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use std::collections::HashMap; use std::str::Chars; use std::iter::Peekable; use std::char; #[derive(Debug)] pub enum JsonValue { Number(f64), Boolean(bool), String(String), Null, Array(Vec<JsonValue>), Object(HashMap<String, JsonValue>), } #[derive(Debug)] pub struct JsonParseError { msg: String, line: usize, col: usize, } impl JsonParseError { fn new(msg: String, line: usize, col: usize) -> JsonParseError { JsonParseError {msg: msg, line: line, col: col} } } pub type JsonParseResult = Result<JsonValue, JsonParseError>; pub struct JsonParser<'a> { chars: Peekable<Chars<'a>>, line: usize, col: usize, } impl<'a> JsonParser<'a> { pub fn for_string(s: &String) -> JsonParser { JsonParser::for_chars(s.chars()) } pub fn for_str(s: &str) -> JsonParser { JsonParser::for_chars(s.chars()) } pub fn for_chars(c: Chars) -> JsonParser { JsonParser {chars: c.peekable(), line: 0, col: 0} } fn err(&self, msg: String) -> JsonParseResult { Err(self.error(msg)) } fn error(&self, msg: String) -> JsonParseError { JsonParseError::new(msg, self.line, self.col) } fn unexpected_eof(&self) -> Result<char, JsonParseError> { Err(JsonParseError::new(String::from("Unexpected EOF"), self.line, self.col)) } fn peek(&mut self) -> Result<char, JsonParseError> { loop { match self.chars.peek() { Some(c) => { if !c.is_whitespace() { return Ok(*c); } if *c == '\n' { self.col = 0; self.line += 1; } else { self.col += 1; } }, None => break, } self.chars.next(); } self.unexpected_eof() } fn next(&mut self) -> Result<char, JsonParseError> { while let Some(c) = self.chars.next() { self.col += 1; if !c.is_whitespace() { return Ok(c); } if c == '\n' { self.col = 0; self.line += 1; } } self.unexpected_eof() } fn next_wo_skip(&mut self) -> Result<char, JsonParseError> { match self.chars.next() { Some(c) => Ok(c), None => self.unexpected_eof(), } } pub fn parse_object(&mut self) -> JsonParseResult { if try!(self.next()) != '{' { return self.err(String::from("Object must starts with '{'")); } let mut m = HashMap::new(); loop { let c = try!(self.peek()); if c == '}' { let _ = self.next(); break; } let key = match try!(self.parse()) { JsonValue::String(s) => s, v => return self.err(format!("Key of object must be string but found {:?}", v)), }; let c = try!(self.next()); if c != ':' { return self.err(format!("':' is expected after key of object but actually found '{}'", c)); } m.insert(key, try!(self.parse())); match try!(self.peek()) { ',' => { let _ = self.next(); }, '}' => {}, c => return self.err(format!("',' is expected for object but actually found '{}'", c)), } } Ok(JsonValue::Object(m)) } pub fn parse_array(&mut self) -> JsonParseResult { if try!(self.next()) != '[' { return self.err(String::from("Array must starts with '['")); } let mut v = vec![]; loop { let c = try!(self.peek()); if c == ']' { let _ = self.next(); break; } v.push(try!(self.parse())); match try!(self.peek()) { ',' => { let _ = self.next(); }, ']' => {}, c => return self.err(format!("',' is expected for array but actually found '{}'", c)), } } Ok(JsonValue::Array(v)) } fn parse_special_char(&mut self) -> Result<char, JsonParseError> { Ok( match try!(self.next()) { '\\' => '\\', '"' => '"', 'b' => '\u{0008}', 'f' => '\u{000c}', 'n' => '\n', 'r' => '\r', 't' => '\t', 'u' => { let mut u = 0 as u32; for _ in 0..4 { let c = try!(self.next()); let h = match c.to_digit(16) { Some(n) => n, None => return Err(self.error(format!("Unicode character must be \\uXXXX (X is hex character) format but found '{}'", c))), }; u = u * 0x10 + h; } match char::from_u32(u) { Some(c) => c, None => return Err(self.error(format!("Cannot convert \\u{:x} in unicode character", u))), } }, c => c, } ) } pub fn parse_string(&mut self) -> JsonParseResult { if try!(self.next()) != '"' { return self.err(String::from("String must starts with double quote")); } let mut s = String::new(); loop { s.push( match try!(self.next_wo_skip()) { '\\' => try!(self.parse_special_char()), '"' => break, c => c, } ); } Ok(JsonValue::String(s)) } fn parse_name(&mut self, s: &'static str) -> Option<JsonParseError> { for c in s.chars() { match self.next_wo_skip() { Ok(x) if x != c => { return Some( JsonParseError::new( format!("err while parsing '{}', invalid character '{}' found", s, c), self.line, self.col, ) ); }, Ok(_) => {}, Err(e) => return Some(e), } } None } pub fn parse_null(&mut self) -> JsonParseResult { match self.parse_name("null") { Some(err) => Err(err), None => Ok(JsonValue::Null), } } pub fn parse_true(&mut self) -> JsonParseResult { match self.parse_name("true") { Some(err) => Err(err), None => Ok(JsonValue::Boolean(true)), } } pub fn parse_false(&mut self) -> JsonParseResult { match self.parse_name("false") { Some(err) => Err(err), None => Ok(JsonValue::Boolean(false)), } } pub fn parse_number(&mut self) -> JsonParseResult { let mut c = try!(self.next()); let negative = match c { '-' => { c = try!(self.next()); true }, _ => false, }; let mut s = c.to_string(); loop { let d = match self.chars.peek() { Some(x) => *x, None => break, }; s.push( match d { '0'...'9' | '.' | 'e' | 'E' => d, _ => break, } ); self.chars.next(); } let n: f64 = match s.parse() { Ok(num) => num, Err(_) => return self.err(format!("Invalid number: {}", s)), }; Ok(JsonValue::Number(if negative { -n } else { n })) } pub fn parse(&mut self) -> JsonParseResult { match try!(self.peek()) { '1'...'9' | '-' => self.parse_number(), '"' => self.parse_string(), '[' => self.parse_array(), '{' => self.parse_object(), 't' => self.parse_true(), 'f' => self.parse_false(), 'n' => self.parse_null(), c => self.err(format!("Invalid character: {}", c)), } } }