gotosocial/vendor/github.com/ugorji/go/codec/reader.go
2023-02-25 12:12:40 +00:00

607 lines
13 KiB
Go

// Copyright (c) 2012-2020 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a MIT license found in the LICENSE file.
package codec
import (
"bufio"
"bytes"
"io"
"strings"
)
// decReader abstracts the reading source, allowing implementations that can
// read from an io.Reader or directly off a byte slice with zero-copying.
type decReader interface {
// readx will return a view of the []byte if decoding from a []byte, OR
// read into the implementation scratch buffer if possible i.e. n < len(scratchbuf), OR
// create a new []byte and read into that
readx(n uint) []byte
readb([]byte)
readn1() byte
readn2() [2]byte
readn3() [3]byte
readn4() [4]byte
readn8() [8]byte
// readn1eof() (v uint8, eof bool)
// // read up to 8 bytes at a time
// readn(num uint8) (v [8]byte)
numread() uint // number of bytes read
// skip any whitespace characters, and return the first non-matching byte
skipWhitespace() (token byte)
// jsonReadNum will include last read byte in first element of slice,
// and continue numeric characters until it sees a non-numeric char
// or EOF. If it sees a non-numeric character, it will unread that.
jsonReadNum() []byte
// jsonReadAsisChars will read json plain characters (anything but " or \)
// and return a slice terminated by a non-json asis character.
jsonReadAsisChars() []byte
// skip will skip any byte that matches, and return the first non-matching byte
// skip(accept *bitset256) (token byte)
// readTo will read any byte that matches, stopping once no-longer matching.
// readTo(accept *bitset256) (out []byte)
// readUntil will read, only stopping once it matches the 'stop' byte (which it excludes).
readUntil(stop byte) (out []byte)
}
// ------------------------------------------------
type unreadByteStatus uint8
// unreadByteStatus goes from
// undefined (when initialized) -- (read) --> canUnread -- (unread) --> canRead ...
const (
unreadByteUndefined unreadByteStatus = iota
unreadByteCanRead
unreadByteCanUnread
)
// const defBufReaderSize = 4096
// --------------------
// ioReaderByteScanner contains the io.Reader and io.ByteScanner interfaces
type ioReaderByteScanner interface {
io.Reader
io.ByteScanner
// ReadByte() (byte, error)
// UnreadByte() error
// Read(p []byte) (n int, err error)
}
// ioReaderByteScannerT does a simple wrapper of a io.ByteScanner
// over a io.Reader
type ioReaderByteScannerT struct {
r io.Reader
l byte // last byte
ls unreadByteStatus // last byte status
_ [2]byte // padding
b [4]byte // tiny buffer for reading single bytes
}
func (z *ioReaderByteScannerT) ReadByte() (c byte, err error) {
if z.ls == unreadByteCanRead {
z.ls = unreadByteCanUnread
c = z.l
} else {
_, err = z.Read(z.b[:1])
c = z.b[0]
}
return
}
func (z *ioReaderByteScannerT) UnreadByte() (err error) {
switch z.ls {
case unreadByteCanUnread:
z.ls = unreadByteCanRead
case unreadByteCanRead:
err = errDecUnreadByteLastByteNotRead
case unreadByteUndefined:
err = errDecUnreadByteNothingToRead
default:
err = errDecUnreadByteUnknown
}
return
}
func (z *ioReaderByteScannerT) Read(p []byte) (n int, err error) {
if len(p) == 0 {
return
}
var firstByte bool
if z.ls == unreadByteCanRead {
z.ls = unreadByteCanUnread
p[0] = z.l
if len(p) == 1 {
n = 1
return
}
firstByte = true
p = p[1:]
}
n, err = z.r.Read(p)
if n > 0 {
if err == io.EOF && n == len(p) {
err = nil // read was successful, so postpone EOF (till next time)
}
z.l = p[n-1]
z.ls = unreadByteCanUnread
}
if firstByte {
n++
}
return
}
func (z *ioReaderByteScannerT) reset(r io.Reader) {
z.r = r
z.ls = unreadByteUndefined
z.l = 0
}
// ioDecReader is a decReader that reads off an io.Reader.
type ioDecReader struct {
rr ioReaderByteScannerT // the reader passed in, wrapped into a reader+bytescanner
n uint // num read
blist *bytesFreelist
bufr []byte // buffer for readTo/readUntil
br ioReaderByteScanner // main reader used for Read|ReadByte|UnreadByte
bb *bufio.Reader // created internally, and reused on reset if needed
x [64 + 40]byte // for: get struct field name, swallow valueTypeBytes, etc
}
func (z *ioDecReader) reset(r io.Reader, bufsize int, blist *bytesFreelist) {
z.blist = blist
z.n = 0
z.bufr = z.blist.check(z.bufr, 256)
z.br = nil
var ok bool
if bufsize <= 0 {
z.br, ok = r.(ioReaderByteScanner)
if !ok {
z.rr.reset(r)
z.br = &z.rr
}
return
}
// bufsize > 0 ...
// if bytes.[Buffer|Reader], no value in adding extra buffer
// if bufio.Reader, no value in extra buffer unless size changes
switch bb := r.(type) {
case *strings.Reader:
z.br = bb
case *bytes.Buffer:
z.br = bb
case *bytes.Reader:
z.br = bb
case *bufio.Reader:
if bb.Size() == bufsize {
z.br = bb
}
}
if z.br == nil {
if z.bb != nil && z.bb.Size() == bufsize {
z.bb.Reset(r)
} else {
z.bb = bufio.NewReaderSize(r, bufsize)
}
z.br = z.bb
}
}
func (z *ioDecReader) numread() uint {
return z.n
}
func (z *ioDecReader) readn1() (b uint8) {
b, err := z.br.ReadByte()
halt.onerror(err)
z.n++
return
}
func (z *ioDecReader) readn2() (bs [2]byte) {
z.readb(bs[:])
return
}
func (z *ioDecReader) readn3() (bs [3]byte) {
z.readb(bs[:])
return
}
func (z *ioDecReader) readn4() (bs [4]byte) {
z.readb(bs[:])
return
}
func (z *ioDecReader) readn8() (bs [8]byte) {
z.readb(bs[:])
return
}
func (z *ioDecReader) readx(n uint) (bs []byte) {
if n == 0 {
return zeroByteSlice
}
if n < uint(len(z.x)) {
bs = z.x[:n]
} else {
bs = make([]byte, n)
}
nn, err := readFull(z.br, bs)
z.n += nn
halt.onerror(err)
return
}
func (z *ioDecReader) readb(bs []byte) {
if len(bs) == 0 {
return
}
nn, err := readFull(z.br, bs)
z.n += nn
halt.onerror(err)
}
// func (z *ioDecReader) readn1eof() (b uint8, eof bool) {
// b, err := z.br.ReadByte()
// if err == nil {
// z.n++
// } else if err == io.EOF {
// eof = true
// } else {
// halt.onerror(err)
// }
// return
// }
func (z *ioDecReader) jsonReadNum() (bs []byte) {
z.unreadn1()
z.bufr = z.bufr[:0]
LOOP:
// i, eof := z.readn1eof()
i, err := z.br.ReadByte()
if err == io.EOF {
return z.bufr
}
if err != nil {
halt.onerror(err)
}
z.n++
if isNumberChar(i) {
z.bufr = append(z.bufr, i)
goto LOOP
}
z.unreadn1()
return z.bufr
}
func (z *ioDecReader) jsonReadAsisChars() (bs []byte) {
z.bufr = z.bufr[:0]
LOOP:
i := z.readn1()
z.bufr = append(z.bufr, i)
if i == '"' || i == '\\' {
return z.bufr
}
goto LOOP
}
func (z *ioDecReader) skipWhitespace() (token byte) {
LOOP:
token = z.readn1()
if isWhitespaceChar(token) {
goto LOOP
}
return
}
// func (z *ioDecReader) readUntil(stop byte) []byte {
// z.bufr = z.bufr[:0]
// LOOP:
// token := z.readn1()
// z.bufr = append(z.bufr, token)
// if token == stop {
// return z.bufr[:len(z.bufr)-1]
// }
// goto LOOP
// }
func (z *ioDecReader) readUntil(stop byte) []byte {
z.bufr = z.bufr[:0]
LOOP:
token := z.readn1()
if token == stop {
return z.bufr
}
z.bufr = append(z.bufr, token)
goto LOOP
}
func (z *ioDecReader) unreadn1() {
err := z.br.UnreadByte()
halt.onerror(err)
z.n--
}
// ------------------------------------
// bytesDecReader is a decReader that reads off a byte slice with zero copying
//
// Note: we do not try to convert index'ing out of bounds to an io.EOF.
// instead, we let it bubble up to the exported Encode/Decode method
// and recover it as an io.EOF.
//
// Every function here MUST defensively check bounds either explicitly
// or via a bounds check.
//
// see panicValToErr(...) function in helper.go.
type bytesDecReader struct {
b []byte // data
c uint // cursor
}
func (z *bytesDecReader) reset(in []byte) {
z.b = in[:len(in):len(in)] // reslicing must not go past capacity
z.c = 0
}
func (z *bytesDecReader) numread() uint {
return z.c
}
// Note: slicing from a non-constant start position is more expensive,
// as more computation is required to decipher the pointer start position.
// However, we do it only once, and it's better than reslicing both z.b and return value.
func (z *bytesDecReader) readx(n uint) (bs []byte) {
// x := z.c + n
// bs = z.b[z.c:x]
// z.c = x
bs = z.b[z.c : z.c+n]
z.c += n
return
}
func (z *bytesDecReader) readb(bs []byte) {
copy(bs, z.readx(uint(len(bs))))
}
// MARKER: do not use this - as it calls into memmove (as the size of data to move is unknown)
// func (z *bytesDecReader) readnn(bs []byte, n uint) {
// x := z.c
// copy(bs, z.b[x:x+n])
// z.c += n
// }
// func (z *bytesDecReader) readn(num uint8) (bs [8]byte) {
// x := z.c + uint(num)
// copy(bs[:], z.b[z.c:x]) // slice z.b completely, so we get bounds error if past
// z.c = x
// return
// }
// func (z *bytesDecReader) readn1() uint8 {
// z.c++
// return z.b[z.c-1]
// }
// MARKER: readn{1,2,3,4,8} should throw an out of bounds error if past length.
// MARKER: readn1: explicitly ensure bounds check is done
// MARKER: readn{2,3,4,8}: ensure you slice z.b completely so we get bounds error if past end.
func (z *bytesDecReader) readn1() (v uint8) {
v = z.b[z.c]
z.c++
return
}
func (z *bytesDecReader) readn2() (bs [2]byte) {
// copy(bs[:], z.b[z.c:z.c+2])
// bs[1] = z.b[z.c+1]
// bs[0] = z.b[z.c]
bs = okBytes2(z.b[z.c : z.c+2])
z.c += 2
return
}
func (z *bytesDecReader) readn3() (bs [3]byte) {
// copy(bs[1:], z.b[z.c:z.c+3])
bs = okBytes3(z.b[z.c : z.c+3])
z.c += 3
return
}
func (z *bytesDecReader) readn4() (bs [4]byte) {
// copy(bs[:], z.b[z.c:z.c+4])
bs = okBytes4(z.b[z.c : z.c+4])
z.c += 4
return
}
func (z *bytesDecReader) readn8() (bs [8]byte) {
// copy(bs[:], z.b[z.c:z.c+8])
bs = okBytes8(z.b[z.c : z.c+8])
z.c += 8
return
}
func (z *bytesDecReader) jsonReadNum() []byte {
z.c-- // unread
i := z.c
LOOP:
// gracefully handle end of slice, as end of stream is meaningful here
if i < uint(len(z.b)) && isNumberChar(z.b[i]) {
i++
goto LOOP
}
z.c, i = i, z.c
// MARKER: 20230103: byteSliceOf here prevents inlining of jsonReadNum
// return byteSliceOf(z.b, i, z.c)
return z.b[i:z.c]
}
func (z *bytesDecReader) jsonReadAsisChars() []byte {
i := z.c
LOOP:
token := z.b[i]
i++
if token == '"' || token == '\\' {
z.c, i = i, z.c
return byteSliceOf(z.b, i, z.c)
// return z.b[i:z.c]
}
goto LOOP
}
func (z *bytesDecReader) skipWhitespace() (token byte) {
i := z.c
LOOP:
token = z.b[i]
if isWhitespaceChar(token) {
i++
goto LOOP
}
z.c = i + 1
return
}
func (z *bytesDecReader) readUntil(stop byte) (out []byte) {
i := z.c
LOOP:
if z.b[i] == stop {
out = byteSliceOf(z.b, z.c, i)
// out = z.b[z.c:i]
z.c = i + 1
return
}
i++
goto LOOP
}
// --------------
type decRd struct {
rb bytesDecReader
ri *ioDecReader
decReader
bytes bool // is bytes reader
// MARKER: these fields below should belong directly in Encoder.
// we pack them here for space efficiency and cache-line optimization.
mtr bool // is maptype a known type?
str bool // is slicetype a known type?
be bool // is binary encoding
js bool // is json handle
jsms bool // is json handle, and MapKeyAsString
cbor bool // is cbor handle
cbreak bool // is a check breaker
}
// From out benchmarking, we see the following impact performance:
//
// - functions that are too big to inline
// - interface calls (as no inlining can occur)
//
// decRd is designed to embed a decReader, and then re-implement some of the decReader
// methods using a conditional branch.
//
// We only override the ones where the bytes version is inlined AND the wrapper method
// (containing the bytes version alongside a conditional branch) is also inlined.
//
// We use ./run.sh -z to check.
//
// Right now, only numread and "carefully crafted" readn1 can be inlined.
func (z *decRd) numread() uint {
if z.bytes {
return z.rb.numread()
}
return z.ri.numread()
}
func (z *decRd) readn1() (v uint8) {
if z.bytes {
// return z.rb.readn1()
// MARKER: calling z.rb.readn1() prevents decRd.readn1 from being inlined.
// copy code, to manually inline and explicitly return here.
// Keep in sync with bytesDecReader.readn1
v = z.rb.b[z.rb.c]
z.rb.c++
return
}
return z.ri.readn1()
}
// func (z *decRd) readn4() [4]byte {
// if z.bytes {
// return z.rb.readn4()
// }
// return z.ri.readn4()
// }
// func (z *decRd) readn3() [3]byte {
// if z.bytes {
// return z.rb.readn3()
// }
// return z.ri.readn3()
// }
// func (z *decRd) skipWhitespace() byte {
// if z.bytes {
// return z.rb.skipWhitespace()
// }
// return z.ri.skipWhitespace()
// }
type devNullReader struct{}
func (devNullReader) Read(p []byte) (int, error) { return 0, io.EOF }
func (devNullReader) Close() error { return nil }
func readFull(r io.Reader, bs []byte) (n uint, err error) {
var nn int
for n < uint(len(bs)) && err == nil {
nn, err = r.Read(bs[n:])
if nn > 0 {
if err == io.EOF {
// leave EOF for next time
err = nil
}
n += uint(nn)
}
}
// do not do this below - it serves no purpose
// if n != len(bs) && err == io.EOF { err = io.ErrUnexpectedEOF }
return
}
var _ decReader = (*decRd)(nil)