25.6.htm

This ECMA Standard specifies the form and establishes the interpretation of programs written in the

using System;  
class Test  
{  
   static void Main() {  
      int[,,] a = new int[2,3,4];  
      unsafe {  
         fixed (int* p = a) {  
            for (int i = 0; i < a.Length; ++i)  // treat as linear  
            p[i] = i;  
         }  
      }  
      
      for (int i = 0; i < 2; ++i)  
      for (int j = 0; j < 3; ++j) {  
         for (int k = 0; k < 4; ++k)  
         Console.Write("[{0},{1},{2}] = {3,2} ", i, j, k,  
         a[i,j,k]);  
         Console.WriteLine();  
      }  
   }  
}  
</pre>which produces the output: <pre class="code-example">
[0,0,0] =  0 [0,0,1] =  1 [0,0,2] =  2 [0,0,3] =  3  
[0,1,0] =  4 [0,1,1] =  5 [0,1,2] =  6 [0,1,3] =  7  
[0,2,0] =  8 [0,2,1] =  9 [0,2,2] = 10 [0,2,3] = 11  
[1,0,0] = 12 [1,0,1] = 13 [1,0,2] = 14 [1,0,3] = 15  
[1,1,0] = 16 [1,1,1] = 17 [1,1,2] = 18 [1,1,3] = 19  
[1,2,0] = 20 [1,2,1] = 21 [1,2,2] = 22 [1,2,3] = 23  
</pre>end example]</span> </span><span class="paragraph"><span class="example">[Example: In the example <pre class="code-example">
class Test  
{  
   unsafe static void Fill(int* p, int count, int value) {  
      for (; count != 0; count--) *p++ = value;  
   }  
   static void Main() {  
      int[] a = new int[100];  
      unsafe {  
         fixed (int* p = a) Fill(p, 100, -1);  
      }  
   }  
}  
</pre>a fixed statement is used to fix an array so its address can be passed to a method that takes a pointer. end example]</span> </span><span class="locator">
     Paragraph 9</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P9S1"></a>A char* value produced by fixing a string instance always points to a null-terminated string.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P9S2"></a>Within a fixed statement that obtains a pointer p to a string instance s, the pointer values ranging from p to p + s.Length  -1 represent addresses of the characters in the string, and the pointer value p + s.Length always points to a null character (the character with value '\0').</span> </span><span class="locator">
     Paragraph 10</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P10S1"></a>Modifying objects of managed type through fixed pointers can result in undefined behavior.</span> <span class="note">[Note: For example, because strings are immutable, it is the programmer's responsibility to ensure that the characters referenced by a pointer to a fixed string are not modified. end note]</span> </span><span class="paragraph"><span class="note">[Note: The automatic null-termination of strings is particularly convenient when calling external APIs that expect "C-style" strings. Note, however, that a string instance is permitted to contain null characters. If such null characters are present, the string will appear truncated when treated as a null-terminated char*. end note]</span> </span><span class="ruler"></span><table><tr><td><table align="left" bgcolor="navy"><tr bgcolor="navy"><td><font face="Arial,sans-serif" size="6" color="yellow"><strong>{ JSL }</strong></font></td></tr></table></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Jagger Software Ltd</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Company # 4070126</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>VAT # 762 5213 42</strong></font></td></tr></table><img src="valid-html401.png" align="left" height="31" width="88" alt="Valid HTML 4.01" /><img src="vcss.gif" align="left" height="31" width="88" alt="Valid CSS" /></body></html>