gb-emu: initial commit

Add a mostly non-functional Gameboy CPU and the skeleton
of a Gameboy assembler intended for unit tests.

src/gbasm/assemble.c

@@ -0,0 +1,39 @@
+#include <stdlib.h>
+
+#include "gbasm/assemble.h"
+#include "gbasm/parser.h"
+#include "gbasm/types.h"
+#include "gbasm/errors.h"
+#include "gbasm/opcodes.h"
+#include "common.h"
+
+#define GBASM_MAX_INSTS 1024
+
+struct gb_asm_prog *prog;
+
+int gbasm_assemble(char *program, struct emitter *emitter)
+{
+	struct gbasm_parsed_inst insts[GBASM_MAX_INSTS];
+	int num_insts;
+
+	num_insts = gbasm_parse_buffer(program, insts, ARRAY_SIZE(insts));
+	if (num_insts < 0) {
+		return num_insts;
+	}
+
+	DEBUG_LOG("parsed %d instructions\n", num_insts);
+	
+	for (int i = 0; i < num_insts; i++) {
+		DEBUG_LOG("emitting %s\n", insts[i].opcode);
+		const struct gbasm_op_info *info = gbasm_get_opcode_info(insts[i].opcode);
+		if (info == NULL) {
+			gbasm_unknown_opcode_error(&insts[i]);
+		}
+		
+		info->check(&insts[i], info);
+		info->emit(emitter, &insts[i]);
+	}
+	
+	return 0;
+}
+