1 files changed, 97 insertions, 0 deletions
diff --git a/modules/util/string.go b/modules/util/string.go
new file mode 100644
index 00000000..cf50f591
--- /dev/null
+++ b/modules/util/string.go
@@ -0,0 +1,97 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package util
+
+import "unsafe"
+
+func isSnakeCaseUpper(c byte) bool {
+	return 'A' <= c && c <= 'Z'
+}
+
+func isSnakeCaseLowerOrNumber(c byte) bool {
+	return 'a' <= c && c <= 'z' || '0' <= c && c <= '9'
+}
+
+// ToSnakeCase convert the input string to snake_case format.
+//
+// Some samples.
+//
+//	"FirstName"  => "first_name"
+//	"HTTPServer" => "http_server"
+//	"NoHTTPS"    => "no_https"
+//	"GO_PATH"    => "go_path"
+//	"GO PATH"    => "go_path"      // space is converted to underscore.
+//	"GO-PATH"    => "go_path"      // hyphen is converted to underscore.
+func ToSnakeCase(input string) string {
+	if len(input) == 0 {
+		return ""
+	}
+
+	var res []byte
+	if len(input) == 1 {
+		c := input[0]
+		if isSnakeCaseUpper(c) {
+			res = []byte{c + 'a' - 'A'}
+		} else if isSnakeCaseLowerOrNumber(c) {
+			res = []byte{c}
+		} else {
+			res = []byte{'_'}
+		}
+	} else {
+		res = make([]byte, 0, len(input)*4/3)
+		pos := 0
+		needSep := false
+		for pos < len(input) {
+			c := input[pos]
+			if c >= 0x80 {
+				res = append(res, c)
+				pos++
+				continue
+			}
+			isUpper := isSnakeCaseUpper(c)
+			if isUpper || isSnakeCaseLowerOrNumber(c) {
+				end := pos + 1
+				if isUpper {
+					// skip the following upper letters
+					for end < len(input) && isSnakeCaseUpper(input[end]) {
+						end++
+					}
+					if end-pos > 1 && end < len(input) && isSnakeCaseLowerOrNumber(input[end]) {
+						end--
+					}
+				}
+				// skip the following lower or number letters
+				for end < len(input) && (isSnakeCaseLowerOrNumber(input[end]) || input[end] >= 0x80) {
+					end++
+				}
+				if needSep {
+					res = append(res, '_')
+				}
+				res = append(res, input[pos:end]...)
+				pos = end
+				needSep = true
+			} else {
+				res = append(res, '_')
+				pos++
+				needSep = false
+			}
+		}
+		for i := 0; i < len(res); i++ {
+			if isSnakeCaseUpper(res[i]) {
+				res[i] += 'a' - 'A'
+			}
+		}
+	}
+	return UnsafeBytesToString(res)
+}
+
+// UnsafeBytesToString uses Go's unsafe package to convert a byte slice to a string.
+func UnsafeBytesToString(b []byte) string {
+	return unsafe.String(unsafe.SliceData(b), len(b))
+}
+
+// UnsafeStringToBytes uses Go's unsafe package to convert a string to a byte slice.
+func UnsafeStringToBytes(s string) []byte {
+	return unsafe.Slice(unsafe.StringData(s), len(s))
+}