Skip to content

writer: add WriteUint method #5

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
gucio321 wants to merge 2 commits into
base: main
Choose a base branch
from
Open

writer: add WriteUint method #5

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
cab297a
writer: add WriteUint method
gucio321 Jun 16, 2021
671188d
WriteUint: add uint8 case; add comment
gucio321 Jun 16, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
57 changes: 52 additions & 5 deletions writer.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ import "fmt"
// of the bits is in a byte slice.
type Writer struct {
// all of the bytes written by this Writer
bytes []byte
bytes []byte

// bitBuffer is a single byte used for storing individual bits that are written.
// When a byte-boundary is passed, this byte is appended to the bytes slice
Expand All @@ -22,7 +22,6 @@ type Writer struct {
endianness
}


// Bytes returns a copy of the byte buffer
func (w *Writer) Bytes() []byte {
bytes := append([]byte{}, w.bytes...)
Expand All @@ -40,13 +39,19 @@ func (w *Writer) Bytes() []byte {
func (w *Writer) Write(args ...interface{}) (bitsWritten int, err error) {
for idx := range args {
switch v := args[idx].(type) {
case byte :
case uint16, uint32, uint64:
if num, err := w.WriteUint(v); err != nil {
break
} else {
bitsWritten += num
}
case byte:
if num, err := w.WriteByte(v); err != nil {
break
} else {
bitsWritten += num
}
case []byte :
case []byte:
if num, err := w.WriteBytes(v); err != nil {
break
} else {
Expand All @@ -72,6 +77,48 @@ func (w *Writer) Write(args ...interface{}) (bitsWritten int, err error) {
return bitsWritten, err
}

// WriteUint writes an unigned intager value to stream
func (w *Writer) WriteUint(i interface{}) (bitsWritten int, err error) {
const (
bytesPerInt16 = 2
bytesPerInt32 = 4
bytesPerInt64 = 8
)

var l int
var data []byte

switch i.(type) {
case uint8:
w.WriteByte(i.(uint8))
case uint16:
l = bytesPerInt16
data = make([]byte, l)
for idx := 0; idx < l; idx++ {
shift := idx * bitsPerByte
data[idx] = byte(i.(uint16) >> shift)
}
case uint32:
l = bytesPerInt32
data = make([]byte, l)
for idx := 0; idx < l; idx++ {
shift := idx * bitsPerByte
data[idx] = byte(i.(uint32) >> shift)
}
case uint64:
l = bytesPerInt32
data = make([]byte, l)
for idx := 0; idx < l; idx++ {
shift := idx * bitsPerByte
data[idx] = byte(i.(uint64) >> shift)
}
default:
return 0, fmt.Errorf("value of type %T isn't untyped intager or doesn't specify its size", i)
}

return w.WriteBytes(data)
}

// WriteBytes writes the given bytes
func (w *Writer) WriteBytes(b []byte) (bitsWritten int, err error) {
for idx := range b {
Expand Down Expand Up @@ -124,7 +171,7 @@ func (w *Writer) WriteBit(b bool) (bitsWritten int, err error) {
w.bitOffset++

if b {
w.bitBuffer |= 1<<shift
w.bitBuffer |= 1 << shift
}

if w.bitOffset >= bitsPerByte {
Expand Down
99 changes: 78 additions & 21 deletions writer_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -80,17 +80,20 @@ func TestWriter_WriteBits(t *testing.T) {
"empty",
state{[]byte{}, 0b110, 3},
Bits{F, F, F, T},
[]byte{0b_1000_110}},
[]byte{0b_1000_110},
},
{
"start unaligned, end aligned",
state{[]byte{1, 2, 3, 4}, 0b11, 3},
Bits{T, T, T, T},
[]byte{1, 2, 3, 4, 0b_0111_1011}},
[]byte{1, 2, 3, 4, 0b_0111_1011},
},
{
"start unaligned, end unaligned",
state{[]byte{1, 2, 3, 4}, 0b10, 4},
Bits{F, F, F, F, T},
[]byte{1, 2, 3, 4, 0b_0000_0010, 0b1}},
[]byte{1, 2, 3, 4, 0b_0000_0010, 0b1},
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand Down Expand Up @@ -171,30 +174,36 @@ func TestWriter_WriteByte(t *testing.T) {
wantBitsWritten int
expectedBytes []byte
}{
{"from empty, write 0x1",
{
"from empty, write 0x1",
state{
existingBytes: nil,
},
[]byte{0x1},
8,
[]byte{0x1}},
[]byte{0x1},
},

{"with existing bytes, aligned, multiple bytes",
{
"with existing bytes, aligned, multiple bytes",
state{
existingBytes: []byte{3, 2},
},
[]byte{2, 1},
16,
[]byte{3, 2, 2, 1}},
[]byte{3, 2, 2, 1},
},

{"with existing bytes, unaligned",
{
"with existing bytes, unaligned",
state{
existingBytes: []byte{6, 9, 4},
bitOffset: 1,
},
[]byte{1},
8,
[]byte{6, 9, 4, 2, 0}},
[]byte{6, 9, 4, 2, 0},
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand Down Expand Up @@ -243,30 +252,36 @@ func TestWriter_WriteBytes(t *testing.T) {
wantBitsWritten int
expectedBytes []byte
}{
{"from empty, write 0x1",
{
"from empty, write 0x1",
state{
existingBytes: nil,
},
[]byte{0x1},
8,
[]byte{0x1}},
[]byte{0x1},
},

{"with existing bytes, aligned, multiple bytes",
{
"with existing bytes, aligned, multiple bytes",
state{
existingBytes: []byte{3, 2},
},
[]byte{2, 1},
16,
[]byte{3, 2, 2, 1}},
[]byte{3, 2, 2, 1},
},

{"with existing bytes, unaligned",
{
"with existing bytes, unaligned",
state{
existingBytes: []byte{6, 9, 4},
bitOffset: 1,
},
[]byte{1},
8,
[]byte{6, 9, 4, 2, 0}},
[]byte{6, 9, 4, 2, 0},
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand All @@ -278,7 +293,6 @@ func TestWriter_WriteBytes(t *testing.T) {
}

totalBitsWritten, err := w.WriteBytes(tt.bytesToWrite)

if err != nil {
t.Errorf("WriteBytes() error = %v", err)
return
Expand Down Expand Up @@ -319,35 +333,40 @@ func TestWriter_Write(t *testing.T) {
args{args: []interface{}{F, F, byte(3)}},
10,
[]byte{0b_0000_1100, 0},
false},
false,
},
{
"from non-empty, combo write, end unaligned",
fields{},
args{args: []interface{}{F, byte(3), []byte{0b0101_0101, 0b0011_0011, 0b0000_1111}}},
33,
[]byte{0b_0000_0110, 0b_1010_1010, 0b_0110_0110, 0b_0001_1110, 0},
false},
false,
},
{
"bad arg string",
fields{},
args{args: []interface{}{"123"}},
0,
nil,
true},
true,
},
{
"bad arg int64",
fields{},
args{args: []interface{}{int64(1234567)}},
0,
nil,
true},
true,
},
{
"mixed with bad args",
fields{},
args{args: []interface{}{F, T, F, int64(1234567)}},
3,
[]byte{2},
true},
true,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand Down Expand Up @@ -376,3 +395,41 @@ func TestWriter_Write(t *testing.T) {
})
}
}

func TestWriter_WriteUint(t *testing.T) {
tests := []struct {
name string
uintsToWrite []interface{}
wantBitsWritten int
expectedBytes []byte
}{
{"write uint16", []interface{}{uint16(18), uint16(100), uint16(480)}, 48, []byte{18, 0, 100, 0, 224, 1}},
{"write uint32", []interface{}{uint32(1024), uint32(40000), uint32(256)}, 96, []byte{0, 4, 0, 0, 64, 156, 0, 0, 0, 1, 0, 0}},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
w := &Writer{}

totalBitsWritten := 0

for idx := range tt.uintsToWrite {
bitsWritten, err := w.WriteUint(tt.uintsToWrite[idx])

totalBitsWritten += bitsWritten

if err != nil {
t.Errorf("WriteBool() error = %v", err)
return
}
}

if totalBitsWritten != tt.wantBitsWritten {
t.Errorf("WriteUint() gotBitsWritten = %v, want %v", totalBitsWritten, tt.wantBitsWritten)
}

if got := w.Bytes(); !reflect.DeepEqual(got, tt.expectedBytes) {
t.Errorf("Bytes() = %v, want %v", got, tt.expectedBytes)
}
})
}
}