/*
* Copyright 2021 ByteDance Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package decoder
import (
`bytes`
`io`
`sync`
`github.com/bytedance/sonic/internal/native`
`github.com/bytedance/sonic/internal/native/types`
`github.com/bytedance/sonic/internal/rt`
`github.com/bytedance/sonic/option`
)
var (
minLeftBufferShift uint = 1
)
// StreamDecoder is the decoder context object for streaming input.
type StreamDecoder struct {
r io.Reader
buf []byte
scanp int
scanned int64
err error
Decoder
}
var bufPool = sync.Pool{
New: func () interface{} {
return make([]byte, 0, option.DefaultDecoderBufferSize)
},
}
// NewStreamDecoder adapts to encoding/json.NewDecoder API.
//
// NewStreamDecoder returns a new decoder that reads from r.
func NewStreamDecoder(r io.Reader) *StreamDecoder {
return &StreamDecoder{r : r}
}
// Decode decodes input stream into val with corresponding data.
// Redundantly bytes may be read and left in its buffer, and can be used at next call.
// Either io error from underlying io.Reader (except io.EOF)
// or syntax error from data will be recorded and stop subsequently decoding.
func (self *StreamDecoder) Decode(val interface{}) (err error) {
// read more data into buf
if self.More() {
// println(string(self.buf))
var s = self.scanp
try_skip:
var e = len(self.buf)
// println("s:", s, "e:", e, "scanned:",self.scanned, "scanp:",self.scanp, self.buf)
var src = rt.Mem2Str(self.buf[s:e])
// if len(src) > 5 {
// println(src[:5], src[len(src)-5:])
// } else {
// println(src)
// }
// try skip
var x = 0;
if y := native.SkipOneFast(&src, &x); y < 0 {
if self.readMore() {
// println("more")
goto try_skip
} else {
// println("no more")
err = SyntaxError{e, self.s, types.ParsingError(-s), ""}
self.setErr(err)
return
}
} else {
s = y + s
e = x + s
}
// println("decode: ", s, e)
// must copy string here for safety
self.Decoder.Reset(string(self.buf[s:e]))
err = self.Decoder.Decode(val)
if err != nil {
self.setErr(err)
return
}
self.scanp = e
_, empty := self.scan()
if empty {
// println("recycle")
// no remain valid bytes, thus we just recycle buffer
mem := self.buf
self.buf = nil
bufPool.Put(mem[:0])
} else {
// println("keep")
// remain undecoded bytes, move them onto head
n := copy(self.buf, self.buf[self.scanp:])
self.buf = self.buf[:n]
}
self.scanned += int64(self.scanp)
self.scanp = 0
}
return self.err
}
// InputOffset returns the input stream byte offset of the current decoder position.
// The offset gives the location of the end of the most recently returned token and the beginning of the next token.
func (self *StreamDecoder) InputOffset() int64 {
// println("input offset",self.scanned, self.scanp)
return self.scanned + int64(self.scanp)
}
// Buffered returns a reader of the data remaining in the Decoder's buffer.
// The reader is valid until the next call to Decode.
func (self *StreamDecoder) Buffered() io.Reader {
return bytes.NewReader(self.buf[self.scanp:])
}
// More reports whether there is another element in the
// current array or object being parsed.
func (self *StreamDecoder) More() bool {
if self.err != nil {
return false
}
c, err := self.peek()
return err == nil && c != ']' && c != '}'
}
// More reports whether there is another element in the
// current array or object being parsed.
func (self *StreamDecoder) readMore() bool {
if self.err != nil {
return false
}
var err error
var n int
for {
// Grow buffer if not large enough.
l := len(self.buf)
realloc(&self.buf)
n, err = self.r.Read(self.buf[l:cap(self.buf)])
self.buf = self.buf[: l+n]
self.scanp = l
_, empty := self.scan()
if !empty {
return true
}
// buffer has been scanned, now report any error
if err != nil {
self.setErr(err)
return false
}
}
}
func (self *StreamDecoder) setErr(err error) {
self.err = err
mem := self.buf[:0]
self.buf = nil
bufPool.Put(mem)
}
func (self *StreamDecoder) peek() (byte, error) {
var err error
for {
c, empty := self.scan()
if !empty {
return byte(c), nil
}
// buffer has been scanned, now report any error
if err != nil {
self.setErr(err)
return 0, err
}
err = self.refill()
}
}
func (self *StreamDecoder) scan() (byte, bool) {
for i := self.scanp; i < len(self.buf); i++ {
c := self.buf[i]
if isSpace(c) {
continue
}
self.scanp = i
return c, false
}
return 0, true
}
func isSpace(c byte) bool {
return types.SPACE_MASK & (1 << c) != 0
}
func (self *StreamDecoder) refill() error {
// Make room to read more into the buffer.
// First slide down data already consumed.
if self.scanp > 0 {
self.scanned += int64(self.scanp)
n := copy(self.buf, self.buf[self.scanp:])
self.buf = self.buf[:n]
self.scanp = 0
}
// Grow buffer if not large enough.
realloc(&self.buf)
// Read. Delay error for next iteration (after scan).
n, err := self.r.Read(self.buf[len(self.buf):cap(self.buf)])
self.buf = self.buf[0 : len(self.buf)+n]
return err
}
func realloc(buf *[]byte) bool {
l := uint(len(*buf))
c := uint(cap(*buf))
if c == 0 {
// println("use pool!")
*buf = bufPool.Get().([]byte)
return true
}
if c - l <= c >> minLeftBufferShift {
// println("realloc!")
e := l+(l>>minLeftBufferShift)
if e <= c {
e = c*2
}
tmp := make([]byte, l, e)
copy(tmp, *buf)
*buf = tmp
return true
}
return false
}