chaokunyang commented on code in PR #1566: URL: https://github.com/apache/incubator-fury/pull/1566#discussion_r1577883590
########## go/fury/meta/meta_string_encoder.go: ########## @@ -0,0 +1,261 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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 meta + +import ( + "fmt" + "unicode" +) + +type Encoder struct { + specialChar1 byte + specialChar2 byte +} + +func NewEncoder(specialCh1 byte, specialCh2 byte) *Encoder { + return &Encoder{ + specialChar1: specialCh1, + specialChar2: specialCh2, + } +} + +// Encode the input string to MetaString using adaptive encoding +func (e *Encoder) Encode(input string) MetaString { + encoding := e.ComputeEncoding(input) + return e.EncodeWithEncoding(input, encoding) +} + +// EncodeWithEncoding Encodes the input string to MetaString using specified encoding. +func (e *Encoder) EncodeWithEncoding(input string, encoding Encoding) MetaString { + if len(input) > 32767 { + panic("Long meta string than 32767 is not allowed") + } + // execute encoding algorithm according to the encoding mode + length := len(input) + switch encoding { + case LOWER_SPECIAL: + return MetaString{ + inputString: input, + encoding: encoding, + specialChar1: e.specialChar1, + specialChar2: e.specialChar2, + outputBytes: e.EncodeLowerSpecial(input), + numChars: length, + numBits: length * 5, + } + case LOWER_UPPER_DIGIT_SPECIAL: + return MetaString{ + inputString: input, + encoding: encoding, + specialChar1: e.specialChar1, + specialChar2: e.specialChar2, + outputBytes: e.EncodeLowerUpperDigitSpecial(input), + numChars: length, + numBits: length * 6, + } + case FIRST_TO_LOWER_SPECIAL: + return MetaString{ + inputString: input, + encoding: encoding, + specialChar1: e.specialChar1, + specialChar2: e.specialChar2, + outputBytes: e.EncodeFirstToLowerSpecial(input), + numChars: length, + numBits: length * 5, + } + case ALL_TO_LOWER_SPECIAL: + return MetaString{ + inputString: input, + encoding: encoding, + specialChar1: e.specialChar1, + specialChar2: e.specialChar2, + outputBytes: e.EncodeAllToLowerSpecial(input), + numChars: length, + numBits: (countUppers(input) + length) * 5, + } + default: + // UTF-8 Encoding, Stay the same + outputBytes := []byte(input) + return MetaString{ + inputString: input, + encoding: encoding, + specialChar1: e.specialChar1, + specialChar2: e.specialChar2, + outputBytes: outputBytes, + numChars: len(outputBytes), + numBits: len(outputBytes) * 8, + } + } +} + +func (e *Encoder) EncodeLowerSpecial(input string) []byte { + return e.EncodeGeneric([]byte(input), 5) +} + +func (e *Encoder) EncodeLowerUpperDigitSpecial(input string) []byte { + return e.EncodeGeneric([]byte(input), 6) +} + +func (e *Encoder) EncodeFirstToLowerSpecial(input string) []byte { + // all chars in string are ASCII, so we can modify input[0] directly + chars := []byte(input) + chars[0] = chars[0] - 'A' + 'a' // chars[0] is sure to exist and is upper letter + return e.EncodeGeneric(chars, 5) +} + +func (e *Encoder) EncodeAllToLowerSpecial(input string) []byte { + chars := make([]byte, 0) + for i := 0; i < len(input); i++ { + if input[i] >= 'A' && input[i] <= 'Z' { + chars = append(chars, '|') + chars = append(chars, input[i]-'A'+'a') + } else { + chars = append(chars, input[i]) + } + } + return e.EncodeGeneric(chars, 5) +} + +func (e *Encoder) EncodeGeneric(chars []byte, bitsPerChar int) []byte { + result := make([]byte, (len(chars)*bitsPerChar+7)/8) + currentBit := 0 + for _, c := range chars { + var value byte + if bitsPerChar == 5 { + value = e.charToValueLowerSpecial(c) + } else if bitsPerChar == 6 { + value = e.charToValueLowerUpperDigitSpecial(c) + } + // Use currentBit to figure out where the result should be filled + // abc encoded as [00000] [000,01] [00010] [0, corresponding to three bytes, which are 0, 68, 0 (68 = 64 + 4) + // In order, put the highest bit first, then the lower + for i := bitsPerChar - 1; i >= 0; i-- { + if (value & (1 << i)) > 0 { + bytePos := currentBit / 8 + bitPos := currentBit % 8 + result[bytePos] |= 1 << (7 - bitPos) + } + currentBit++ + } + } + return result +} + +func (e *Encoder) ComputeEncoding(input string) Encoding { + statistics := e.computeStringStatistics(input) + if statistics.canLowerSpecialEncoded { + return LOWER_SPECIAL + } + if statistics.canLowerUpperDigitSpecialEncoded { + // Here, the string contains only letters, numbers, and two special symbols + if statistics.digitCount != 0 { + return LOWER_UPPER_DIGIT_SPECIAL + } + upperCount := statistics.upperCount + chars := []byte(input) + if upperCount == 1 && chars[0] >= 'A' && chars[0] <= 'Z' { + return FIRST_TO_LOWER_SPECIAL + } + if (len(chars)+upperCount)*5 < len(chars)*6 { + return ALL_TO_LOWER_SPECIAL + } + return LOWER_UPPER_DIGIT_SPECIAL + } + return UTF_8 +} + +type stringStatistics struct { + digitCount int + upperCount int + canLowerSpecialEncoded bool + canLowerUpperDigitSpecialEncoded bool +} + +func (e *Encoder) computeStringStatistics(input string) *stringStatistics { + digitCount, upperCount := 0, 0 + canLowerSpecialEncoded := true + canLowerUpperDigitSpecialEncoded := true + for _, c := range []byte(input) { + if canLowerUpperDigitSpecialEncoded { + if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || + c >= '0' && c <= '9' || c == e.specialChar1 || c == e.specialChar2) { + canLowerUpperDigitSpecialEncoded = false + } + } + + if canLowerSpecialEncoded { + if !(c >= 'a' && c <= 'z' || c == '.' || c == '_' || c == '$' || c == '|') { + canLowerSpecialEncoded = false + } + } + + if c >= '0' && c <= '9' { + digitCount++ + } + + if c >= 'A' && c <= 'Z' { + upperCount++ + } + } + return &stringStatistics{ + digitCount: digitCount, + upperCount: upperCount, + canLowerSpecialEncoded: canLowerSpecialEncoded, + canLowerUpperDigitSpecialEncoded: canLowerUpperDigitSpecialEncoded, + } +} + +func countUppers(str string) int { + cnt := 0 + for _, c := range str { + if unicode.IsUpper(c) { + cnt++ + } + } + return cnt +} + +func (e *Encoder) charToValueLowerSpecial(c byte) byte { + if c >= 'a' && c <= 'z' { + return c - 'a' + } else if c == '.' { + return 26 + } else if c == '_' { + return 27 + } else if c == '$' { + return 28 + } else if c == '|' { + return 29 + } + panic(fmt.Sprintf("Unsupported character for LOWER_SPECIAL encoding: %v\n", c)) Review Comment: Could we return an error instead of panic? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
