go-rfc8259/fractionalnumber/parse.go

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2023-11-05 06:23:12 +00:00
package rfc8259fractionalnumber
import (
"io"
"sourcecode.social/reiver/go-erorr"
"sourcecode.social/reiver/go-rfc8259/errors"
)
// Parse tries to parse the JSON fractional-number literal.
// If it succeeds, then it return nil.
// If it failed, it returns an error.
//
// IETF RFC-8259 calls a fractional number an "int" with this definition:
//
// digit1-9 = %x31-39 ; 1-9
//
// int = zero / ( digit1-9 *DIGIT )
//
// zero = %x30 ; 0
//
// To avoid confusion, rather than calling this "Int" as IETF RFC-8259 does (as in other contexts
// often "int" and "integer" include negative numbers) we call this "FractionalNumber".
//
// Example usage:
//
// var runescanner io.RuneScanner
//
// // ...
//
// var dst rfc8259fractionalnumber.FractionalNumber
// err := rfc8259fractionalnumber.Parse(runescanner, &dst)
//
// if nil != err {
// return err
// }
//
// fmt.Printf("dst = %#v\n", dst)
func Parse(runescanner io.RuneScanner, dst *FractionalNumber) 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 '.' != r {
return erorr.Errorf("rfc8259: JSON parser encountered a problem — when trying to parse a fractional-number, expected the first character to be '.', but actually was %q (%U)", r, r)
}
p = append(p, "."...)
}
{
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 fractional-number, expected the second character to be '0', '1', '2', '3', '4', '5', '6', '7', '8', or '9', but actually was %q (%U)", 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
}