zlog/json.go

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package zerolog
import "unicode/utf8"
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const hex = "0123456789abcdef"
// appendJSONString encodes the input string to json and appends
// the encoded string to the input byte slice.
//
// The operation loops though each byte in the string looking
// for characters that need json or utf8 encoding. If the string
// does not need encoding, then the string is appended in it's
// entirety to the byte slice.
// If we encounter a byte that does need encoding, switch up
// the operation and perform a byte-by-byte read-encode-append.
func appendJSONString(dst []byte, s string) []byte {
// Start with a double quote.
dst = append(dst, '"')
// Loop through each character in the string.
for i := 0; i < len(s); i++ {
// Check if the character needs encoding. Control characters, slashes,
// and the double quote need json encoding. Bytes above the ascii
// boundary needs utf8 encoding.
if s[i] < ' ' || s[i] == '\\' || s[i] == '"' || s[i] > 126 {
// We encountered a character that needs to be encoded. Let's
// append the previous simple characters to the byte slice
// and switch our operation to read and encode the remainder
// characters byte-by-byte.
dst = append(dst, s[:i]...)
for i < len(s) {
if b := s[i]; b < utf8.RuneSelf {
switch b {
case '"', '\\':
dst = append(dst, '\\', b)
case '\b':
dst = append(dst, '\\', 'b')
case '\f':
dst = append(dst, '\\', 'f')
case '\n':
dst = append(dst, '\\', 'n')
case '\r':
dst = append(dst, '\\', 'r')
case '\t':
dst = append(dst, '\\', 't')
default:
if b >= 0x20 {
dst = append(dst, b)
} else {
dst = append(dst, '\\', 'u', '0', '0',
hex[b>>4], hex[b&0xF])
}
}
i++
continue
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}
r, size := utf8.DecodeRuneInString(s[i:])
if r == utf8.RuneError && size == 1 {
dst = append(dst, `\ufffd`...)
i++
continue
}
dst = append(dst, s[i:i+size]...)
i += size
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}
// End with a double quote
return append(dst, '"')
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}
}
// The string has no need for encoding an therefore is directly
// appended to the byte slice.
dst = append(dst, s...)
// End with a double quote
return append(dst, '"')
}