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use std::fs; use std::io::{self, Write}; use std::path::Path; use std::str; use rustc_serialize::Encodable; use { BorrowBytes, ByteString, Result, Encoded, Error, RecordTerminator, }; /// The quoting style to use when writing CSV data. #[derive(Clone, Copy)] pub enum QuoteStyle { /// This puts quotes around every field. Always. Always, /// This puts quotes around fields only when necessary. /// /// They are necessary when fields are empty or contain a quote, delimiter /// or record terminator. /// /// This is the default. Necessary, /// This *never* writes quotes. /// /// If a field requires quotes, then the writer will report an error. Never, } /// A CSV writer. /// /// This writer provides a convenient interface for encoding CSV data. While /// creating CSV data is much easier than parsing it, having a writer can /// be convenient because it can handle quoting for you automatically. /// Moreover, this particular writer supports `Encodable` types, which makes /// it easy to write your custom types as CSV records. /// /// All CSV data produced by this writer, with default options, conforms with /// [RFC 4180](http://tools.ietf.org/html/rfc4180). (If certain options like /// flexible record lengths are enabled, then compliance with RFC 4180 cannot /// be guaranteed.) /// /// One slight deviation is that records with a single empty field are always /// encoded as `""`. This ensures that the record is not skipped since some /// CSV parsers will ignore consecutive record terminators (like the one in /// this crate). /// /// ### Example /// /// Here's an example that encodes word pairs and their edit distances: /// /// ```rust /// let records = vec![ /// ("sticker", "mortals", 7), /// ("bribed", "personae", 7), /// ("wobbling", "poncing", 4), /// ("interposed", "emmett", 9), /// ("chocolate", "refile", 7), /// ]; /// /// let mut wtr = csv::Writer::from_memory(); /// for record in records.into_iter() { /// let result = wtr.encode(record); /// assert!(result.is_ok()); /// } /// ``` pub struct Writer<W: Write> { buf: io::BufWriter<W>, delimiter: u8, record_terminator: RecordTerminator, flexible: bool, quote: u8, escape: u8, double_quote: bool, quote_style: QuoteStyle, first_len: usize, } impl Writer<fs::File> { /// Creates a new `Writer` that writes CSV data to the file path given. /// /// The file is created if it does not already exist and is truncated /// otherwise. pub fn from_file<P: AsRef<Path>>(path: P) -> Result<Writer<fs::File>> { Ok(Writer::from_writer(try!(fs::File::create(path)))) } } impl<W: io::Write> Writer<W> { /// Creates a new CSV writer that writes to the `io::Write` given. /// /// Note that the writer is buffered for you automatically. pub fn from_writer(w: W) -> Writer<W> { Writer::from_buffer(io::BufWriter::new(w)) } /// Creates a new CSV writer that writes to the buffer given. /// /// This lets you specify your own buffered writer (e.g., use a different /// capacity). All other constructors wrap the writer given in a buffer /// with default capacity. pub fn from_buffer(buf: io::BufWriter<W>) -> Writer<W> { Writer { buf: buf, delimiter: b',', record_terminator: RecordTerminator::Any(b'\n'), flexible: false, quote: b'"', escape: b'\\', double_quote: true, quote_style: QuoteStyle::Necessary, first_len: 0, } } } impl Writer<Vec<u8>> { /// Creates a new CSV writer that writes to an in memory buffer. At any /// time, `as_string` or `as_bytes` can be called to retrieve the /// cumulative CSV data. pub fn from_memory() -> Writer<Vec<u8>> { Writer::from_writer(Vec::with_capacity(1024 * 64)) } /// Returns the written CSV data as a string. pub fn as_string<'r>(&'r mut self) -> &'r str { match self.buf.flush() { // shouldn't panic with Vec<u8> Err(err) => panic!("Error flushing to Vec<u8>: {}", err), // This seems suspicious. If the client only writes `String` // values, then this can never fail. If the client is writing // byte strings, then they should be calling `as_bytes` instead. Ok(()) => str::from_utf8(&**self.buf.get_ref()).unwrap(), } } /// Returns the encoded CSV data as raw bytes. pub fn as_bytes<'r>(&'r mut self) -> &'r [u8] { match self.buf.flush() { // shouldn't panic with Vec<u8> Err(err) => panic!("Error flushing to Vec<u8>: {}", err), Ok(()) => &**self.buf.get_ref(), } } /// Convert the Writer into a string of written CSV data pub fn into_string(self) -> String { // This seems suspicious. If the client only writes `String` // values, then this can never fail. If the client is writing // byte strings, then they should be calling `to_bytes` instead. String::from_utf8(self.into_bytes()).unwrap() } /// Convert the Writer into a vector of encoded CSV bytes. pub fn into_bytes(mut self) -> Vec<u8> { match self.buf.flush() { // shouldn't panic with Vec<u8> Err(err) => panic!("Error flushing to Vec<u8>: {}", err), // won't panic with in-memory writer (i.e. Vec<u8>) Ok(()) => self.buf.into_inner().unwrap(), } } } impl<W: io::Write> Writer<W> { /// Writes a record by encoding any `Encodable` value. /// /// This is the most convenient way to write CSV data. Most Rust types /// map to CSV data in a straight forward way. A vector is just a sequence /// of fields. Similarly for a struct. Enumerations of zero or one /// arguments are supported too. (Enums with zero arguments encode to their /// name, while enums of one argument encode to their constituent value.) /// Option types are also supported (`None` encodes to an empty field). /// /// ### Example /// /// This example encodes word pairs that may or may not have their /// edit distances computed. /// /// ```rust /// extern crate rustc_serialize; /// # extern crate csv; /// # fn main() { /// /// #[derive(RustcEncodable)] /// struct Distance { /// name1: &'static str, /// name2: &'static str, /// dist: Option<usize>, /// } /// /// let records = vec![ /// Distance { name1: "sticker", name2: "mortals", dist: None }, /// Distance { name1: "bribed", name2: "personae", dist: Some(7) }, /// ]; /// /// let mut wtr = csv::Writer::from_memory(); /// for record in records.into_iter() { /// let result = wtr.encode(record); /// assert!(result.is_ok()); /// } /// assert_eq!(wtr.as_string(), /// "sticker,mortals,\nbribed,personae,7\n"); /// # } /// ``` pub fn encode<E>(&mut self, e: E) -> Result<()> where E: Encodable { let mut erecord = Encoded::new(); try!(e.encode(&mut erecord)); self.write(erecord.unwrap().into_iter()) } /// Writes a record of strings (Unicode or raw bytes). /// /// This is meant to be the standard method provided by most CSV writers. /// That is, it writes a record of strings---no more and no less. /// /// This method accepts an iterator of *fields* for a single record. Each /// field must satisfy `BorrowBytes`, which allows the caller to control /// allocation. /// /// ### Example /// /// This shows how to write string records. /// /// ```rust /// let records = vec![ /// vec!["sticker", "mortals", "7"], /// vec!["bribed", "personae", "7"], /// vec!["wobbling", "poncing", "4"], /// vec!["interposed", "emmett", "9"], /// vec!["chocolate", "refile", "7"], /// ]; /// /// let mut wtr = csv::Writer::from_memory(); /// for record in records.into_iter() { /// let result = wtr.write(record.into_iter()); /// assert!(result.is_ok()); /// } /// ``` /// /// This shows how to write records that do not correspond to a valid UTF-8 /// encoding. (Note the use of Rust's byte string syntax!) /// /// ```rust /// let mut wtr = csv::Writer::from_memory(); /// let result = wtr.write(vec![&b"\xff"[..], &b"\x00"[..]].into_iter()); /// assert!(result.is_ok()); /// /// assert_eq!(wtr.as_bytes(), b"\xff,\x00\n"); /// ``` pub fn write<'a, I>(&mut self, r: I) -> Result<()> where I: Iterator, <I as Iterator>::Item: BorrowBytes { self.write_iter(r.map(|f| Ok(f))) } /// Writes a record of results. If any of the results resolve to an error, /// then writing stops and that error is returned. #[doc(hidden)] pub fn write_iter<'a, I, F>(&mut self, r: I) -> Result<()> where I: Iterator<Item=Result<F>>, F: BorrowBytes { let delim = self.delimiter; let mut count = 0; let mut last_len = 0; for field in r { if count > 0 { try!(self.w_bytes(&[delim])); } count += 1; let field = try!(field); last_len = field.borrow_bytes().len(); try!(self.w_user_bytes(field.borrow_bytes())); } // This tomfoolery makes sure that a record with a single empty field // is encoded as `""`. Otherwise, you end up with a run of consecutive // record terminators, which are ignored by some CSV parsers (such // as the one in this library). if count == 1 && last_len == 0 { let q = self.quote; try!(self.w_bytes(&[q, q])); } try!(self.w_lineterm()); self.set_first_len(count) } /// Flushes the underlying buffer. pub fn flush(&mut self) -> Result<()> { self.buf.flush().map_err(From::from) } } impl<W: io::Write> Writer<W> { /// The delimiter to use when writing CSV data. /// /// Since the CSV writer is meant to be mostly encoding agnostic, you must /// specify the delimiter as a single ASCII byte. For example, to write /// tab-delimited data, you would use `b'\t'`. /// /// The default value is `b','`. pub fn delimiter(mut self, delimiter: u8) -> Writer<W> { self.delimiter = delimiter; self } /// Whether to allow flexible length records when writing CSV data. /// /// When this is set to `true`, records in the CSV data can have different /// lengths. By default, this is disabled, which will cause the CSV writer /// to return an error if it tries to write a record that has a different /// length than other records it has already written. pub fn flexible(mut self, yes: bool) -> Writer<W> { self.flexible = yes; self } /// Sets the record terminator to use when writing CSV data. /// /// By default, this is `RecordTerminator::Any(b'\n')`. If you want to /// use CRLF (`\r\n`) line endings, then use `RecordTerminator:CRLF`. pub fn record_terminator(mut self, term: RecordTerminator) -> Writer<W> { self.record_terminator = term; self } /// Set the quoting style to use when writing CSV data. /// /// By default, this is set to `QuoteStyle::Necessary`, which will only /// use quotes when they are necessary to preserve the integrity of data. pub fn quote_style(mut self, style: QuoteStyle) -> Writer<W> { self.quote_style = style; self } /// Set the quote character to use when writing CSV data. /// /// Since the CSV parser is meant to be mostly encoding agnostic, you must /// specify the quote as a single ASCII byte. For example, to write /// single quoted data, you would use `b'\''`. /// /// The default value is `b'"'`. pub fn quote(mut self, quote: u8) -> Writer<W> { self.quote = quote; self } /// Set the escape character to use when writing CSV data. /// /// This is only used when `double_quote` is set to `false`. /// /// Since the CSV parser is meant to be mostly encoding agnostic, you must /// specify the escape as a single ASCII byte. /// /// The default value is `b'\\'`. pub fn escape(mut self, escape: u8) -> Writer<W> { self.escape = escape; self } /// Set the quoting escape mechanism. /// /// When enabled (which is the default), quotes are escaped by doubling /// them. e.g., `"` escapes to `""`. /// /// When disabled, quotes are escaped with the escape character (which /// is `\\` by default). pub fn double_quote(mut self, yes: bool) -> Writer<W> { self.double_quote = yes; self } } impl<W: io::Write> Writer<W> { fn err<'a, S, T>(&self, msg: S) -> Result<T> where S: Into<String> { Err(Error::Encode(msg.into())) } fn w_bytes(&mut self, s: &[u8]) -> Result<()> { self.buf.write_all(s).map_err(Error::Io) } fn w_user_bytes(&mut self, s: &[u8]) -> Result<()> { if try!(self.should_quote(s)) { let quoted = self.quote_field(s); self.w_bytes(&*quoted) } else { self.w_bytes(s) } } fn w_lineterm(&mut self) -> Result<()> { match self.record_terminator { RecordTerminator::CRLF => self.w_bytes(b"\r\n"), RecordTerminator::Any(b) => self.w_bytes(&[b]), } } fn set_first_len(&mut self, cur_len: usize) -> Result<()> { if cur_len == 0 { return self.err("Records must have length greater than 0.") } if !self.flexible { if self.first_len == 0 { self.first_len = cur_len; } else if self.first_len != cur_len { return self.err(format!( "Record has length {} but other records have length {}", cur_len, self.first_len)) } } Ok(()) } fn should_quote(&self, field: &[u8]) -> Result<bool> { let needs = || field.iter().any(|&b| self.byte_needs_quotes(b)); match self.quote_style { QuoteStyle::Always => Ok(true), QuoteStyle::Necessary => Ok(needs()), QuoteStyle::Never => { if !needs() { Ok(false) } else { self.err(format!( "Field requires quotes, but quote style \ is 'Never': '{}'", String::from_utf8_lossy(field))) } } } } fn byte_needs_quotes(&self, b: u8) -> bool { b == self.delimiter || self.record_terminator == b || b == self.quote // This is a bit hokey. By default, the record terminator is // '\n', but we still need to quote '\r' because the reader // interprets '\r' as a record terminator by default. || b == b'\r' || b == b'\n' } fn quote_field(&self, mut s: &[u8]) -> ByteString { let mut buf = Vec::with_capacity(s.len() + 2); buf.push(self.quote); loop { match s.iter().position(|&v| v == self.quote) { None => { buf.extend(s.iter().map(|&x|x)); break } Some(next_quote) => { buf.extend(s[..next_quote].iter().map(|&x|x)); if self.double_quote { buf.push(self.quote); buf.push(self.quote); } else { buf.push(self.escape); buf.push(self.quote); } s = &s[next_quote + 1..]; } } } buf.push(self.quote); buf } }