buf

Documentation

Index

• type Buffer
  • func NewBuffer(opt *Options) (b *Buffer, err error)
  • func (bfr *Buffer) Abort() (err error)
  • func (bfr *Buffer) Cleanup() (err error)
  • func (bfr *Buffer) Close() (err error)
  • func (bfr *Buffer) Read(p []byte) (n int, err error)
  • func (bfr *Buffer) Reset()
  • func (bfr *Buffer) Stats() stat.Stats
  • func (bfr *Buffer) Write(p []byte) (n int, err error)
  • func (bfr *Buffer) WriteLine(ln []byte) (err error)
• type Options
  • func NewOptions() *Options

Examples

• Buffer.Abort
• Buffer.Cleanup
• Buffer.Close
• Buffer.Read
• Buffer.Stats
• Buffer.Write
• Buffer.WriteLine
• NewBuffer
• NewOptions

Types

type Buffer

type Buffer struct {
	// contains filtered or unexported fields
}

Buffer implements both StatsReadCloser and StatsWriteCloser interfaces.

Buffer is meant to abstract away the details of writing and reading to either a file buffer or in-memory buffer.

Buffer will: - compress writes if Options.Compress is true. - keep track of buffer statistics - calculate MD5 checksum on calling Close() - calculate the buffer size - provide the tmp file path in the file stats. - clean up tmp file if Abort() or Cleanup() are called.

func NewBuffer

func NewBuffer(opt *Options) (b *Buffer, err error)

Example

bfr, err := NewBuffer(nil)
if bfr == nil {
	return
}

fmt.Println(err)                   // output: <nil>
fmt.Println(bfr.sts.Created != "") // output: true
fmt.Println(bfr.w != nil)          // output true
fmt.Println(bfr.wGzip)             // output <nil>
fmt.Println(bfr.wSize != nil)      // output true
fmt.Println(bfr.bBuf != nil)       // output: true
fmt.Println(bfr.fBuf)              // output <nil>
fmt.Println(bfr.r != nil)          // output true
fmt.Println(bfr.hshr != nil)       // output true

Output:

<nil>
true
true
<nil>
true
true
<nil>
true
true

func (*Buffer) Abort

func (bfr *Buffer) Abort() (err error)

Abort will clear the buffer (remove tmp file if exists) and prevent further buffer writes.

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
bfr.WriteLine([]byte("test line"))
bfr.WriteLine([]byte("test line"))
err := bfr.Abort()

fmt.Println(err) // output: <nil>

Output:

<nil>

func (*Buffer) Cleanup

func (bfr *Buffer) Cleanup() (err error)

Cleanup will remove the tmp file (if exists) or reset the in-memory buffer (if used).

Cleanup should not be used until the user is done with the contents of the buffer.

Cleanup is called automatically as part of the abort process but since the user may wish to read from the buffer after closing, Cleanup will need to be called after Close, especially if using compression since Close flushes the compression buffer and finalizes writing.

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
bfr.WriteLine([]byte("test line"))
bfr.WriteLine([]byte("test line"))

err := bfr.Cleanup()

// bytes should be re-set
// so reading from bBuf should return EOF
b := make([]byte, 1)
n, bErr := bfr.bBuf.Read(b)

fmt.Println(err)  // output: <nil>
fmt.Println(n)    // output: 0
fmt.Println(bErr) // output: EOF

Output:

<nil>
0
EOF

func (*Buffer) Close

func (bfr *Buffer) Close() (err error)

Close prevents further writing and flushes writes to the underlying buffer.

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
bfr.WriteLine([]byte("test line"))
bfr.WriteLine([]byte("test line"))

fmt.Println(bfr.sts.Checksum == "") // output: true
fmt.Println(bfr.sts.Size)           // output: 0

err := bfr.Close()

fmt.Println(err)                    // output: <nil>
fmt.Println(bfr.sts.Checksum != "") // output: true
fmt.Println(bfr.sts.Size)           // output: 20

// closing again has no effect
err = bfr.Close()

fmt.Println(err)                    // output: <nil>
fmt.Println(bfr.sts.Checksum != "") // output: true
fmt.Println(bfr.sts.Size)           // output: 20

Output:

true
0
<nil>
true
20
<nil>
true
20

func (*Buffer) Read

func (bfr *Buffer) Read(p []byte) (n int, err error)

Read will read the raw underlying buffer bytes. If the buffer is writing with compression it will not decompress on reads. Read is made for reading the final written bytes and copying them to the final location.

Close should be called before Read as Close will sync the underlying buffer. This is especially important when using compression and/or a tmp file.

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
bfr.Write([]byte("test line\n"))
bfr.Write([]byte("test line\n"))

// read
b := make([]byte, 20)
bfr.Read(b)

fmt.Print(string(b)) // output: test line, test line

Output:

test line
test line

func (*Buffer) Reset

func (bfr *Buffer) Reset()

Reset will reset the in-memory buffer (if used) and remove the reference to the tmp file (if exists)

Reset does not verify that the tmp file is closed

func (*Buffer) Stats

func (bfr *Buffer) Stats() stat.Stats

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
bfr.WriteLine([]byte("test line"))
bfr.WriteLine([]byte("test line"))
sts := bfr.Stats()

fmt.Println(sts.ByteCnt) // output: 20
fmt.Println(sts.LineCnt) // output: 2

Output:

20
2

func (*Buffer) Write

func (bfr *Buffer) Write(p []byte) (n int, err error)

Write will write to the underlying buffer. The underlying bytes writing will be compressed if compression was specified on buffer initialization.

Write is thread safe.

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
n1, err1 := bfr.Write([]byte("test line\n"))
n2, err2 := bfr.Write([]byte("test line\n"))

// read
b := make([]byte, 20)
bfr.Read(b)

fmt.Println(n1)               // output: 10
fmt.Println(err1)             // output: <nil>
fmt.Println(n2)               // output: 10
fmt.Println(err2)             // output: <nil>
fmt.Print(string(b))          // output: test line, test line
fmt.Println(bfr.sts.ByteCnt)  // output: 20
fmt.Println(bfr.sts.LineCnt)  // output: 0
fmt.Println(bfr.wSize.Size()) // output: 20

Output:

10
<nil>
10
<nil>
test line
test line
20
0
20

func (*Buffer) WriteLine

func (bfr *Buffer) WriteLine(ln []byte) (err error)

WriteLine will write to the underlying buffer. The underlying bytes writing will be compressed if compression was specified on buffer initialization.

WriteLine is thread safe.

Example

bfr, _ := NewBuffer(nil)
if bfr == nil {
	return
}

// write first
err1 := bfr.WriteLine([]byte("test line"))
err2 := bfr.WriteLine([]byte("test line"))

// read
b := make([]byte, 20)
bfr.Read(b)

fmt.Println(err1)             // output: <nil>
fmt.Println(err2)             // output: <nil>
fmt.Print(string(b))          // output: test line, test line
fmt.Println(bfr.sts.ByteCnt)  // output: 20
fmt.Println(bfr.sts.LineCnt)  // output: 2
fmt.Println(bfr.wSize.Size()) // output: 20

Output:

<nil>
<nil>
test line
test line
20
2
20

type Options

type Options struct {
	// UseFileBuf specifies to use a tmp file for the delayed writing.
	// Can optionally also specify the tmp directory and tmp name
	// prefix.
	UseFileBuf bool

	// FileBufDir optionally specifies the temp directory. If not specified then
	// the os default temp dir is used.
	FileBufDir string

	// FileBufPrefix optionally specifies the temp file prefix.
	// The full tmp file name is randomly generated and guaranteed
	// not to conflict with existing files. A prefix can help one find
	// the tmp file.
	FileBufPrefix string

	// Compress set to true will turn on gzip compression.
	// Writes will be compressed but reads will read raw
	// compressed bytes.
	Compress bool

	// CompressLevel type of compression used on the file
	// gzip.BestSpeed = 1 // quick but very little compression
	// gzip.BestCompression = 9 // smallest size but takes longer
	// gzip.DefaultCompression = -1 // balance between speed and size
	CompressLevel int

	// KeepFailed files when using a file buffer and the
	// copy commands fails
	KeepFailed bool
}

func NewOptions

func NewOptions() *Options

Example

opt := NewOptions()
if opt == nil {
	return
}

fmt.Println(opt.FileBufDir)    // output:
fmt.Println(opt.UseFileBuf)    // output: false
fmt.Println(opt.FileBufPrefix) // output:
fmt.Println(opt.Compress)      // output: false

Output:


false

false