string literal adress question

[Frankolinox]

lalala

[Charles Pegge]

In Basic and Asm:

Code: [Select]


function Reverse(string s) as string
string t=s
sys le=len t
for i=1 to le
mid t,i,mid s,le-i+1
next
return t
end function

print reverse "abcdefghijklmnopqrstuvwxyz"

function Reverse(string s) as string
string t=s
sys le=len t
addr edi,t
addr esi,s
mov ecx,le
dec ecx
(
 mov al,[esi]
 mov [edi+ecx],al
 inc esi
 dec ecx
 jge repeat
)
return t
end function


print reverse "abcdefghijklmnopqrstuvwxyz"

And another using byte pointers:

Code: [Select]

function Reverse(string s) as string
string t=s
sys le=len t
byte a at (strptr s)
byte b at (le-1+strptr t)
for i=1 to le
b=a : @b-- : @a++
next
return t
end function

print reverse "abcdefghijklmnopqrstuvwxyz"



[Charles Pegge]

Hi Frank, If you mean translation from string to integer, and integer to string:

string to sys

string s="abcd"
sys     a
a="0x"+s 'auto-conversion val()
print hex a

and back to string again:

s=hex a
print s

[Charles Pegge]

Will this do?

Code: [Select]

'Reading String as array of integers

string s="Oxygen"

long a at (strptr s)

print hex(a[1],8)+"    "+hex(a[2],8)

'Reading array of integers as string

zstring z at (@a)

print z



[Aurel]

Situation will be much better if we can use cast
something like this:

string s="promo"
sys p = *<string>s
print p

ahhh whishes

Hmm Charles
I still don't understand real purpose of this at

[Charles Pegge]

Recent Oxygen releases also support the equivalent C-like syntax:

long*a=strptr s

Code: [Select]

'Reading String as array of integers

string s="Oxygen"

long*a=strptr s

print hex(a[1],8)+"    "+hex(a[2],8)

'Reading array of integers as string

zstring*z=@a

print z


[Aurel]

Hmm yes it looks that only solution is zstring *z

Charles
What Free Basic have ...i think something like reinterpret_cast or
something like that?

Is C way *<type>p correct  ?
because  i am not sure , and i can agree that syntax is little bit strange ...
what you think ?

[Charles Pegge]

You can cast with round '()' brackets, but it is not necessary to cast here. Oxygen accepts any expression for a pointer in this kind of definition.

[Aurel]

Cast with brackets ?
How?

[Charles Pegge]

Integers reverse the order of the 4 ascii codes: thus you will see a reversal in their hex values:

This is due to the x86 processor taking the 1st byte of an integer as being the lowest. This behaviour of the Processor is often termed:  little-endian

"abcdefgh" --->

int 1 = 0x68676665 'dcba'
int 2 = 0x6C6B6A69 'hgfe'

You could look at the string as an array of bytes, instead of an array of 32bit integers. It is less confusing, and you will not be troubled by these order effects.

Code: [Select]

s="Oxygen"
byte a at (strptr s)
print hex(a[1],2)+" "+hex(a[2],2)+" "+
     +hex(a[3],2)+" "+hex(a[4],2)+" "+
     +hex(a[5],2)+" "+hex(a[6],2)+" "


[Emil_halim]

Hi Charles,

i see that

long*a=strptr s

is the same as

long a at (strptr s)

am i wright ?

if so we need some doc that shade some light on Oxygen basic , it has may goodies but need to be clear in help file.