From e51de87fd226b1afbc6baa4a62234e4e885cf09a Mon Sep 17 00:00:00 2001
From: notsomeidiot123 <kiminosei321@gmail.com>
Date: Thu, 19 Sep 2024 12:04:32 -0400
Subject: [PATCH] Diskwrite typedefs for FAT32

---
 kernel.elf        |   1 +
 tools/diskwrite.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 111 insertions(+)
 create mode 100644 kernel.elf

diff --git a/kernel.elf b/kernel.elf
new file mode 100644
index 0000000..b45ef6f
--- /dev/null
+++ b/kernel.elf
@@ -0,0 +1 @@
+Hello, World!
\ No newline at end of file
diff --git a/tools/diskwrite.c b/tools/diskwrite.c
index 288dfa4..ab18306 100644
--- a/tools/diskwrite.c
+++ b/tools/diskwrite.c
@@ -1,10 +1,110 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdint.h>
+
+#define FILE_END    0xFFFFFFFF
+#define FILE_FREE   0x00000000
+
+typedef uint8_t *buffer_t;
+
+typedef struct{
+    uint8_t jmp[3];
+    char oem[8];
+    uint16_t bytes_per_sector;
+    uint8_t sectors_per_cluster;
+    uint16_t reserved_sectors;
+    uint8_t fat_count;
+    uint16_t root_dir_entries;
+    uint16_t sectors_in_volume_small;
+    uint8_t media_descriptor;
+    uint16_t sectors_per_fat_small;
+    uint16_t sectors_per_track;
+    uint16_t heads_per_volume;
+    uint32_t partition_start;
+    uint32_t large_sector_count;
+    
+    uint32_t sectors_per_fat;
+    uint16_t flags;
+    uint16_t fat_verno;
+    uint32_t root_dir_cluster;
+    uint16_t fsinfo_sector;
+    uint16_t backup_boot_sector;
+    uint8_t reserved[12];
+    uint8_t drive_no;
+    uint8_t nt_flags;
+    uint8_t sig;
+    uint32_t vol_uuid;
+    char volid[11];
+    char sysid[8];
+}__attribute__((packed))fat_bpb_t;
+
+typedef struct{
+    uint32_t lead_sig;
+    uint8_t reserved[480];
+    uint32_t sig0;
+    uint32_t last_free_cluster;
+    uint32_t cluster_search_start;
+    uint8_t reserved0[12];
+    uint32_t trail_sig;
+}fsinfo_t;
+
+typedef struct{
+    fat_bpb_t bpb;
+    fsinfo_t fsinfo;
+    uint32_t *file_table;
+}fat_info;
+
+int read_sector(FILE *file, uint32_t sector_start, uint32_t count, buffer_t buf){
+    int result = fseek(file, sector_start * 512, SEEK_SET);
+    if(result){
+        return result;
+    }
+    fflush(stdout);
+    memset(buf, 0, count * 512);
+    result = fread(buf, 512, count, file);
+    return result;
+}
+
+int write_sector(FILE *file, uint32_t sector_start, uint32_t count, buffer_t buf){
+    int result = fseek(file, sector_start * 512, SEEK_SET);
+    if(result){
+        return result;
+    }
+    result = fwrite(buf, 512, count, file);
+    return result;
+}
+
+int detect_repair_fs(FILE *file, fat_info *info){
+    buffer_t boot_sector = malloc(512);
+    read_sector(file, 0, 1, boot_sector);
+    memcpy(&(info->bpb), boot_sector, 90);
+    buffer_t fat = malloc(info->bpb.sectors_per_fat * info->bpb.fat_count * info->bpb.bytes_per_sector);
+    printf("allocated 0x%x bytes for fat\n", (info->bpb.sectors_per_fat * info->bpb.fat_count * info->bpb.bytes_per_sector));
+    read_sector(file, info->bpb.reserved_sectors, info->bpb.fat_count * info->bpb.sectors_per_fat, fat);
+    info->file_table = fat;
+    if(!fat[info->bpb.root_dir_cluster]){
+        write_cluster_value(info, FILE_END, info->bpb.root_dir_cluster);
+    }
+}
+
+void write_cluster_value(fat_info *info, uint32_t value, uint32_t cluster){
+    for(int i = 0; i < info->bpb.fat_count; i++){
+        info->file_table[cluster + i * info->bpb.sectors_per_fat * info->bpb.bytes_per_sector] = value;
+    }
+}
+
+int fat_write_back(FILE *file, fat_info *info){
+    
+}
 
 int main(int argc, char **argv){
     char **files = malloc(512);
     int filec = 0;
+    FILE *output_file = 0;
+    
+    fat_info info = {};
+    
     printf("write files to virtual disk\n");
     if(argc == 1 || !strcmp(argv[1], "help")){
         printf("Usage:\ndiskwrite <input files> -o <output file>");
@@ -17,8 +117,18 @@ int main(int argc, char **argv){
             if(i >= argc){
                 printf("Error: No output file specified!\n");
             }
+            printf("OF: %s\n", argv[i]);
+            output_file = fopen(argv[i], "r+");
+            continue;
         }
         files[filec++] = argv[i];
+        printf("IF: %s\n", argv[i]);
     }
+    if(filec == 0){
+        printf("Nothing to do, no files to write\n");
+        return 0;
+    }
+    detect_repair_fs(output_file, &info);
+    printf("Finished. Exiting...\n");
     return 0;
 }
\ No newline at end of file