blocks|key|2776666|text|循环将继续，直到"*field“为null。也就是说，数组的末尾应该有一个空结束符(不存在的行)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2776667|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The loop will continue until "*field" is null. i.e. the array should have a null-terminator (a non-existing row) at the end.

blocks|key|4566538|text|所以*field表示一行，而**field表示表？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4566539|4566540|在声明语法中，是的。|4566541|4566542|如果*field是行，*field怎么可能为null|blockquote|4566543|4566544|4566545|如果代码的作者注意保留不变量，那么就像对argv所做的那样，field由空指针终止。也就是说，一个有n行的表是一个n%2B1指针数组，其中最后一个指针必须始终为空。这是一种常见的C约定，消除了对显式计数的需要。|4566546|entityMap^0|2|6|E|7|0|0|0|0|2|6|B|6|0|0|0|K|4|U|5|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|X|8|@]|D|@]|E|$]]|$1|G|3|H|5|6|7|Y|8|@]|D|@]|E|$]]|$1|I|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|15|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|16|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|17|8|@$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|R|$]]

<blockquote>
 So <code>*field</code> means a row, and <code>**field</code> mean a table?
</blockquote>

In declaration syntax, yes.

<blockquote>
 how could <code>*field</code> be null if <code>*field</code> is a row
</blockquote>

If the authors of the code take care to preserve the invariant that <code>field</code> is terminated by a null pointer, as is done with <code>argv</code>. I.e., a table of n rows is an array of n+1 pointers, the last of which must always be null. This is a common C convention that obviates the need for an explicit count.

blocks|key|4566598|text|您确定Field+**是一个二维数组吗？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4566599|类型为Field+**的变量不一定表示字段的二维数组。它可以是指向字段的指针的一维数组的指针。由于以下几个原因，存储指针数组可能比存储结构数组更方便:可以独立地为结构分配内存，不必使用memcpy将结构添加到列表中，并且某些列表操作的开销会更低。实际上，这是在libusb中完成的，其中libusb_device+**类型的变量表示usb设备的(一维)列表。|4566600|entityMap|0|LINK|mutability|MUTABLE|url|http://libusb.sourceforge.net/api-1.0/group__dev.html^0|3|8|0|3|8|3Z|G|3M|6|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|H|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

Are you sure that <code>Field **</code> is a two-dimensional array?

A variable of type <code>Field **</code> does not necessarily represent a two-dimensional array of Fields. It could be a pointer to a one-dimensional array of pointers to Fields. Storing an array of pointers could be more convenient than storing an array of structs for several reasons: you can allocate the memory for the structs independently, you don't have to use memcpy to add a struct to the list, and certain list operations will be less expensive. In fact, this is done in <a href="http://libusb.sourceforge.net/api-1.0/group__dev.html" rel="nofollow">libusb</a>, where a variable of type <code>libusb_device **</code> represents a (one-dimensional) list of usb devices.

blocks|key|2776875|text|如果一行有5列，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2776876|是第一列，那么field%2B4就是最后一列|blockquote|2776877|2776878|2776879|是的，但是，你可以这么说|2776880|2776881|和field%2B5是列的末尾，这意味着空值|2776882|2776883|2776884|仅当您将数组初始化为null终止时。|2776885|如果知道表中有多少列，就可以迭代到最后一列，而不是;+*field+;。|offset|length|style|CODE|2776886|entityMap^0|0|0|0|0|0|0|0|0|0|0|P|A|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$]]|$1|E|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|11|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|12|8|@]|9|@]|A|$]]|$1|J|3|K|5|D|7|13|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|16|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|17|8|@$R|18|S|19|T|U]]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|W|$]]

<blockquote>
 Or can I say if a row has 5 columns, and field is the first column, then field+4 is the last column field
</blockquote>

Yes, but, you can say that

<blockquote>
 and field+5 is the end of the column which means null
</blockquote>

only if you initialized the array to be null-terminated.

And if you know how many columns your table has, you can iterate until you reach the last column instead of <code>; *field ;</code>.

For the following example (from mysql source code), it uses Field **field. I am in trouble to think it as a 2 dimension array of Field.

<pre><code>typedef struct st_table_share 
{ 
 ....... 
 Field **field; 
 .... 
} 

for (Field **field=table-&gt;field ; *field ; field++) 
{ 
 ... 
</code></pre>

Can I think it in this way, a table contains many rows and a row contains multiple columns/fields. So *field means a row, and **field mean a table? 

If that's true, for the following code

<pre><code>for (Field **field=table-&gt;field ; *field ; field++)
</code></pre>

it will exit when *field is null, so how could *field be null if *field is a row. Or can I say if a row has 5 columns, and field is the first column, then field+4 is the last column field, and field+5 is the end of the column which means null, so that the for loop will exit?

double pointer in loop

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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对于下面的示例(来自mysql源代码)，它使用Field **field。我很难把它想成一个二维数组的Field。typedef struct st_table_share  {    .......    Field **field;             ....  }  for (Field **field=t...

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