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ClusterToLBA to fastcall

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cleanup of NextCluster
This commit is contained in:
Elaina Claus
2024-10-17 20:36:05 -04:00
parent 046821ff7a
commit 45aeb9b3d0
1 changed files with 20 additions and 38 deletions
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56
include/fat32/FAT32_SYS.inc
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@@ -40,8 +40,7 @@ InitFATDriver:
sub sp, 0x6 sub sp, 0x6
.calc_active_part: .calc_active_part:
mov bx, [partition_offset_ptr] mov bx, [partition_offset]
mov cx, word [ds:bx]
mov ax, partition_table mov ax, partition_table
add ax, cx add ax, cx
mov si, ax ; si = offset to active partition mov si, ax ; si = offset to active partition
@@ -222,44 +221,29 @@ NextCluster:
mov edx, dword [bp + 4] mov edx, dword [bp + 4]
mov si, fat32_nc_data ; instead of push/pop and moving the data back mov si, fat32_nc_data ; instead of push/pop and moving the data back
mov di, fat32_bpb ; load si & di then use xchg mov di, fat32_bpb ; load si & di then use xchg
mov bx, fat32_state
.calc_offset: .calc_offset:
; fat_offset = active_cluster * 4 ; fat_offset = active_cluster * 4
mov eax, 4 mov eax, 4
mul edx mul edx
jc NextCluster.error_cfdivz jc NextCluster.error_cfdivz
mov dword [si + FAT32_NextClusterData_t.fat_offset], eax ; move lower 32 bits to fat offset mov dword [si + FAT32_NextClusterData_t.fat_offset], eax ; move lower 32 bits to fat offset
.calc_fat_sector: .calc_fat_sector:
; fat_sector = first_fat_sector + (fat_offset / sector_size) ; fat_sector = first_fat_sector + (fat_offset / sector_size)
; entry_offset = fat_offset % sector_size ; entry_offset = fat_offset % sector_size
mov edx, 0xffff_0000 xor edx, edx
and edx, eax movzx ecx, word [di + FAT32_bpb_t.bytes_per_sector_word]
shr edx, 16 cmp eax, 0
xchg si, di ; switch to fat32_bpb in si
mov cx, word [si + FAT32_bpb_t.bytes_per_sector_word]
xchg si, di
cmp edx, 0
je NextCluster.error_cfdivz je NextCluster.error_cfdivz
div cx ; DX:AX / cx = fat_sector - first_fat_sector in AX div ecx ; eDX:eAX / eCX = fat_sector - first_fat_sector in eAX
; DX = remainder (fat_offset mod sector_size) ; eDX = remainder (fat_offset mod sector_size)
mov ecx, 0x0000_ffff
and edx, ecx
mov dword [si + FAT32_NextClusterData_t.entry_offset], edx mov dword [si + FAT32_NextClusterData_t.entry_offset], edx
mov ecx, dword [bx + FAT32_State_t.first_fat_sector_32]
xchg si, di ; switch to fat32_bpb in si
mov ecx, dword [si + FAT32_State_t.first_fat_sector_32]
xchg si, di
mov edx, 0x0000ffff
and eax, edx
add eax, ecx ; fat_sector + first_fat_sector add eax, ecx ; fat_sector + first_fat_sector
mov dword [si + FAT32_NextClusterData_t.fat_sector], eax mov dword [si + FAT32_NextClusterData_t.fat_sector], eax
.load_fat_table: .load_fat_table:
mov bx, word [boot_drive_ptr] mov ax, word [boot_drive]
movzx ax, byte [ds:bx]
push ax push ax
mov ax, 0x1 mov ax, 0x1
@@ -304,20 +288,21 @@ NextCluster:
.error_cfdivz: .error_cfdivz:
ERROR STAGE2_FAT32_NCLUS_CFDIVZ ERROR STAGE2_FAT32_NCLUS_CFDIVZ
; uint32_t ClusterToLBA(uint32_t cluster) ; __fastcall16 uint32_t ClusterToLBA(uint32_t cluster)
; input = dword cluster in eax
ALIGN 4, db 0x90 ALIGN 4, db 0x90
ClusterToLBA: ClusterToLBA:
__CDECL16_ENTRY __FASTCALL16_ENTRY
.func: .func:
mov dword eax, [bp + 4]
sub eax, 2 sub eax, 2
movzx edx, byte [fat32_bpb + FAT32_bpb_t.sectors_per_cluster_byte] movzx edx, byte [fat32_bpb + FAT32_bpb_t.sectors_per_cluster_byte]
mul edx mul edx ; result in eax, error on carry
jc ClusterToLBA.error jc ClusterToLBA.error
add eax, dword [fat32_state + FAT32_State_t.first_data_sector_32] add eax, dword [fat32_state + FAT32_State_t.first_data_sector_32]
jc ClusterToLBA.error
; eax contains the LBA now ; eax contains the LBA now
.endp: .endp:
__CDECL16_EXIT __FASTCALL16_EXIT
ret ret
.error: .error:
ERROR STAGE2_FAT32_CLS2LBA_CF ERROR STAGE2_FAT32_CLS2LBA_CF
@@ -330,24 +315,21 @@ ReadFATCluster:
.func: .func:
print_string ReadFATCluster_info print_string ReadFATCluster_info
mov bx, word [boot_drive_ptr] mov ax, word [boot_drive]
movzx ax, byte [ds:bx]
push ax push ax
mov ax, 0x1 ; count = 1 mov ax, 0x1 ; count = 1
push ax push ax
mov eax, dword [bp + 8] mov eax, dword [bp + 8]
push dword eax call ClusterToLBA ; __fastcall16 uint32_t ClusterToLBA(uint32_t cluster)
call ClusterToLBA
add sp, 0x4
; eax contains the LBA now ; eax contains the LBA now
push dword eax ; lba = ClusterToLBA(..) push dword eax ; lba = ClusterToLBA(..)
mov ax, fat_buffer ; offset = fat_buffer (in mem.inc) mov ax, word [bp + 6] ; offset
push ax push ax
xor ax, ax ; segment = 0x0000, our buffer is in the first 64 KiB mov ax, word [bp + 4]
push ax push ax
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset, ; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba, ; uint32_t lba,