Quote: Rainer Wrote:
<<A C string of length 0 is just a "\000". A NULL pointer is not a string.
A unallocated variable, be it anything from a simple basic variable
like an int*, to the most complex of struct variables, is simply a
placeholder for a memory address, or a pointer devoid of space, apart
from the space for a memory address.
Pointers can be any type of data. I used to put their flexibility in
my Delphi Pascal projects. I also used null pointers as follows:
type
TRecordTypeID = (message0, message1, message2, message3);
var
aDynamicRecord: Pointer;
type
TDynamicRecord = record
RecordTypeID: integer;
ActualRecord: Pointer;
end;
This is equivalent to:
enum TRecordTypeID = {message0, message1, message2, message3};
void* aDynamicRecord;
typedef struct TDynamicRecord {
TRecordTypeID RecordTypeID;
void* ActualRecord;
};
Lazarus and Delphi provide a class, TList, which is a list of untyped
pointers. This is like: C++'s
vector <void*> my_little_vector_that_can_hold_anything;
OR, if my memory serves me right, C's:
void** weirdo_var;
Therefore, to push variables onto the list, it requires type casting,
which is fully supported, and dynamic allocation functions to allocate
and FREE memory.
On 25/08/2015, Irrwahn <irrw...@freenet.de> wrote:
> On Tue, 25 Aug 2015 13:49:39 +0100, Rainer Weikusat wrote:
>> "tilt!" <t...@linuxfoo.de> writes:
>>> On 08/25/2015 02:09 PM, Rainer Weikusat wrote:
>>>> Considering that this enforces some kind of 'bastard URL-encoding'
>>>> (using + as prefix instead of %) for all other bytes, it's also going
>>>> make people who believe that UTF-8 would be a well supported way to
>>>> represent non-ASCII characters very unhappy.
>>>
>>> 1. This encoding is not about URLs but filenames.
>
> <snip>
>
>>> 2. It is not safe to assume that SSIDs contain UTF-8.
>>>
>>> The relevant IEEE standard is botched.
>>>
>>> https://en.wikipedia.org/wiki/Service_set_%28802.11_network%29
>>>
>>> "Note that the 2012 version of the 802.11 standard defines a
>>> primitive SSIDEncoding, an Enumeration of UNSPECIFIED and UTF-8,
>>> indicating how the array of octets can be interpreted."
>>>
>>> Imagining how many service sets still operate using the pre-2012
>>> standard (and/or are botched implementations themselves that fail
>>> to recognize the issue), i think it is safe to assume that the
>>> character encoding of an SSID is "UNSPECIFIED" in the general case.
>>>
>>> Therefore, it is handled encoding-agnostic on a byte-per-byte basis,
>>> and this is what the code accomplishes.
>>
>> The code replaces everything which is neither an ASCII letter nor a
>> digit nor - with a three byte escape sequence composed of + followed by
>> the hexadecimal representation of the byte value. This implies that it
>> will eliminate any use of non-ASCII letters both UTF-8 and otherwise.
>
> Since the encoding is solely used to construct names for configuration
> files (one per SSID), the only inconvenience I can think of is you might
> end up with completely unintelligible names for those files, and only in
> extreme cases. AIUI these files are not intended to be maintained by a user
> or administrator but rather only be created, manipulated or destroyed by
> the software.
>
> Unless you are manually debugging the software in an environment which is
> crowded with wireless stations "ééééé", "ééééá", "ééééç" and the like, you
> shouldn't worry too much about it. As a user, you shouldn't care at all -
> could as well use a sensible hashing algorithm, or some database, or black
> magic. Or just go with hex encoding from the get go, since an SSID is just
> a sequence of octets. "\x00\x00\x00\x00" (in C string literal notation)
> would make a perfectly fine SSID, composed of five (sic!) null bytes, but
> it is not a sensible code sequence in any character set I am aware of.
>
> It is totally sensible to break down the character set to something that
> is more or less guaranteed to be valid for building names in any file
> system currently in use on this planet. That having said, I'm not sure how
> the dash (minus) ended up in the allowed character set, as this would allow
> for names starting with '-', which is not something I would consider good
> style, but other's mileages may vary.
>
> As mentioned above: if there is any real issue with the code at all, it is
> the fact that null characters (zero bytes) are not handled correctly by the
> code. But that's a feat it has in common with many consumer WiFi appliance
> configuration utilities (and a pile of professional tools too, I suspect).
>
> --
> Irrwahn
>
>
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