[AssemblyInstruction::] The Assembly Construct.

Defining the assembly construct.

@h Definition.
For what this does and why it is used, see //inter: Textual Inter//.

=
void AssemblyInstruction::define_construct(void) {
	inter_construct *IC = InterInstruction::create_construct(ASSEMBLY_IST, I"assembly");
	InterInstruction::specify_syntax(IC, I"assembly TOKEN");
	InterInstruction::data_extent_always(IC, 1);
	InterInstruction::allow_in_depth_range(IC, 1, INFINITELY_DEEP);
	InterInstruction::permit(IC, INSIDE_CODE_PACKAGE_ICUP);
	METHOD_ADD(IC, CONSTRUCT_READ_MTID, AssemblyInstruction::read);
	METHOD_ADD(IC, CONSTRUCT_VERIFY_MTID, AssemblyInstruction::verify);
	METHOD_ADD(IC, CONSTRUCT_WRITE_MTID, AssemblyInstruction::write);
}

@h Instructions.
In bytecode, the frame of an |assembly| instruction is laid out with the
compulsory words -- see //Inter Nodes// -- followed by:

@d WHICH_ASSEMBLY_IFLD (DATA_IFLD + 0)

=
inter_error_message *AssemblyInstruction::new(inter_bookmark *IBM, inter_ti which,
	inter_ti level, inter_error_location *eloc) {
	inter_tree_node *P = Inode::new_with_1_data_field(IBM, ASSEMBLY_IST,
		/* WHICH_ASSEMBLY_IFLD: */ which,
		eloc, (inter_ti) level);
	inter_error_message *E = VerifyingInter::instruction(InterBookmark::package(IBM), P);
	if (E) return E;
	NodePlacement::move_to_moving_bookmark(P, IBM);
	return NULL;
}

@ Verification consists only of sanity checks. Note that |WHICH_ASSEMBLY_IFLD|
is required to be one of these:

@e ASM_ARROW_ASMMARKER from 1
@e ASM_SP_ASMMARKER
@e ASM_RTRUE_ASMMARKER
@e ASM_RFALSE_ASMMARKER
@e ASM_NEG_ASMMARKER
@e ASM_NEG_RTRUE_ASMMARKER
@e ASM_NEG_RFALSE_ASMMARKER

=
void AssemblyInstruction::verify(inter_construct *IC, inter_tree_node *P,
	inter_package *owner, inter_error_message **E) {
	inter_ti which = P->W.instruction[WHICH_ASSEMBLY_IFLD];
	if ((which == 0) || (which > ASM_NEG_RFALSE_ASMMARKER)) {
		*E = Inode::error(P, I"bad assembly marker code", NULL);
		return;
	}
}

@h Creating from textual Inter syntax.

=
void AssemblyInstruction::read(inter_construct *IC, inter_bookmark *IBM,
	inter_line_parse *ilp, inter_error_location *eloc, inter_error_message **E) {
	text_stream *marker_text = ilp->mr.exp[0];
	inter_ti which = 0;
	     if (Str::eq(marker_text, I"store_to"))              which = ASM_ARROW_ASMMARKER;
	else if (Str::eq(marker_text, I"stack"))                 which = ASM_SP_ASMMARKER;
	else if (Str::eq(marker_text, I"return_true_if_true"))   which = ASM_RTRUE_ASMMARKER;
	else if (Str::eq(marker_text, I"return_false_if_true"))  which = ASM_RFALSE_ASMMARKER;
	else if (Str::eq(marker_text, I"branch_if_false"))       which = ASM_NEG_ASMMARKER;
	else if (Str::eq(marker_text, I"return_true_if_false"))  which = ASM_NEG_RTRUE_ASMMARKER;
	else if (Str::eq(marker_text, I"return_false_if_false")) which = ASM_NEG_RFALSE_ASMMARKER;
	else { *E = InterErrors::plain(I"unrecognised 'assembly' marker", eloc); return; }

	*E = AssemblyInstruction::new(IBM, which, (inter_ti) ilp->indent_level, eloc);
}

@h Writing to textual Inter syntax.

=
void AssemblyInstruction::write(inter_construct *IC, OUTPUT_STREAM, inter_tree_node *P) {
	inter_ti which = AssemblyInstruction::which_marker(P);
	switch (which) {
		case ASM_ARROW_ASMMARKER:      WRITE("assembly store_to"); break;
		case ASM_SP_ASMMARKER:         WRITE("assembly stack"); break;
		case ASM_RTRUE_ASMMARKER:      WRITE("assembly return_true_if_true"); break;
		case ASM_RFALSE_ASMMARKER:     WRITE("assembly return_false_if_true"); break;
		case ASM_NEG_ASMMARKER:        WRITE("assembly branch_if_false"); break;
		case ASM_NEG_RTRUE_ASMMARKER:  WRITE("assembly return_true_if_false"); break;
		case ASM_NEG_RFALSE_ASMMARKER: WRITE("assembly return_false_if_false"); break;
	}
}

@h Access function.

=
inter_ti AssemblyInstruction::which_marker(inter_tree_node *P) {
	inter_ti which = P->W.instruction[WHICH_ASSEMBLY_IFLD];
	if ((which == 0) || (which > ASM_NEG_RFALSE_ASMMARKER))
		internal_error("bad assembly marker");
	return which;
}