 2}, 3},
{3, goSum3, 0, 0, "sum3_c", 0, "call_callback3", []int64{1, 2, 3}, 6},
{5, goSum5, 0, 0, "sum5_c", 0, "call_callback5", []int64{1, 2, 3, 4, 5}, 15},
{10, goSum10, 0, 0, "sum10_c", 0, "call_callback10", []int64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 55},
{14, goSum15, 0, 0, "sum14_c", 0, "call_callback14", []int64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}, 105},
{15, goSum15, 0, 0, "sum15_c", 0, "call_callback15", []int64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}, 120},
}
// Build C library for benchmarking
libFileName := filepath.Join(b.TempDir(), "libbenchmark.so")
if err := buildSharedLib("CC", libFileName, filepath.Join("testdata", "benchmarktest", "benchmark.c")); err != nil {
b.Fatalf("Failed to build C library: %v", err)
}
b.Cleanup(func() {
os.Remove(libFileName)
})
libHandle, err := load.OpenLibrary(libFileName)
if err != nil {
b.Fatalf("Failed to load C library: %v", err)
}
b.Cleanup(func() {
if err := load.CloseLibrary(libHandle); err != nil {
b.Fatalf("Failed to close library: %s", err)
}
})
// Create callbacks and load C functions
for i := range testCases {
testCases[i].goFnPtr = purego.NewCallback(testCases[i].goFn)
cFn, err := load.OpenSymbol(libHandle, testCases[i].cFnName)
if err != nil {
b.Fatalf("Failed to load C function %s: %v", testCases[i].cFnName, err)
}
testCases[i].cFnPtr = cFn
cCallbackFn, err := load.OpenSymbol(libHandle, testCases[i].cCallbackName)
if err != nil {
b.Fatalf("Failed to load C callback wrapper %s: %v", testCases[i].cCallbackName, err)
}
testCases[i].cCallbackPtr = cCallbackFn
}
b.Run("RegisterFunc/Callback", func(b *testing.B) {
for _, tc := range testCases {
b.Run(fmt.Sprintf("%dargs", tc.n), func(b *testing.B) {
b.ReportAllocs()
registerFn := makeRegisterFunc(tc.n)
purego.RegisterFunc(registerFn, tc.goFnPtr)
b.ResetTimer()
result := callRegisterFunc(registerFn, tc.n, tc.args, b.N)
b.StopTimer()
if result != tc.expectedSum {
b.Fatalf("RegisterFunc/Callback: expected sum %d, got %d", tc.expectedSum, result)
}
})
}
})
// Benchmark RegisterFunc with C functions
b.Run("RegisterFunc/CFunc", func(b *testing.B) {
for _, tc := range testCases {
b.Run(fmt.Sprintf("%dargs", tc.n), func(b *testing.B) {
b.ReportAllocs()
registerFn := makeRegisterFunc(tc.n)
purego.RegisterFunc(registerFn, tc.cFnPtr)
b.ResetTimer()
result := callRegisterFunc(registerFn, tc.n, tc.args, b.N)
b.StopTimer()
if result != tc.expectedSum {
b.Fatalf("RegisterFunc/CFunc: expected sum %d, got %d", tc.expectedSum, result)
}
})
}
})
// Benchmark SyscallN with Go callbacks
b.Run("SyscallN/Callback", func(b *testing.B) {
for _, tc := range testCases {
b.Run(fmt.Sprintf("%dargs", tc.n), func(b *testing.B) {
b.ReportAllocs()
args := int64sToUintptrs(tc.args)
var result uintptr
b.ResetTimer()
for i := 0; i < b.N; i++ {
result, _, _ = purego.SyscallN(tc.goFnPtr, args...)
}
b.StopTimer()
if int64(result) != tc.expectedSum {
b.Fatalf("SyscallN/Callback: expected sum %d, got %d", tc.expectedSum, result)
}
})
}
})
// Benchmark SyscallN with C functions
b.Run("SyscallN/CFunc", func(b *testing.B) {
for _, tc := range testCases {
b.Run(fmt.Sprintf("%dargs", tc.n), func(b *testing.B) {
b.ReportAllocs()
args := int64sToUintptrs(tc.args)
var result uintptr
b.ResetTimer()
for i := 0; i < b.N; i++ {
result, _, _ = purego.SyscallN(tc.cFnPtr, args...)
}
b.StopTimer()
if int64(result) != tc.expectedSum {
b.Fatalf("SyscallN/CFunc: expected sum %d, got %d", tc.expectedSum, result)
}
})
}
})
// Benchmark round-trip: Go → C → Go callback (realistic use case)
b.Run("RoundTrip/GoC", func(b *testing.B) {
for _, tc := range testCases {
b.Run(fmt.Sprintf("%dargs", tc.n), func(b *testing.B) {
b.ReportAllocs()
// Build args: first arg is callback pointer, rest are the arguments
args := int64sToUintptrs(tc.args)
callbackArgs := make([]uintptr, len(args)+1)
callbackArgs[0] = tc.goFnPtr
copy(callbackArgs[1:], args)
// Skip if total args (callback + args) exceeds or meets limit
// SyscallN has issues with exactly 15 or more arguments
if len(callbackArgs) >= 15 {
b.Skipf("Round-trip with %d args + callback (%d total) exceeds/meets SyscallN limit", tc.n, len(callbackArgs))
}
var result uintptr
b.ResetTimer()
for i := 0; i < b.N; i++ {
result, _, _ = purego.SyscallN(tc.cCallbackPtr, callbackArgs...)
}
b.StopTimer()
if int64(result) != tc.expectedSum {
b.Fatalf("RoundTrip: expected sum %d, got %d", tc.expectedSum, result)
}
})
}
})
}
// makeRegisterFunc creates a function pointer of the appropriate signature
func makeRegisterFunc(n int) any {
switch n {
case 1:
return new(func(int64) int64)
case 2:
return new(func(int64, int64) int64)
case 3:
return new(func(int64, int64, int64) int64)
case 5:
return new(func(int64, int64, int64, int64, int64) int64)
case 10:
return new(func(int64, int64, int64, int64, int64, int64, int64, int64, int64, int64) int64)
case 14:
return new(func(int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64) int64)
case 15:
return new(func(int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64) int64)
default:
panic(fmt.Sprintf("unsupported arg count: %d", n))
}
}
// callRegisterFunc calls the registered function with the appropriate number of arguments
func callRegisterFunc(registerFn any, n int, args []int64, iterations int) int64 {
var result int64
switch n {
case 1:
f := registerFn.(*func(int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0])
}
case 2:
f := registerFn.(*func(int64, int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0], args[1])
}
case 3:
f := registerFn.(*func(int64, int64, int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0], args[1], args[2])
}
case 5:
f := registerFn.(*func(int64, int64, int64, int64, int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0], args[1], args[2], args[3], args[4])
}
case 10:
f := registerFn.(*func(int64, int64, int64, int64, int64, int64, int64, int64, int64, int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0], args[1], args[2], args[3], args[4],
args[5], args[6], args[7], args[8], args[9])
}
case 14:
f := registerFn.(*func(int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0], args[1], args[2], args[3], args[4],
args[5], args[6], args[7], args[8], args[9],
args[10], args[11], args[12], args[13])
}
case 15:
f := registerFn.(*func(int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64, int64) int64)
for i := 0; i < iterations; i++ {
result = (*f)(args[0], args[1], args[2], args[3], args[4],
args[5], args[6], args[7], args[8], args[9],
args[10], args[11], args[12], args[13], args[14])
}
default:
panic(fmt.Sprintf("unsupported arg count: %d", n))
}
return result
}
// int64sToUintptrs converts []int64 to []uintptr for SyscallN
func int64sToUintptrs(args []int64) []uintptr {
result := make([]uintptr, len(args))
for i, v := range args {
result[i] = uintptr(v)
}
return result
}
func goSum1(a1 int64) int64 { return a1 }
func goSum2(a1, a2 int64) int64 { return a1 + a2 }
func goSum3(a1, a2, a3 int64) int64 { return a1 + a2 + a3 }
func goSum5(a1, a2, a3, a4, a5 int64) int64 { return a1 + a2 + a3 + a4 + a5 }
func goSum10(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10 int64) int64 {
return a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10
}
func goSum15(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 int64) int64 {
return a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10 + a11 + a12 + a13 + a14 + a15
}
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