github.com/whtcorpsinc/MilevaDB-Prod@v0.0.0-20211104133533-f57f4be3b597/soliton/berolinaSQL/parser.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package BerolinaSQL
    15  
    16  import (
    17  	"strconv"
    18  	"unicode"
    19  
    20  	"github.com/whtcorpsinc/errors"
    21  )
    22  
    23  var (
    24  	// ErrPatternNotMatch represents an error that patterns doesn't match.
    25  	ErrPatternNotMatch = errors.New("Pattern not match")
    26  )
    27  
    28  // Match matches the `pat` at least `times`, and returns the match, the rest and the error
    29  func Match(buf string, pat func(byte) bool, times int) (string, string, error) {
    30  	var i int
    31  	for i = 0; i < len(buf) && pat(buf[i]); i++ {
    32  	}
    33  	if i < times {
    34  		return "", buf, ErrPatternNotMatch
    35  	}
    36  	return buf[:i], buf[i:], nil
    37  }
    38  
    39  // MatchOne matches only one time with pat
    40  func MatchOne(buf string, pat func(byte) bool) (string, error) {
    41  	if len(buf) == 0 || !pat(buf[0]) {
    42  		return buf, ErrPatternNotMatch
    43  	}
    44  	return buf[1:], nil
    45  }
    46  
    47  // AnyPunct matches an arbitrary punctuation
    48  func AnyPunct(buf string) (string, error) {
    49  	return MatchOne(buf, func(b byte) bool {
    50  		return unicode.IsPunct(rune(b))
    51  	})
    52  }
    53  
    54  // AnyChar matches an arbitrary character
    55  func AnyChar(buf string) (string, error) {
    56  	return MatchOne(buf, func(byte) bool {
    57  		return true
    58  	})
    59  }
    60  
    61  // Char matches a character: c
    62  func Char(buf string, c byte) (string, error) {
    63  	return MatchOne(buf, func(x byte) bool {
    64  		return x == c
    65  	})
    66  }
    67  
    68  // Space matches at least `times` spaces
    69  func Space(buf string, times int) (string, error) {
    70  	_, rest, err := Match(buf, func(c byte) bool {
    71  		return unicode.IsSpace(rune(c))
    72  	}, times)
    73  	return rest, err
    74  }
    75  
    76  // Space0 matches at least 0 space.
    77  func Space0(buf string) string {
    78  	rest, err := Space(buf, 0)
    79  	if err != nil {
    80  		panic(err)
    81  	}
    82  	return rest
    83  }
    84  
    85  // Digit matches at least `times` digits
    86  func Digit(buf string, times int) (string, string, error) {
    87  	return Match(buf, func(c byte) bool {
    88  		return unicode.IsDigit(rune(c))
    89  	}, times)
    90  }
    91  
    92  // Number matches a series of digits and convert it to an int
    93  func Number(str string) (int, string, error) {
    94  	digits, rest, err := Digit(str, 1)
    95  	if err != nil {
    96  		return 0, str, err
    97  	}
    98  	num, err := strconv.Atoi(digits)
    99  	return num, rest, err
   100  }