macos_pprof_bias.go

package main

import (
	"bytes"
	"compress/gzip"
	"io"
	"os"
	"testing"
)

func TestInterleavedIO(t *testing.T) {
	// Open big file with random data
	inFile, err := os.Open("random.data")
	if err != nil {
		t.Fatal("could not open input file: create with `dd if=/dev/random of=random.data bs=1MB count=250`", err)
	}
	defer inFile.Close()

	// Open the output file.
	outFile, err := os.Create("random.data.gz")
	if err != nil {
		t.Fatal("could not open input file: ", err)
	}
	defer outFile.Close()

	// Create the gzip writer.
	gw := gzip.NewWriter(outFile)

	// Compress the data from inFile by copying it to gw
	if _, err := io.Copy(gw, inFile); err != nil {
		t.Fatal("failed to copy data ", err)
	}
	if err := gw.Flush(); err != nil {
		t.Fatal("failed to flush gzip writer ", err)
	}
}

func TestSequentialIO(t *testing.T) {
	// Read all input data into memory
	input, err := os.ReadFile("random.data")
	if err != nil {
		t.Fatal("failed to read input file: create with `dd if=/dev/random of=random.data bs=1MB count=250`", err)
	}

	// Gzip compress inData into output (in memory, no I/O)
	var output bytes.Buffer
	gw := gzip.NewWriter(&output)
	if _, err := gw.Write(input); err != nil {
		t.Fatal("failed to write data ", err)
	}
	if err := gw.Flush(); err != nil {
		t.Fatal("failed to flush gzip writer ", err)
	}

	// Write outFile to disk
	if err := os.WriteFile("random.data.gz", output.Bytes(), 0666); err != nil {
		t.Fatal("failed to write gzip data", err)
	}
}