/
jsonDecoderTerminals.go
368 lines (341 loc) · 9.35 KB
/
jsonDecoderTerminals.go
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package json
// License note: the string and numeric parsers here borrow
// heavily from the golang stdlib json parser scanner.
// That code is originally Copyright 2010 The Go Authors,
// and is governed by a BSD-style license.
import (
"fmt"
"io"
"strconv"
"unicode"
"unicode/utf16"
"unicode/utf8"
"github.com/ipsn/go-ipfs/gxlibs/github.com/polydawn/refmt/tok"
)
func (d *Decoder) decodeString() (string, error) {
// First quote has already been eaten.
// Start tracking the byte slice; real string starts here.
d.r.Track()
// Scan until scanner tells us end of string.
for step := strscan_normal; step != nil; {
majorByte, err := d.r.Readn1()
if err != nil {
return "", err
}
step, err = step(majorByte)
if err != nil {
return "", err
}
}
// Unread one. The scan loop consumed the trailing quote already,
// which we don't want to pass onto the parser.
d.r.Unreadn1()
// Parse!
s, ok := parseString(d.r.StopTrack())
if !ok {
//return string(s), fmt.Errorf("string parse misc fail")
}
// Swallow the trailing quote again.
d.r.Readn1()
return string(s), nil
}
// Scan steps are looped over the stream to find how long the string is.
// A nil step func is returned to indicate the string is done.
// Actually parsing the string is done by 'parseString()'.
type strscanStep func(c byte) (strscanStep, error)
// The default string scanning step state. Starts here.
func strscan_normal(c byte) (strscanStep, error) {
if c == '"' { // done!
return nil, nil
}
if c == '\\' {
return strscan_esc, nil
}
if c < 0x20 { // Unprintable bytes are invalid in a json string.
return nil, fmt.Errorf("invalid unprintable byte in string literal: 0x%x", c)
}
return strscan_normal, nil
}
// "esc" is the state after reading `"\` during a quoted string.
func strscan_esc(c byte) (strscanStep, error) {
switch c {
case 'b', 'f', 'n', 'r', 't', '\\', '/', '"':
return strscan_normal, nil
case 'u':
return strscan_escU, nil
}
return nil, fmt.Errorf("invalid byte in string escape sequence: 0x%x", c)
}
// "escU" is the state after reading `"\u` during a quoted string.
func strscan_escU(c byte) (strscanStep, error) {
if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
return strscan_escU1, nil
}
return nil, fmt.Errorf("invalid byte in \\u hexadecimal character escape: 0x%x", c)
}
// "escU1" is the state after reading `"\u1` during a quoted string.
func strscan_escU1(c byte) (strscanStep, error) {
if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
return strscan_escU12, nil
}
return nil, fmt.Errorf("invalid byte in \\u hexadecimal character escape: 0x%x", c)
}
// "escU12" is the state after reading `"\u12` during a quoted string.
func strscan_escU12(c byte) (strscanStep, error) {
if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
return strscan_escU123, nil
}
return nil, fmt.Errorf("invalid byte in \\u hexadecimal character escape: 0x%x", c)
}
// "escU123" is the state after reading `"\u123` during a quoted string.
func strscan_escU123(c byte) (strscanStep, error) {
if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
return strscan_normal, nil
}
return nil, fmt.Errorf("invalid byte in \\u hexadecimal character escape: 0x%x", c)
}
// Convert a json string byte sequence that is a complete string (quotes from
// the outside dropped) bytes ready to be flipped into a go string.
func parseString(s []byte) (t []byte, ok bool) {
// Check for unusual characters. If there are none,
// then no unquoting is needed, so return a slice of the
// original bytes.
r := 0
for r < len(s) {
c := s[r]
if c == '\\' || c == '"' || c < ' ' {
break
}
if c < utf8.RuneSelf {
r++
continue
}
rr, size := utf8.DecodeRune(s[r:])
if rr == utf8.RuneError && size == 1 {
break
}
r += size
}
if r == len(s) {
return s, true
}
b := make([]byte, len(s)+2*utf8.UTFMax)
w := copy(b, s[0:r])
for r < len(s) {
// Out of room? Can only happen if s is full of
// malformed UTF-8 and we're replacing each
// byte with RuneError.
if w >= len(b)-2*utf8.UTFMax {
nb := make([]byte, (len(b)+utf8.UTFMax)*2)
copy(nb, b[0:w])
b = nb
}
switch c := s[r]; {
case c == '\\':
r++
if r >= len(s) {
return
}
switch s[r] {
default:
return
case '"', '\\', '/', '\'':
b[w] = s[r]
r++
w++
case 'b':
b[w] = '\b'
r++
w++
case 'f':
b[w] = '\f'
r++
w++
case 'n':
b[w] = '\n'
r++
w++
case 'r':
b[w] = '\r'
r++
w++
case 't':
b[w] = '\t'
r++
w++
case 'u':
r--
rr := getu4(s[r:])
if rr < 0 {
return
}
r += 6
if utf16.IsSurrogate(rr) {
rr1 := getu4(s[r:])
if dec := utf16.DecodeRune(rr, rr1); dec != unicode.ReplacementChar {
// A valid pair; consume.
r += 6
w += utf8.EncodeRune(b[w:], dec)
break
}
// Invalid surrogate; fall back to replacement rune.
rr = unicode.ReplacementChar
}
w += utf8.EncodeRune(b[w:], rr)
}
// Quote, control characters are invalid.
case c == '"', c < ' ':
return
// ASCII
case c < utf8.RuneSelf:
b[w] = c
r++
w++
// Coerce to well-formed UTF-8.
default:
rr, size := utf8.DecodeRune(s[r:])
r += size
w += utf8.EncodeRune(b[w:], rr)
}
}
return b[0:w], true
}
// getu4 decodes \uXXXX from the beginning of s, returning the hex value,
// or it returns -1.
func getu4(s []byte) rune {
if len(s) < 6 || s[0] != '\\' || s[1] != 'u' {
return -1
}
r, err := strconv.ParseUint(string(s[2:6]), 16, 64)
if err != nil {
return -1
}
return rune(r)
}
// Returns *either* an int or a float -- json is ambigous.
// An int is preferred if possible.
func (d *Decoder) decodeNumber(majorByte byte) (tok.TokenType, int64, float64, error) {
// First byte has already been eaten.
// Easiest to unread1, so we can use track, then swallow it again.
d.r.Unreadn1()
d.r.Track()
d.r.Readn1()
// Scan until scanner tells us end of numeric.
// Pick the first scanner stepfunc based on the leading byte.
var step numscanStep
switch majorByte {
case '-':
step = numscan_neg
case '0':
step = numscan_0
case '1', '2', '3', '4', '5', '6', '7', '8', '9':
step = numscan_1
default:
panic("unreachable")
}
for {
b, err := d.r.Readn1()
if err == io.EOF {
break
}
if err != nil {
return 0, 0, 0, err
}
step, err = step(b)
if step == nil {
// Unread one. The scan loop consumed one char beyond the end
// (this is necessary in json!),
// which the next part of the decoder will need elsewhere.
d.r.Unreadn1()
break
}
if err != nil {
return 0, 0, 0, err
}
}
// Parse!
// *This is not a fast parse*.
// Try int first; if it fails try float; if that fails return the float error.
s := string(d.r.StopTrack())
if i, err := strconv.ParseInt(s, 10, 64); err == nil {
return tok.TInt, i, 0, nil
}
f, err := strconv.ParseFloat(s, 64)
return tok.TFloat64, 0, f, err
}
// Scan steps are looped over the stream to find how long the number is.
// A nil step func is returned to indicate the string is done.
// Actually parsing the string is done by 'parseString()'.
type numscanStep func(c byte) (numscanStep, error)
// numscan_neg is the state after reading `-` during a number.
func numscan_neg(c byte) (numscanStep, error) {
if c == '0' {
return numscan_0, nil
}
if '1' <= c && c <= '9' {
return numscan_1, nil
}
return nil, fmt.Errorf("invalid byte in numeric literal: 0x%x", c)
}
// numscan_1 is the state after reading a non-zero integer during a number,
// such as after reading `1` or `100` but not `0`.
func numscan_1(c byte) (numscanStep, error) {
if '0' <= c && c <= '9' {
return numscan_1, nil
}
return numscan_0(c)
}
// numscan_0 is the state after reading `0` during a number.
func numscan_0(c byte) (numscanStep, error) {
if c == '.' {
return numscan_dot, nil
}
if c == 'e' || c == 'E' {
return numscan_e, nil
}
return nil, nil
}
// numscan_dot is the state after reading the integer and decimal point in a number,
// such as after reading `1.`.
func numscan_dot(c byte) (numscanStep, error) {
if '0' <= c && c <= '9' {
return numscan_dot0, nil
}
return nil, fmt.Errorf("invalid byte after decimal in numeric literal: 0x%x", c)
}
// numscan_dot0 is the state after reading the integer, decimal point, and subsequent
// digits of a number, such as after reading `3.14`.
func numscan_dot0(c byte) (numscanStep, error) {
if '0' <= c && c <= '9' {
return numscan_dot0, nil
}
if c == 'e' || c == 'E' {
return numscan_e, nil
}
return nil, nil
}
// numscan_e is the state after reading the mantissa and e in a number,
// such as after reading `314e` or `0.314e`.
func numscan_e(c byte) (numscanStep, error) {
if c == '+' || c == '-' {
return numscan_eSign, nil
}
return numscan_eSign(c)
}
// numscan_eSign is the state after reading the mantissa, e, and sign in a number,
// such as after reading `314e-` or `0.314e+`.
func numscan_eSign(c byte) (numscanStep, error) {
if '0' <= c && c <= '9' {
return numscan_e0, nil
}
return nil, fmt.Errorf("invalid byte in exponent of numeric literal: 0x%x", c)
}
// numscan_e0 is the state after reading the mantissa, e, optional sign,
// and at least one digit of the exponent in a number,
// such as after reading `314e-2` or `0.314e+1` or `3.14e0`.
func numscan_e0(c byte) (numscanStep, error) {
if '0' <= c && c <= '9' {
return numscan_e0, nil
}
return nil, nil
}