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