1*627f7eb2Smrg /** 2*627f7eb2Smrg * Implementation of array cast support routines. 3*627f7eb2Smrg * 4*627f7eb2Smrg * Copyright: Copyright Digital Mars 2004 - 2016. 5*627f7eb2Smrg * License: Distributed under the 6*627f7eb2Smrg * $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost Software License 1.0). 7*627f7eb2Smrg * Authors: Walter Bright, Sean Kelly 8*627f7eb2Smrg * Source: $(DRUNTIMESRC src/rt/_arraycast.d) 9*627f7eb2Smrg */ 10*627f7eb2Smrg 11*627f7eb2Smrg module rt.arraycast; 12*627f7eb2Smrg 13*627f7eb2Smrg /****************************************** 14*627f7eb2Smrg * Runtime helper to convert dynamic array of one 15*627f7eb2Smrg * type to dynamic array of another. 16*627f7eb2Smrg * Adjusts the length of the array. 17*627f7eb2Smrg * Throws an error if new length is not aligned. 18*627f7eb2Smrg */ 19*627f7eb2Smrg 20*627f7eb2Smrg extern (C) 21*627f7eb2Smrg 22*627f7eb2Smrg @trusted nothrow _d_arraycast(size_t tsize,size_t fsize,void[]a)23*627f7eb2Smrgvoid[] _d_arraycast(size_t tsize, size_t fsize, void[] a) 24*627f7eb2Smrg { 25*627f7eb2Smrg auto length = a.length; 26*627f7eb2Smrg 27*627f7eb2Smrg auto nbytes = length * fsize; 28*627f7eb2Smrg if (nbytes % tsize != 0) 29*627f7eb2Smrg { 30*627f7eb2Smrg throw new Error("array cast misalignment"); 31*627f7eb2Smrg } 32*627f7eb2Smrg length = nbytes / tsize; 33*627f7eb2Smrg *cast(size_t *)&a = length; // jam new length 34*627f7eb2Smrg return a; 35*627f7eb2Smrg } 36*627f7eb2Smrg 37*627f7eb2Smrg unittest 38*627f7eb2Smrg { 39*627f7eb2Smrg byte[int.sizeof * 3] b; 40*627f7eb2Smrg int[] i; 41*627f7eb2Smrg short[] s; 42*627f7eb2Smrg 43*627f7eb2Smrg i = cast(int[])b; 44*627f7eb2Smrg assert(i.length == 3); 45*627f7eb2Smrg 46*627f7eb2Smrg s = cast(short[])b; 47*627f7eb2Smrg assert(s.length == 6); 48*627f7eb2Smrg 49*627f7eb2Smrg s = cast(short[])i; 50*627f7eb2Smrg assert(s.length == 6); 51*627f7eb2Smrg } 52*627f7eb2Smrg 53