fox32rom: Add read and seek routines for RYFS

boot.asm

@@ -60,7 +60,6 @@ start_boot_process_ryfs:
     mov r0, kernel_file_name
     mov r1, 0
     mov r2, KERNEL_FILE_STRUCT
-    mov r3, TEMP_SECTOR_BUF
     call ryfs_open
 
     mov r0, KERNEL_FILE_STRUCT

fox32rom.def

@@ -54,6 +54,10 @@ menu_update_event:                        jmp [0xF004401C]
 ; disk jump table
 read_sector:                              jmp [0xF0045000]
 write_sector:                             jmp [0xF0045004]
+ryfs_open:                                jmp [0xF0045008]
+ryfs_seek:                                jmp [0xF004500C]
+ryfs_read:                                jmp [0xF0045010]
+ryfs_read_whole_file:                     jmp [0xF0045014]
 
 ; memory copy/compare jump table
 copy_memory_bytes:                        jmp [0xF0046000]

main.asm

@@ -192,6 +192,10 @@ get_rom_version:
     org.pad 0xF0045000
     data.32 read_sector
     data.32 write_sector
+    data.32 ryfs_open
+    data.32 ryfs_seek
+    data.32 ryfs_read
+    data.32 ryfs_read_whole_file
 
     ; memory copy/compare jump table
     org.pad 0xF0046000

ryfs.asm

@@ -1,19 +1,18 @@
 ; RYFS routines
 
-; open a file from a RYFS-formatted disk
-; inputs:
-; r0: pointer to file name string (8.3 format, for example "test    txt" for test.txt)
-; r1: disk ID
-; r2: file struct: pointer to a blank 8 byte file struct as described below
-; r3: pointer to sector buffer
-; outputs:
-; r0: first file sector
-;
 ; file struct:
 ;   file_disk: 1 byte
 ;   file_first_sector: 2 bytes
 ;   file_seek_offset: 4 bytes
 ;   file_reserved: 1 byte
+
+; open a file from a RYFS-formatted disk
+; inputs:
+; r0: pointer to file name string (8.3 format, for example "test    txt" for test.txt)
+; r1: disk ID
+; r2: file struct: pointer to a blank file struct
+; outputs:
+; r0: first file sector
 ryfs_open:
     push r1
     push r2
@@ -26,12 +25,12 @@ ryfs_open:
 
     push r0
     mov r0, 1
-    mov r2, r3
+    mov r2, TEMP_SECTOR_BUF
     call read_sector
     pop r0
 
     ; point to the file name of the first directory entry
-    mov r1, r3
+    mov r1, TEMP_SECTOR_BUF
     add r1, 20
     mov r2, 11 ; compare 11 bytes
 ryfs_open_find_dir_entry_loop:
@@ -53,6 +52,165 @@ ryfs_open_found_dir_entry:
     pop r1
     ret
 
+; seek specified file to the specified offset
+; inputs:
+; r0: byte offset
+; r1: pointer to file struct
+; outputs:
+; none
+ryfs_seek:
+    push r1
+
+    add r1, 3
+    mov [r1], r0
+
+    pop r1
+    ret
+
+; read specified number of bytes into the specified buffer
+; inputs:
+; r0: number of bytes to read
+; r1: pointer to file struct
+; r2: pointer to destination buffer
+; outputs:
+; none
+ryfs_read:
+    push r0
+    push r1
+    push r2
+    push r3
+    push r4
+    push r5
+    push r10
+    push r11
+    push r12
+
+    ; number_of_sectors_to_load = ceil(input r0, 506) / 506
+
+    ; first, ceil the number of bytes to multiple of 506
+    ; value_temp = value / 506
+    ; if value % 506 != 0:
+    ;   value_temp++
+    ; value_ceil = value_temp * 506
+    mov r10, r0
+    mov r11, r0
+    mov r12, 506
+    div r11, r12
+    rem r10, r12
+    ifnz inc r11
+    mul r11, r12
+    div r11, r12
+    mov r3, r11 ; r3: number_of_sectors_to_load
+
+    mov r10, r1
+    add r10, 3
+    mov r4, [r10]
+
+    mov r10, r4
+    mov r11, r4
+    mov r12, 506
+    div r11, r12
+    rem r10, r12
+    ifnz inc r11
+    mul r11, r12
+    div r11, r12
+    mov r4, r11 ; r4: number of sectors to traverse
+
+    ; start_sector = traverse through linked sectors starting at file_struct.file_first_sector
+
+    push r0
+    push r1
+    push r2
+    mov r10, r1
+    ; read the file's first sector into the temp buffer
+    movz.8 r1, [r10] ; file_disk
+    inc r10
+    movz.16 r0, [r10] ; file_first_sector
+    mov r31, r4
+ryfs_read_traverse_sectors_loop:
+    mov r2, TEMP_SECTOR_BUF
+    call read_sector
+    mov r4, r0
+    add r2, 2 ; point to next sector number
+    movz.16 r0, [r2] ; load next sector number
+    cmp r31, 0 ; if we started at zero, then don't attempt to loop
+    ifnz loop ryfs_read_traverse_sectors_loop
+    pop r2
+    pop r1
+    pop r0
+
+    ; r4: start_sector
+
+    ; total_bytes_remaining = input r0
+    ; this_sector = start_sector
+    ; for range 0..number_of_sectors_to_load:
+    ;   load this_sector into temporary buffer
+    ;   bytes_to_load = if total_bytes_remaining >= 506
+    ;     506
+    ;   else:
+    ;     total_bytes_remaining
+    ;   for range 0..bytes_to_load:
+    ;     load byte from temporary buffer into destination buffer
+    ;   this_sector = this_sector.next
+
+    mov r10, r0 ; r10: total_bytes_remaining
+ryfs_read_sector_loop:
+    push r0
+    push r1
+    push r2
+    ; read this sector into the temp buffer
+    mov r0, r4
+    movz.8 r1, [r1] ; file_disk
+    mov r2, TEMP_SECTOR_BUF
+    call read_sector
+    pop r2
+    pop r1
+    pop r0
+
+    ; r11: bytes_to_load
+    cmp r10, 506
+    ifgteq mov r11, 506
+    iflt mov r11, r10
+
+    push r0
+    push r1
+    push r2
+
+    ; calculate the seek offset
+    mov r12, r1
+    add r12, 3
+    mov r5, [r12]
+    rem r5, 506
+
+    ; copy the sector data to the destination buffer
+    mov r0, TEMP_SECTOR_BUF
+    add r0, 6
+    add r0, r5 ; add the seek offset
+    mov r1, r2
+    mov r2, r11
+    call copy_memory_bytes
+    pop r2
+    pop r1
+    pop r0
+
+    dec r10
+    ifnz jmp ryfs_read_sector_loop
+
+    ; file_struct.file_seek_offset += input r0
+    add r1, 3
+    add [r1], r0
+
+    pop r12
+    pop r11
+    pop r10
+    pop r5
+    pop r4
+    pop r3
+    pop r2
+    pop r1
+    pop r0
+    ret
+
 ; read a whole file into the specified buffer
 ; FIXME: this will always load a multiple of 506 bytes, even if the file is smaller
 ; inputs:
@@ -60,12 +218,6 @@ ryfs_open_found_dir_entry:
 ; r1: pointer to destination buffer
 ; outputs:
 ; none
-;
-; file struct:
-; file_disk: 1 byte
-; file_first_sector: 2 bytes
-; file_seek_offset: 4 bytes
-; file_reserved: 1 byte
 ryfs_read_whole_file:
     push r0
     push r1