From 4361041d09d939f35fba361b4ca2a0cca72576d9 Mon Sep 17 00:00:00 2001
From: d0p1 <contact@d0p1.eu>
Date: Sun, 3 Mar 2024 16:38:54 +0100
Subject: [PATCH] feat(tools): list file in fat12 root directory

---
 tools/fat.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 104 insertions(+), 10 deletions(-)

diff --git a/tools/fat.c b/tools/fat.c
index e18838f..17838fd 100644
--- a/tools/fat.c
+++ b/tools/fat.c
@@ -32,7 +32,24 @@ typedef struct
   uint8_t fs_type[8];
 } __attribute__((packed)) BiosParamBlock;
 
+typedef struct
+{
+  uint8_t  name[8];
+  uint8_t  ext[3];
+  uint8_t  attr;
+  uint16_t reserved0;
+  uint16_t creation_time;
+  uint16_t creation_date;
+  uint16_t access_date;
+  uint16_t reserved1;
+  uint16_t mod_time;
+  uint16_t mod_date;
+  uint16_t start;
+  uint32_t size;
+} __attribute__((packed)) Entry;
+
 static const char *prg_name;
+static int sector_size = 512;
 
 static void
 fatal(const char *str, ...)
@@ -48,27 +65,104 @@ fatal(const char *str, ...)
   exit(EXIT_FAILURE);
 }
 
+static void
+read_sector(uint8_t *dest, int sect, FILE *fp)
+{
+  if (fseek(fp, sect*sector_size, SEEK_SET) != 0) goto fatal_sect;
+  if (fread(dest, 1, sector_size, fp) != sector_size) goto fatal_sect;
+
+  return;
+
+ fatal_sect:
+  fatal("Can't read sector %d", sect);
+}
+
+static void
+dump_bpb(BiosParamBlock *bpb)
+{
+  char label[12];
+
+  printf("Bytes per logical sector: %hd\n", bpb->bytes_per_sector);
+  sector_size = bpb->bytes_per_sector;
+  printf("Logical sectors per cluster: %d\n", bpb->sectors_per_cluster);
+  printf("Reserved logical sectors: %hd\n", bpb->reserved_sectors);
+  printf("Number of FATs: %d\n", bpb->number_of_FATs);
+  printf("Root directory entries: %hd\n", bpb->root_entries);
+  printf("Total logical sectors: %hd\n", bpb->logical_sectors);
+  printf("Logical sectors per FAT: %hd\n", bpb->sectors_per_FAT);
+  printf("Serial: %X\n", bpb->serial);
+  memset(label, 0, 12);
+  strncpy(label, bpb->label, 11);
+  printf("Label: '%s'\n", label);
+  printf("signature: %X\n", bpb->signature);
+}
+
+static void
+dump_entry(Entry *entry)
+{
+  char filename[9];
+  char ext[4];
+  int i;
+
+  if (entry->name[0] == 0x0) return;
+
+  memset(filename, 0, 9);
+  strncpy(filename, entry->name, 8);
+  memset(ext, 0, 4);
+  strncpy(ext, entry->ext, 3);
+  for (i = 7; i > 0; i--)
+    {
+      if (filename[i] == ' ')
+	{
+	  filename[i] = '\0';
+	}
+      else
+	{
+	  break;
+	}
+    }
+
+  printf("%s.%s\n", filename, ext);
+}
+
 static void
 dump(const char *img)
 {
   FILE *fp;
-  BiosParamBlock bpb;
-  char label[12];
+  BiosParamBlock *bpb;
+  uint8_t buffer[512];
+  int root_start;
+  int root_size;
+  int i;
+  int j;
 
   fp = fopen(img, "rb");
   if (fp == NULL) fatal("Can't open '%s': %s", img, strerror(errno));
 
-  if (fread(&bpb, 1, sizeof(BiosParamBlock), fp) != sizeof(BiosParamBlock))
+  read_sector(buffer, 0, fp);
+  if (buffer[511] != 0xAA || buffer[510] != 0x55)
     {
-      fatal("Can't read BPB");
+      fatal("MBR not found");
+    }
+
+  bpb = (BiosParamBlock *)buffer;
+
+  dump_bpb(bpb);
+
+  root_start = bpb->sectors_per_FAT * bpb->number_of_FATs;
+  root_start += bpb->reserved_sectors;
+
+  root_size = bpb->root_entries / (sector_size >> 0x5);
+
+  for (i = 0; i < root_size; i++)
+    {
+      read_sector(buffer, root_start + i, fp);
+      for (j = 0; j < sector_size; j+=32)
+	{
+	  dump_entry((Entry *)(buffer + j));
+	}
     }
 
-  printf("Bytes per logical sector: %hd\n", bpb.bytes_per_sector);
-  printf("Logical sectors per cluster: %d\n", bpb.sectors_per_cluster);
-  memset(label, 0, 12);
-  strncpy(label, bpb.label, 11);
-  printf("Label: '%s'\n", label);
-  printf("signature: %X\n", bpb.signature);
   fclose(fp);
   exit(EXIT_SUCCESS);
 }