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auto merge of #15419 : erickt/rust/json, r=pcwalton
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This speeds up json serialization by removing most of the allocations.
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@bors
bors committed Jul 5, 2014
2 parents 459f155 + 67c8a8d commit 9f2a43c
Showing 1 changed file with 87 additions and 37 deletions.
124 changes: 87 additions & 37 deletions src/libserialize/json.rs
View file
Expand Up @@ -256,22 +256,63 @@ fn io_error_to_error(io: io::IoError) -> ParserError {
pub type EncodeResult = io::IoResult<()>;
pub type DecodeResult<T> = Result<T, DecoderError>;

fn escape_str(s: &str) -> String {
let mut escaped = String::from_str("\"");
for c in s.chars() {
match c {
'"' => escaped.push_str("\\\""),
'\\' => escaped.push_str("\\\\"),
'\x08' => escaped.push_str("\\b"),
'\x0c' => escaped.push_str("\\f"),
'\n' => escaped.push_str("\\n"),
'\r' => escaped.push_str("\\r"),
'\t' => escaped.push_str("\\t"),
_ => escaped.push_char(c),
pub fn escape_bytes(wr: &mut io::Writer, bytes: &[u8]) -> Result<(), io::IoError> {
try!(wr.write_str("\""));

let mut start = 0;

for (i, byte) in bytes.iter().enumerate() {
let escaped = match *byte {
b'"' => "\\\"",
b'\\' => "\\\\",
b'\x08' => "\\b",
b'\x0c' => "\\f",
b'\n' => "\\n",
b'\r' => "\\r",
b'\t' => "\\t",
_ => { continue; }
};

if start < i {
try!(wr.write(bytes.slice(start, i)));
}
};
escaped.push_char('"');
escaped

try!(wr.write_str(escaped));

start = i + 1;
}

if start != bytes.len() {
try!(wr.write(bytes.slice_from(start)));
}

wr.write_str("\"")
}

fn escape_str(writer: &mut io::Writer, v: &str) -> Result<(), io::IoError> {
escape_bytes(writer, v.as_bytes())
}

fn escape_char(writer: &mut io::Writer, v: char) -> Result<(), io::IoError> {
let mut buf = [0, .. 4];
v.encode_utf8(buf);
escape_bytes(writer, buf)
}

fn spaces(wr: &mut io::Writer, mut n: uint) -> Result<(), io::IoError> {
static len: uint = 16;
static buf: [u8, ..len] = [b' ', ..len];

while n >= len {
try!(wr.write(buf));
n -= len;
}

if n > 0 {
wr.write(buf.slice_to(n))
} else {
Ok(())
}
}

fn fmt_number_or_null(v: f64) -> String {
Expand All @@ -281,10 +322,6 @@ fn fmt_number_or_null(v: f64) -> String {
}
}

fn spaces(n: uint) -> String {
String::from_char(n, ' ')
}

/// A structure for implementing serialization to JSON.
pub struct Encoder<'a> {
writer: &'a mut io::Writer,
Expand Down Expand Up @@ -348,10 +385,10 @@ impl<'a> ::Encoder<io::IoError> for Encoder<'a> {
fn emit_f32(&mut self, v: f32) -> EncodeResult { self.emit_f64(v as f64) }

fn emit_char(&mut self, v: char) -> EncodeResult {
self.emit_str(str::from_char(v).as_slice())
escape_char(self.writer, v)
}
fn emit_str(&mut self, v: &str) -> EncodeResult {
write!(self.writer, "{}", escape_str(v))
escape_str(self.writer, v)
}

fn emit_enum(&mut self, _name: &str, f: |&mut Encoder<'a>| -> EncodeResult) -> EncodeResult {
Expand All @@ -367,10 +404,10 @@ impl<'a> ::Encoder<io::IoError> for Encoder<'a> {
// Bunny => "Bunny"
// Kangaroo(34,"William") => {"variant": "Kangaroo", "fields": [34,"William"]}
if cnt == 0 {
write!(self.writer, "{}", escape_str(name))
escape_str(self.writer, name)
} else {
try!(write!(self.writer, "{{\"variant\":"));
try!(write!(self.writer, "{}", escape_str(name)));
try!(escape_str(self.writer, name));
try!(write!(self.writer, ",\"fields\":["));
try!(f(self));
write!(self.writer, "]}}")
Expand Down Expand Up @@ -415,7 +452,8 @@ impl<'a> ::Encoder<io::IoError> for Encoder<'a> {
idx: uint,
f: |&mut Encoder<'a>| -> EncodeResult) -> EncodeResult {
if idx != 0 { try!(write!(self.writer, ",")); }
try!(write!(self.writer, "{}:", escape_str(name)));
try!(escape_str(self.writer, name));
try!(write!(self.writer, ":"));
f(self)
}

Expand Down Expand Up @@ -541,10 +579,10 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
}

fn emit_char(&mut self, v: char) -> EncodeResult {
self.emit_str(str::from_char(v).as_slice())
escape_char(self.writer, v)
}
fn emit_str(&mut self, v: &str) -> EncodeResult {
write!(self.writer, "{}", escape_str(v))
escape_str(self.writer, v)
}

fn emit_enum(&mut self,
Expand All @@ -559,14 +597,18 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
cnt: uint,
f: |&mut PrettyEncoder<'a>| -> EncodeResult) -> EncodeResult {
if cnt == 0 {
write!(self.writer, "{}", escape_str(name))
escape_str(self.writer, name)
} else {
self.indent += 2;
try!(write!(self.writer, "[\n{}{},\n", spaces(self.indent),
escape_str(name)));
try!(write!(self.writer, "[\n"));
try!(spaces(self.writer, self.indent));
try!(escape_str(self.writer, name));
try!(write!(self.writer, ",\n"));
try!(f(self));
self.indent -= 2;
write!(self.writer, "\n{}]", spaces(self.indent))
try!(write!(self.writer, "\n"));
try!(spaces(self.writer, self.indent));
write!(self.writer, "]")
}
}

Expand All @@ -576,7 +618,7 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
if idx != 0 {
try!(write!(self.writer, ",\n"));
}
try!(write!(self.writer, "{}", spaces(self.indent)));
try!(spaces(self.writer, self.indent));
f(self)
}

Expand Down Expand Up @@ -607,7 +649,9 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
self.indent += 2;
try!(f(self));
self.indent -= 2;
write!(self.writer, "\n{}}}", spaces(self.indent))
try!(write!(self.writer, "\n"));
try!(spaces(self.writer, self.indent));
write!(self.writer, "}}")
}
}

Expand All @@ -620,7 +664,9 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
} else {
try!(write!(self.writer, ",\n"));
}
try!(write!(self.writer, "{}{}: ", spaces(self.indent), escape_str(name)));
try!(spaces(self.writer, self.indent));
try!(escape_str(self.writer, name));
try!(write!(self.writer, ": "));
f(self)
}

Expand Down Expand Up @@ -665,7 +711,9 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
self.indent += 2;
try!(f(self));
self.indent -= 2;
write!(self.writer, "\n{}]", spaces(self.indent))
try!(write!(self.writer, "\n"));
try!(spaces(self.writer, self.indent));
write!(self.writer, "]")
}
}

Expand All @@ -677,7 +725,7 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
} else {
try!(write!(self.writer, ",\n"));
}
try!(write!(self.writer, "{}", spaces(self.indent)));
try!(spaces(self.writer, self.indent));
f(self)
}

Expand All @@ -691,7 +739,9 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
self.indent += 2;
try!(f(self));
self.indent -= 2;
write!(self.writer, "\n{}}}", spaces(self.indent))
try!(write!(self.writer, "\n"));
try!(spaces(self.writer, self.indent));
write!(self.writer, "}}")
}
}

Expand All @@ -703,7 +753,7 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
} else {
try!(write!(self.writer, ",\n"));
}
try!(write!(self.writer, "{}", spaces(self.indent)));
try!(spaces(self.writer, self.indent));
// ref #12967, make sure to wrap a key in double quotes,
// in the event that its of a type that omits them (eg numbers)
let mut buf = MemWriter::new();
Expand Down

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