[API Proposal]: System.Convert base on ReadOnlySpan<char>

[universorum]

Background and motivation

Consider the string Value: 0xff. If the API only accept the string, we will need create the new string instance by str[^2..].

In the API inside, many method like ParseNumbers.StringToInt (internal class) and int.Parse already accpet the ReadOnlySpan<char> type. Why we cannot pass the ReadOnlySpan<char> to API to avoid alloc?

also #22848

API Proposal

namespace System;

public static class Convert
{
    public static byte   ToByte(ReadOnlySpan<char>? value);
    public static byte   ToByte(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static byte   ToByte(ReadOnlySpan<char>? value, int fromBase);
    public static sbyte  ToSByte(ReadOnlySpan<char>? value);
    public static sbyte  ToSByte(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static sbyte  ToSByte(ReadOnlySpan<char>? value, int fromBase);
    public static short  ToInt16(ReadOnlySpan<char>? value);
    public static short  ToInt16(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static short  ToInt16(ReadOnlySpan<char>? value, int fromBase);
    public static ushort ToUInt16(ReadOnlySpan<char>? value);
    public static ushort ToUInt16(ReadOnlySpan<char>? value, int fromBase);
    public static ushort ToUInt16(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static int    ToInt32(ReadOnlySpan<char>? value);
    public static int    ToInt32(ReadOnlySpan<char>? value, int fromBase);
    public static int    ToInt32(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static uint   ToUInt32(ReadOnlySpan<char>? value);
    public static uint   ToUInt32(ReadOnlySpan<char>? value, int fromBase);
    public static uint   ToUInt32(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static long   ToInt64(ReadOnlySpan<char>? value);
    public static long   ToInt64(ReadOnlySpan<char>? value, int fromBase);
    public static long   ToInt64(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static ulong  ToUInt64(ReadOnlySpan<char>? value);
    public static ulong  ToUInt64(ReadOnlySpan<char>? value, IFormatProvider? provider);
    public static ulong  ToUInt64(ReadOnlySpan<char>? value, int fromBase);
}

API Usage

var str = "Value: 0xff"
long result = Convert.ToInt64(str.AsSpan()[^2..], 16);

Alternative Designs

No response

Risks

No response

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[huoyaoyuan]

The Convert pattern is deprecated for a long time. But we do need a better way to convert with different bases.

[AmrAlSayed0]

@huoyaoyuan Out of curiosity, deprecated in favor of what?

[huoyaoyuan]

deprecated in favor of what?

Parse methods on each type, like int.Parse and int.TryParse.

[tannergooding]

But we do need a better way to convert with different bases.

This largely already exists. Convert only supports a fixed set of bases today: 2, 8, 10, and 16

All of these except octal (8) are supported via passing in the relevant NumberStyles options to the int.Parse and related APIs nowadays

[huoyaoyuan]

All of these except octal (8) are supported via passing in the relevant NumberStyles options to the int.Parse and related APIs nowadays

Yes, but it's still gap we can improve: add octal options to NumberStyles, and dispatch NumberStyles based on numeric base values.

[stephentoub]

and dispatch NumberStyles based on numeric base values

I don't think I've ever seen a meaningful example where fromBase wasn't a constant. What's the scenario for this?

[colejohnson66]

Duplicate of #61397?