1 /** 2 * Implementation of array cast support routines. 3 * 4 * Copyright: Copyright Digital Mars 2004 - 2016. 5 * License: Distributed under the 6 * $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost Software License 1.0). 7 * Authors: Walter Bright, Sean Kelly 8 * Source: $(DRUNTIMESRC src/rt/_arraycast.d) 9 */ 10 11 module rt.arraycast; 12 13 /****************************************** 14 * Runtime helper to convert dynamic array of one 15 * type to dynamic array of another. 16 * Adjusts the length of the array. 17 * Throws an error if new length is not aligned. 18 */ 19 20 extern (C) 21 22 @trusted nothrow _d_arraycast(size_t tsize,size_t fsize,void[]a)23void[] _d_arraycast(size_t tsize, size_t fsize, void[] a) 24 { 25 auto length = a.length; 26 27 auto nbytes = length * fsize; 28 if (nbytes % tsize != 0) 29 { 30 throw new Error("array cast misalignment"); 31 } 32 length = nbytes / tsize; 33 *cast(size_t *)&a = length; // jam new length 34 return a; 35 } 36 37 unittest 38 { 39 byte[int.sizeof * 3] b; 40 int[] i; 41 short[] s; 42 43 i = cast(int[])b; 44 assert(i.length == 3); 45 46 s = cast(short[])b; 47 assert(s.length == 6); 48 49 s = cast(short[])i; 50 assert(s.length == 6); 51 } 52 53