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package jsoniter
import (
"fmt"
"unicode/utf16"
)
// ReadString read string from iterator
func (iter *Iterator) ReadString() (ret string) {
c := iter.nextToken()
if c == '"' {
for i := iter.head; i < iter.tail; i++ {
c := iter.buf[i]
if c == '"' {
ret = string(iter.buf[iter.head:i])
iter.head = i + 1
return ret
} else if c == '\\' {
break
} else if c < ' ' {
iter.ReportError("ReadString",
fmt.Sprintf(`invalid control character found: %d`, c))
return
}
}
return iter.readStringSlowPath()
} else if c == 'n' {
iter.skipThreeBytes('u', 'l', 'l')
return ""
}
iter.ReportError("ReadString", `expects " or n, but found `+string([]byte{c}))
return
}
func (iter *Iterator) readStringSlowPath() (ret string) {
var str []byte
var c byte
for iter.Error == nil {
c = iter.readByte()
if c == '"' {
return string(str)
}
if c == '\\' {
c = iter.readByte()
str = iter.readEscapedChar(c, str)
} else {
str = append(str, c)
}
}
iter.ReportError("readStringSlowPath", "unexpected end of input")
return
}
func (iter *Iterator) readEscapedChar(c byte, str []byte) []byte {
switch c {
case 'u':
r := iter.readU4()
if utf16.IsSurrogate(r) {
c = iter.readByte()
if iter.Error != nil {
return nil
}
if c != '\\' {
iter.unreadByte()
str = appendRune(str, r)
return str
}
c = iter.readByte()
if iter.Error != nil {
return nil
}
if c != 'u' {
str = appendRune(str, r)
return iter.readEscapedChar(c, str)
}
r2 := iter.readU4()
if iter.Error != nil {
return nil
}
combined := utf16.DecodeRune(r, r2)
if combined == '\uFFFD' {
str = appendRune(str, r)
str = appendRune(str, r2)
} else {
str = appendRune(str, combined)
}
} else {
str = appendRune(str, r)
}
case '"':
str = append(str, '"')
case '\\':
str = append(str, '\\')
case '/':
str = append(str, '/')
case 'b':
str = append(str, '\b')
case 'f':
str = append(str, '\f')
case 'n':
str = append(str, '\n')
case 'r':
str = append(str, '\r')
case 't':
str = append(str, '\t')
default:
iter.ReportError("readEscapedChar",
`invalid escape char after \`)
return nil
}
return str
}
// ReadStringAsSlice read string from iterator without copying into string form.
// The []byte can not be kept, as it will change after next iterator call.
func (iter *Iterator) ReadStringAsSlice() (ret []byte) {
c := iter.nextToken()
if c == '"' {
for i := iter.head; i < iter.tail; i++ {
// require ascii string and no escape
// for: field name, base64, number
if iter.buf[i] == '"' {
// fast path: reuse the underlying buffer
ret = iter.buf[iter.head:i]
iter.head = i + 1
return ret
}
}
readLen := iter.tail - iter.head
copied := make([]byte, readLen, readLen*2)
copy(copied, iter.buf[iter.head:iter.tail])
iter.head = iter.tail
for iter.Error == nil {
c := iter.readByte()
if c == '"' {
return copied
}
copied = append(copied, c)
}
return copied
}
iter.ReportError("ReadStringAsSlice", `expects " or n, but found `+string([]byte{c}))
return
}
func (iter *Iterator) readU4() (ret rune) {
for i := 0; i < 4; i++ {
c := iter.readByte()
if iter.Error != nil {
return
}
if c >= '0' && c <= '9' {
ret = ret*16 + rune(c-'0')
} else if c >= 'a' && c <= 'f' {
ret = ret*16 + rune(c-'a'+10)
} else if c >= 'A' && c <= 'F' {
ret = ret*16 + rune(c-'A'+10)
} else {
iter.ReportError("readU4", "expects 0~9 or a~f, but found "+string([]byte{c}))
return
}
}
return ret
}
const (
t1 = 0x00 // 0000 0000
tx = 0x80 // 1000 0000
t2 = 0xC0 // 1100 0000
t3 = 0xE0 // 1110 0000
t4 = 0xF0 // 1111 0000
t5 = 0xF8 // 1111 1000
maskx = 0x3F // 0011 1111
mask2 = 0x1F // 0001 1111
mask3 = 0x0F // 0000 1111
mask4 = 0x07 // 0000 0111
rune1Max = 1<<7 - 1
rune2Max = 1<<11 - 1
rune3Max = 1<<16 - 1
surrogateMin = 0xD800
surrogateMax = 0xDFFF
maxRune = '\U0010FFFF' // Maximum valid Unicode code point.
runeError = '\uFFFD' // the "error" Rune or "Unicode replacement character"
)
func appendRune(p []byte, r rune) []byte {
// Negative values are erroneous. Making it unsigned addresses the problem.
switch i := uint32(r); {
case i <= rune1Max:
p = append(p, byte(r))
return p
case i <= rune2Max:
p = append(p, t2|byte(r>>6))
p = append(p, tx|byte(r)&maskx)
return p
case i > maxRune, surrogateMin <= i && i <= surrogateMax:
r = runeError
fallthrough
case i <= rune3Max:
p = append(p, t3|byte(r>>12))
p = append(p, tx|byte(r>>6)&maskx)
p = append(p, tx|byte(r)&maskx)
return p
default:
p = append(p, t4|byte(r>>18))
p = append(p, tx|byte(r>>12)&maskx)
p = append(p, tx|byte(r>>6)&maskx)
p = append(p, tx|byte(r)&maskx)
return p
}
}