1 // Copyright 2015 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 precis 6 7 import ( 8 "unicode" 9 "unicode/utf8" 10 11 "golang.org/x/text/transform" 12 ) 13 14 type nickAdditionalMapping struct { 15 // TODO: This transformer needs to be stateless somehow… 16 notStart bool 17 prevSpace bool 18 } 19 20 func (t *nickAdditionalMapping) Reset() { 21 t.prevSpace = false 22 t.notStart = false 23 } 24 25 func (t *nickAdditionalMapping) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { 26 // RFC 8266 §2.1. Rules 27 // 28 // 2. Additional Mapping Rule: The additional mapping rule consists of 29 // the following sub-rules. 30 // 31 // a. Map any instances of non-ASCII space to SPACE (U+0020); a 32 // non-ASCII space is any Unicode code point having a general 33 // category of "Zs", naturally with the exception of SPACE 34 // (U+0020). (The inclusion of only ASCII space prevents 35 // confusion with various non-ASCII space code points, many of 36 // which are difficult to reproduce across different input 37 // methods.) 38 // 39 // b. Remove any instances of the ASCII space character at the 40 // beginning or end of a nickname (e.g., "stpeter " is mapped to 41 // "stpeter"). 42 // 43 // c. Map interior sequences of more than one ASCII space character 44 // to a single ASCII space character (e.g., "St Peter" is 45 // mapped to "St Peter"). 46 for nSrc < len(src) { 47 r, size := utf8.DecodeRune(src[nSrc:]) 48 if size == 0 { // Incomplete UTF-8 encoding 49 if !atEOF { 50 return nDst, nSrc, transform.ErrShortSrc 51 } 52 size = 1 53 } 54 if unicode.Is(unicode.Zs, r) { 55 t.prevSpace = true 56 } else { 57 if t.prevSpace && t.notStart { 58 dst[nDst] = ' ' 59 nDst += 1 60 } 61 if size != copy(dst[nDst:], src[nSrc:nSrc+size]) { 62 nDst += size 63 return nDst, nSrc, transform.ErrShortDst 64 } 65 nDst += size 66 t.prevSpace = false 67 t.notStart = true 68 } 69 nSrc += size 70 } 71 return nDst, nSrc, nil 72 } 73