Add dstringwriter.

lib/std/core/dstring.c3

@@ -360,7 +360,7 @@ fn StringData* DString.data(DString str) @inline @private
 	return (StringData*)str;
 }
 
-fn void DString.reserve(DString* str, usz addition) @private
+fn void DString.reserve(DString* str, usz addition)
 {
 	StringData* data = str.data();
 	if (!data)
@@ -375,6 +375,35 @@ fn void DString.reserve(DString* str, usz addition) @private
 	*str = (DString)realloc(data, StringData.sizeof + new_capacity, .using = data.allocator);
 }
 
+fn usz! DString.read_from_stream(DString* string, Stream* reader)
+{
+	if (reader.supports_available())
+	{
+		usz total_read = 0;
+		while (usz available = reader.available()?)
+		{
+			string.reserve(available);
+			StringData* data = string.data();
+			usz len = reader.read(data.chars[data.len..(data.capacity - 1)])?;
+			total_read += len;
+			data.len += len;
+		}
+		return total_read;
+	}
+	usz total_read = 0;
+	while (true)
+	{
+		// Reserve at least 16 bytes
+		string.reserve(16);
+		StringData* data = string.data();
+		// Read into the rest of the buffer
+		usz read = reader.read(data.chars[data.len..(data.capacity - 1)])?;
+		data.len += read;
+		// Ok, we reached the end.
+		if (read < 16) return total_read;
+		// Otherwise go another round
+	}
+}
 
 struct StringData @private
 {

lib/std/io/stream/dstringwriter.c3

@@ -0,0 +1,14 @@
+module std::io;
+
+fn Stream DString.as_stream(DString* dstring)
+{
+	return { .fns = &dstring_interface, .data = dstring };
+}
+
+StreamInterface dstring_interface = {
+	.destroy_fn = fn (s) => ((DString*)s.data).free(),
+	.len_fn = fn (s) => ((DString*)s.data).len(),
+	.write_fn = fn (s, char[] bytes) { ((DString*)s.data).append_chars((String)bytes); return bytes.len; },
+	.write_byte_fn = fn (s, char c) => ((DString*)s.data).append_char(c),
+	.read_stream_fn = fn (s, reader) => ((DString*)s.data).read_from_stream(reader),
+};

src/compiler/sema_expr.c

@@ -2607,21 +2607,21 @@ static inline bool sema_expr_analyse_slice(SemaContext *context, Expr *expr)
 	bool end_from_end = expr->subscript_expr.range.end_from_end;
 
 	// Check range
-	if (type->type_kind == TYPE_POINTER)
+	if (type->type_kind == TYPE_POINTER || type->type_kind == TYPE_FLEXIBLE_ARRAY)
 	{
 		if (start_from_end)
 		{
-			SEMA_ERROR(start, "Indexing from the end is not allowed for pointers.");
+			SEMA_ERROR(start, "Indexing from the end is not allowed for pointers or flexible array members.");
 			return false;
 		}
 		if (!end)
 		{
-			SEMA_ERROR(expr, "Omitting end index is not allowed for pointers.");
+			SEMA_ERROR(expr, "Omitting end index is not allowed for pointers or flexible array members.");
 			return false;
 		}
 		if (end && end_from_end)
 		{
-			SEMA_ERROR(end, "Indexing from the end is not allowed for pointers.");
+			SEMA_ERROR(end, "Indexing from the end is not allowed for pointers or flexible array members.");
 			return false;
 		}
 	}

test/unit/stdlib/io/dstringstream.c3

@@ -0,0 +1,17 @@
+module std::io @test;
+
+fn void! test_writing()
+{
+	DString foo;
+	foo.init();
+	Stream s = foo.as_stream();
+	s.write("hello")!!;
+	s.write_byte('-')!!;
+	s.write("what?")!!;
+	ByteReader r;
+	String test_str = "2134";
+	r.init(test_str);
+	s.read_from(&&r.as_stream())?;
+	String o = foo.str();
+	assert(o == "hello-what?2134");
+}