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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [encoding/] [ascii85/] [ascii85.go] - Blame information for rev 774

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// Copyright 2009 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 ascii85 implements the ascii85 data encoding
// as used in the btoa tool and Adobe's PostScript and PDF document formats.
package ascii85
 
import (
        "io"
        "strconv"
)
 
/*
 * Encoder
 */
 
// Encode encodes src into at most MaxEncodedLen(len(src))
// bytes of dst, returning the actual number of bytes written.
//
// The encoding handles 4-byte chunks, using a special encoding
// for the last fragment, so Encode is not appropriate for use on
// individual blocks of a large data stream.  Use NewEncoder() instead.
//
// Often, ascii85-encoded data is wrapped in <~ and ~> symbols.
// Encode does not add these.
func Encode(dst, src []byte) int {
        if len(src) == 0 {
                return 0
        }
 
        n := 0
        for len(src) > 0 {
                dst[0] = 0
                dst[1] = 0
                dst[2] = 0
                dst[3] = 0
                dst[4] = 0
 
                // Unpack 4 bytes into uint32 to repack into base 85 5-byte.
                var v uint32
                switch len(src) {
                default:
                        v |= uint32(src[3])
                        fallthrough
                case 3:
                        v |= uint32(src[2]) << 8
                        fallthrough
                case 2:
                        v |= uint32(src[1]) << 16
                        fallthrough
                case 1:
                        v |= uint32(src[0]) << 24
                }
 
                // Special case: zero (!!!!!) shortens to z.
                if v == 0 && len(src) >= 4 {
                        dst[0] = 'z'
                        dst = dst[1:]
                        n++
                        continue
                }
 
                // Otherwise, 5 base 85 digits starting at !.
                for i := 4; i >= 0; i-- {
                        dst[i] = '!' + byte(v%85)
                        v /= 85
                }
 
                // If src was short, discard the low destination bytes.
                m := 5
                if len(src) < 4 {
                        m -= 4 - len(src)
                        src = nil
                } else {
                        src = src[4:]
                }
                dst = dst[m:]
                n += m
        }
        return n
}
 
// MaxEncodedLen returns the maximum length of an encoding of n source bytes.
func MaxEncodedLen(n int) int { return (n + 3) / 4 * 5 }
 
// NewEncoder returns a new ascii85 stream encoder.  Data written to
// the returned writer will be encoded and then written to w.
// Ascii85 encodings operate in 32-bit blocks; when finished
// writing, the caller must Close the returned encoder to flush any
// trailing partial block.
func NewEncoder(w io.Writer) io.WriteCloser { return &encoder{w: w} }
 
type encoder struct {
        err  error
        w    io.Writer
        buf  [4]byte    // buffered data waiting to be encoded
        nbuf int        // number of bytes in buf
        out  [1024]byte // output buffer
}
 
func (e *encoder) Write(p []byte) (n int, err error) {
        if e.err != nil {
                return 0, e.err
        }
 
        // Leading fringe.
        if e.nbuf > 0 {
                var i int
                for i = 0; i < len(p) && e.nbuf < 4; i++ {
                        e.buf[e.nbuf] = p[i]
                        e.nbuf++
                }
                n += i
                p = p[i:]
                if e.nbuf < 4 {
                        return
                }
                nout := Encode(e.out[0:], e.buf[0:])
                if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
                        return n, e.err
                }
                e.nbuf = 0
        }
 
        // Large interior chunks.
        for len(p) >= 4 {
                nn := len(e.out) / 5 * 4
                if nn > len(p) {
                        nn = len(p)
                }
                nn -= nn % 4
                if nn > 0 {
                        nout := Encode(e.out[0:], p[0:nn])
                        if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
                                return n, e.err
                        }
                }
                n += nn
                p = p[nn:]
        }
 
        // Trailing fringe.
        for i := 0; i < len(p); i++ {
                e.buf[i] = p[i]
        }
        e.nbuf = len(p)
        n += len(p)
        return
}
 
// Close flushes any pending output from the encoder.
// It is an error to call Write after calling Close.
func (e *encoder) Close() error {
        // If there's anything left in the buffer, flush it out
        if e.err == nil && e.nbuf > 0 {
                nout := Encode(e.out[0:], e.buf[0:e.nbuf])
                e.nbuf = 0
                _, e.err = e.w.Write(e.out[0:nout])
        }
        return e.err
}
 
/*
 * Decoder
 */
 
type CorruptInputError int64
 
func (e CorruptInputError) Error() string {
        return "illegal ascii85 data at input byte " + strconv.FormatInt(int64(e), 10)
}
 
// Decode decodes src into dst, returning both the number
// of bytes written to dst and the number consumed from src.
// If src contains invalid ascii85 data, Decode will return the
// number of bytes successfully written and a CorruptInputError.
// Decode ignores space and control characters in src.
// Often, ascii85-encoded data is wrapped in <~ and ~> symbols.
// Decode expects these to have been stripped by the caller.
//
// If flush is true, Decode assumes that src represents the
// end of the input stream and processes it completely rather
// than wait for the completion of another 32-bit block.
//
// NewDecoder wraps an io.Reader interface around Decode.
//
func Decode(dst, src []byte, flush bool) (ndst, nsrc int, err error) {
        var v uint32
        var nb int
        for i, b := range src {
                if len(dst)-ndst < 4 {
                        return
                }
                switch {
                case b <= ' ':
                        continue
                case b == 'z' && nb == 0:
                        nb = 5
                        v = 0
                case '!' <= b && b <= 'u':
                        v = v*85 + uint32(b-'!')
                        nb++
                default:
                        return 0, 0, CorruptInputError(i)
                }
                if nb == 5 {
                        nsrc = i + 1
                        dst[ndst] = byte(v >> 24)
                        dst[ndst+1] = byte(v >> 16)
                        dst[ndst+2] = byte(v >> 8)
                        dst[ndst+3] = byte(v)
                        ndst += 4
                        nb = 0
                        v = 0
                }
        }
        if flush {
                nsrc = len(src)
                if nb > 0 {
                        // The number of output bytes in the last fragment
                        // is the number of leftover input bytes - 1:
                        // the extra byte provides enough bits to cover
                        // the inefficiency of the encoding for the block.
                        if nb == 1 {
                                return 0, 0, CorruptInputError(len(src))
                        }
                        for i := nb; i < 5; i++ {
                                // The short encoding truncated the output value.
                                // We have to assume the worst case values (digit 84)
                                // in order to ensure that the top bits are correct.
                                v = v*85 + 84
                        }
                        for i := 0; i < nb-1; i++ {
                                dst[ndst] = byte(v >> 24)
                                v <<= 8
                                ndst++
                        }
                }
        }
        return
}
 
// NewDecoder constructs a new ascii85 stream decoder.
func NewDecoder(r io.Reader) io.Reader { return &decoder{r: r} }
 
type decoder struct {
        err     error
        readErr error
        r       io.Reader
        end     bool       // saw end of message
        buf     [1024]byte // leftover input
        nbuf    int
        out     []byte // leftover decoded output
        outbuf  [1024]byte
}
 
func (d *decoder) Read(p []byte) (n int, err error) {
        if len(p) == 0 {
                return 0, nil
        }
        if d.err != nil {
                return 0, d.err
        }
 
        for {
                // Copy leftover output from last decode.
                if len(d.out) > 0 {
                        n = copy(p, d.out)
                        d.out = d.out[n:]
                        return
                }
 
                // Decode leftover input from last read.
                var nn, nsrc, ndst int
                if d.nbuf > 0 {
                        ndst, nsrc, d.err = Decode(d.outbuf[0:], d.buf[0:d.nbuf], d.readErr != nil)
                        if ndst > 0 {
                                d.out = d.outbuf[0:ndst]
                                d.nbuf = copy(d.buf[0:], d.buf[nsrc:d.nbuf])
                                continue // copy out and return
                        }
                }
 
                // Out of input, out of decoded output.  Check errors.
                if d.err != nil {
                        return 0, d.err
                }
                if d.readErr != nil {
                        d.err = d.readErr
                        return 0, d.err
                }
 
                // Read more data.
                nn, d.readErr = d.r.Read(d.buf[d.nbuf:])
                d.nbuf += nn
        }
        panic("unreachable")
}

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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [encoding/] [ascii85/] [ascii85.go] - Blame information for rev 774

Line No.	Rev	Author	Line
1	747	jeremybenn	`// Copyright 2009 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 ascii85 implements the ascii85 data encoding`
6			`// as used in the btoa tool and Adobe's PostScript and PDF document formats.`
7			`package ascii85`
8
9			`import (`
10			`"io"`
11			`"strconv"`
12			`)`
13
14			`/*`
15			`* Encoder`
16			`*/`
17
18			`// Encode encodes src into at most MaxEncodedLen(len(src))`
19			`// bytes of dst, returning the actual number of bytes written.`
20			`//`
21			`// The encoding handles 4-byte chunks, using a special encoding`
22			`// for the last fragment, so Encode is not appropriate for use on`
23			`// individual blocks of a large data stream. Use NewEncoder() instead.`
24			`//`
25			`// Often, ascii85-encoded data is wrapped in <~ and ~> symbols.`
26			`// Encode does not add these.`
27			`func Encode(dst, src []byte) int {`
28			`if len(src) == 0 {`
29			`return 0`
30			`}`
31
32			`n := 0`
33			`for len(src) > 0 {`
34			`dst[0] = 0`
35			`dst[1] = 0`
36			`dst[2] = 0`
37			`dst[3] = 0`
38			`dst[4] = 0`
39
40			`// Unpack 4 bytes into uint32 to repack into base 85 5-byte.`
41			`var v uint32`
42			`switch len(src) {`
43			`default:`
44			`v \|= uint32(src[3])`
45			`fallthrough`
46			`case 3:`
47			`v \|= uint32(src[2]) << 8`
48			`fallthrough`
49			`case 2:`
50			`v \|= uint32(src[1]) << 16`
51			`fallthrough`
52			`case 1:`
53			`v \|= uint32(src[0]) << 24`
54			`}`
55
56			`// Special case: zero (!!!!!) shortens to z.`
57			`if v == 0 && len(src) >= 4 {`
58			`dst[0] = 'z'`
59			`dst = dst[1:]`
60			`n++`
61			`continue`
62			`}`
63
64			`// Otherwise, 5 base 85 digits starting at !.`
65			`for i := 4; i >= 0; i-- {`
66			`dst[i] = '!' + byte(v%85)`
67			`v /= 85`
68			`}`
69
70			`// If src was short, discard the low destination bytes.`
71			`m := 5`
72			`if len(src) < 4 {`
73			`m -= 4 - len(src)`
74			`src = nil`
75			`} else {`
76			`src = src[4:]`
77			`}`
78			`dst = dst[m:]`
79			`n += m`
80			`}`
81			`return n`
82			`}`
83
84			`// MaxEncodedLen returns the maximum length of an encoding of n source bytes.`
85			`func MaxEncodedLen(n int) int { return (n + 3) / 4 * 5 }`
86
87			`// NewEncoder returns a new ascii85 stream encoder. Data written to`
88			`// the returned writer will be encoded and then written to w.`
89			`// Ascii85 encodings operate in 32-bit blocks; when finished`
90			`// writing, the caller must Close the returned encoder to flush any`
91			`// trailing partial block.`
92			`func NewEncoder(w io.Writer) io.WriteCloser { return &encoder{w: w} }`
93
94			`type encoder struct {`
95			`err error`
96			`w io.Writer`
97			`buf [4]byte // buffered data waiting to be encoded`
98			`nbuf int // number of bytes in buf`
99			`out [1024]byte // output buffer`
100			`}`
101
102			`func (e *encoder) Write(p []byte) (n int, err error) {`
103			`if e.err != nil {`
104			`return 0, e.err`
105			`}`
106
107			`// Leading fringe.`
108			`if e.nbuf > 0 {`
109			`var i int`
110			`for i = 0; i < len(p) && e.nbuf < 4; i++ {`
111			`e.buf[e.nbuf] = p[i]`
112			`e.nbuf++`
113			`}`
114			`n += i`
115			`p = p[i:]`
116			`if e.nbuf < 4 {`
117			`return`
118			`}`
119			`nout := Encode(e.out[0:], e.buf[0:])`
120			`if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {`
121			`return n, e.err`
122			`}`
123			`e.nbuf = 0`
124			`}`
125
126			`// Large interior chunks.`
127			`for len(p) >= 4 {`
128			`nn := len(e.out) / 5 * 4`
129			`if nn > len(p) {`
130			`nn = len(p)`
131			`}`
132			`nn -= nn % 4`
133			`if nn > 0 {`
134			`nout := Encode(e.out[0:], p[0:nn])`
135			`if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {`
136			`return n, e.err`
137			`}`
138			`}`
139			`n += nn`
140			`p = p[nn:]`
141			`}`
142
143			`// Trailing fringe.`
144			`for i := 0; i < len(p); i++ {`
145			`e.buf[i] = p[i]`
146			`}`
147			`e.nbuf = len(p)`
148			`n += len(p)`
149			`return`
150			`}`
151
152			`// Close flushes any pending output from the encoder.`
153			`// It is an error to call Write after calling Close.`
154			`func (e *encoder) Close() error {`
155			`// If there's anything left in the buffer, flush it out`
156			`if e.err == nil && e.nbuf > 0 {`
157			`nout := Encode(e.out[0:], e.buf[0:e.nbuf])`
158			`e.nbuf = 0`
159			`_, e.err = e.w.Write(e.out[0:nout])`
160			`}`
161			`return e.err`
162			`}`
163
164			`/*`
165			`* Decoder`
166			`*/`
167
168			`type CorruptInputError int64`
169
170			`func (e CorruptInputError) Error() string {`
171			`return "illegal ascii85 data at input byte " + strconv.FormatInt(int64(e), 10)`
172			`}`
173
174			`// Decode decodes src into dst, returning both the number`
175			`// of bytes written to dst and the number consumed from src.`
176			`// If src contains invalid ascii85 data, Decode will return the`
177			`// number of bytes successfully written and a CorruptInputError.`
178			`// Decode ignores space and control characters in src.`
179			`// Often, ascii85-encoded data is wrapped in <~ and ~> symbols.`
180			`// Decode expects these to have been stripped by the caller.`
181			`//`
182			`// If flush is true, Decode assumes that src represents the`
183			`// end of the input stream and processes it completely rather`
184			`// than wait for the completion of another 32-bit block.`
185			`//`
186			`// NewDecoder wraps an io.Reader interface around Decode.`
187			`//`
188			`func Decode(dst, src []byte, flush bool) (ndst, nsrc int, err error) {`
189			`var v uint32`
190			`var nb int`
191			`for i, b := range src {`
192			`if len(dst)-ndst < 4 {`
193			`return`
194			`}`
195			`switch {`
196			`case b <= ' ':`
197			`continue`
198			`case b == 'z' && nb == 0:`
199			`nb = 5`
200			`v = 0`
201			`case '!' <= b && b <= 'u':`
202			`v = v*85 + uint32(b-'!')`
203			`nb++`
204			`default:`
205			`return 0, 0, CorruptInputError(i)`
206			`}`
207			`if nb == 5 {`
208			`nsrc = i + 1`
209			`dst[ndst] = byte(v >> 24)`
210			`dst[ndst+1] = byte(v >> 16)`
211			`dst[ndst+2] = byte(v >> 8)`
212			`dst[ndst+3] = byte(v)`
213			`ndst += 4`
214			`nb = 0`
215			`v = 0`
216			`}`
217			`}`
218			`if flush {`
219			`nsrc = len(src)`
220			`if nb > 0 {`
221			`// The number of output bytes in the last fragment`
222			`// is the number of leftover input bytes - 1:`
223			`// the extra byte provides enough bits to cover`
224			`// the inefficiency of the encoding for the block.`
225			`if nb == 1 {`
226			`return 0, 0, CorruptInputError(len(src))`
227			`}`
228			`for i := nb; i < 5; i++ {`
229			`// The short encoding truncated the output value.`
230			`// We have to assume the worst case values (digit 84)`
231			`// in order to ensure that the top bits are correct.`
232			`v = v*85 + 84`
233			`}`
234			`for i := 0; i < nb-1; i++ {`
235			`dst[ndst] = byte(v >> 24)`
236			`v <<= 8`
237			`ndst++`
238			`}`
239			`}`
240			`}`
241			`return`
242			`}`
243
244			`// NewDecoder constructs a new ascii85 stream decoder.`
245			`func NewDecoder(r io.Reader) io.Reader { return &decoder{r: r} }`
246
247			`type decoder struct {`
248			`err error`
249			`readErr error`
250			`r io.Reader`
251			`end bool // saw end of message`
252			`buf [1024]byte // leftover input`
253			`nbuf int`
254			`out []byte // leftover decoded output`
255			`outbuf [1024]byte`
256			`}`
257
258			`func (d *decoder) Read(p []byte) (n int, err error) {`
259			`if len(p) == 0 {`
260			`return 0, nil`
261			`}`
262			`if d.err != nil {`
263			`return 0, d.err`
264			`}`
265
266			`for {`
267			`// Copy leftover output from last decode.`
268			`if len(d.out) > 0 {`
269			`n = copy(p, d.out)`
270			`d.out = d.out[n:]`
271			`return`
272			`}`
273
274			`// Decode leftover input from last read.`
275			`var nn, nsrc, ndst int`
276			`if d.nbuf > 0 {`
277			`ndst, nsrc, d.err = Decode(d.outbuf[0:], d.buf[0:d.nbuf], d.readErr != nil)`
278			`if ndst > 0 {`
279			`d.out = d.outbuf[0:ndst]`
280			`d.nbuf = copy(d.buf[0:], d.buf[nsrc:d.nbuf])`
281			`continue // copy out and return`
282			`}`
283			`}`
284
285			`// Out of input, out of decoded output. Check errors.`
286			`if d.err != nil {`
287			`return 0, d.err`
288			`}`
289			`if d.readErr != nil {`
290			`d.err = d.readErr`
291			`return 0, d.err`
292			`}`
293
294			`// Read more data.`
295			`nn, d.readErr = d.r.Read(d.buf[d.nbuf:])`
296			`d.nbuf += nn`
297			`}`
298			`panic("unreachable")`
299			`}`