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| amiga:development_environments:basic:amos_professional:extension_development [2024/02/23 07:26] – Topaz | amiga:development_environments:basic:amos_professional:extension_development [2024/03/18 21:15] (current) – Topaz | ||
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| When you want to demand string space, you apply for it with `L_Demande`. | When you want to demand string space, you apply for it with `L_Demande`. | ||
| - | The requested length goes into D3. It does not have to be even. You get the base address in both A0 and A1. | + | The requested length goes into D3. It has to be even. You get the base address in both A0 and A1. |
| This is an AMOS string, so the first two bytes are the size of the string as a word. Then the string comes after. | This is an AMOS string, so the first two bytes are the size of the string as a word. Then the string comes after. | ||
| - | Then, you have to eventually hand `HiChaine(A5)` (be sure to preserve A5) the ending address of the string, rounded up to the nearest 2. I'm guessing you're now setting the end of the string area in memory manually. | + | Then, you have to eventually hand `HiChaine(A5)` (be sure to preserve A5) the ending address of the string. |
| Make sure you don't try to allocate a zero width string with this! It will fail hard. | Make sure you don't try to allocate a zero width string with this! It will fail hard. | ||
| Line 103: | Line 103: | ||
| moveq # | moveq # | ||
| rts | rts | ||
| + | ``` | ||
| + | |||
| + | Here's a better version: | ||
| + | |||
| + | ```asm | ||
| + | ; D4 contains your string length | ||
| + | MOVE.L D4,D3 | ||
| + | AND.W #$FFFE,D3 | ||
| + | ADDQ #2,D3 ; round up to the nearest 2 | ||
| + | |||
| + | Rjsr L_Demande ; string is in A0/A1 | ||
| + | LEA 2(A0, | ||
| + | MOVE.L A1, | ||
| + | MOVE.L A0,A1 ; put A1 back | ||
| + | MOVE.W D4,(A0)+ ; put length of string at start of memory | ||
| + | .stringstuff | ||
| + | MOVE.B (A2)+,(A0)+ | ||
| + | BNE .stringstuff ; copy until null terminator | ||
| + | ``` | ||
| + | |||
| + | You know your string code is working if you can do this: | ||
| + | |||
| + | ```basic | ||
| + | A$=My String Function$ ' returns " | ||
| + | Print " | ||
| ``` | ``` | ||