add equivilant functionality from std.mem.indexOf{Any,None} to reader.*Delim*

[MahdiGMK]

There are some use cases in which you may want to read until a whitespace or discard all whitespaces.

[MahdiGMK]

It is also possible to make it ~generic :

// this code is taken from zig 0.15.0 stdlib => peekDelimiterInclusive
// with std.mem.indexOfScalar replaced with indexOfPos_func
fn peekUntilInclusiveGeneric(reader: *std.io.Reader, indexOfPos_func: fn (buf:[]u8, pos:usize) ?usize) ![]u8 {
    const buffer = reader.buffer[0..reader.end];
    const seek = reader.seek;
    if (indexOfPos_func(u8, buffer, seek)) |end| {
        @branchHint(.likely);
        return buffer[seek..end + 1];
    }
    try reader.rebase(reader.buffer.len);
    while (reader.buffer.len - reader.end != 0) {
        const end_cap = reader.buffer[reader.end..];
        var writer: std.io.Writer = .fixed(end_cap);
        const n = reader.vtable.stream(reader, &writer, .limited(end_cap.len)) catch |err| switch (err) {
            error.WriteFailed => unreachable,
            else => |e| return e,
        };
        reader.end += n;
        if (indexOfPos_func(end_cap[0..n], 0)) |end| {
            return reader.buffer[0 .. reader.end - n + end + 1];
        }
    }
    return error.StreamTooLong;
}

and usage will be :

fn foo(reader: *Reader) {
    reader.peekUntilInclusiveGeneric(struct { 
        pub fn indexOf(buf:[]u8, pos:usize) ?usize {
            return std.mem.indexOfAnyPos(u8, buf, pos, std.ascii.whitespace);
        }
    }.indexOf);
}

also the original peekDelimiterInclusive would be :

fn peekDelimiterInclusive_new(reader: *std.io.Reader, delim: u8) ?usize) ![]u8 {
    return reader.peekUntilInclusiveGeneric(struct { 
        pub fn indexOf(buf:[]u8, pos:usize) ?usize {
            return std.mem.indexOfScalarPos(u8, buf, pos, delim);
        }
    }.indexOf);
}