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Do some precomputation to speed up Match: convert the field name to bytes, and pick an efficient case-folding comparison function. These are taken from the encoding/json code. The files fold.go and fold_test.go are exact copies of the 1.7.3 versions in encoding/json. Change-Id: I69e748b2e6a65f0c83441a1791cb3d7f71c86094 Reviewed-on: https://code-review.googlesource.com/9551 Reviewed-by: Michael Darakananda <pongad@google.com> Reviewed-by: Jun Mukai <mukai@google.com>
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| Original file line number | Diff line number | Diff line change |
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| // Copyright 2016 Google Inc. All Rights Reserved. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package fields | ||
|
|
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| // This file was copied from https://go.googlesource.com/go/+/go1.7.3/src/encoding/json/fold.go. | ||
| // Only the license and package were changed. | ||
|
|
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| import ( | ||
| "bytes" | ||
| "unicode/utf8" | ||
| ) | ||
|
|
||
| const ( | ||
| caseMask = ^byte(0x20) // Mask to ignore case in ASCII. | ||
| kelvin = '\u212a' | ||
| smallLongEss = '\u017f' | ||
| ) | ||
|
|
||
| // foldFunc returns one of four different case folding equivalence | ||
| // functions, from most general (and slow) to fastest: | ||
| // | ||
| // 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8 | ||
| // 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S') | ||
| // 3) asciiEqualFold, no special, but includes non-letters (including _) | ||
| // 4) simpleLetterEqualFold, no specials, no non-letters. | ||
| // | ||
| // The letters S and K are special because they map to 3 runes, not just 2: | ||
| // * S maps to s and to U+017F 'ſ' Latin small letter long s | ||
| // * k maps to K and to U+212A 'K' Kelvin sign | ||
| // See https://play.golang.org/p/tTxjOc0OGo | ||
| // | ||
| // The returned function is specialized for matching against s and | ||
| // should only be given s. It's not curried for performance reasons. | ||
| func foldFunc(s []byte) func(s, t []byte) bool { | ||
| nonLetter := false | ||
| special := false // special letter | ||
| for _, b := range s { | ||
| if b >= utf8.RuneSelf { | ||
| return bytes.EqualFold | ||
| } | ||
| upper := b & caseMask | ||
| if upper < 'A' || upper > 'Z' { | ||
| nonLetter = true | ||
| } else if upper == 'K' || upper == 'S' { | ||
| // See above for why these letters are special. | ||
| special = true | ||
| } | ||
| } | ||
| if special { | ||
| return equalFoldRight | ||
| } | ||
| if nonLetter { | ||
| return asciiEqualFold | ||
| } | ||
| return simpleLetterEqualFold | ||
| } | ||
|
|
||
| // equalFoldRight is a specialization of bytes.EqualFold when s is | ||
| // known to be all ASCII (including punctuation), but contains an 's', | ||
| // 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t. | ||
| // See comments on foldFunc. | ||
| func equalFoldRight(s, t []byte) bool { | ||
| for _, sb := range s { | ||
| if len(t) == 0 { | ||
| return false | ||
| } | ||
| tb := t[0] | ||
| if tb < utf8.RuneSelf { | ||
| if sb != tb { | ||
| sbUpper := sb & caseMask | ||
| if 'A' <= sbUpper && sbUpper <= 'Z' { | ||
| if sbUpper != tb&caseMask { | ||
| return false | ||
| } | ||
| } else { | ||
| return false | ||
| } | ||
| } | ||
| t = t[1:] | ||
| continue | ||
| } | ||
| // sb is ASCII and t is not. t must be either kelvin | ||
| // sign or long s; sb must be s, S, k, or K. | ||
| tr, size := utf8.DecodeRune(t) | ||
| switch sb { | ||
| case 's', 'S': | ||
| if tr != smallLongEss { | ||
| return false | ||
| } | ||
| case 'k', 'K': | ||
| if tr != kelvin { | ||
| return false | ||
| } | ||
| default: | ||
| return false | ||
| } | ||
| t = t[size:] | ||
|
|
||
| } | ||
| if len(t) > 0 { | ||
| return false | ||
| } | ||
| return true | ||
| } | ||
|
|
||
| // asciiEqualFold is a specialization of bytes.EqualFold for use when | ||
| // s is all ASCII (but may contain non-letters) and contains no | ||
| // special-folding letters. | ||
| // See comments on foldFunc. | ||
| func asciiEqualFold(s, t []byte) bool { | ||
| if len(s) != len(t) { | ||
| return false | ||
| } | ||
| for i, sb := range s { | ||
| tb := t[i] | ||
| if sb == tb { | ||
| continue | ||
| } | ||
| if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') { | ||
| if sb&caseMask != tb&caseMask { | ||
| return false | ||
| } | ||
| } else { | ||
| return false | ||
| } | ||
| } | ||
| return true | ||
| } | ||
|
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| // simpleLetterEqualFold is a specialization of bytes.EqualFold for | ||
| // use when s is all ASCII letters (no underscores, etc) and also | ||
| // doesn't contain 'k', 'K', 's', or 'S'. | ||
| // See comments on foldFunc. | ||
| func simpleLetterEqualFold(s, t []byte) bool { | ||
| if len(s) != len(t) { | ||
| return false | ||
| } | ||
| for i, b := range s { | ||
| if b&caseMask != t[i]&caseMask { | ||
| return false | ||
| } | ||
| } | ||
| return true | ||
| } |
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