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确定正则表达式中存在哪些命名捕获？

发布于 2024-12-10 11:46:01 字数 122 浏览 2 评论 0原文

给定一个带有命名捕获的正则表达式，是否可以确定 re 中存在哪些命名捕获？

注意：我只有正则表达式 - 我没有与 re 匹配的字符串。我想知道是否有一种方法可以查看 re 的结构并找到 re 中使用的所有命名捕获。

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吃颗糖壮壮胆 2024-12-17 11:46:01

在一般情况下这是不可能的，因为有人可能会插入 (??{....}) 代码，该代码插入会变成在比赛执行期间使用对迄今未见过的名称进行命名捕获的内容。

在特定情况下，您也许能够从 C API 深入了解底层结构。 Devel::Peek 建议您可能想要探索的一些地方：

% perl -MDevel::Peek -le 'Dump qr/(?<foo>\w+) (?&foo)/'
SV = IV(0x8033ac) at 0x8033b0
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x803d40
  SV = REGEXP(0x8173d8) at 0x803d40
    REFCNT = 1
    FLAGS = (OBJECT,POK,FAKE,pPOK)
    PV = 0x216fc0 "(?^:(?<foo>\\w+) (?&foo))"
    CUR = 24
    LEN = 0
    STASH = 0x803b50    "Regexp"
    EXTFLAGS = 0x600000 (USE_INTUIT_NOML,USE_INTUIT_ML)
    INTFLAGS = 0x1
    NPARENS = 1
    LASTPAREN = 0
    LASTCLOSEPAREN = 0
    MINLEN = 3
    MINLENRET = 3
    GOFS = 0
    PRE_PREFIX = 4
    SEEN_EVALS = 0
    SUBLEN = 0
    SUBBEG = 0x0
    ENGINE = 0x162b60
    MOTHER_RE = 0x80fab0
    PAREN_NAMES = 0x80fa40
    SUBSTRS = 0x2044b0
    PPRIVATE = 0x206360
    OFFS = 0x204280

例如，PAREN_NAMES 看起来很有前途。

但这似乎需要很多工作。你想这样做是为了什么？

That’s not possible in the general case, because someone could have a (??{....}) code insert that turns into something that uses a named capture of a hitherto unseen name during match execution time.

In a specific case you might be able to dig into the underlying structure from the C API. Devel::Peek suggests some places you might want to poke around:

% perl -MDevel::Peek -le 'Dump qr/(?<foo>\w+) (?&foo)/'
SV = IV(0x8033ac) at 0x8033b0
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x803d40
  SV = REGEXP(0x8173d8) at 0x803d40
    REFCNT = 1
    FLAGS = (OBJECT,POK,FAKE,pPOK)
    PV = 0x216fc0 "(?^:(?<foo>\\w+) (?&foo))"
    CUR = 24
    LEN = 0
    STASH = 0x803b50    "Regexp"
    EXTFLAGS = 0x600000 (USE_INTUIT_NOML,USE_INTUIT_ML)
    INTFLAGS = 0x1
    NPARENS = 1
    LASTPAREN = 0
    LASTCLOSEPAREN = 0
    MINLEN = 3
    MINLENRET = 3
    GOFS = 0
    PRE_PREFIX = 4
    SEEN_EVALS = 0
    SUBLEN = 0
    SUBBEG = 0x0
    ENGINE = 0x162b60
    MOTHER_RE = 0x80fab0
    PAREN_NAMES = 0x80fa40
    SUBSTRS = 0x2044b0
    PPRIVATE = 0x206360
    OFFS = 0x204280

For example, PAREN_NAMES looks promising.

But that seems like a lot of work. What do you want to do this for?

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