Check-in [70896f73e9]
Overview
Comment:Additional fixes and code simplification for MinReader
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 70896f73e95a9811868d697c2c2f59eb9899c3ab
User & Date: spaskalev on 2014-12-23 18:39:59
Other Links: manifest | tags
Context
2014-12-23
18:52
Renamed MinReader to BlockReader. The later is now used by predictor's decompressor to simplify the code and deal away with the need for internal buffering. check-in: 38f8e62c81 user: spaskalev tags: trunk
18:39
Additional fixes and code simplification for MinReader check-in: 70896f73e9 user: spaskalev tags: trunk
14:27
minReader fixes check-in: 4195e7817d user: spaskalev tags: trunk
Changes

Modified src/0dev.org/ioutil/ioutil.go from [4d4fd7d642] to [3d22f83cbe].

1
2
3
4

5
6
7
8
9
10
11
1
2
3
4
5
6
7
8
9
10
11
12




+







// Package ioutil contains various constructs for io operations
package ioutil

import (
	//"fmt"
	"io"
)

// An function alias type that implements io.Writer
type WriterFunc func([]byte) (int, error)

// Delegates the call to the WriterFunc while implementing io.Writer
22
23
24
25
26
27
28
29

30
31
32


33
34


35
36

37
38
39
40
41
42
43
44







45
46
47
48



49
50
51
52

53

54
55
56
57
58


59
60
61
62


63
64

65
66
67
68
69

70
71
23
24
25
26
27
28
29

30
31


32
33
34
35
36
37
38

39
40
41






42
43
44
45
46
47
48
49



50
51
52
53
54
55
56
57

58
59
60



61
62
63
64
65

66
67
68

69
70
71



72
73
74







-
+

-
-
+
+


+
+

-
+


-
-
-
-
-
-
+
+
+
+
+
+
+

-
-
-
+
+
+




+
-
+


-
-
-
+
+



-
+
+

-
+


-
-
-
+


}

// Returns a reader that will delegate calls to Read(...) while ensuring
// that the output buffer will never be smaller than the required size
func MinReader(reader io.Reader, size int) io.Reader {
	var buffer []byte = make([]byte, 0, size)

	return ReaderFunc(func(output []byte) (readCount int, e error) {
	return ReaderFunc(func(output []byte) (int, error) {
		var (
			bufferLength int = len(buffer)
			err          error
			readCount int
			err       error
		)
	start:
		//fmt.Println("Requesting read with length ", len(output), "buffer's length is ", len(buffer))

		// Reply with the buffered data if there is any
		if bufferLength > 0 {
		if len(buffer) > 0 {
			readCount = copy(output, buffer)

			if readCount < bufferLength {
				// Advance the data in the buffer
				buffer = buffer[:copy(buffer, buffer[readCount:])]
			} else {
				// Clear the buffer
				buffer = buffer[:0]
			// Advance the data in the buffer
			buffer = buffer[:copy(buffer, buffer[readCount:])]

			//fmt.Println("After buffer read - buffer lenght is", len(buffer))

			if len(buffer) == 0 {
				return readCount, err
			}
			// Stage any error for returning
			e, err = err, nil
			return readCount, e

			// Do not propagate an error until the buffer is exhausted
			return readCount, nil
		}

		// Delegate if the buffer is empty and the destination buffer is large enough
		if len(output) >= size {
			//fmt.Println("Delegating read for output length ", len(output), " and size ", size)
			return reader.Read(output[:len(output)/size])
			return reader.Read(output[:(len(output)/size)*size])
		}

		// Extend the buffer up to the desired size and perform a Read
		buffer = buffer[:size]
		readCount, err = reader.Read(buffer)
		// Perform a read into the buffer
		readCount, err = reader.Read(buffer[:size])

		// Size the buffer down to the read data size and restart
		buffer = buffer[:readCount]
		bufferLength = len(buffer)

		//fmt.Println("Read into buffer: ", len(buffer), "bytes")

		if bufferLength > 0 {
		if len(buffer) > 0 {
			goto start
		}
		// Stage any error for returning
		e, err = err, nil
		return 0, e
		return 0, err
	})
}