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// Copyright 2010 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 gzip
 
import (
        "compress/flate"
        "errors"
        "hash"
        "hash/crc32"
        "io"
)
 
// These constants are copied from the flate package, so that code that imports
// "compress/gzip" does not also have to import "compress/flate".
const (
        NoCompression      = flate.NoCompression
        BestSpeed          = flate.BestSpeed
        BestCompression    = flate.BestCompression
        DefaultCompression = flate.DefaultCompression
)
 
// A Compressor is an io.WriteCloser that satisfies writes by compressing data written
// to its wrapped io.Writer.
type Compressor struct {
        Header
        w          io.Writer
        level      int
        compressor io.WriteCloser
        digest     hash.Hash32
        size       uint32
        closed     bool
        buf        [10]byte
        err        error
}
 
// NewWriter calls NewWriterLevel with the default compression level.
func NewWriter(w io.Writer) (*Compressor, error) {
        return NewWriterLevel(w, DefaultCompression)
}
 
// NewWriterLevel creates a new Compressor writing to the given writer.
// Writes may be buffered and not flushed until Close.
// Callers that wish to set the fields in Compressor.Header must
// do so before the first call to Write or Close.
// It is the caller's responsibility to call Close on the WriteCloser when done.
// level is the compression level, which can be DefaultCompression, NoCompression,
// or any integer value between BestSpeed and BestCompression (inclusive).
func NewWriterLevel(w io.Writer, level int) (*Compressor, error) {
        z := new(Compressor)
        z.OS = 255 // unknown
        z.w = w
        z.level = level
        z.digest = crc32.NewIEEE()
        return z, nil
}
 
// GZIP (RFC 1952) is little-endian, unlike ZLIB (RFC 1950).
func put2(p []byte, v uint16) {
        p[0] = uint8(v >> 0)
        p[1] = uint8(v >> 8)
}
 
func put4(p []byte, v uint32) {
        p[0] = uint8(v >> 0)
        p[1] = uint8(v >> 8)
        p[2] = uint8(v >> 16)
        p[3] = uint8(v >> 24)
}
 
// writeBytes writes a length-prefixed byte slice to z.w.
func (z *Compressor) writeBytes(b []byte) error {
        if len(b) > 0xffff {
                return errors.New("gzip.Write: Extra data is too large")
        }
        put2(z.buf[0:2], uint16(len(b)))
        _, err := z.w.Write(z.buf[0:2])
        if err != nil {
                return err
        }
        _, err = z.w.Write(b)
        return err
}
 
// writeString writes a string (in ISO 8859-1 (Latin-1) format) to z.w.
func (z *Compressor) writeString(s string) error {
        // GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
        var err error
        needconv := false
        for _, v := range s {
                if v == 0 || v > 0xff {
                        return errors.New("gzip.Write: non-Latin-1 header string")
                }
                if v > 0x7f {
                        needconv = true
                }
        }
        if needconv {
                b := make([]byte, 0, len(s))
                for _, v := range s {
                        b = append(b, byte(v))
                }
                _, err = z.w.Write(b)
        } else {
                _, err = io.WriteString(z.w, s)
        }
        if err != nil {
                return err
        }
        // GZIP strings are NUL-terminated.
        z.buf[0] = 0
        _, err = z.w.Write(z.buf[0:1])
        return err
}
 
func (z *Compressor) Write(p []byte) (int, error) {
        if z.err != nil {
                return 0, z.err
        }
        var n int
        // Write the GZIP header lazily.
        if z.compressor == nil {
                z.buf[0] = gzipID1
                z.buf[1] = gzipID2
                z.buf[2] = gzipDeflate
                z.buf[3] = 0
                if z.Extra != nil {
                        z.buf[3] |= 0x04
                }
                if z.Name != "" {
                        z.buf[3] |= 0x08
                }
                if z.Comment != "" {
                        z.buf[3] |= 0x10
                }
                put4(z.buf[4:8], uint32(z.ModTime.Unix()))
                if z.level == BestCompression {
                        z.buf[8] = 2
                } else if z.level == BestSpeed {
                        z.buf[8] = 4
                } else {
                        z.buf[8] = 0
                }
                z.buf[9] = z.OS
                n, z.err = z.w.Write(z.buf[0:10])
                if z.err != nil {
                        return n, z.err
                }
                if z.Extra != nil {
                        z.err = z.writeBytes(z.Extra)
                        if z.err != nil {
                                return n, z.err
                        }
                }
                if z.Name != "" {
                        z.err = z.writeString(z.Name)
                        if z.err != nil {
                                return n, z.err
                        }
                }
                if z.Comment != "" {
                        z.err = z.writeString(z.Comment)
                        if z.err != nil {
                                return n, z.err
                        }
                }
                z.compressor = flate.NewWriter(z.w, z.level)
        }
        z.size += uint32(len(p))
        z.digest.Write(p)
        n, z.err = z.compressor.Write(p)
        return n, z.err
}
 
// Calling Close does not close the wrapped io.Writer originally passed to NewWriter.
func (z *Compressor) Close() error {
        if z.err != nil {
                return z.err
        }
        if z.closed {
                return nil
        }
        z.closed = true
        if z.compressor == nil {
                z.Write(nil)
                if z.err != nil {
                        return z.err
                }
        }
        z.err = z.compressor.Close()
        if z.err != nil {
                return z.err
        }
        put4(z.buf[0:4], z.digest.Sum32())
        put4(z.buf[4:8], z.size)
        _, z.err = z.w.Write(z.buf[0:8])
        return z.err
}

Line No.	Rev	Author	Line
1	747	jeremybenn	`// Copyright 2010 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 gzip`
6
7			`import (`
8			`"compress/flate"`
9			`"errors"`
10			`"hash"`
11			`"hash/crc32"`
12			`"io"`
13			`)`
14
15			`// These constants are copied from the flate package, so that code that imports`
16			`// "compress/gzip" does not also have to import "compress/flate".`
17			`const (`
18			`NoCompression = flate.NoCompression`
19			`BestSpeed = flate.BestSpeed`
20			`BestCompression = flate.BestCompression`
21			`DefaultCompression = flate.DefaultCompression`
22			`)`
23
24			`// A Compressor is an io.WriteCloser that satisfies writes by compressing data written`
25			`// to its wrapped io.Writer.`
26			`type Compressor struct {`
27			`Header`
28			`w io.Writer`
29			`level int`
30			`compressor io.WriteCloser`
31			`digest hash.Hash32`
32			`size uint32`
33			`closed bool`
34			`buf [10]byte`
35			`err error`
36			`}`
37
38			`// NewWriter calls NewWriterLevel with the default compression level.`
39			`func NewWriter(w io.Writer) (*Compressor, error) {`
40			`return NewWriterLevel(w, DefaultCompression)`
41			`}`
42
43			`// NewWriterLevel creates a new Compressor writing to the given writer.`
44			`// Writes may be buffered and not flushed until Close.`
45			`// Callers that wish to set the fields in Compressor.Header must`
46			`// do so before the first call to Write or Close.`
47			`// It is the caller's responsibility to call Close on the WriteCloser when done.`
48			`// level is the compression level, which can be DefaultCompression, NoCompression,`
49			`// or any integer value between BestSpeed and BestCompression (inclusive).`
50			`func NewWriterLevel(w io.Writer, level int) (*Compressor, error) {`
51			`z := new(Compressor)`
52			`z.OS = 255 // unknown`
53			`z.w = w`
54			`z.level = level`
55			`z.digest = crc32.NewIEEE()`
56			`return z, nil`
57			`}`
58
59			`// GZIP (RFC 1952) is little-endian, unlike ZLIB (RFC 1950).`
60			`func put2(p []byte, v uint16) {`
61			`p[0] = uint8(v >> 0)`
62			`p[1] = uint8(v >> 8)`
63			`}`
64
65			`func put4(p []byte, v uint32) {`
66			`p[0] = uint8(v >> 0)`
67			`p[1] = uint8(v >> 8)`
68			`p[2] = uint8(v >> 16)`
69			`p[3] = uint8(v >> 24)`
70			`}`
71
72			`// writeBytes writes a length-prefixed byte slice to z.w.`
73			`func (z *Compressor) writeBytes(b []byte) error {`
74			`if len(b) > 0xffff {`
75			`return errors.New("gzip.Write: Extra data is too large")`
76			`}`
77			`put2(z.buf[0:2], uint16(len(b)))`
78			`_, err := z.w.Write(z.buf[0:2])`
79			`if err != nil {`
80			`return err`
81			`}`
82			`_, err = z.w.Write(b)`
83			`return err`
84			`}`
85
86			`// writeString writes a string (in ISO 8859-1 (Latin-1) format) to z.w.`
87			`func (z *Compressor) writeString(s string) error {`
88			`// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).`
89			`var err error`
90			`needconv := false`
91			`for _, v := range s {`
92			`if v == 0 \|\| v > 0xff {`
93			`return errors.New("gzip.Write: non-Latin-1 header string")`
94			`}`
95			`if v > 0x7f {`
96			`needconv = true`
97			`}`
98			`}`
99			`if needconv {`
100			`b := make([]byte, 0, len(s))`
101			`for _, v := range s {`
102			`b = append(b, byte(v))`
103			`}`
104			`_, err = z.w.Write(b)`
105			`} else {`
106			`_, err = io.WriteString(z.w, s)`
107			`}`
108			`if err != nil {`
109			`return err`
110			`}`
111			`// GZIP strings are NUL-terminated.`
112			`z.buf[0] = 0`
113			`_, err = z.w.Write(z.buf[0:1])`
114			`return err`
115			`}`
116
117			`func (z *Compressor) Write(p []byte) (int, error) {`
118			`if z.err != nil {`
119			`return 0, z.err`
120			`}`
121			`var n int`
122			`// Write the GZIP header lazily.`
123			`if z.compressor == nil {`
124			`z.buf[0] = gzipID1`
125			`z.buf[1] = gzipID2`
126			`z.buf[2] = gzipDeflate`
127			`z.buf[3] = 0`
128			`if z.Extra != nil {`
129			`z.buf[3] \|= 0x04`
130			`}`
131			`if z.Name != "" {`
132			`z.buf[3] \|= 0x08`
133			`}`
134			`if z.Comment != "" {`
135			`z.buf[3] \|= 0x10`
136			`}`
137			`put4(z.buf[4:8], uint32(z.ModTime.Unix()))`
138			`if z.level == BestCompression {`
139			`z.buf[8] = 2`
140			`} else if z.level == BestSpeed {`
141			`z.buf[8] = 4`
142			`} else {`
143			`z.buf[8] = 0`
144			`}`
145			`z.buf[9] = z.OS`
146			`n, z.err = z.w.Write(z.buf[0:10])`
147			`if z.err != nil {`
148			`return n, z.err`
149			`}`
150			`if z.Extra != nil {`
151			`z.err = z.writeBytes(z.Extra)`
152			`if z.err != nil {`
153			`return n, z.err`
154			`}`
155			`}`
156			`if z.Name != "" {`
157			`z.err = z.writeString(z.Name)`
158			`if z.err != nil {`
159			`return n, z.err`
160			`}`
161			`}`
162			`if z.Comment != "" {`
163			`z.err = z.writeString(z.Comment)`
164			`if z.err != nil {`
165			`return n, z.err`
166			`}`
167			`}`
168			`z.compressor = flate.NewWriter(z.w, z.level)`
169			`}`
170			`z.size += uint32(len(p))`
171			`z.digest.Write(p)`
172			`n, z.err = z.compressor.Write(p)`
173			`return n, z.err`
174			`}`
175
176			`// Calling Close does not close the wrapped io.Writer originally passed to NewWriter.`
177			`func (z *Compressor) Close() error {`
178			`if z.err != nil {`
179			`return z.err`
180			`}`
181			`if z.closed {`
182			`return nil`
183			`}`
184			`z.closed = true`
185			`if z.compressor == nil {`
186			`z.Write(nil)`
187			`if z.err != nil {`
188			`return z.err`
189			`}`
190			`}`
191			`z.err = z.compressor.Close()`
192			`if z.err != nil {`
193			`return z.err`
194			`}`
195			`put4(z.buf[0:4], z.digest.Sum32())`
196			`put4(z.buf[4:8], z.size)`
197			`_, z.err = z.w.Write(z.buf[0:8])`
198			`return z.err`
199			`}`

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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [compress/] [gzip/] [gzip.go] - Blame information for rev 861