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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package lzw

import (
        "io"
        "io/ioutil"
        "os"
        "runtime"
        "testing"
)

var filenames = []string{
        "../testdata/e.txt",
        "../testdata/pi.txt",
}

// testFile tests that compressing and then decompressing the given file with
// the given options yields equivalent bytes to the original file.
func testFile(t *testing.T, fn string, order Order, litWidth int) {
        // Read the file, as golden output.
        golden, err := os.Open(fn)
        if err != nil {
                t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
                return
        }
        defer golden.Close()

        // Read the file again, and push it through a pipe that compresses at the write end, and decompresses at the read end.
        raw, err := os.Open(fn)
        if err != nil {
                t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
                return
        }

        piper, pipew := io.Pipe()
        defer piper.Close()
        go func() {
                defer raw.Close()
                defer pipew.Close()
                lzww := NewWriter(pipew, order, litWidth)
                defer lzww.Close()
                var b [4096]byte
                for {
                        n, err0 := raw.Read(b[:])
                        if err0 != nil && err0 != io.EOF {
                                t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
                                return
                        }
                        _, err1 := lzww.Write(b[:n])
                        if err1 != nil {
                                t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
                                return
                        }
                        if err0 == io.EOF {
                                break
                        }
                }
        }()
        lzwr := NewReader(piper, order, litWidth)
        defer lzwr.Close()

        // Compare the two.
        b0, err0 := ioutil.ReadAll(golden)
        b1, err1 := ioutil.ReadAll(lzwr)
        if err0 != nil {
                t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
                return
        }
        if err1 != nil {
                t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
                return
        }
        if len(b1) != len(b0) {
                t.Errorf("%s (order=%d litWidth=%d): length mismatch %d != %d", fn, order, litWidth, len(b1), len(b0))
                return
        }
        for i := 0; i < len(b0); i++ {
                if b1[i] != b0[i] {
                        t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x != 0x%02x\n", fn, order, litWidth, i, b1[i], b0[i])
                        return
                }
        }
}

func TestWriter(t *testing.T) {
        for _, filename := range filenames {
                for _, order := range [...]Order{LSB, MSB} {
                        // The test data "2.71828 etcetera" is ASCII text requiring at least 6 bits.
                        for _, litWidth := range [...]int{6, 7, 8} {
                                testFile(t, filename, order, litWidth)
                        }
                }
        }
}

func benchmarkEncoder(b *testing.B, n int) {
        b.StopTimer()
        b.SetBytes(int64(n))
        buf0, _ := ioutil.ReadFile("../testdata/e.txt")
        buf0 = buf0[:10000]
        buf1 := make([]byte, n)
        for i := 0; i < n; i += len(buf0) {
                copy(buf1[i:], buf0)
        }
        buf0 = nil
        runtime.GC()
        b.StartTimer()
        for i := 0; i < b.N; i++ {
                w := NewWriter(ioutil.Discard, LSB, 8)
                w.Write(buf1)
                w.Close()
        }
}

func BenchmarkEncoder1e4(b *testing.B) {
        benchmarkEncoder(b, 1e4)
}

func BenchmarkEncoder1e5(b *testing.B) {
        benchmarkEncoder(b, 1e5)
}

func BenchmarkEncoder1e6(b *testing.B) {
        benchmarkEncoder(b, 1e6)
}