checkpoint

1 files changed, 157 insertions, 0 deletions

diff --git a/archived/old_sim8086/8086disassembler.c b/archived/old_sim8086/8086disassembler.c
new file mode 100644
index 0000000..91e1a59
--- /dev/null
+++ b/archived/old_sim8086/8086disassembler.c
@@ -0,0 +1,157 @@
+/*
+	8086 asm disassembler
+    For now this assumes that instructions are two bytes long.
+*/
+
+#include <stdio.h>
+#include <string.h>
+
+#define     INSTRUCTION_MASK   0b11111100
+#define     D_MASK             (1 << 1)
+#define     W_MASK             1
+#define     REG_MASK           0b00111000
+#define     MOD_MASK           0b00000111
+#define     INSTRUCTION_MOV    0b10001000
+
+void print_reg(unsigned char reg, int wide_flag);
+
+int main(int argc, char **argv)
+{
+	FILE *file;
+	char *filename = argv[1];
+
+	if (argc < 2)
+	{
+		printf("No argument provided.\n");
+		return 1;
+	}
+	
+	file = fopen(filename ,"rb");
+	
+	if (file == NULL)
+	{
+		printf("File, %s not found.\n", filename);
+		return 1;
+	}
+	
+	char file_byte;
+	unsigned char reg, mod, c;
+
+	/* flags */
+	int is_reg_destination = 0;
+	int is_wide_operation = 0;
+	char instruction[4];
+	
+	/* print useful header */
+	printf("; %s disassembly:\n", filename);
+	printf("bits 16\n");
+	
+
+	while ((file_byte = fgetc(file)) != EOF)
+	{
+		/* get the six first instruction bits */
+		c = file_byte & INSTRUCTION_MASK;
+		if (c == INSTRUCTION_MOV)
+			strcpy(instruction, "mov\0");
+		else
+			strcpy(instruction, "ERR\0");
+
+		/* check D bit */
+		/* NOTE: This shift could be defined to show that this is the D-mask */
+		c = file_byte & D_MASK;
+		is_reg_destination = c ? 1 : 0;
+
+		/* check W bit */
+		c = file_byte & 1;
+		is_wide_operation = c ? 1 : 0;
+
+		file_byte = fgetc(file);
+
+		/* get REG */
+		c = file_byte & REG_MASK;
+		reg = c >> 3;
+
+		/* get R/M */
+		c = file_byte & MOD_MASK;
+		mod = c;
+
+		/* print the decoded instructions */
+		printf("%s ", instruction);
+
+		/* print operands */
+		if (is_reg_destination)
+			print_reg(reg, is_wide_operation);
+		else
+			print_reg(mod, is_wide_operation);
+		printf(", ");
+		if (is_reg_destination)
+			print_reg(mod, is_wide_operation);
+		else
+			print_reg(reg, is_wide_operation);
+
+		printf("\n");
+	}
+
+	fclose(file);
+	
+	return 0;
+}
+
+void print_reg(unsigned char reg, int wide_flag)
+{
+	switch (reg)
+	{
+		case 0b000:
+			if (wide_flag)
+				printf("ax");
+			else
+				printf("al");
+			break;
+		case 0b001:
+			if (wide_flag)
+				printf("cx");
+			else
+				printf("cl");
+			break;
+		case 0b010:
+			if (wide_flag)
+				printf("dx");
+			else
+				printf("dl");
+			break;
+		case 0b011:
+			if (wide_flag)
+				printf("bx");
+			else
+				printf("bl");
+			break;
+		case 0b100:
+			if (wide_flag)
+				printf("sp");
+			else
+				printf("ah");
+			break;
+		case 0b101:
+			if (wide_flag)
+				printf("bp");
+			else
+				printf("ch");
+			break;
+		case 0b110:
+			if (wide_flag)
+				printf("si");
+			else
+				printf("dh");
+			break;
+		case 0b111:
+			if (wide_flag)
+				printf("di");
+			else
+				printf("dh");
+			break;
+		default:
+			/* unknown register */
+			printf("ER");
+			break;
+	}
+}
\ No newline at end of file