Implement CHARVAL function (#1701)

src/asm/charmap.cpp

@@ -189,7 +189,7 @@ bool charmap_HasChar(std::string const &mapping) {
 	return charmap.nodes[nodeIdx].isTerminal();
 }
 
-size_t charmap_CharSize(std::string const &mapping) {
+static CharmapNode const *charmapEntry(std::string const &mapping) {
 	Charmap const &charmap = *currentCharmap;
 	size_t nodeIdx = 0;
 
@@ -197,12 +197,24 @@ size_t charmap_CharSize(std::string const &mapping) {
 		nodeIdx = charmap.nodes[nodeIdx].next[static_cast<uint8_t>(c)];
 
 		if (!nodeIdx) {
-			return 0;
+			return nullptr;
 		}
 	}
 
-	CharmapNode const &node = charmap.nodes[nodeIdx];
-	return node.isTerminal() ? node.value.size() : 0;
+	return &charmap.nodes[nodeIdx];
+}
+
+size_t charmap_CharSize(std::string const &mapping) {
+	CharmapNode const *node = charmapEntry(mapping);
+	return node && node->isTerminal() ? node->value.size() : 0;
+}
+
+std::optional<int32_t> charmap_CharValue(std::string const &mapping, size_t idx) {
+	if (CharmapNode const *node = charmapEntry(mapping);
+	    node && node->isTerminal() && idx < node->value.size()) {
+		return node->value[idx];
+	}
+	return std::nullopt;
 }
 
 std::vector<int32_t> charmap_Convert(std::string const &input) {

src/asm/lexer.cpp

@@ -259,6 +259,7 @@ static std::unordered_map<std::string, int, CaseInsensitive, CaseInsensitive> ke
     {"CHARLEN",       T_(OP_CHARLEN)       },
     {"CHARSIZE",      T_(OP_CHARSIZE)      },
     {"CHARSUB",       T_(OP_CHARSUB)       },
+    {"CHARVAL",       T_(OP_CHARVAL)       },
     {"INCHARMAP",     T_(OP_INCHARMAP)     },
     {"REVCHAR",       T_(OP_REVCHAR)       },
 

src/asm/parser.y

@@ -287,6 +287,7 @@
 %token OP_CHARLEN "CHARLEN"
 %token OP_CHARSIZE "CHARSIZE"
 %token OP_CHARSUB "CHARSUB"
+%token OP_CHARVAL "CHARVAL"
 %token OP_COS "COS"
 %token OP_DEF "DEF"
 %token OP_FDIV "FDIV"
@@ -1580,6 +1581,24 @@ relocexpr_no_str:
 		}
 		$$.makeNumber(charSize);
 	}
+	| OP_CHARVAL LPAREN string COMMA iconst RPAREN {
+		if (size_t len = charmap_CharSize($3); len != 0) {
+			uint32_t idx = adjustNegativeIndex($5, len, "CHARVAL");
+			if (std::optional<int32_t> val = charmap_CharValue($3, idx); val.has_value()) {
+				$$.makeNumber(*val);
+			} else {
+				warning(
+				    WARNING_BUILTIN_ARG,
+				    "CHARVAL: Index %" PRIu32 " is past the end of the character mapping\n",
+				    idx
+				);
+				$$.makeNumber(0);
+			}
+		} else {
+			::error("CHARVAL: No character mapping for \"%s\"\n", $3.c_str());
+			$$.makeNumber(0);
+		}
+	}
 	| LPAREN relocexpr RPAREN {
 		$$ = std::move($2);
 	}