auto merge of #18980 : erickt/rust/reader, r=erickt

This continues the work @thestinger started in #18885 (which hasn't landed yet, so wait for that to land before landing this one). Instead of adding more methods to `BufReader`, this just allows a `&[u8]` to be used directly as a `Reader`. It also adds an impl of `Writer` for `&mut [u8]`.

src/libcore/result.rs

@@ -444,15 +444,14 @@ impl<T, E> Result<T, E> {
     /// ignoring I/O and parse errors:
     ///
     /// ```
-    /// use std::io::{BufReader, IoResult};
+    /// use std::io::IoResult;
     ///
-    /// let buffer = "1\n2\n3\n4\n";
+    /// let mut buffer = &mut b"1\n2\n3\n4\n";
-    /// let mut reader = BufReader::new(buffer.as_bytes());
     ///
     /// let mut sum = 0;
     ///
-    /// while !reader.eof() {
+    /// while !buffer.is_empty() {
-    ///     let line: IoResult<String> = reader.read_line();
+    ///     let line: IoResult<String> = buffer.read_line();
     ///     // Convert the string line to a number using `map` and `from_str`
     ///     let val: IoResult<int> = line.map(|line| {
     ///         from_str::<int>(line.as_slice().trim_right()).unwrap_or(0)

src/libgraphviz/lib.rs

@@ -547,7 +547,7 @@ mod tests {
     use self::NodeLabels::*;
     use super::{Id, LabelText, LabelStr, EscStr, Labeller};
     use super::{Nodes, Edges, GraphWalk, render};
-    use std::io::{BufReader, IoResult};
+    use std::io::IoResult;
     use std::str;
 
     /// each node is an index in a vector in the graph.
@@ -698,8 +698,7 @@ mod tests {
     fn test_input(g: LabelledGraph) -> IoResult<String> {
         let mut writer = Vec::new();
         render(&g, &mut writer).unwrap();
-        let mut r = BufReader::new(writer[]);
+        (&mut writer.as_slice()).read_to_string()
-        r.read_to_string()
     }
 
     // All of the tests use raw-strings as the format for the expected outputs,
@@ -811,8 +810,7 @@ r#"digraph hasse_diagram {
                  edge(1, 3, ";"),    edge(2, 3, ";"   )));
 
         render(&g, &mut writer).unwrap();
-        let mut r = BufReader::new(writer[]);
+        let r = (&mut writer.as_slice()).read_to_string();
-        let r = r.read_to_string();
 
         assert_eq!(r.unwrap().as_slice(),
 r#"digraph syntax_tree {

src/libstd/io/buffered.rs

@@ -406,7 +406,7 @@ mod test {
     use prelude::*;
     use super::*;
     use super::super::{IoResult, EndOfFile};
-    use super::super::mem::{MemReader, BufReader};
+    use super::super::mem::MemReader;
     use self::test::Bencher;
     use str::StrPrelude;
 
@@ -626,14 +626,14 @@ mod test {
     #[test]
     fn read_char_buffered() {
         let buf = [195u8, 159u8];
-        let mut reader = BufferedReader::with_capacity(1, BufReader::new(&buf));
+        let mut reader = BufferedReader::with_capacity(1, buf[]);
         assert_eq!(reader.read_char(), Ok('ß'));
     }
 
     #[test]
     fn test_chars() {
         let buf = [195u8, 159u8, b'a'];
-        let mut reader = BufferedReader::with_capacity(1, BufReader::new(&buf));
+        let mut reader = BufferedReader::with_capacity(1, buf[]);
         let mut it = reader.chars();
         assert_eq!(it.next(), Some(Ok('ß')));
         assert_eq!(it.next(), Some(Ok('a')));

src/libstd/io/mem.rs

@@ -206,6 +206,41 @@ impl Buffer for MemReader {
     fn consume(&mut self, amt: uint) { self.pos += amt; }
 }
 
+impl<'a> Reader for &'a [u8] {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
+        if self.is_empty() { return Err(io::standard_error(io::EndOfFile)); }
+
+        let write_len = min(buf.len(), self.len());
+        {
+            let input = self[..write_len];
+            let output = buf[mut ..write_len];
+            slice::bytes::copy_memory(output, input);
+        }
+
+        *self = self.slice_from(write_len);
+
+        Ok(write_len)
+    }
+}
+
+impl<'a> Buffer for &'a [u8] {
+    #[inline]
+    fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> {
+        if self.is_empty() {
+            Err(io::standard_error(io::EndOfFile))
+        } else {
+            Ok(*self)
+        }
+    }
+
+    #[inline]
+    fn consume(&mut self, amt: uint) {
+        *self = self[amt..];
+    }
+}
+
+
 /// Writes to a fixed-size byte slice
 ///
 /// If a write will not fit in the buffer, it returns an error and does not
@@ -362,6 +397,16 @@ mod test {
     use self::test::Bencher;
     use str::StrPrelude;
 
+    #[test]
+    fn test_vec_writer() {
+        let mut writer = Vec::new();
+        writer.write(&[0]).unwrap();
+        writer.write(&[1, 2, 3]).unwrap();
+        writer.write(&[4, 5, 6, 7]).unwrap();
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
+        assert_eq!(writer.as_slice(), b);
+    }
+
     #[test]
     fn test_mem_writer() {
         let mut writer = MemWriter::new();
@@ -385,6 +430,8 @@ mod test {
             assert_eq!(writer.tell(), Ok(8));
             writer.write(&[]).unwrap();
             assert_eq!(writer.tell(), Ok(8));
+
+            assert!(writer.write(&[1]).is_err());
         }
         let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
         assert_eq!(buf.as_slice(), b);
@@ -457,6 +504,32 @@ mod test {
         assert!(reader.read(&mut buf).is_err());
     }
 
+    #[test]
+    fn test_slice_reader() {
+        let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
+        let mut reader = &mut in_buf.as_slice();
+        let mut buf = [];
+        assert_eq!(reader.read(&mut buf), Ok(0));
+        let mut buf = [0];
+        assert_eq!(reader.read(&mut buf), Ok(1));
+        assert_eq!(reader.len(), 7);
+        let b: &[_] = &[0];
+        assert_eq!(buf.as_slice(), b);
+        let mut buf = [0, ..4];
+        assert_eq!(reader.read(&mut buf), Ok(4));
+        assert_eq!(reader.len(), 3);
+        let b: &[_] = &[1, 2, 3, 4];
+        assert_eq!(buf.as_slice(), b);
+        assert_eq!(reader.read(&mut buf), Ok(3));
+        let b: &[_] = &[5, 6, 7];
+        assert_eq!(buf[0..3], b);
+        assert!(reader.read(&mut buf).is_err());
+        let mut reader = &mut in_buf.as_slice();
+        assert_eq!(reader.read_until(3).unwrap(), vec!(0, 1, 2, 3));
+        assert_eq!(reader.read_until(3).unwrap(), vec!(4, 5, 6, 7));
+        assert!(reader.read(&mut buf).is_err());
+    }
+
     #[test]
     fn test_buf_reader() {
         let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];

src/libstd/io/util.rs

@@ -273,7 +273,7 @@ impl<T: Iterator<u8>> Reader for IterReader<T> {
 
 #[cfg(test)]
 mod test {
-    use io::{MemReader, BufReader, ByRefReader};
+    use io::{MemReader, ByRefReader};
     use io;
     use boxed::Box;
     use super::*;
@@ -395,8 +395,7 @@ mod test {
 
     #[test]
     fn limit_reader_buffer() {
-        let data = "0123456789\n0123456789\n";
+        let r = &mut b"0123456789\n0123456789\n";
-        let mut r = BufReader::new(data.as_bytes());
         {
             let mut r = LimitReader::new(r.by_ref(), 3);
             assert_eq!(r.read_line(), Ok("012".to_string()));

src/libtime/lib.rs

@@ -32,7 +32,6 @@ use self::Fmt::*;
 
 use std::fmt::Show;
 use std::fmt;
-use std::io::BufReader;
 use std::num::SignedInt;
 use std::string::String;
 use std::time::Duration;
@@ -1187,7 +1186,7 @@ pub fn strptime(s: &str, format: &str) -> Result<Tm, ParseError> {
         }
     }
 
-    let mut rdr = BufReader::new(format.as_bytes());
+    let mut rdr: &[u8] = format.as_bytes();
     let mut tm = Tm {
         tm_sec: 0_i32,
         tm_min: 0_i32,
@@ -1211,13 +1210,13 @@ pub fn strptime(s: &str, format: &str) -> Result<Tm, ParseError> {
         let next = range.next;
 
         let mut buf = [0];
-        let c = match rdr.read(&mut buf) {
+        let c = match (&mut rdr).read(&mut buf) {
             Ok(..) => buf[0] as char,
             Err(..) => break
         };
         match c {
             '%' => {
-                let ch = match rdr.read(&mut buf) {
+                let ch = match (&mut rdr).read(&mut buf) {
                     Ok(..) => buf[0] as char,
                     Err(..) => break
                 };
@@ -1233,7 +1232,7 @@ pub fn strptime(s: &str, format: &str) -> Result<Tm, ParseError> {
         }
     }
 
-    if pos == len && rdr.tell().unwrap() == format.len() as u64 {
+    if pos == len && (&mut rdr).is_empty() {
         Ok(Tm {
             tm_sec: tm.tm_sec,
             tm_min: tm.tm_min,