go-rfc8259/exponentnumber/parse.go

147 lines
3.0 KiB
Go

package rfc8259exponentnumber
import (
"io"
"sourcecode.social/reiver/go-erorr"
"sourcecode.social/reiver/go-rfc8259/errors"
)
// Parse tries to parse the JSON exponent-number literal.
// If it succeeds, then it return nil.
// If it failed, it returns an error.
//
// IETF RFC-8259 calls a exponent number an "int" with this definition:
//
// e = %x65 / %x45 ; e E
//
// exp = e [ minus / plus ] 1*DIGIT
//
// minus = %x2D ; -
//
// plus = %x2B ; +
//
// Example usage:
//
// var runescanner io.RuneScanner
//
// // ...
//
// var dst rfc8259exponentnumber.ExponentNumber
// err := rfc8259exponentnumber.Parse(runescanner, &dst)
//
// if nil != err {
// return err
// }
//
// fmt.Printf("dst = %#v\n", dst)
func Parse(runescanner io.RuneScanner, dst *ExponentNumber) error {
if nil == runescanner {
return rfc8259errors.ErrNilRuneScanner
}
if nil == dst {
return rfc8259errors.ErrNilDestination
}
var buffer [256]byte
var p []byte = buffer[0:0]
{
var r rune
{
var err error
r, _, err = runescanner.ReadRune()
if nil != err {
if io.EOF == err {
return rfc8259errors.ErrUnexpectedEndOfFile
}
return rfc8259errors.ErrProblemReadingRune(err)
}
}
if 'E' != r && 'e' != r {
return erorr.Errorf("rfc8259: JSON parser encountered a problem — when trying to parse a exponent-number, expected the first character to be 'E', or 'e', but actually was %q (%U)", r, r)
}
p = append(p, string(r)...)
}
{
var r rune
{
var err error
r, _, err = runescanner.ReadRune()
if nil != err {
if io.EOF == err {
return rfc8259errors.ErrUnexpectedEndOfFile
}
return rfc8259errors.ErrProblemReadingRune(err)
}
}
switch r {
case '+', '-':
p = append(p, string(r)...)
default:
if err := runescanner.UnreadRune(); nil != err {
return rfc8259errors.ErrProblemUnreadingRune(err, r)
}
}
}
{
var r rune
{
var err error
r, _, err = runescanner.ReadRune()
if nil != err {
if io.EOF == err {
return rfc8259errors.ErrUnexpectedEndOfFile
}
return rfc8259errors.ErrProblemReadingRune(err)
}
}
switch r {
case '0', '1','2','3','4','5','6','7','8','9':
p = append(p, string(r)...)
default:
return erorr.Errorf("rfc8259: JSON parser encountered a problem — when trying to parse a exponent-number, expected the character after %q to be '0', '1', '2', '3', '4', '5', '6', '7', '8', or '9', but actually was %q (%U)", string(p), r, r)
}
}
loop: for {
var r rune
{
var err error
r, _, err = runescanner.ReadRune()
if nil != err && io.EOF != err {
return rfc8259errors.ErrProblemReadingRune(err)
}
if io.EOF == err {
/////////////////////// BREAK
break loop
}
switch r {
case '0','1','2','3','4','5','6','7','8','9':
p = append(p, string(r)...)
default:
if err := runescanner.UnreadRune(); nil != err {
return rfc8259errors.ErrProblemUnreadingRune(err, r)
}
/////////////////////// BREAK
break loop
}
}
}
*dst = Something(string(p))
return nil
}