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use crate::value::Value;
use std::char;
use std::collections::HashMap;
pub fn consume_ws(dat: &str) -> &str {
dat.trim_start()
}
pub fn parse_string(dat: &str) -> Option<(String, &str)> {
let mut ret = String::with_capacity(dat.len());
let mut cur = &dat[1..];
while !cur.is_empty() {
if let Some(i) = cur.find('\\') {
ret.push_str(&cur[..i]);
let chr = cur.as_bytes()[i + 1];
if chr == b'u' {
let hex = &cur[i + 2..i + 6];
if hex.len() != 4 {
return None;
}
if let Ok(v) = u16::from_str_radix(hex, 16) {
ret.push(char::from_u32(v as u32)?);
cur = &cur[i + 6..];
} else {
return None;
}
} else {
let parsed = match chr {
b'"' => '"',
b'\\' => '\\',
b'/' => '/',
b'b' => '\x08',
b'f' => '\x0c',
b'n' => '\n',
b'r' => '\r',
b't' => '\t',
_ => return None,
};
ret.push(parsed);
cur = &cur[i + 2..];
}
} else {
let v = cur.find('"')?;
ret.push_str(&cur[..v]);
return Some((ret, &cur[v + 1..]));
}
}
None
}
pub fn parse_bool(dat: &str) -> Option<(bool, &str)> {
if dat.starts_with("true") {
return Some((true, &dat[4..]));
} else if dat.starts_with("false") {
return Some((false, &dat[5..]));
}
None
}
pub fn parse_null(dat: &str) -> Option<((), &str)> {
if dat.starts_with("null") {
return Some(((), &dat[4..]));
}
None
}
pub fn parse_int_or_float(dat: &str) -> Option<(Value, &str)> {
let mut end = dat.len();
let dat_bytes = dat.as_bytes();
let mut is_float = false;
for (i, v) in dat_bytes.iter().enumerate() {
match v {
b'0'..=b'9' | b'-' | b'+' => {}
b'e' | b'.' => {
is_float = true;
}
_ => {
end = i;
break;
}
};
}
return Some((
if is_float {
Value::Float(dat[..end].parse().ok()?)
} else {
Value::Integer(dat[..end].parse().ok()?)
}, &dat[end..]
));
}
pub fn parse_object(dat: &str) -> Option<(HashMap<String, Value>, &str)> {
let mut cur = consume_ws(&dat[1..]);
let mut ret = HashMap::<String, Value>::new();
if *cur.as_bytes().get(0)? == b'}' {
return Some((ret, &cur[1..]));
}
while !cur.is_empty() {
let (key, rest) = parse_string(cur)?;
cur = consume_ws(rest);
if *cur.as_bytes().get(0)? != b':' {
return None;
}
let (val, remainder) = parse_element(&cur[1..])?;
ret.insert(key, val);
cur = remainder;
match *cur.as_bytes().get(0)? {
b',' => {
cur = consume_ws(&cur[1..]);
}
b'}' => return Some((ret, &cur[1..])),
_ => return None,
}
}
None
}
pub fn parse_array(dat: &str) -> Option<(Vec<Value>, &str)> {
let mut cur = consume_ws(&dat[1..]);
let mut ret = Vec::<Value>::new();
if *cur.as_bytes().get(0)? == b']' {
return Some((ret, &cur[1..]));
}
while !cur.is_empty() {
let (val, rest) = parse_element(cur)?;
ret.push(val);
match *rest.as_bytes().get(0)? {
b',' => {
cur = consume_ws(&rest[1..]);
}
b']' => {
cur = &rest[1..];
break;
}
_ => return None,
};
}
Some((ret, cur))
}
macro_rules! do_fst {
(|$name:pat| $body:expr) => {
|($name, snd)| ($body, snd)
};
($func:path) => {
|(fst, snd)| ($func(fst), snd)
};
}
pub fn parse_value(dat: &str) -> Option<(Value, &str)> {
match dat.as_bytes()[0] {
b'{' => parse_object(dat).map(do_fst!(Value::Object)),
b'-' | b'0'..=b'9' => parse_int_or_float(dat),
b'"' => parse_string(dat).map(do_fst!(Value::String)),
b't' | b'f' => parse_bool(dat).map(do_fst!(Value::Boolean)),
b'n' => parse_null(dat).map(do_fst!(|_| Value::Null)),
b'[' => parse_array(dat).map(do_fst!(Value::Array)),
_ => None,
}
}
pub fn parse_element(dat: &str) -> Option<(Value, &str)> {
let trimmed = consume_ws(dat);
let (val, rest) = parse_value(trimmed)?;
Some((val, consume_ws(rest)))
}