blocks|key|201463|text|根据MSDN的Data+Type+Summary+(VS2012)，布尔值的大小取决于实现平台。但是，如果您查看the+same+page+for+VS2003，它确实显示布尔值是2个字节。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|201464|ECMA-335第III.1.1.1节规定：|201465|201466|求值堆栈只能保存4字节或8字节的整数，但其他位置(参数、局部变量、静态变量、数组元素、字段)可以保存1字节或2字节的整数。出于堆栈操作的目的，bool+(§III.1.1.2)和char类型分别被视为无符号的1字节和2字节整数。从这些位置加载到堆栈上会将它们转换为4字节值|blockquote|201467|201468|201469|第III.1.1.2节规定：|201470|CLI类型占用内存中的1个字节。|201471|全零的位模式表示值为false。设置了任何一个或多个位(类似于非零整数)的位模式表示值为true。出于堆栈操作的目的，布尔值被视为无符号1字节整数|201472|201473|201474|201475|因此，考虑到这一点，我感到更困惑的是，为什么你得到2而不是1|201476|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/47zceaw7%2528v=vs.110%2529.aspx|1|http://msdn.microsoft.com/en-us/library/47zceaw7%2528v=vs.71%2529.aspx^0|7|Q|0|1K|O|1|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@$A|17|B|18|1|19]|$A|1A|B|1B|1|1C]]|C|$]]|$1|D|3|E|5|6|7|1D|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|1E|8|@]|9|@]|C|$]]|$1|G|3|H|5|I|7|1F|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|1G|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|1H|8|@]|9|@]|C|$]]|$1|L|3|M|5|6|7|1I|8|@]|9|@]|C|$]]|$1|N|3|O|5|6|7|1J|8|@]|9|@]|C|$]]|$1|P|3|Q|5|I|7|1K|8|@]|9|@]|C|$]]|$1|R|3|-4|5|6|7|1L|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1M|8|@]|9|@]|C|$]]|$1|T|3|-4|5|6|7|1N|8|@]|9|@]|C|$]]|$1|U|3|V|5|6|7|1O|8|@]|9|@]|C|$]]|$1|W|3|-4|5|6|7|1P|8|@]|9|@]|C|$]]]|X|$Y|$5|Z|10|11|C|$12|13]]|14|$5|Z|10|11|C|$12|15]]]]

According to MSDN's <a href="http://msdn.microsoft.com/en-us/library/47zceaw7%28v=vs.110%29.aspx" rel="nofollow">Data Type Summary (VS2012)</a> the size of Boolean is dependent on the implementing platform. However if you look at <a href="http://msdn.microsoft.com/en-us/library/47zceaw7%28v=vs.71%29.aspx" rel="nofollow">the same page for VS2003</a> it does say that Boolean is 2 bytes.

ECMA-335 section III.1.1.1 states:

<blockquote>
 The evaluation stack only holds 4- or 8-byte integers, but other
 locations (arguments, local variables, statics, array elements, fields) can hold 1 - or
 2-byte integers. For the purpose of stack operations the bool (§III.1.1.2) and char
 types are treated as unsigned 1-byte and 2-byte integers respectively. Loading from
 these locations onto the stack converts them to 4-byte values
</blockquote>

And section III.1.1.2 states:

<blockquote>
 A CLI Boolean type occupies 1 byte in memory. A bit pattern of all zeroes denotes a value of false. A bit pattern with any one or more bits set (analogous to a non-zero integer) denotes a value of true. For the purpose of stack operations boolean values are treated as unsigned 1-byte integers
</blockquote>

<hr>

So given that, I feel only more confused as to why you get 2 and not 1

blocks|key|3044639|text|对于用户定义的类型和对象变量，Len函数返回FilePut函数将其写入文件时的大小。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3044640|如果一个对象包含一个字符串，它将返回字符串的长度。如果对象包含任何其他类型，它将返回对象的大小，因为它将由FilePut函数写入文件。|blockquote|3044641|3044642|3044643|Len()是一个遗留函数，应该只在从上一代Visual+Basic项目移植过来的代码中使用。它通常出现在涉及VB值的二进制序列化的代码中。基本类型的大小在这些旧版本中是不同的。例如，Integer是16位的，解释了你在web上发现的大量使用Long的糟糕的pinvoke声明。Boolean是一个隐藏在引擎盖下的VARIANT_BOOL，一个16位的值。更奇怪的是，将其True值转换为-1而不是1。|offset|length|style|CODE|3044644|显然，对于由VB6程序编写的文件中存在的大量数据，采用.NET大小将是一个严重的破坏性更改。或通过TCP连接发送的二进制数据。等等。因此，Len()函数返回遗留的大小。|3044645|entityMap^0|0|0|0|0|2J|7|3U|7|55|4|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$]]|$1|E|3|-4|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]|$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|P|$]]

<blockquote>
 With user-defined types and Object variables, the Len function returns the size as it will be written to the file by the FilePut function. If an Object contains a String, it will return the length of the string. If an Object contains any other type, it will return the size of the object as it will be written to the file by the FilePut function. 
</blockquote>

Len() is a legacy function, it should only be used in code that was ported from previous generation Visual Basic projects. Where it would typically appear in code that involved binary serialization of VB values. Sizes of basic types were different in those old versions. <code>Integer</code> was 16 bits for example, explaining the great number of bad pinvoke declarations you find in the web that use Long. And <code>Boolean</code> was a VARIANT_BOOL under the hood, a 16-bit value. Furthermore quirky by having its <code>True</code> value convert to -1 instead 1.

Clearly adopting the .NET sizes would have been a heavily breaking change to a lot of data that exists in files written by a VB6 program. Or binary data sent across a TCP connection. Etcetera. Accordingly, the Len() function returns the legacy sizes.

This question originates from <a href="https://stackoverflow.com/q/14425449/897326">here</a>. I tried this statement in VS to see what happens:

<pre><code>Len(Name &lt;= 3)
</code></pre>

According to <a href="https://stackoverflow.com/questions/204256/why-does-boolean-consume-more-memory-than-char">this answer</a> and also <a href="https://stackoverflow.com/questions/294905/why-in-net-system-boolean-takes-4-byte">this one</a>, Boolean should consume 4 bytes. According to MSDN, <a href="http://msdn.microsoft.com/en-us/library/dxsw58z6%28v=vs.90%29.aspx" rel="nofollow noreferrer">Len Function in VB</a>

<blockquote>
 Returns an integer containing either the number of characters in a
 string or the nominal number of bytes required to store a variable.
</blockquote>

<code>Name &lt;= 3</code> should convert 3 to String and perform string comparison, returning a boolean value, so <code>Len</code> should evaluate number of bytes in it, which should be 4. For some reason, above code returns 2, regardless of the second parameter. In other words, <code>Len(True)</code> also returns 2. Tried for different platform targets (32 and 64) - same thing.

Why does <code>Len(Boolean)</code> return 2 instead of 4?

Boolean is two bytes in .NET?

这个问题源于。我在VS中尝试了下面的语句，看看会发生什么：Len(Name <= 3)根据和的说法，Boolean应该占用4个字节。根据MSDN的说法，返回一个整数，其中包含字符串中的字符数或存储变量所需的标称字节数。Name <= 3应该将3转换为字符串，并执行字符串比较，返回一个布尔值，因此Len应该计算其中的字节...

问布尔值在.NET中是两个字节吗？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问布尔值在.NET中是两个字节吗？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问布尔值在.NET中是两个字节吗？
EN