From 61f1852420f06e840d3cb7f0c40fcaae83d118a1 Mon Sep 17 00:00:00 2001
From: Nigel <nigelbarink@hotmail.com>
Date: Sat, 25 Feb 2023 21:03:10 +0100
Subject: [PATCH] Added file reading without cluster chain following

---
 kernel/kernel.cpp                      |  2 ++
 kernel/storage/filesystems/FAT/FAT.cpp | 43 ++++++++------------------
 kernel/storage/filesystems/FAT/FAT.h   |  1 +
 3 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/kernel/kernel.cpp b/kernel/kernel.cpp
index f10b3cf..48081dc 100644
--- a/kernel/kernel.cpp
+++ b/kernel/kernel.cpp
@@ -122,6 +122,8 @@ extern "C" void kernel ()
         printf(" [Size: %d bytes, Attributes: %d]\n", entry->ATTR, entry->FileSize);
         if(entry->ATTR & FAT::ATTRIBUTES::ATTR_DIRECTORY ){
             FAT::OpenSubdir(entry, bpb);
+        } else {
+            FAT::readFile(entry, bpb);
         }
 
     }
diff --git a/kernel/storage/filesystems/FAT/FAT.cpp b/kernel/storage/filesystems/FAT/FAT.cpp
index 7a635e4..19619a0 100644
--- a/kernel/storage/filesystems/FAT/FAT.cpp
+++ b/kernel/storage/filesystems/FAT/FAT.cpp
@@ -146,8 +146,6 @@ uint16_t FAT::GetFATEntry (BiosParameterBlock* bpb, unsigned int cluster){
 
 }
 
-
-
 uint16_t FAT::DetermineFreeSpace()
 {
     // Loop through all FAT entries in all FAT's
@@ -180,8 +178,6 @@ unsigned int FAT::RootDirSize(BiosParameterBlock* bpb)
 
 }
 
-
-
 uint16_t* ReadFAT (BiosParameterBlock& bpb ,  bool DEBUG = false ) {
     uint32_t FATAddress = /*StartAddress*/ 0x00 +  bpb.RsvdSecCnt ;
     uint16_t* FAT = (uint16_t*)malloc(sizeof (uint16_t) * 256);
@@ -253,42 +249,29 @@ void FAT::OpenSubdir(DIR* directory, BiosParameterBlock* bpb ){
             printf("LFN\n");
         }
 
-
-
-
-
-
-
-
     }
 
-
-
 }
 
+void FAT::readFile(DIR* fileEntry , BiosParameterBlock* bpb){
+    unsigned int cluster = fileEntry->FstClusLo;
+    unsigned int FATEntry = FAT::GetFATEntry(bpb, cluster);
+    unsigned int root_dir_sectors = FAT::RootDirSize(bpb);
+    unsigned int fat_size = bpb->FATSz16;
+    unsigned int first_data_sector = bpb->RsvdSecCnt + (bpb->NumFATs * fat_size) + root_dir_sectors;
+    unsigned int file_data_sector = ((cluster -2) * bpb->SecPerClus) + first_data_sector;
+    printf("FAT entry = %x\n", FATEntry);
+    uint16_t data[256];
+    ATAPIO::Read(ATAPIO_PORT::Primary, DEVICE_DRIVE::MASTER, file_data_sector, data);
 
-void readFile(uint32_t DataRegion, DIR* entry, uint16_t FATentry, BiosParameterBlock& bpb ){
-    printf("Show contents");
-
-    printf("Start cluster of the file: 0x%x\n", entry->FileSize);
-
-    printf("IS it only 1 cluster? %s\n", FATentry == 0xFFFF ? "Yes" : "No");
-
-    uint32_t sector = DataRegion + ((entry->FileSize - 0x02) * bpb.SecPerClus);
-
-
-    uint16_t dataBlob[256];
-    ATAPIO::Read(ATAPIO_PORT::Primary, DEVICE_DRIVE::MASTER, sector, dataBlob);
-    for (unsigned short n: dataBlob) {
+    for (unsigned short n : data)
+    {
         kterm_put(n & 0x00ff);
-
         kterm_put(n >> 8);
     }
-    kterm_put('\n');
+
 }
 
-
-
 /*
 file fsysFatDirectory (const char* DirectoryName){
     file file;
diff --git a/kernel/storage/filesystems/FAT/FAT.h b/kernel/storage/filesystems/FAT/FAT.h
index 1627aab..4d5ed59 100644
--- a/kernel/storage/filesystems/FAT/FAT.h
+++ b/kernel/storage/filesystems/FAT/FAT.h
@@ -83,6 +83,7 @@ public:
     static int GetSectorOfRootDirectory(BiosParameterBlock*);
     static unsigned int RootDirSize(BiosParameterBlock*);
     static void OpenSubdir (DIR*, BiosParameterBlock*);
+    static void readFile(DIR*, BiosParameterBlock*);