Escape control characters in JSON strings #427
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rcoh
reviewed
May 27, 2021
| }); | ||
| last = index + 1; | ||
| fn escape_string_inner(start: &[u8], rest: &[u8]) -> String { | ||
| let mut escaped = start.to_vec(); |
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I would probably try to pre-allocate enough capacity here:
let mut escaped = Vec::with_capacity(start.len() + rest.len() + 1);
escaped.copy_from_slice(start)| } | ||
| escaped.push_str(&value[last..end]); | ||
| Cow::Owned(escaped) | ||
| // Our input was originally valid UTF-8, and we didn't do anything to invalidate it |
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the safety argument is actually a little more subtle here:
- We only escaped bytes that were already single character code points
- We only replaced them with valid UTF-8
| let mut escaped = start.to_vec(); | ||
| for byte in rest { | ||
| match byte { | ||
| b'"' => escaped.extend("\\\"".bytes()), |
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did you use bytes() here instead of b to make it clear that these were valid strings before being turned into bytes?
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No, I just didn't think to use b.
rcoh
approved these changes
May 27, 2021
| // - The original input was valid UTF-8 since it came in as a `&str` | ||
| // - Only single-byte code points were escaped | ||
| // - The escape sequences are valid UTF-8 | ||
| debug_assert!(String::from_utf8(escaped.clone()).is_ok()); |
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nit:
Suggested change
| debug_assert!(String::from_utf8(escaped.clone()).is_ok()); | |
| debug_assert!(std::str::from_utf8(escaped).is_ok()); |
| } | ||
|
|
||
| use proptest::proptest; | ||
| proptest! { | ||
| #[test] | ||
| fn matches_serde_json(s: String) { | ||
| fn matches_serde_json(s in ".*") { | ||
| assert_eq!( | ||
| serde_json::to_string(&s).unwrap(), | ||
| format!(r#""{}""#, escape_string(&s)) |
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Suggested change
| format!(r#""{}""#, escape_string(&s)) | |
| escape_string(&s) |
Cow and String are comparable
rcoh
reviewed
May 27, 2021
| @@ -70,10 +70,9 @@ mod test { | |||
| proptest! { | |||
| #[test] | |||
| fn matches_serde_json(s in ".*") { | |||
| assert_eq!( | |||
| serde_json::to_string(&s).unwrap(), | |||
| format!(r#""{}""#, escape_string(&s)) | |||
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you probably want to enable rustfmt on save
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Looks like the proptest macro hid the assert_eq from the formatter.
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This escapes the control characters in range 0x00-0x1F (inclusive), and also reworks the escaping so that it should be more performant. It now only iterates over the input string exactly once, rather than once to see if escaping is necessary, and then once again to escape, and there's no longer any conversion to
char.To verify it correctly escapes everything, I ran the following additional test (not included in the PR since it takes approximately 100 seconds in a debug test run):
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