mirror of https://github.com/nmlgc/ReC98.git
56 lines
2.0 KiB
PHP
56 lines
2.0 KiB
PHP
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; Reimplementation of TASM's ARG directive for those weirdly micro-optimized
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; ASM functions that keep their base pointer in BX. The ENTER instruction of
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; the original ARG directive is replaced with ´MOV BX, SP`. Afterwards, use
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; `ret_bx` to emit the correct `RET` instruction for the given number of
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; parameters.
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; [distance] must be either NEAR or FAR, matching the function this macro is
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; used in.
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;
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; [params] uses the same colon-separated `name:type` syntax as the original
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; ARG directive. Since all of those functions (thankfully) use the Pascal
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; calling convention, they need to be declared in reverse order, compared to
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; the C declaration.
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; Unfortunately, the names can't be prefixed with @@, as that would make them
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; local to the macro. Hacking around this with NOLOCALS, PUSHSTATE, and
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; POPSTATE would break local labels for the usage code. So, just use a single
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; @ instead... or a clean namespace.
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;
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; MODDERS: Replace with the regular ARG and RET directives in the usage code,
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; and delete this file.
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arg_bx macro distance:req, params:vararg
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; Expanding a text macro on the left side of `=` only seems to work in
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; QUIRKS mode?!
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PUSHSTATE
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QUIRKS
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@bp = ((-distance and 0FFFFh) * word)
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@sp = @bp
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for @@param, params
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@@colon_pos instr <@@param>, <:>
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@@name substr <@@param>, 1, (@@colon_pos - 1)
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@@type substr <@@param>, (@@colon_pos + 1)
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@@local_err substr <@@param>, 1, 2
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errifidn @@local_err, <@@> "arg_bx: @@ in parameter names is not supported"
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; % at the beginning of the line (!) forces expansion of the text
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; macro @@name... in QUIRKS mode.
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% @@name = @@type ptr ss:[bx+@sp]
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; The stack is word-aligned...
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@sp = (@sp + ((@@type + 1) and (not 1)))
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endm
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ret_bx macro
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ret (@sp - @bp)
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endm
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POPSTATE
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; This allows `ret_bx` to be used in functions with no parameters as well,
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; e.g. if parameters were removed between games. Simply don't pass any
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; [params], and this macro will turn itself to a no-op, with `ret_bx` not
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; clearing any parameters either.
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if (@sp ne @bp)
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mov bx, sp
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endif
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endm
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