RFC 中的“*”（星号）是什么意思？

Question

引自https://www.rfc-editor.org/rfc/rfc5987#section-3.2.1：

In order to include character set and language information, this
specification modifies the RFC 2616 grammar to be:

 parameter     = reg-parameter / ext-parameter

 reg-parameter = parmname LWSP "=" LWSP value

 ext-parameter = parmname "*" LWSP "=" LWSP ext-value

 parmname      = 1*attr-char

 ext-value     = charset  "'" [ language ] "'" value-chars
               ; like RFC 2231's <extended-initial-value>
               ; (see [RFC2231], Section 7)

 charset       = "UTF-8" / "ISO-8859-1" / mime-charset

 mime-charset  = 1*mime-charsetc

*在parmname = 1*attr-char中是什么意思？ mime-charset = 1*mime-charsetc.

也有同样的问题

我所知道的是 "*" 在 ext-parameter = parmname "*" LWSP "=" LWSP ext-value 中的意思恰好是 * 本身，因为 RFC 显示了 ext-parameter = parmname "*" LWSP "=" LWSP ext-value 的示例：

title*=iso-8859-1'en'%A3%20rates

Answer 1

它是一个描述有效重复次数的量词。

"1*element" requires at least one element.

参见 RFC 2616 section 2.1 - 增强 BNF：

*rule
      The character "*" preceding an element indicates repetition. The
      full form is "<n>*<m>element" indicating at least <n> and at most
      <m> occurrences of element. Default values are 0 and infinity so
      that "*(element)" allows any number, including zero; "1*element"
      requires at least one; and "1*2element" allows one or two.

Answer 2

您引用的规范说：

This specification uses the ABNF (Augmented Backus-Naur Form)
notation defined in [RFC5234]. The following core rules are included by reference, as defined in [RFC5234], Appendix B.1: ALPHA (letters), DIGIT (decimal 0-9), HEXDIG (hexadecimal 0-9/A-F/a-f), and LWSP
(linear whitespace).

转到 RFC 5234，您会发现 https://www.rfc-editor.org/rfc/rfc5234#section-3.6

RFC 中的“*”（星号）是什么意思？

What does "*" (asterisk) mean in RFC?

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