| // Copyright 2018 The CUE Authors |
| // |
| // 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 strings implements simple functions to manipulate UTF-8 encoded |
| // strings.package strings. |
| // |
| // Some of the functions in this package are specifically intended as field |
| // constraints. For instance, MaxRunes as used in this CUE program |
| // |
| // import "strings" |
| // |
| // myString: strings.MaxRunes(5) |
| // |
| // specifies that the myString should be at most 5 code points. |
| package strings |
| |
| import ( |
| "fmt" |
| "strings" |
| "unicode" |
| ) |
| |
| // ByteAt reports the ith byte of the underlying strings or byte. |
| func ByteAt(b []byte, i int) (byte, error) { |
| if i < 0 || i >= len(b) { |
| return 0, fmt.Errorf("index out of range") |
| } |
| return b[i], nil |
| } |
| |
| // ByteSlice reports the bytes of the underlying string data from the start |
| // index up to but not including the end index. |
| func ByteSlice(b []byte, start, end int) ([]byte, error) { |
| if start < 0 || start > end || end > len(b) { |
| return nil, fmt.Errorf("index out of range") |
| } |
| return b[start:end], nil |
| } |
| |
| // Runes returns the Unicode code points of the given string. |
| func Runes(s string) []rune { |
| return []rune(s) |
| } |
| |
| // MinRunes reports whether the number of runes (Unicode codepoints) in a string |
| // is at least a certain minimum. MinRunes can be used a a field constraint to |
| // except all strings for which this property holds. |
| func MinRunes(s string, max int) bool { |
| // TODO: CUE strings cannot be invalid UTF-8. In case this changes, we need |
| // to use the following conversion to count properly: |
| // s, _ = unicodeenc.UTF8.NewDecoder().String(s) |
| return len([]rune(s)) <= max |
| } |
| |
| // MaxRunes reports whether the number of runes (Unicode codepoints) in a string |
| // exceeds a certain maximum. MaxRunes can be used a a field constraint to |
| // except all strings for which this property holds |
| func MaxRunes(s string, max int) bool { |
| // See comment in MinRunes implementation. |
| return len([]rune(s)) <= max |
| } |
| |
| // ToTitle returns a copy of the string s with all Unicode letters that begin |
| // words mapped to their title case. |
| func ToTitle(s string) string { |
| // Use a closure here to remember state. |
| // Hackish but effective. Depends on Map scanning in order and calling |
| // the closure once per rune. |
| prev := ' ' |
| return strings.Map( |
| func(r rune) rune { |
| if unicode.IsSpace(prev) { |
| prev = r |
| return unicode.ToTitle(r) |
| } |
| prev = r |
| return r |
| }, |
| s) |
| } |
| |
| // ToCamel returns a copy of the string s with all Unicode letters that begin |
| // words mapped to lower case. |
| func ToCamel(s string) string { |
| // Use a closure here to remember state. |
| // Hackish but effective. Depends on Map scanning in order and calling |
| // the closure once per rune. |
| prev := ' ' |
| return strings.Map( |
| func(r rune) rune { |
| if unicode.IsSpace(prev) { |
| prev = r |
| return unicode.ToLower(r) |
| } |
| prev = r |
| return r |
| }, |
| s) |
| } |