141 lines
5.1 KiB
Go
141 lines
5.1 KiB
Go
package wsutil
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import (
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"fmt"
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"io"
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)
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// ErrInvalidUTF8 is returned by UTF8 reader on invalid utf8 sequence.
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var ErrInvalidUTF8 = fmt.Errorf("invalid utf8")
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// UTF8Reader implements io.Reader that calculates utf8 validity state after
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// every read byte from Source.
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//
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// Note that in some cases client must call r.Valid() after all bytes are read
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// to ensure that all of them are valid utf8 sequences. That is, some io helper
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// functions such io.ReadAtLeast or io.ReadFull could discard the error
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// information returned by the reader when they receive all of requested bytes.
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// For example, the last read sequence is invalid and UTF8Reader returns number
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// of bytes read and an error. But helper function decides to discard received
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// error due to all requested bytes are completely read from the source.
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//
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// Another possible case is when some valid sequence become split by the read
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// bound. Then UTF8Reader can not make decision about validity of the last
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// sequence cause it is not fully read yet. And if the read stops, Valid() will
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// return false, even if Read() by itself dit not.
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type UTF8Reader struct {
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Source io.Reader
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accepted int
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state uint32
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codep uint32
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}
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// NewUTF8Reader creates utf8 reader that reads from r.
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func NewUTF8Reader(r io.Reader) *UTF8Reader {
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return &UTF8Reader{
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Source: r,
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}
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}
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// Reset resets utf8 reader to read from r.
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func (u *UTF8Reader) Reset(r io.Reader) {
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u.Source = r
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u.state = 0
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u.codep = 0
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}
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// Read implements io.Reader.
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func (u *UTF8Reader) Read(p []byte) (n int, err error) {
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n, err = u.Source.Read(p)
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accepted := 0
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s, c := u.state, u.codep
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for i := 0; i < n; i++ {
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c, s = decode(s, c, p[i])
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if s == utf8Reject {
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u.state = s
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return accepted, ErrInvalidUTF8
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}
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if s == utf8Accept {
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accepted = i + 1
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}
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}
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u.state, u.codep = s, c
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u.accepted = accepted
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return n, err
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}
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// Valid checks current reader state. It returns true if all read bytes are
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// valid UTF-8 sequences, and false if not.
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func (u *UTF8Reader) Valid() bool {
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return u.state == utf8Accept
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}
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// Accepted returns number of valid bytes in last Read().
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func (u *UTF8Reader) Accepted() int {
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return u.accepted
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}
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// Below is port of UTF-8 decoder from http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
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//
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// Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to
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// deal in the Software without restriction, including without limitation the
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// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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// sell copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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// IN THE SOFTWARE.
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const (
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utf8Accept = 0
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utf8Reject = 12
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)
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var utf8d = [...]byte{
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// The first part of the table maps bytes to character classes that
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// to reduce the size of the transition table and create bitmasks.
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
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8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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10, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 11, 6, 6, 6, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
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// The second part is a transition table that maps a combination
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// of a state of the automaton and a character class to a state.
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0, 12, 24, 36, 60, 96, 84, 12, 12, 12, 48, 72, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
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12, 0, 12, 12, 12, 12, 12, 0, 12, 0, 12, 12, 12, 24, 12, 12, 12, 12, 12, 24, 12, 24, 12, 12,
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12, 12, 12, 12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 12, 12, 24, 12, 12,
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12, 12, 12, 12, 12, 12, 12, 36, 12, 36, 12, 12, 12, 36, 12, 12, 12, 12, 12, 36, 12, 36, 12, 12,
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12, 36, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
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}
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func decode(state, codep uint32, b byte) (uint32, uint32) {
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t := uint32(utf8d[b])
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if state != utf8Accept {
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codep = (uint32(b) & 0x3f) | (codep << 6)
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} else {
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codep = (0xff >> t) & uint32(b)
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}
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return codep, uint32(utf8d[256+state+t])
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}
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