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77 lines
2.9 KiB
OpenEdge ABL
77 lines
2.9 KiB
OpenEdge ABL
[DefaultValueInstruction::] The DefaultValue Construct.
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Defining the defaultvalue construct.
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@h Definition.
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For what this does and why it is used, see //inter: Textual Inter//.
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=
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void DefaultValueInstruction::define_construct(void) {
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inter_construct *IC = InterInstruction::create_construct(DEFAULTVALUE_IST, I"defaultvalue");
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InterInstruction::specify_syntax(IC, I"defaultvalue TOKEN = TOKENS");
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InterInstruction::fix_instruction_length_between(IC, 5, 5);
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InterInstruction::permit(IC, INSIDE_PLAIN_PACKAGE_ICUP);
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METHOD_ADD(IC, CONSTRUCT_READ_MTID, DefaultValueInstruction::read);
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METHOD_ADD(IC, CONSTRUCT_VERIFY_MTID, DefaultValueInstruction::verify);
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METHOD_ADD(IC, CONSTRUCT_WRITE_MTID, DefaultValueInstruction::write);
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}
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@h Instructions.
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In bytecode, the frame of an |defaultvalue| instruction is laid out with the two
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compulsory words |ID_IFLD| and |LEVEL_IFLD|, followed by:
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@d TYPE_DEF_IFLD 2
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@d VAL1_DEF_IFLD 3
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@d VAL2_DEF_IFLD 4
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=
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inter_error_message *DefaultValueInstruction::new(inter_bookmark *IBM,
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inter_symbol *typename, inter_pair val, inter_ti level, inter_error_location *eloc) {
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inter_tree_node *P = Inode::new_with_3_data_fields(IBM, DEFAULTVALUE_IST,
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/* TYPE_DEF_IFLD: */ InterSymbolsTable::id_at_bookmark(IBM, typename),
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/* VAL1_DEF_IFLD: */ InterValuePairs::to_word1(val),
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/* VAL2_DEF_IFLD: */ InterValuePairs::to_word2(val),
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eloc, level);
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inter_error_message *E = VerifyingInter::instruction(InterBookmark::package(IBM), P);
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if (E) return E;
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NodePlacement::move_to_moving_bookmark(P, IBM);
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return NULL;
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}
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@ Verification consists only of sanity checks. Note that the |TYPE_DEF_IFLD|
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field must contain a valid symbol ID -- of a |typename| -- and cannot be a more
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general TID. So you cannot have an instruction setting the default value of,
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say, |int32|.
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=
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void DefaultValueInstruction::verify(inter_construct *IC, inter_tree_node *P,
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inter_package *owner, inter_error_message **E) {
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*E = VerifyingInter::SID_field(owner, P, TYPE_DEF_IFLD, TYPENAME_IST);
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}
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@h Creating from textual Inter syntax.
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=
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void DefaultValueInstruction::read(inter_construct *IC, inter_bookmark *IBM,
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inter_line_parse *ilp, inter_error_location *eloc, inter_error_message **E) {
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inter_symbol *typename =
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TextualInter::find_symbol(IBM, eloc, ilp->mr.exp[0], TYPENAME_IST, E);
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if (*E) return;
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inter_pair val = InterValuePairs::undef();
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*E = TextualInter::parse_pair(ilp->line, eloc, IBM, InterTypes::from_type_name(typename),
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ilp->mr.exp[1], &val);
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if (*E) return;
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*E = DefaultValueInstruction::new(IBM, typename, val, (inter_ti) ilp->indent_level, eloc);
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}
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@h Writing to textual Inter syntax.
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=
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void DefaultValueInstruction::write(inter_construct *IC, OUTPUT_STREAM, inter_tree_node *P) {
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inter_symbol *typename = InterSymbolsTable::symbol_from_ID_at_node(P, TYPE_DEF_IFLD);
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WRITE("defaultvalue %S = ", InterSymbol::identifier(typename));
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TextualInter::write_pair(OUT, P, InterValuePairs::get(P, VAL1_DEF_IFLD), FALSE);
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}
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