Create fat16.c

Add implementation for fat16 filesystem

kernel/fat16.c

@@ -0,0 +1,107 @@
+#include "fat16.h"
+#include "ata.h"   // Use ata_read_sector and ata_write_sector
+#include "print.h" // For debugging
+#include <string.h> // For string manipulation
+
+// Global variables
+static fat16_boot_sector_t boot_sector;
+static uint32_t root_dir_sector = FAT16_ROOT_DIR_SECTOR;
+
+// Read a sector from the disk using ATA
+bool read_sector(uint32_t lba, uint8_t* buffer) {
+    return ata_read_sector(lba, buffer);
+}
+
+// Write a sector to the disk using ATA
+bool write_sector(uint32_t lba, const uint8_t* buffer) {
+    return ata_write_sector(lba, buffer);
+}
+
+// Parse the boot sector to retrieve basic file system info
+bool parse_fat16_boot_sector(void) {
+    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
+
+    // Read the boot sector
+    if (!read_sector(FAT16_BOOT_SECTOR, sector_buffer)) {
+        print_string("[FAT16] Failed to read boot sector\n");
+        return false;
+    }
+
+    // Cast to boot sector structure
+    memcpy(&boot_sector, sector_buffer, sizeof(fat16_boot_sector_t));
+
+    // Check for FAT16 signature
+    if (boot_sector.oem_name[0] != 'F' || boot_sector.oem_name[1] != 'A' || boot_sector.oem_name[2] != 'T') {
+        print_string("[FAT16] Invalid FAT16 boot sector signature\n");
+        return false;
+    }
+
+    print_string("[FAT16] FAT16 boot sector parsed successfully\n");
+    return true;
+}
+
+// Parse the root directory
+bool parse_fat16_root_dir(void) {
+    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
+
+    for (int i = 0; i < (boot_sector.max_root_entries / (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t))); i++) {
+        // Read root directory sector
+        if (!read_sector(root_dir_sector + i, sector_buffer)) {
+            print_string("[FAT16] Failed to read root directory sector\n");
+            return false;
+        }
+
+        // Parse the root directory entries
+        for (int j = 0; j < (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t)); j++) {
+            fat16_dir_entry_t* entry = (fat16_dir_entry_t*)&sector_buffer[j * sizeof(fat16_dir_entry_t)];
+            if (entry->name[0] == 0x00) {
+                // End of directory entries
+                return true;
+            }
+            if (entry->name[0] != 0xE5) {
+                // Print file name (8.3 format)
+                char filename[12];
+                strncpy(filename, (char*)entry->name, 8);
+                filename[8] = '.';
+                strncpy(&filename[9], (char*)entry->ext, 3);
+                filename[11] = '\0';
+                print_string(filename);
+                print_string("\n");
+            }
+        }
+    }
+    return true;
+}
+
+// Read a specific directory entry from the FAT16 root directory
+bool read_fat16_entry(uint16_t entry_index, fat16_dir_entry_t* entry) {
+    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
+    uint32_t sector_num = FAT16_ROOT_DIR_SECTOR + (entry_index / (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t)));
+    uint16_t entry_offset = entry_index % (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t));
+
+    // Read the sector
+    if (!read_sector(sector_num, sector_buffer)) {
+        print_string("[FAT16] Failed to read root directory sector\n");
+        return false;
+    }
+
+    // Get the entry
+    memcpy(entry, &sector_buffer[entry_offset * sizeof(fat16_dir_entry_t)], sizeof(fat16_dir_entry_t));
+    return true;
+}
+
+// Mount the FAT16 filesystem
+bool mount_fat16(void) {
+    // Parse the boot sector
+    if (!parse_fat16_boot_sector()) {
+        return false;
+    }
+
+    // Parse the root directory
+    if (!parse_fat16_root_dir()) {
+        return false;
+    }
+
+    print_string("[FAT16] Filesystem mounted successfully\n");
+    return true;
+}

kernel/fat16.h

@@ -0,0 +1,60 @@
+#ifndef FAT16_H
+#define FAT16_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+/* FAT16 Constants */
+#define FAT16_SECTOR_SIZE        512
+#define FAT16_CLUSTER_SIZE       1
+#define FAT16_MAX_FILENAME_LEN   11   // 8.3 format
+#define FAT16_ROOT_DIR_ENTRIES   224  // Fat16 root directory entries (typically 512 bytes per entry)
+
+#define FAT16_BOOT_SECTOR        0
+#define FAT16_FAT1_SECTOR        1
+#define FAT16_FAT2_SECTOR        2
+#define FAT16_ROOT_DIR_SECTOR    19  // First sector of root directory
+
+/* Boot Sector */
+typedef struct {
+    uint8_t jmp[3];               // Jump instruction to code
+    uint8_t oem_name[8];          // OEM Name
+    uint16_t bytes_per_sector;    // Bytes per sector (512)
+    uint8_t sectors_per_cluster;  // Sectors per cluster
+    uint16_t reserved_sectors;    // Reserved sectors
+    uint8_t num_fats;             // Number of FAT tables
+    uint16_t max_root_entries;    // Max number of root directory entries
+    uint16_t total_sectors_16;    // Total sectors in FAT16
+    uint8_t media_type;           // Media type (0xF8 = fixed drive)
+    uint16_t sectors_per_fat;    // Sectors per FAT table
+    uint16_t sectors_per_track;  // Sectors per track (for CHS addressing)
+    uint16_t num_heads;          // Number of heads (for CHS addressing)
+    uint32_t hidden_sectors;     // Hidden sectors (before the partition)
+    uint32_t total_sectors_32;   // Total sectors in FAT16 (extended)
+} __attribute__((packed)) fat16_boot_sector_t;
+
+/* FAT16 Directory Entry */
+typedef struct {
+    uint8_t name[8];   // File name (8 chars)
+    uint8_t ext[3];    // File extension (3 chars)
+    uint8_t attributes; // File attributes (e.g., directory, read-only)
+    uint8_t reserved;   // Reserved
+    uint8_t creation_time[2]; // Creation time
+    uint8_t creation_date[2]; // Creation date
+    uint8_t last_access_date[2]; // Last access date
+    uint8_t first_cluster_high[2]; // High part of first cluster number
+    uint8_t last_mod_time[2];  // Last modification time
+    uint8_t last_mod_date[2];  // Last modification date
+    uint8_t first_cluster_low[2];  // Low part of first cluster number
+    uint32_t file_size;         // File size in bytes
+} __attribute__((packed)) fat16_dir_entry_t;
+
+/* Function Prototypes */
+bool mount_fat16(void);
+bool read_sector(uint32_t lba, uint8_t* buffer);
+bool write_sector(uint32_t lba, const uint8_t* buffer);
+bool parse_fat16_boot_sector(void);
+bool parse_fat16_root_dir(void);
+bool read_fat16_entry(uint16_t entry_index, fat16_dir_entry_t* entry);
+
+#endif // FAT16_H

klibc/include/string.h

@@ -3,12 +3,13 @@
 
 #include <stddef.h>
 
-extern int memcmp(const void* s1, const void* s2, size_t n);
+extern int memcmp(const void *s1, const void *s2, size_t n);
-extern void* memmove(void* dst, const void* src, size_t n);
+extern void *memmove(void *dst, const void *src, size_t n);
-extern void* memcpy(void* dst, const void* src, size_t n);
+extern void *memcpy(void *dst, const void *src, size_t n);
-extern void* memset(void* dst, int c, size_t n);
+extern void *memset(void *dst, int c, size_t n);
 
-extern size_t strlen(const char* s);
+extern size_t strlen(const char *s);
-extern int strcmp(const char* s1, const char* s2);
+extern int strcmp(const char *s1, const char *s2);
+extern char *strncpy(char *dst, const char *src, size_t n);
 
 #endif  // CLASSICOS_KLIBC_STRING_H

klibc/src/string.c

@@ -1,8 +1,8 @@
 #include <string.h>
 
-int memcmp(const void* s1, const void* s2, size_t n) {
+int memcmp(const void *s1, const void *s2, size_t n) {
-    const unsigned char* c1 = s1;
+    const unsigned char *c1 = s1;
-    const unsigned char* c2 = s2;
+    const unsigned char *c2 = s2;
     int d = 0;
 
     while (n--) {
@@ -13,9 +13,9 @@ int memcmp(const void* s1, const void* s2, size_t n) {
     return d;
 }
 
-void* memmove(void* dst, const void* src, size_t n) {
+void *memmove(void *dst, const void *src, size_t n) {
-    const char* p = src;
+    const char *p = src;
-    char* q = dst;
+    char *q = dst;
 #if defined(__i386__) || defined(__x86_64__)
     if (q < p) {
         __asm__ volatile("cld; rep; movsb" : "+c"(n), "+S"(p), "+D"(q));
@@ -41,9 +41,9 @@ void* memmove(void* dst, const void* src, size_t n) {
     return dst;
 }
 
-void* memcpy(void* dst, const void* src, size_t n) {
+void *memcpy(void *dst, const void *src, size_t n) {
-    const char* p = src;
+    const char *p = src;
-    char* q = dst;
+    char *q = dst;
 #if defined(__i386__)
     size_t nl = n >> 2;
     __asm__ volatile("cld ; rep ; movsl ; movl %3,%0 ; rep ; movsb"
@@ -63,8 +63,8 @@ void* memcpy(void* dst, const void* src, size_t n) {
     return dst;
 }
 
-void* memset(void* dst, int c, size_t n) {
+void *memset(void *dst, int c, size_t n) {
-    char* q = dst;
+    char *q = dst;
 
 #if defined(__i386__)
     size_t nl = n >> 2;
@@ -86,15 +86,15 @@ void* memset(void* dst, int c, size_t n) {
     return dst;
 }
 
-size_t strlen(const char* s) {
+size_t strlen(const char *s) {
-    const char* ss = s;
+    const char *ss = s;
     while (*ss) ss++;
     return ss - s;
 }
 
-int strcmp(const char* s1, const char* s2) {
+int strcmp(const char *s1, const char *s2) {
-    const unsigned char* c1 = (const unsigned char*)s1;
+    const unsigned char *c1 = (const unsigned char *)s1;
-    const unsigned char* c2 = (const unsigned char*)s2;
+    const unsigned char *c2 = (const unsigned char *)s2;
     unsigned char ch;
     int d = 0;
 
@@ -105,3 +105,19 @@ int strcmp(const char* s1, const char* s2) {
 
     return d;
 }
+
+char *strncpy(char *dst, const char *src, size_t n) {
+    char *q = dst;
+    const char *p = src;
+    char ch;
+
+    while (n) {
+        n--;
+        *q++ = ch = *p++;
+        if (!ch) break;
+    }
+
+    memset(q, 0, n);
+
+    return dst;
+}