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number.go
82 lines (74 loc) · 1.92 KB
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number.go
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// Copyright 2019 Santhosh Kumar Tekuri
//
// 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
//
// https://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 json
func (d *ByteDecoder) number() Token {
if d.pos == len(d.buf) {
return d.unexpectedEOF()
}
mark := d.pos
// optional -
if d.buf[d.pos] == '-' {
d.pos++
if d.pos == len(d.buf) {
return d.unexpectedEOF()
}
}
// digits
b := d.buf[d.pos]
switch {
case b == '0':
d.pos++
case '1' <= b && b <= '9':
d.pos++
for d.pos < len(d.buf) && digit(d.buf[d.pos]) {
d.pos++
}
default:
if mark == d.pos {
return d.error("looking for beginning of value")
}
return d.error("in numeric literal")
}
// fraction: dot followed by one or more digits
if d.pos < len(d.buf) && d.buf[d.pos] == '.' {
d.pos++
if d.pos == len(d.buf) || !digit(d.buf[d.pos]) {
return d.error("after decimal point in numeric literal")
}
for d.pos < len(d.buf) && digit(d.buf[d.pos]) {
d.pos++
}
}
// exponent: e/E optional(+/-) followed by one or more digits
if d.pos < len(d.buf) {
if b = d.buf[d.pos]; b == 'e' || b == 'E' {
d.pos++
if d.pos < len(d.buf) {
if b = d.buf[d.pos]; b == '+' || b == '-' {
d.pos++
}
}
if d.pos == len(d.buf) || !digit(d.buf[d.pos]) {
return d.error("in exponent of numeric literal")
}
for d.pos < len(d.buf) && digit(d.buf[d.pos]) {
d.pos++
}
}
}
return Token{Kind: Num, Data: d.buf[mark:d.pos]}
}
func digit(p byte) bool {
return '0' <= p && p <= '9'
}