Add pretty printer to a T: Write, closes #89

Author: maciejhirsz

src/codegen.rs

@@ -308,6 +308,53 @@ impl<'a, W> Generator for WriterGenerator<'a, W> where W: Write {
     }
 }
 
+
+pub struct PrettyWriterGenerator<'a, W: 'a + Write> {
+    writer: &'a mut W,
+    dent: u16,
+    spaces_per_indent: u16,
+}
+
+impl<'a, W> PrettyWriterGenerator<'a, W> where W: 'a + Write {
+    pub fn new(writer: &'a mut W) -> Self {
+        PrettyWriterGenerator {
+            writer: writer,
+            dent: 0,
+            spaces_per_indent: 4,
+        }
+    }
+}
+
+impl<'a, W> Generator for PrettyWriterGenerator<'a, W> where W: Write {
+    type T = W;
+
+    #[inline(always)]
+    fn get_writer(&mut self) -> &mut W {
+        &mut self.writer
+    }
+
+    #[inline(always)]
+    fn write_min(&mut self, slice: &[u8], _: u8) -> io::Result<()> {
+        self.writer.write_all(slice)
+    }
+
+    fn new_line(&mut self) -> io::Result<()> {
+        try!(self.write_char(b'\n'));
+        for _ in 0..(self.dent * self.spaces_per_indent) {
+            try!(self.write_char(b' '));
+        }
+        Ok(())
+    }
+
+    fn indent(&mut self) {
+        self.dent += 1;
+    }
+
+    fn dedent(&mut self) {
+        self.dent -= 1;
+    }
+}
+
 // From: https://github.com/dtolnay/fastwrite/blob/master/src/lib.rs#L68
 //
 // LLVM is not able to lower `Vec::extend_from_slice` into a memcpy, so this

src/value/mod.rs

@@ -8,7 +8,7 @@ use short::Short;
 use number::Number;
 use object::Object;
 use iterators::{ Members, MembersMut, Entries, EntriesMut };
-use codegen::{ Generator, PrettyGenerator, DumpGenerator, WriterGenerator };
+use codegen::{ Generator, PrettyGenerator, DumpGenerator, WriterGenerator, PrettyWriterGenerator };
 
 mod implements;
 
@@ -108,10 +108,10 @@ impl JsonValue {
         gen.write_json(self)
     }
 
-    // pub fn to_writer_pretty<W: Write>(&self, writer: &mut W) -> io::Error {
-    //     let mut gen = PrettyWriterGenerator::new(writer);
-    //     gen.write_json(self)
-    // }
+    pub fn to_writer_pretty<W: Write>(&self, writer: &mut W) -> io::Result<()> {
+        let mut gen = PrettyWriterGenerator::new(writer);
+        gen.write_json(self)
+    }
 
     pub fn is_string(&self) -> bool {
         match *self {

tests/value.rs

@@ -517,7 +517,20 @@ fn writer_generator() {
 
     let mut buf = Vec::new();
 
-    data.to_writer(&mut buf);
+    data.to_writer(&mut buf).expect("Can't fail with a Vec");
 
     assert_eq!(String::from_utf8(buf).unwrap(), r#"{"foo":["bar",100,true]}"#);
 }
+
+#[test]
+fn pretty_writer_generator() {
+    let data = object!{
+        "foo" => array!["bar", 100, true]
+    };
+
+    let mut buf = Vec::new();
+
+    data.to_writer_pretty(&mut buf).expect("Can't fail with a Vec");
+
+    assert_eq!(String::from_utf8(buf).unwrap(), "{\n    \"foo\": [\n        \"bar\",\n        100,\n        true\n    ]\n}");
+}