Java打印unicode故障

Question

我目前正在编写一个程序来读取java类文件.目前,我正在读取类文件的Constant-Pool(在此处阅读)并将其打印到控制台.但是当它被打印出来时,一些unicode似乎以这种方式弄乱我的终端,它看起来像这样(如果重要的话,我正在阅读的类文件是从Kotlin编译的,而终端I我使用的是IntelliJ IDEA终端,虽然在使用常规Ubuntu终端时似乎没有出现问题.): 我注意到的是一个奇怪的Unicode序列,我认为它可能是某种逃逸序列.

这是没有奇怪的unicode序列的整个输出:

{1=UTF8: (42)'deerangle/decompiler/main/DecompilerMainKt', 2=Class index: 1, 3=UTF8: (16)'java/lang/Object', 4=Class index: 3, 5=UTF8: (4)'main', 6=UTF8: (22)'([Ljava/lang/String;)V', 7=UTF8: (35)'Lorg/jetbrains/annotations/NotNull;', 8=UTF8: (4)'args', 9=String index: 8, 10=UTF8: (30)'kotlin/jvm/internal/Intrinsics', 11=Class index: 10, 12=UTF8: (23)'checkParameterIsNotNull', 13=UTF8: (39)'(Ljava/lang/Object;Ljava/lang/String;)V', 14=Method name index: 12; Type descriptor index: 13, 15=Bootstrap method attribute index: 11; NameType index: 14, 16=UTF8: (12)'java/io/File', 17=Class index: 16, 18=UTF8: (6)'<init>', 19=UTF8: (21)'(Ljava/lang/String;)V', 20=Method name index: 18; Type descriptor index: 19, 21=Bootstrap method attribute index: 17; NameType index: 20, 22=UTF8: (15)'getAbsolutePath', 23=UTF8: (20)'()Ljava/lang/String;', 24=Method name index: 22; Type descriptor index: 23, 25=Bootstrap method attribute index: 17; NameType index: 24, 26=UTF8: (16)'java/lang/System', 27=Class index: 26, 28=UTF8: (3)'out', 29=UTF8: (21)'Ljava/io/PrintStream;', 30=Method name index: 28; Type descriptor index: 29, 31=Bootstrap method attribute index: 27; NameType index: 30, 32=UTF8: (19)'java/io/PrintStream', 33=Class index: 32, 34=UTF8: (5)'print', 35=UTF8: (21)'(Ljava/lang/Object;)V', 36=Method name index: 34; Type descriptor index: 35, 37=Bootstrap method attribute index: 33; NameType index: 36, 38=UTF8: (19)'[Ljava/lang/String;', 39=Class index: 38, 40=UTF8: (17)'Lkotlin/Metadata;', 41=UTF8: (2)'mv', 42=Int: 1, 43=Int: 11, 44=UTF8: (2)'bv', 45=Int: 0, 46=Int: 2, 47=UTF8: (1)'k', 48=UTF8: (2)'d1', 49=UTF8: (58)'WEIRD_UNICODE_SEQUENCE', 50=UTF8: (2)'d2', 51=UTF8: (0)'', 52=UTF8: (10)'Decompiler', 53=UTF8: (17)'DecompilerMain.kt', 54=UTF8: (4)'Code', 55=UTF8: (18)'LocalVariableTable', 56=UTF8: (15)'LineNumberTable', 57=UTF8: (13)'StackMapTable', 58=UTF8: (36)'RuntimeInvisibleParameterAnnotations', 59=UTF8: (10)'SourceFile', 60=UTF8: (20)'SourceDebugExtension', 61=UTF8: (25)'RuntimeVisibleAnnotations'}
AccessFlags: {ACC_PUBLIC, ACC_FINAL, ACC_SUPER}

这是在Sublime Text中打开的Unicode序列:

关于这一切的问题是:为什么这个Unicode打破了IntelliJ IDEA中的控制台,这在Kotlin-Class-Files中是常见的,在打印之前可以做些什么来从String中删除所有这些"转义序列"？

Answer 1

出于某种不可思议的原因,当Sun Microsystems设计Java时,他们决定使用非UTF8编码在常量池中编码字符串.它是仅由java编译器和类加载器使用的自定义编码.

更糟糕的是,在JVM文档中他们决定称之为UTF8.但它不是 UTF8,他们选择的名称会引起很多不必要的混淆.所以,我在这里推测的是你看到他们称之为UTF8,所以你把它当作真正的 UTF8 来对待,结果就是你收到了垃圾.

您需要查找CONSTANT_Utf8_infoJVM规范中的描述并编写一个根据其规范对字符串进行解码的算法.

为方便起见,这里有一些我编写的代码:

public static char[] charsFromBytes( byte[] bytes )
{
    int t = 0;
    int end = bytes.length;
    for( int s = 0;  s < end;  )
    {
        int b1 = bytes[s] & 0xff;
        if( b1 >> 4 >= 0 && b1 >> 4 <= 7 ) /* 0x0xxx_xxxx */
            s++;
        else if( b1 >> 4 >= 12 && b1 >> 4 <= 13 ) /* 0x110x_xxxx 0x10xx_xxxx */
            s += 2;
        else if( b1 >> 4 == 14 ) /* 0x1110_xxxx 0x10xx_xxxx 0x10xx_xxxx */
            s += 3;
        t++;
    }
    char[] chars = new char[t];
    t = 0;
    for( int s = 0;  s < end;  )
    {
        int b1 = bytes[s++] & 0xff;
        if( b1 >> 4 >= 0 && b1 >> 4 <= 7 ) /* 0x0xxx_xxxx */
            chars[t++] = (char)b1;
        else if( b1 >> 4 >= 12 && b1 >> 4 <= 13 ) /* 0x110x_xxxx 0x10xx_xxxx */
        {
            assert s < end : new IncompleteUtf8Exception( s );
            int b2 = bytes[s++] & 0xff;
            assert (b2 & 0xc0) == 0x80 : new MalformedUtf8Exception( s - 1 );
            chars[t++] = (char)(((b1 & 0x1f) << 6) | (b2 & 0x3f));
        }
        else if( b1 >> 4 == 14 ) /* 0x1110_xxxx 0x10xx_xxxx 0x10xx_xxxx */
        {
            assert s < end : new IncompleteUtf8Exception( s );
            int b2 = bytes[s++] & 0xff;
            assert (b2 & 0xc0) == 0x80 : new MalformedUtf8Exception( s - 1 );
            assert s < end : new IncompleteUtf8Exception( s );
            int b3 = bytes[s++] & 0xff;
            assert (b3 & 0xc0) == 0x80 : new MalformedUtf8Exception( s - 1 );
            chars[t++] = (char)(((b1 & 0x0f) << 12) | ((b2 & 0x3f) << 6) | (b3 & 0x3f));
        }
        else
            assert false;
    }
    return chars;
}