window_test.go

Documentation: internal/zstd

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package zstd
     6  
     7  import (
     8  	"bytes"
     9  	"fmt"
    10  	"testing"
    11  )
    12  
    13  func makeSequence(start, n int) (seq []byte) {
    14  	for i := 0; i < n; i++ {
    15  		seq = append(seq, byte(start+i))
    16  	}
    17  	return
    18  }
    19  
    20  func TestWindow(t *testing.T) {
    21  	for size := 0; size <= 3; size++ {
    22  		for i := 0; i <= 2*size; i++ {
    23  			a := makeSequence('a', i)
    24  			for j := 0; j <= 2*size; j++ {
    25  				b := makeSequence('a'+i, j)
    26  				for k := 0; k <= 2*size; k++ {
    27  					c := makeSequence('a'+i+j, k)
    28  
    29  					t.Run(fmt.Sprintf("%d-%d-%d-%d", size, i, j, k), func(t *testing.T) {
    30  						testWindow(t, size, a, b, c)
    31  					})
    32  				}
    33  			}
    34  		}
    35  	}
    36  }
    37  
    38  // testWindow tests window by saving three sequences of bytes to it.
    39  // Third sequence tests read offset that can become non-zero only after second save.
    40  func testWindow(t *testing.T, size int, a, b, c []byte) {
    41  	var w window
    42  	w.reset(size)
    43  
    44  	w.save(a)
    45  	w.save(b)
    46  	w.save(c)
    47  
    48  	var tail []byte
    49  	tail = append(tail, a...)
    50  	tail = append(tail, b...)
    51  	tail = append(tail, c...)
    52  
    53  	if len(tail) > size {
    54  		tail = tail[len(tail)-size:]
    55  	}
    56  
    57  	if w.len() != uint32(len(tail)) {
    58  		t.Errorf("wrong data length: got: %d, want: %d", w.len(), len(tail))
    59  	}
    60  
    61  	var from, to uint32
    62  	for from = 0; from <= uint32(len(tail)); from++ {
    63  		for to = from; to <= uint32(len(tail)); to++ {
    64  			got := w.appendTo(nil, from, to)
    65  			want := tail[from:to]
    66  
    67  			if !bytes.Equal(got, want) {
    68  				t.Errorf("wrong data at [%d:%d]: got %q, want %q", from, to, got, want)
    69  			}
    70  		}
    71  	}
    72  }
    73
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