Re: dmd Regression(?): bigEndianToNative buffer slice allows only literals
I reported this as a regression https://issues.dlang.org/show_bug.cgi?id=14582
dmd Regression(?): bigEndianToNative buffer slice allows only literals
The std.batmanip bigEndianToNative has a regression where the
slice range doesn't work with variables (only literals).
Is the syntax incorrect or is this a regression in dmd?
Using this main.d:
import std.bitmanip;
int main(string args[])
{
auto datain = new ubyte[16];
// this syntax works
ushort descriptorLength =
bigEndianToNative!ushort(datain[2..4]);
// this syntax fails (worked in previous version)
int offset = 2;
descriptorLength = bigEndianToNative!ushort(cast(ubyte[2])
datain[offset..offset+2]);
return 0;
}
I get this error on the command line:
main.d(14): Error: cannot cast expression
datain[cast(uint)offset..cast(uint)(offset + 2)] of type ubyte[]
to ubyte[2]
Re: bitmanip bigEndianToNative using a buffer slice?
On Wednesday, 22 October 2014 at 01:08:52 UTC, ketmar via Digitalmars-d-learn wrote: the short answer: uint fromBuf = bigEndianToNative!uint(cast(ubyte[4])buffer[offset..offset+4]); ketmar, we meet again! Your explanation is great and that solved my problem. Thank you. Maybe I'll try out templates next...
bitmanip bigEndianToNative using a buffer slice?
I'm trying to create a primitive type given a specific buffer
slice. I can place the uint into a sliced buffer but I'm getting
compiler errors when using a slice to create the uint. Still new
to Dlang and unfamiliar with the template system.
How do I get this working?
import std.bitmanip;
int main()
{
size_t offset = 3;
ubyte[10] buffer;
buffer[offset..offset+4] = nativeToBigEndian!uint(cast(uint)
104387);
// compiler error
uint fromBuf =
bigEndianToNative!uint(buffer[offset..offset+4]);
return 0;
}
The compiler error:
./test.d(11): Error: template std.bitmanip.bigEndianToNative does
not match any function template declaration. Candidates are:
/usr/include/dmd/phobos/std/bitmanip.d(1689):
std.bitmanip.bigEndianToNative(T, ulong n)(ubyte[n] val) if
(canSwapEndianness!(T) && n == T.sizeof)
./test.d(11): Error: template std.bitmanip.bigEndianToNative(T,
ulong n)(ubyte[n] val) if (canSwapEndianness!(T) && n ==
T.sizeof) cannot deduce template function from argument types
!(uint)(ubyte[])
./test.d(11): Error: template instance bigEndianToNative!(uint)
errors instantiating template
Re: String created from buffer has wrong length and strip() result is incorrect
On Saturday, 18 October 2014 at 00:53:57 UTC, ketmar via Digitalmars-d-learn wrote: On Sat, 18 Oct 2014 00:32:09 + Lucas Burson via Digitalmars-d-learn wrote: Wow, your changes made it much simpler. Thank you for the suggestions and expertise ketmar :)
Re: String created from buffer has wrong length and strip() result is incorrect
On Friday, 17 October 2014 at 17:40:09 UTC, ketmar via
Digitalmars-d-learn wrote:
i developed a habit of making such buffers one byte bigger than
necessary and just setting the last byte to 0 before
converting. this
way it's guaranteed to be 0-terminated.
Perfect, great idea. Below is my utility method to pull strings
out of a buffer.
/**
* Get a string from buffer where the string spans [offset_start,
offset_end).
* Params:
*buffer = Buffer with an ASCII string to obtain.
*offset_start = Beginning byte offset within the buffer
where the string starts.
*offset_end = Ending byte offset which is not included in
the string.
*/
string bufferGetString(ubyte[] buffer, ulong offset_start, ulong
offset_end)
in
{
assert(buffer != null);
assert(offset_start < offset_end);
assert(offset_end <= buffer.length);
}
body
{
ulong bufflen = offset_end - offset_start;
// add one to the lenth for null-termination
ubyte[] temp = new ubyte[bufflen+1];
temp[0..bufflen] = buffer[offset_start..offset_end];
temp[bufflen] = '\0';
return strip(to!string(cast(const char*) temp.ptr));
}
unittest
{
ubyte[] no_null = [' ', 'A', 'B', 'C', ' '];
assert("ABC" == bufferGetString(no_null, 0, no_null.length));
assert("ABC" == bufferGetString(no_null, 1, no_null.length-1));
assert("A" == bufferGetString(no_null, 1, 2));
}
Re: String created from buffer has wrong length and strip() result is incorrect
On Friday, 17 October 2014 at 15:30:52 UTC, ketmar via Digitalmars-d-learn wrote: On Fri, 17 Oct 2014 15:24:21 + Lucas Burson via Digitalmars-d-learn wrote: So given the below buffer would I use fromStringz (is this in the stdlib?) to cast it from a null-terminated buffer to a good string? Shouldn't the compiler give a warning about casting a buffer to a string without using fromStringz? if you are really-really sure that your buffer is null-terminated, you can use this trick: import std.conv; string s = to!string(cast(char*)buff.ptr); please note, that this is NOT SAFE. you'd better doublecheck that your buffer is not empty and is null-terminated. The buffer is populated from a scsi ioctl so it "should" be only ascii and null-terminated but it's a good idea to harden the code a bit. Thank you for your help!
Re: String created from buffer has wrong length and strip() result is incorrect
On Friday, 17 October 2014 at 08:31:04 UTC, spir via
Digitalmars-d-learn wrote:
On 17/10/14 09:29, thedeemon via Digitalmars-d-learn wrote:
On Friday, 17 October 2014 at 06:29:24 UTC, Lucas Burson wrote:
// This is where things breaks
{
ubyte[] buff = new ubyte[16];
buff[0..ATA_STR.length] = cast(ubyte[])(ATA_STR);
// read the string back from the buffer, stripping
whitespace
string stringFromBuffer =
strip(cast(string)(buff[0..16]));
// this shows strip() doesn't remove all whitespace
writefln("StrFromBuff is '%s'; length %d",
stringFromBuffer,
stringFromBuffer.length);
// !! FAILS. stringFromBuffer is length 15, not 3.
assert(stringFromBuffer.length == strip(ATA_STR).length);
Unlike C, strings in D are not zero-terminated by default,
they are just arrays,
i.e. a pair of pointer and size. You create an array of 16
bytes and cast it to
string, now you have a 16-chars string. You fill first few
chars with data from
ATA_STR but the rest 10 bytes of the array are still part of
the string, not
initialized with data, so having zeroes. Since this tail of
zeroes is not
whitespace (tabs or spaces etc.) 'strip' doesn't remove it.
Side-note: since your string has those zeroes at the end, strip
only removes the space at start (thus, final size=15), instead
of at both ends.
d
Okay things are becoming more clear. The cast to string is
nothing like the C++ string ctor, I made a bad assumption.
So given the below buffer would I use fromStringz (is this in the
stdlib?) to cast it from a null-terminated buffer to a good
string? Shouldn't the compiler give a warning about casting a
buffer to a string without using fromStringz?
Buffer = [ 0x20, 0x41, 0x54, 0x41, 0x20, 0x00, 0x00, ...]?
String created from buffer has wrong length and strip() result is incorrect
When creating a string from a ubyte[], I have an invalid length
and string.strip() doesn't strip off all whitespace. I'm new to
the language. Is this a compiler issue?
import std.string : strip;
import std.stdio : writefln;
int main()
{
const string ATA_STR = " ATA ";
// this works fine
{
ubyte[] buffer = [' ', 'A', 'T', 'A', ' ' ];
string test = strip(cast(string)(buffer));
assert(test == strip(ATA_STR));
}
// This is where things breaks
{
ubyte[] buff = new ubyte[16];
buff[0..ATA_STR.length] = cast(ubyte[])(ATA_STR);
// read the string back from the buffer, stripping
whitespace
string stringFromBuffer = strip(cast(string)(buff[0..16]));
// this shows strip() doesn't remove all whitespace
writefln("StrFromBuff is '%s'; length %d",
stringFromBuffer, stringFromBuffer.length);
// !! FAILS. stringFromBuffer is length 15, not 3.
assert(stringFromBuffer.length == strip(ATA_STR).length);
}
return 0;
}
