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use serde_json::Value;
/// Your json MUST BE valid and generated by `serde_json::to_vec` before being
/// sent in this function. This function is DUMB and FAST but makes a lot of
/// asumption about the way `serde_json` will generate its input.
///
/// Will return `true` if the JSON contains an object, an array of array
/// or an array containing an object. Returns `false` for everything else.
pub fn should_flatten_from_unchecked_slice(json: &[u8]) -> bool {
if json.is_empty() {
return false;
}
// since the json we receive has been generated by serde_json we know
// it doesn't contains any whitespace at the beginning thus we can check
// directly if we're looking at an object.
if json[0] == b'{' {
return true;
} else if json[0] != b'[' {
// if the json isn't an object or an array it means it's a simple value.
return false;
}
// The array case is a little bit more complex. We are looking for a second
// `[` but we need to ensure that it doesn't appear inside of a string. Thus
// we need to keep track of if we're in a string or not.
// will be used when we met a `\` to skip the next character.
let mut skip_next = false;
let mut in_string = false;
for byte in json.iter().skip(1) {
match byte {
// handle the backlash.
_ if skip_next => skip_next = false,
b'\\' => skip_next = true,
// handle the strings.
byte if in_string => {
if *byte == b'"' {
in_string = false;
}
}
b'"' => in_string = true,
// handle the arrays.
b'[' => return true,
// since we know the json is valid we don't need to ensure the
// array is correctly closed
// handle the objects.
b'{' => return true,
// ignore everything else
_ => (),
}
}
false
}
/// Consider using [`should_flatten_from_unchecked_slice`] when you can.
/// Will returns `true` if the json contains an object, an array of array
/// or an array containing an object.
/// Returns `false` for everything else.
/// This function has been written to test the [`should_flatten_from_unchecked_slice`].
pub fn should_flatten_from_value(json: &Value) -> bool {
match json {
Value::Object(..) => true,
Value::Array(array) => array.iter().any(|value| value.is_array() || value.is_object()),
_ => false,
}
}
#[cfg(test)]
mod tests {
use serde_json::*;
use super::*;
#[test]
fn test_shouldnt_flatten() {
let shouldnt_flatten = vec![
json!(null),
json!(true),
json!(false),
json!("a superb string"),
json!("a string escaping other \"string\""),
json!([null, true, false]),
json!(["hello", "world", "!"]),
json!(["a \"string\" escaping 'an other'", "\"[\"", "\"{\""]),
];
for value in shouldnt_flatten {
assert!(!should_flatten_from_value(&value));
let value = serde_json::to_vec(&value).unwrap();
assert!(!should_flatten_from_unchecked_slice(&value));
}
}
#[test]
fn test_should_flatten() {
let should_flatten = vec![
json!({}),
json!({ "hello": "world" }),
json!(["hello", ["world"]]),
json!([true, true, true, true, true, true, true, true, true, {}]),
];
for value in should_flatten {
assert!(should_flatten_from_value(&value));
let value = serde_json::to_vec(&value).unwrap();
assert!(should_flatten_from_unchecked_slice(&value));
}
}
}