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digitalmars.D.learn - How to cast arrays?

reply Murilo <murilomiranda92 hotmail.com> writes:
How do I cast a ubyte[] into uint[]? It keeps raising an error, I 
have read the documentation saying there are restrictions for 
that concerning the length of the arrays.
Mar 01
next sibling parent Matheus <m mail.com> writes:
On Saturday, 2 March 2019 at 02:14:01 UTC, Murilo wrote:
 How do I cast a ubyte[] into uint[]? It keeps raising an error, 
 I have read the documentation saying there are restrictions for 
 that concerning the length of the arrays.
https://dlang.org/spec/expression.html#cast_expressions "Casting a dynamic array to another dynamic array is done only if the array lengths multiplied by the element sizes match. The cast is done as a type paint, with the array length adjusted to match any change in element size. If there's not a match, a runtime error is generated." Matheus.
Mar 01
prev sibling next sibling parent "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Sat, Mar 02, 2019 at 02:14:01AM +0000, Murilo via Digitalmars-d-learn wrote:
 How do I cast a ubyte[] into uint[]? It keeps raising an error, I have
 read the documentation saying there are restrictions for that
 concerning the length of the arrays.
That depends on what you're trying to accomplish. Are you trying to *reinterpret* the ubytes as uints? I.e., every 4 ubytes will be interpreted as 1 uint? If so, cast(uint[]) is your ticket. And obviously it will require that the .length of the ubyte[] must be a multiple of uint.sizeof, since otherwise the last element would be malformed. And there will probably be alignment issues as well. However, if you're trying to *transcribe* ubyte values into uint, i.e., promote each ubyte value to uint, then what you want is NOT a cast, but a transcription, i.e., copy ubytes into uint with integer promotion. There are various ways of doing this; an obvious one is: ubyte[] bytes = ...; uint[] ints = bytes.map!(b => cast(uint) b).array; T -- Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald Knuth
Mar 01
prev sibling parent Matheus <m mail.com> writes:
On Saturday, 2 March 2019 at 02:14:01 UTC, Murilo wrote:
 How do I cast a ubyte[] into uint[]? It keeps raising an error, 
 I have read the documentation saying there are restrictions for 
 that concerning the length of the arrays.
By the way here is how: void foo(){ ubyte[] x = [1,2]; auto y = (cast(int*) &x)[0..2]; writeln(y); } Matheus.
Mar 01