Separate loading clusters and cluster chains

[nameless-os.git] / boot / x86 / fat32.s

diff --git a/boot/x86/fat32.s b/boot/x86/fat32.s
index caed0361a311af54737594d17b47ae644f517707..75e7904ae5b94a2116529542e0342fb2f1791e0b 100644 (file)
--- a/boot/x86/fat32.s
+++ b/boot/x86/fat32.s
@@ -10,11 +10,24 @@
 ; NOTE: Cluster chain might be the root directory or a file.
 read_cluster_chain:
        push eax
+       push es
+       push di
+       .loop:
+               call read_cluster
+               cmp eax, 0xffffff7
+               jl .loop
+       pop di
+       pop es
+       pop eax
+       ret
+
+; eax - cluster number
+; es:di - where to load the cluster (incremented automatically)
+; RETURN: eax - next cluster number
+read_cluster:
        push ebx
        push ecx
        push edx
-       push es
-       push di
 .loop:
        ; get the first sector of the cluster to read
        push eax
@@ -58,8 +71,6 @@ read_cluster_chain:
        ; reminder for myself: EAX is FAT sector number, (E)BX is offset into FAT sector
        
        ; load the FAT sector we're looking for
-
-       push cx
        push di
        push ebx ; offset
        push es ; we want to read at 0:1000, not STAGE3_SEGMENT:1000
@@ -76,18 +87,10 @@ read_cluster_chain:
        pop ebx ; pop FAT offset back into EBX for cmp
        mov eax, [di+bx]
        pop di
-       pop cx
-       cmp eax, 0xffffff7
-       jl .loop ; if cluster number is lower than the defective cluster value, we're not done
-                ; TODO: perhaps check is it equal defective and error out in that case?
-.done:
        ; cleanup and return
-       pop di
-       pop es
        pop edx
        pop ecx
        pop ebx
-       pop eax
        ret
 
 ; es:di - where to load the sector(s)