111 lines
2.4 KiB
Go
111 lines
2.4 KiB
Go
package rfc8259number
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import (
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"io"
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"sourcecode.social/reiver/go-rfc8259/errors"
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"sourcecode.social/reiver/go-rfc8259/exponentnumber"
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"sourcecode.social/reiver/go-rfc8259/fractionalnumber"
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"sourcecode.social/reiver/go-rfc8259/naturalnumber"
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)
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// Parse tries to parse a JSON number literal.
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// If it succeeds, then it return nil, and sets ‘dst’ to the parsed value.
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// If it failed, it returns an error.
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//
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// Example usage:
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//
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// var rs io.RuneScaner
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//
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// // ...
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//
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// var value rfc8259number.Number
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// err := rfc8259number.Parse(rs, &value)
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//
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// if nil != err {
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// return err
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// }
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//
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// fmt.Printf("value = %#v\n", value)
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func Parse(runescanner io.RuneScanner, dst *Number) error {
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if nil == runescanner {
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return rfc8259errors.ErrNilRuneScanner
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}
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if nil == dst {
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return rfc8259errors.ErrNilDestination
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}
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var natPart rfc8259naturalnumber.NaturalNumber // [ minus ] int
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var fracPart rfc8259fractionalnumber.FractionalNumber // [ frac ]
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var expPart rfc8259exponentnumber.ExponentNumber // [ exp ]
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// [ minus ] int
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{
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if err := rfc8259naturalnumber.Parse(runescanner, &natPart); nil != err {
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return err
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}
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if rfc8259naturalnumber.Nothing() == natPart {
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return rfc8259errors.ErrInternalError("expected the result of a natural-number, but it is actually nothing")
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}
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}
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// [ frac ]
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{
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var r rune
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{
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var err error
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r, _, err = runescanner.ReadRune()
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if nil != err {
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if io.EOF == err {
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natPart.WhenSomething(func(value string){
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*dst = Something(value)
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})
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return nil
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}
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return rfc8259errors.ErrProblemReadingRune(err)
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}
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if err := runescanner.UnreadRune(); nil != err {
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return rfc8259errors.ErrProblemUnreadingRune(err, r)
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}
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}
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if '.' == r {
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if err := rfc8259fractionalnumber.Parse(runescanner, &fracPart); nil != err {
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return err
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}
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}
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}
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// [ exp ]
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{
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var r rune
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{
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var err error
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r, _, err = runescanner.ReadRune()
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if nil != err {
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if io.EOF == err {
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*dst = Something(natPart.GetElse("") + fracPart.GetElse(""))
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return nil
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}
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return rfc8259errors.ErrProblemReadingRune(err)
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}
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if err := runescanner.UnreadRune(); nil != err {
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return rfc8259errors.ErrProblemUnreadingRune(err, r)
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}
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}
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if 'E' == r || 'e' == r {
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if err := rfc8259exponentnumber.Parse(runescanner, &expPart); nil != err {
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return err
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}
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}
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}
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*dst = Something(natPart.GetElse("") + fracPart.GetElse("") + expPart.GetElse(""))
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return nil
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}
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