Concatenating strings?

[christopherpm]

It's been 20 years since I last wrote an Amiga program, but last week I came across some of my old source code. I typed the program in and compiled it, and as I was doing so, the memories came flooding back, and the code still made sense.

However, one thing I cannot for the life of me remember how to do is concatenate 2 or more text strings. Can anyone remind me?

[JonB]

Which language?

[christopherpm]

Sorry - assembler for 68000 using Devpac 3

[thomas]

Please define "string". Fixed-length string? C-style string with 0-byte at the end? BCPL-style string with length-byte in the beginning? Something else?

And how are the strings stored? Do you want to copy the second string to the end of the first string, given that the first string has enough free space behind it? Or do you want to copy both strings into a new buffer which is known to be large enough? Or do you want to allocate a new buffer and eventually free the two old buffers (given that they have been allocated earlier)?

If you want to free buffers, where did you store the size of the buffers?

[christopherpm]

I am saving the contents of a buffer to a file. I have a base filename, and I want to append the day and month (in numerical format) to the filename. Once my buffer has been written, I want to display a message which reads:-

Data saved to <filename>

At the moment, I have declared my filename as such:-

filename: dc.b "myfilename"

[thomas]

Why do you want to concatenate the strings? You can first write "Data save to " and then write filename.

[DrCinicus]

Originally Posted by christopherpm

I am saving the contents of a buffer to a file. I have a base filename, and I want to append the day and month (in numerical format) to the filename. Once my buffer has been written, I want to display a message which reads:-

Data saved to <filename>

At the moment, I have declared my filename as such:-

filename: dc.b "myfilename"

To append the date in a "fixed" format ddmm

AddDate:
    lea    day(pc),a2
    move.b    #'0',(a2)
    move.b    #'7',1(a2)
    lea    month(pc),a2
    move.b    #'0',(a2)
    move.b    #'7',1(a2)
    rts
    
Filename:
        dc.b    'myfilename'
day:    dc.b    'dd'
month:  dc.b    'mm'
        dc.b    0            ' NULL termination

The final filename will be "myfilename0707"

Bye
Fabio

[Photon]

Thomas is correct, usually strings are concatenated as they are being output to the destination, such as the shell window or a file. This also allows you to insert some good logic, conditionals and parsing in between output of "snippets", so it's more flexible and smart.

If you need a function for some reason, it's quite simple:

If a0-a2 points to string 1, string 2, and the concatenated result buffer, all 0-terminated, then a concatenation function can be written with loops: move.b (a0)+,(a2)+ until zero, then subq #1,a2, and move.b (a1)+,(a2)+ until zero.

[hooverphonique]

well, since he wants the concatenated parts in a filename, outputting bit by bit won't work, guys..

[christopherpm]

Thanks - I used Fabio's solution and it worked well for what I need.

[Photon]

Originally Posted by hooverphonique

well, since he wants the concatenated parts in a filename, outputting bit by bit won't work, guys..

Well, the original question was how to concatenate strings, and I did supply the correct pseudocode.

Originally Posted by christopherpm

Thanks - I used Fabio's solution and it worked well for what I need.

Great As per my generic concatenation example, it's a matter of declaring byte storage and just copying the character bytes.

(If you come from C, the address registers are used similarly to char* (byte array pointers).)