From 49b70f0e1fdc79f8448c11b1f6b43cc3f2d41c9b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rados=C5=82aw=20Kujawa?= <radoslaw.kujawa@c0ff33.net>
Date: Thu, 19 Jan 2017 10:59:35 +0100
Subject: [PATCH] Make instruction data read more flexible and split from
 emulation of particular instruction.

---
 src/emulation.c   |  6 ++++-
 src/instruction.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++
 src/instruction.h |  1 +
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/src/emulation.c b/src/emulation.c
index c1bb55f..fc090e6 100644
--- a/src/emulation.c
+++ b/src/emulation.c
@@ -8,7 +8,11 @@ emul_lda(rk65c02emu_t *e, instruction_t *i)
 	instrdef_t id;
 	id = instruction_decode(i->opcode);
 
-	e->regs.A = i->op1;
+	e->regs.A = instruction_data_read_1(e, &id, i);
+
+
+	/* adjust status flags */
+
  
 }
 
diff --git a/src/instruction.c b/src/instruction.c
index b3f4849..d583de1 100644
--- a/src/instruction.c
+++ b/src/instruction.c
@@ -137,3 +137,62 @@ instruction_decode(uint8_t opcode)
 	return id;
 }
 
+uint8_t
+instruction_data_read_1(rk65c02emu_t *e, instrdef_t *id, instruction_t *i)
+{
+	uint8_t rv;	/* data read from the bus */
+//	uint8_t ziaddr; /* indirect zero page address */
+	uint16_t iaddr; /* indirect address */
+
+	rv = 0;
+
+	switch (id->mode) {
+	case ACCUMULATOR:
+		rv = e->regs.A;
+		break;
+	case IMMEDIATE:
+		rv = i->op1;
+		break;
+	case ZP:
+		rv = bus_read_1(e->bus, i->op1);
+		break;
+	case ZPX:
+		/* XXX: wraps around zero page? */
+		rv = bus_read_1(e->bus, i->op1 + e->regs.X);
+		break;
+	case ZPY:
+		rv = bus_read_1(e->bus, i->op1 + e->regs.Y);
+		break;
+	case IZP:
+		iaddr = bus_read_1(e->bus, i->op1);
+		iaddr |= (bus_read_1(e->bus, i->op1 + 1) << 8);
+		rv = bus_read_1(e->bus, iaddr);
+		break;
+	case IZPX:
+/*		ziaddr = bus_read_1(e->bus, i->op1 + e->regs.X);
+		ziaddr |= (bus_read_1(e->bus, i->op1 + e->regs.X + 1) << 8);
+		rv = bus_read_1(e->bus, ziaddr);
+		break;
+*/
+	case IZPY:
+/*
+		iaddr = bus_read_1(e->bus, i->op1 + e->regs.Y);
+		iaddr |= (bus_read_1(e->bus, i->op1 + e->regs.Y + 1) << 8);
+		rv = bus_read_1(e->bus, ziaddr);
+*/
+	case RELATIVE:
+	case ABSOLUTE:
+	case ABSOLUTEX:
+	case ABSOLUTEY:
+	case IABSOLUTE:
+	case IABSOLUTEX:
+
+	default:
+		printf("unhandled addressing mode for opcode %x\n",
+		    i->opcode);
+		break;
+	}
+
+	return rv;
+}
+
diff --git a/src/instruction.h b/src/instruction.h
index 3038820..4075cae 100644
--- a/src/instruction.h
+++ b/src/instruction.h
@@ -43,6 +43,7 @@ instruction_t instruction_fetch(bus_t *, uint16_t);
 instrdef_t instruction_decode(uint8_t);
 void instruction_print(instruction_t *);
 void disassemble(bus_t *, uint16_t);
+uint8_t instruction_data_read_1(rk65c02emu_t *, instrdef_t *, instruction_t *);
 //void instruction_execute(rk65c02emu_t *, instruction_t *);
 
 #endif /* _INSTRUCTION_H_ */