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stringfuncs.go
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stringfuncs.go
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// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package sql
import (
"errors"
"strings"
)
var (
errMalformedEscapeSequence = errors.New("Malformed escape sequence in LIKE clause")
errInvalidTrimArg = errors.New("Trim argument is invalid - this should not happen")
errInvalidSubstringIndexLen = errors.New("Substring start index or length falls outside the string")
)
const (
percent rune = '%'
underscore rune = '_'
runeZero rune = 0
)
func evalSQLLike(text, pattern string, escape rune) (match bool, err error) {
s := []rune{}
prev := runeZero
hasLeadingPercent := false
patLen := len([]rune(pattern))
for i, r := range pattern {
if i > 0 && prev == escape {
switch r {
case percent, escape, underscore:
s = append(s, r)
prev = r
if r == escape {
prev = runeZero
}
default:
return false, errMalformedEscapeSequence
}
continue
}
prev = r
var ok bool
switch r {
case percent:
if len(s) == 0 {
hasLeadingPercent = true
continue
}
text, ok = matcher(text, string(s), hasLeadingPercent)
if !ok {
return false, nil
}
hasLeadingPercent = true
s = []rune{}
if i == patLen-1 {
// Last pattern character is a %, so
// we are done.
return true, nil
}
case underscore:
if len(s) == 0 {
text, ok = dropRune(text)
if !ok {
return false, nil
}
continue
}
text, ok = matcher(text, string(s), hasLeadingPercent)
if !ok {
return false, nil
}
hasLeadingPercent = false
text, ok = dropRune(text)
if !ok {
return false, nil
}
s = []rune{}
case escape:
if i == patLen-1 {
return false, errMalformedEscapeSequence
}
// Otherwise do nothing.
default:
s = append(s, r)
}
}
if hasLeadingPercent {
return strings.HasSuffix(text, string(s)), nil
}
return string(s) == text, nil
}
// matcher - Finds `pat` in `text`, and returns the part remainder of
// `text`, after the match. If leadingPercent is false, `pat` must be
// the prefix of `text`, otherwise it must be a substring.
func matcher(text, pat string, leadingPercent bool) (res string, match bool) {
if !leadingPercent {
res = strings.TrimPrefix(text, pat)
if len(text) == len(res) {
return "", false
}
} else {
parts := strings.SplitN(text, pat, 2)
if len(parts) == 1 {
return "", false
}
res = parts[1]
}
return res, true
}
func dropRune(text string) (res string, ok bool) {
r := []rune(text)
if len(r) == 0 {
return "", false
}
return string(r[1:]), true
}
func evalSQLSubstring(s string, startIdx, length int) (res string, err error) {
rs := []rune(s)
// According to s3 document, if startIdx < 1, it is set to 1.
if startIdx < 1 {
startIdx = 1
}
if startIdx > len(rs) {
startIdx = len(rs) + 1
}
// StartIdx is 1-based in the input
startIdx--
endIdx := len(rs)
if length != -1 {
if length < 0 {
return "", errInvalidSubstringIndexLen
}
if length > (endIdx - startIdx) {
length = endIdx - startIdx
}
endIdx = startIdx + length
}
return string(rs[startIdx:endIdx]), nil
}
const (
trimLeading = "LEADING"
trimTrailing = "TRAILING"
trimBoth = "BOTH"
)
func evalSQLTrim(where *string, trimChars, text string) (result string, err error) {
cutSet := " "
if trimChars != "" {
cutSet = trimChars
}
trimFunc := strings.Trim
switch {
case where == nil:
case *where == trimBoth:
case *where == trimLeading:
trimFunc = strings.TrimLeft
case *where == trimTrailing:
trimFunc = strings.TrimRight
default:
return "", errInvalidTrimArg
}
return trimFunc(text, cutSet), nil
}