Unicode 中的保留字符代码答案

【问题标题】：Reserved character codes in UnicodeUnicode 中的保留字符代码
【发布时间】：2012-03-20 16:16:32
【问题描述】：

为什么 Unicode 有几个保留字符代码？
请参阅两种语言的 Unicode - Kannada 和 Tamil。这两种语言都非常古老，我认为这些语言没有机会获得新字符。
编辑：那他们为什么要通过保留字符代码来浪费一些字符代码？
为什么他们不将保留字符代码放在每个语言字符集的末尾？

【问题讨论】：

我知道我很好奇，但你问的还有其他原因吗？
请解释一下：您的意思是问为什么这些块中有未分配的插槽？
@Oded 我认为你误解了他的问题，因为你的问题是不合逻辑的。我不确定它是否离题。
@MarkRansom 我认为这背后可能有一些程序化原因。
@Oded 对不起，这个问题有点混乱。我说得更清楚了。

标签： unicode character reserved

【解决方案1】：

这与 Unicode 联盟如何分配其分配的块、脚本和代码点有关。比如Block=Tamil，它的开头是这样运行的：

$ unichars '\p{Block=Tamil}' | head -20
U+00B82 ‭ ◌ஂ  GC=Mn SC=Tamil        TAMIL SIGN ANUSVARA
U+00B83 ‭ ஃ  GC=Lo SC=Tamil        TAMIL SIGN VISARGA
U+00B85 ‭ அ  GC=Lo SC=Tamil        TAMIL LETTER A
U+00B86 ‭ ஆ  GC=Lo SC=Tamil        TAMIL LETTER AA
U+00B87 ‭ இ  GC=Lo SC=Tamil        TAMIL LETTER I
U+00B88 ‭ ஈ  GC=Lo SC=Tamil        TAMIL LETTER II
U+00B89 ‭ உ  GC=Lo SC=Tamil        TAMIL LETTER U
U+00B8A ‭ ஊ  GC=Lo SC=Tamil        TAMIL LETTER UU
U+00B8E ‭ எ  GC=Lo SC=Tamil        TAMIL LETTER E
U+00B8F ‭ ஏ  GC=Lo SC=Tamil        TAMIL LETTER EE
U+00B90 ‭ ஐ  GC=Lo SC=Tamil        TAMIL LETTER AI
U+00B92 ‭ ஒ  GC=Lo SC=Tamil        TAMIL LETTER O
U+00B93 ‭ ஓ  GC=Lo SC=Tamil        TAMIL LETTER OO
U+00B94 ‭ ஔ  GC=Lo SC=Tamil        TAMIL LETTER AU
U+00B95 ‭ க  GC=Lo SC=Tamil        TAMIL LETTER KA
U+00B99 ‭ ங  GC=Lo SC=Tamil        TAMIL LETTER NGA
U+00B9A ‭ ச  GC=Lo SC=Tamil        TAMIL LETTER CA
U+00B9C ‭ ஜ  GC=Lo SC=Tamil        TAMIL LETTER JA
U+00B9E ‭ ஞ  GC=Lo SC=Tamil        TAMIL LETTER NYA
U+00B9F ‭ ட  GC=Lo SC=Tamil        TAMIL LETTER TTA

他们倾向于为所有相同“种类”的字符保留 4、8 或 16 个代码点的连续行。是的，那里有差距，但这就像文件系统中的情况一样，一旦你将一个扇区（如果你在一个块中没有单独的扇区，则为块）分配给一个文件，即使该文件没有使用它的所有内容（最终）扇区，您不会将那些未使用的字节赠送给其他进程。无论如何，事物往往会被填充以阻塞边界。

我们没有任何代码用完的风险。

这里是分配区域的开头，以“符号”开头，如该块中第一个分配的代码点所示。间隙可能代表从一种字符到另一种字符的变化。如果您检查块中的前五个代码点的属性，您会看到那些未分配的代码点仍然具有正确的块属性：

$ uniprops -a U+00B80 U+00B81 U+00B82 U+00B83 U+00B84 U+00B85
U+0B80 ‹U+0B80› \N{U+0B80}
    \pC \p{Cn}
    All Any InTamil C Other Cn Unassigned Zzzz Unknown
    Age=Unassigned Bidi_Class=L Bidi_Class=Left_To_Right BC=L Block=Tamil Canonical_Combining_Class=0 Canonical_Combining_Class=Not_Reordered
       CCC=NR Canonical_Combining_Class=NR Decomposition_Type=None DT=None East_Asian_Width=Neutral Grapheme_Cluster_Break=Other GCB=XX
       Grapheme_Cluster_Break=XX Hangul_Syllable_Type=NA Hangul_Syllable_Type=Not_Applicable HST=NA Joining_Group=No_Joining_Group
       JG=NoJoiningGroup Joining_Type=Non_Joining JT=U Joining_Type=U Line_Break=Unknown LB=XX Line_Break=XX Numeric_Type=None NT=None
       Numeric_Value=NaN NV=NaN Present_In=Unassigned IN=Unassigned Script=Unknown SC=Zzzz Script=Zzzz Sentence_Break=Other SB=XX
       Sentence_Break=XX Word_Break=Other WB=XX Word_Break=XX
U+0B81 ‹U+0B81› \N{U+0B81}
    \pC \p{Cn}
    All Any InTamil C Other Cn Unassigned Zzzz Unknown
    Age=Unassigned Bidi_Class=L Bidi_Class=Left_To_Right BC=L Block=Tamil Canonical_Combining_Class=0 Canonical_Combining_Class=Not_Reordered
       CCC=NR Canonical_Combining_Class=NR Decomposition_Type=None DT=None East_Asian_Width=Neutral Grapheme_Cluster_Break=Other GCB=XX
       Grapheme_Cluster_Break=XX Hangul_Syllable_Type=NA Hangul_Syllable_Type=Not_Applicable HST=NA Joining_Group=No_Joining_Group
       JG=NoJoiningGroup Joining_Type=Non_Joining JT=U Joining_Type=U Line_Break=Unknown LB=XX Line_Break=XX Numeric_Type=None NT=None
       Numeric_Value=NaN NV=NaN Present_In=Unassigned IN=Unassigned Script=Unknown SC=Zzzz Script=Zzzz Sentence_Break=Other SB=XX
       Sentence_Break=XX Word_Break=Other WB=XX Word_Break=XX
U+0B82 ‹◌ஂ› \N{TAMIL SIGN ANUSVARA}
    \w \pM \p{Mn}
    All Any Alnum Alpha Alphabetic Assigned InTamil Tamil Is_Tamil Case_Ignorable CI M Mn Gr_Ext Grapheme_Extend Graph GrExt ID_Continue IDC
       Mark Nonspacing_Mark Print Taml Word XID_Continue XIDC X_POSIX_Alnum X_POSIX_Alpha X_POSIX_Graph X_POSIX_Print X_POSIX_Word
    Age=1.1 Bidi_Class=Nonspacing_Mark BC=NSM Bidi_Class=NSM Block=Tamil Canonical_Combining_Class=0 Canonical_Combining_Class=Not_Reordered
       CCC=NR Canonical_Combining_Class=NR Decomposition_Type=None DT=None East_Asian_Width=Neutral Grapheme_Cluster_Break=EX
       Grapheme_Cluster_Break=Extend GCB=EX Hangul_Syllable_Type=NA Hangul_Syllable_Type=Not_Applicable HST=NA Joining_Group=No_Joining_Group
       JG=NoJoiningGroup Joining_Type=T Joining_Type=Transparent JT=T Line_Break=CM Line_Break=Combining_Mark LB=CM Numeric_Type=None NT=None
       Numeric_Value=NaN NV=NaN Present_In=1.1 IN=1.1 Present_In=2.0 IN=2.0 Present_In=2.1 IN=2.1 Present_In=3.0 IN=3.0 Present_In=3.1 IN=3.1
       Present_In=3.2 IN=3.2 Present_In=4.0 IN=4.0 Present_In=4.1 IN=4.1 Present_In=5.0 IN=5.0 Present_In=5.1 IN=5.1 Present_In=5.2 IN=5.2
       Present_In=6.0 IN=6.0 Script=Tamil SC=Taml Script=Taml Sentence_Break=EX Sentence_Break=Extend SB=EX Word_Break=Extend WB=Extend
U+0B83 ‹ஃ› \N{TAMIL SIGN VISARGA}
    \w \pL \p{L_} \p{Lo}
    All Any Alnum Alpha Alphabetic Assigned InTamil Tamil Is_Tamil L Lo Gr_Base Grapheme_Base Graph GrBase ID_Continue IDC ID_Start IDS Letter
       L_ Other_Letter Print Taml Word XID_Continue XIDC XID_Start XIDS X_POSIX_Alnum X_POSIX_Alpha X_POSIX_Graph X_POSIX_Print X_POSIX_Word
    Age=1.1 Bidi_Class=L Bidi_Class=Left_To_Right BC=L Block=Tamil Canonical_Combining_Class=0 Canonical_Combining_Class=Not_Reordered CCC=NR
       Canonical_Combining_Class=NR Decomposition_Type=None DT=None East_Asian_Width=Neutral Grapheme_Cluster_Break=Other GCB=XX
       Grapheme_Cluster_Break=XX Hangul_Syllable_Type=NA Hangul_Syllable_Type=Not_Applicable HST=NA Joining_Group=No_Joining_Group
       JG=NoJoiningGroup Joining_Type=Non_Joining JT=U Joining_Type=U Line_Break=AL Line_Break=Alphabetic LB=AL Numeric_Type=None NT=None
       Numeric_Value=NaN NV=NaN Present_In=1.1 IN=1.1 Present_In=2.0 IN=2.0 Present_In=2.1 IN=2.1 Present_In=3.0 IN=3.0 Present_In=3.1 IN=3.1
       Present_In=3.2 IN=3.2 Present_In=4.0 IN=4.0 Present_In=4.1 IN=4.1 Present_In=5.0 IN=5.0 Present_In=5.1 IN=5.1 Present_In=5.2 IN=5.2
       Present_In=6.0 IN=6.0 Script=Tamil SC=Taml Script=Taml Sentence_Break=LE Sentence_Break=OLetter SB=LE Word_Break=ALetter WB=LE
       Word_Break=LE
U+0B84 ‹U+0B84› \N{U+0B84}
    \pC \p{Cn}
    All Any InTamil C Other Cn Unassigned Zzzz Unknown
    Age=Unassigned Bidi_Class=L Bidi_Class=Left_To_Right BC=L Block=Tamil Canonical_Combining_Class=0 Canonical_Combining_Class=Not_Reordered
       CCC=NR Canonical_Combining_Class=NR Decomposition_Type=None DT=None East_Asian_Width=Neutral Grapheme_Cluster_Break=Other GCB=XX
       Grapheme_Cluster_Break=XX Hangul_Syllable_Type=NA Hangul_Syllable_Type=Not_Applicable HST=NA Joining_Group=No_Joining_Group
       JG=NoJoiningGroup Joining_Type=Non_Joining JT=U Joining_Type=U Line_Break=Unknown LB=XX Line_Break=XX Numeric_Type=None NT=None
       Numeric_Value=NaN NV=NaN Present_In=Unassigned IN=Unassigned Script=Unknown SC=Zzzz Script=Zzzz Sentence_Break=Other SB=XX
       Sentence_Break=XX Word_Break=Other WB=XX Word_Break=XX
U+0B85 ‹அ› \N{TAMIL LETTER A}
    \w \pL \p{L_} \p{Lo}
    All Any Alnum Alpha Alphabetic Assigned InTamil Tamil Is_Tamil L Lo Gr_Base Grapheme_Base Graph GrBase ID_Continue IDC ID_Start IDS Letter
       L_ Other_Letter Print Taml Word XID_Continue XIDC XID_Start XIDS X_POSIX_Alnum X_POSIX_Alpha X_POSIX_Graph X_POSIX_Print X_POSIX_Word
    Age=1.1 Bidi_Class=L Bidi_Class=Left_To_Right BC=L Block=Tamil Canonical_Combining_Class=0 Canonical_Combining_Class=Not_Reordered CCC=NR
       Canonical_Combining_Class=NR Decomposition_Type=None DT=None East_Asian_Width=Neutral Grapheme_Cluster_Break=Other GCB=XX
       Grapheme_Cluster_Break=XX Hangul_Syllable_Type=NA Hangul_Syllable_Type=Not_Applicable HST=NA Joining_Group=No_Joining_Group
       JG=NoJoiningGroup Joining_Type=Non_Joining JT=U Joining_Type=U Line_Break=AL Line_Break=Alphabetic LB=AL Numeric_Type=None NT=None
       Numeric_Value=NaN NV=NaN Present_In=1.1 IN=1.1 Present_In=2.0 IN=2.0 Present_In=2.1 IN=2.1 Present_In=3.0 IN=3.0 Present_In=3.1 IN=3.1
       Present_In=3.2 IN=3.2 Present_In=4.0 IN=4.0 Present_In=4.1 IN=4.1 Present_In=5.0 IN=5.0 Present_In=5.1 IN=5.1 Present_In=5.2 IN=5.2
       Present_In=6.0 IN=6.0 Script=Tamil SC=Taml Script=Taml Sentence_Break=LE Sentence_Break=OLetter SB=LE Word_Break=ALetter WB=LE
       Word_Break=LE

如果您查看其他已分配的块，您会看到同样的事情。将块分割成不相关的东西是没有意义的。

正如我所说，它们不会用完空间，所以我不知道这里有什么问题。

顺便说一句，您可以从我的 Unicode Command-Line Toolchest 获得 Unicode 探索和处理工具，例如 unichars、uniprops、uninames，可以单独从那里获得，也可以通过 CPAN Unicode::Tussle suite 获得整个套件。

【讨论】：