github.com/cockroachdb/cockroachdb-parser@v0.23.3-0.20240213214944-911057d40c9a/pkg/util/jsonbytes/jsonbytes.go

// Copyright 2020 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.

package jsonbytes

import "unicode/utf8"

const hexAlphabet = "0123456789abcdef"

// EncodeString writes a string literal to b as a JSON string.
// Note that the delimiting double quotes are not included.
// Cribbed from https://github.com/golang/go/blob/7badae85f20f1bce4cc344f9202447618d45d414/src/encoding/json/encode.go.
func EncodeString(buf []byte, s string) []byte {
	start := 0
	for i := 0; i < len(s); {
		if b := s[i]; b < utf8.RuneSelf {
			if b >= ' ' && b != '"' && b != '\\' {
				i++
				continue
			}
			if start < i {
				buf = append(buf, s[start:i]...)
			}
			switch b {
			case '\\', '"':
				buf = append(buf, '\\', b)
			case '\n':
				buf = append(buf, '\\', 'n')
			case '\r':
				buf = append(buf, '\\', 'r')
			case '\t':
				buf = append(buf, '\\', 't')
			default:
				// This encodes bytes < 0x20 except for \t, \n and \r.
				// If escapeHTML is set, it also escapes <, >, and &
				// because they can lead to security holes when
				// user-controlled strings are rendered into JSON
				// and served to some browsers.
				buf = append(buf, '\\', 'u', '0', '0', hexAlphabet[b>>4], hexAlphabet[b&0xF])
			}
			i++
			start = i
			continue
		}
		c, size := utf8.DecodeRuneInString(s[i:])
		if c == utf8.RuneError && size == 1 {
			if start < i {
				buf = append(buf, s[start:i]...)
			}
			buf = append(buf, `\ufffd`...)
			i += size
			start = i
			continue
		}
		i += size
	}
	if start < len(s) {
		buf = append(buf, s[start:]...)
	}
	return buf
}