complete first homework

.gitignore

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+main.exe

.vscode/c_cpp_properties.json

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+{
+    "configurations": [
+        {
+            "name": "Win32",
+            "includePath": [
+                "${workspaceFolder}/**",
+                "C:/MinGW/include/**"
+            ],
+            "defines": [
+                "_DEBUG",
+                "UNICODE",
+                "_UNICODE"
+            ],
+            "windowsSdkVersion": "10.0.22000.0",
+            "compilerPath": "C:/MinGW/bin/gcc.exe",
+            "cStandard": "c17",
+            "cppStandard": "c++17",
+            "intelliSenseMode": "windows-gcc-x86",
+            "configurationProvider": "ms-vscode.makefile-tools"
+        }
+    ],
+    "version": 4
+}

.vscode/settings.json

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+{
+    "files.associations": {
+        "stdlib.h": "c",
+        "stdio.h": "c",
+        "os.h": "c",
+        "fcntl.h": "c",
+        "io.h": "c",
+        "errno.h": "c",
+        "stdbool.h": "c"
+    }
+}

Makefile

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+CC=gcc
+CFLAGS=-g -Wall
+INCLUDES=./include
+
+.DEFAULT_GOAL := main
+
+%: src/%.c
+	$(CC) -o $@ $< $(CFLAGS) -I$(INCLUDES)
+
+clean:
+	rm main.exe

examples/many_register_mov.asm

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+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 38
+; ========================================================================
+
+bits 16
+
+mov cx, bx
+mov ch, ah
+mov dx, bx
+mov si, bx
+mov bx, di
+mov al, cl
+mov ch, ch
+mov bx, ax
+mov bx, si
+mov sp, di
+mov bp, ax

examples/single_register_mov.asm

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+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 37
+; ========================================================================
+
+bits 16
+
+mov cx, bx

include/os.h

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+
+#if defined(_WIN32) || defined(_WIN64) || defined(__CYGWIN__)
+	#define IS_WINDOWS
+#elif defined(__linux__)
+	#define IS_LINUX
+#else
+	#error Unable to determine platform
+#endif
+
+#if defined(IS_LINUX)
+    #include <stdio.h>
+    #define MAX_PATH_SIZE PATH_MAX
+#elif defined(IS_WINDOWS)
+    #define MAX_PATH_SIZE 260
+#endif

src/cpu.c

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+#include <inttypes.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+#define u32 uint32_t
+#define u16 uint16_t
+#define u8  uint8_t
+
+struct cpu_state {
+    u16 ax, bx, cx, dx, sp, bp, si, di;
+};
+
+const char *lookup_reg_name(u8 idx, bool wide) {
+    if (wide) {
+        if        (idx == 0b000) {
+            return "ax";
+        } else if (idx == 0b001) {
+            return "cx";
+        } else if (idx == 0b010) {
+            return "dx";
+        } else if (idx == 0b011) {
+            return "bx";
+        } else if (idx == 0b100) {
+            return "sp";
+        } else if (idx == 0b101) {
+            return "bp";
+        } else if (idx == 0b110) {
+            return "si";
+        } else if (idx == 0b111) {
+            return "di";
+        }
+    } else {
+        if        (idx == 0b000) {
+            return "al";
+        } else if (idx == 0b001) {
+            return "cl";
+        } else if (idx == 0b010) {
+            return "dl";
+        } else if (idx == 0b011) {
+            return "bl";
+        } else if (idx == 0b100) {
+            return "ah";
+        } else if (idx == 0b101) {
+            return "ch";
+        } else if (idx == 0b110) {
+            return "dh";
+        } else if (idx == 0b111) {
+            return "bh";
+        }
+    }
+
+    printf("ERROR: Unknown register %d, wide %d", idx, wide);
+    abort();
+}
+
+void dissassemble(FILE *src, FILE *dst) {
+    fprintf(dst, "bits 16\n\n");
+    while (!feof(src)) {
+        u8 byte1 = fgetc(src);
+        u8 byte2 = fgetc(src);
+
+        if ((byte1 & 0b11111100) == 0b10001000) {
+            bool wide = byte1 & 0b1;
+            bool direction = (byte1 & 0b10) >> 1;
+
+            u8 mod =  byte2 & 0b11000000;
+            u8 reg = (byte2 & 0b00111000) >> 3;
+            u8 rm  =  byte2 & 0b00000111;
+            if (mod == 0b11000000) {
+                const char *reg_name = lookup_reg_name(reg, wide);
+                const char *rm_name  = lookup_reg_name(rm, wide);
+                if (direction) {
+                    fprintf(dst, "mov %s, %s\n", reg_name, rm_name);
+                } else {
+                    fprintf(dst, "mov %s, %s\n", rm_name, reg_name);
+                }
+            } else {
+                printf("ERROR: Unsupported mod '%d'", mod);
+                abort();
+            }
+        }
+    }
+}

src/main.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include "os.h"
+#include "cpu.c"
+#include <errno.h>
+
+const char *get_tmp_dir() {
+#ifdef IS_WINDOWS
+	char *dir;
+    if ((dir = getenv("TMPDIR")) != NULL) return dir;
+    if ((dir = getenv("TEMP"))   != NULL) return dir;
+    if ((dir = getenv("TMP"))    != NULL) return dir;
+	return NULL;
+#elif IS_LINUX
+	return "/tmp";
+#endif
+}
+
+void get_tmp_file(char *filename, const char *prefix) {
+	const char *dir = get_tmp_dir();
+	sprintf(filename, "%s\\%sXXXXXX", dir, prefix);
+	int fd = mkstemp(filename);
+	close(fd);
+}
+
+int main() {
+	char tmp_filename[MAX_PATH_SIZE];
+	get_tmp_file(tmp_filename, "nasm_output");
+
+	char *example_filename = "examples/many_register_mov.asm";
+
+	char command[512] = { 0 };
+	snprintf(command, sizeof(command), "nasm \"%s\" -o \"%s\"", example_filename, tmp_filename);
+	if (system(command)) {
+		printf("ERROR: Failed to compile '%s'", example_filename);
+		return -1;
+	}
+
+	FILE *assembly = fopen(tmp_filename, "r");
+	if (assembly == NULL) {
+		printf("ERROR: Opening file '%s': %d\n", tmp_filename, errno);
+		return -1;
+	}
+	dissassemble(assembly, stdout);
+	fclose(assembly);
+
+	remove(tmp_filename);
+
+	return 0;
+}