112 lines
2.6 KiB
NASM
112 lines
2.6 KiB
NASM
; RYFS routines
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; open a file from a RYFS-formatted disk
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; inputs:
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; r0: pointer to file name string (8.3 format, for example "test txt" for test.txt)
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; r1: disk ID
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; r2: file struct: pointer to a blank 8 byte file struct as described below
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; r3: pointer to sector buffer
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; outputs:
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; r0: first file sector
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;
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; file struct:
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; file_disk: 1 byte
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; file_first_sector: 2 bytes
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; file_seek_offset: 4 bytes
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; file_reserved: 1 byte
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ryfs_open:
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push r1
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push r2
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push r10
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; r10: pointer to file struct entry
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mov r10, r2
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mov.8 [r10], r1 ; write file_disk
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inc r10
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push r0
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mov r0, 1
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mov r2, r3
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call read_sector
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pop r0
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; point to the file name of the first directory entry
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mov r1, r3
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add r1, 20
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mov r2, 11 ; compare 11 bytes
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ryfs_open_find_dir_entry_loop:
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call compare_memory_bytes
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ifz jmp ryfs_open_found_dir_entry
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add r1, 16 ; point to the file name in the next directory entry
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jmp ryfs_open_find_dir_entry_loop ; FIXME: this never returns if the file wasn't found
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ryfs_open_found_dir_entry:
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sub r1, 4 ; point to first sector of this file
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mov.16 [r10], [r1] ; write file_first_sector
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add r10, 2
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mov [r10], 0 ; write file_seek_offset
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inc r10
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mov.8 [r10], 0 ; write file_reserved
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movz.16 r0, [r1]
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pop r10
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pop r2
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pop r1
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ret
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; read a whole file into the specified buffer
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; FIXME: this will always load a multiple of 506 bytes, even if the file is smaller
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; inputs:
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; r0: pointer to file struct
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; r1: pointer to destination buffer
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; outputs:
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; none
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;
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; file struct:
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; file_disk: 1 byte
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; file_first_sector: 2 bytes
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; file_seek_offset: 4 bytes
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; file_reserved: 1 byte
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ryfs_read_whole_file:
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push r0
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push r1
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push r2
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push r10
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push r11
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mov r10, r0
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mov r11, r1
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; read the first sector into the temp buffer
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movz.8 r1, [r0] ; file_disk
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inc r0
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movz.16 r0, [r0] ; file_first_sector
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ryfs_read_whole_file_sector_loop:
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mov r2, TEMP_SECTOR_BUF
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call read_sector
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; copy the sector data to the destination buffer
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mov r0, TEMP_SECTOR_BUF
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add r0, 6
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mov r1, r11
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mov r2, 506
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call copy_memory_bytes
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; check to see if this is the last sector
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; FIXME: if this is the last sector, it should respect the sector size field in the header
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sub r0, 4
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cmp.16 [r0], 0
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ifz jmp ryfs_read_whole_file_last_sector
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; there are more sectors left, load them
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movz.16 r0, [r0] ; sector number
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mov r1, [r10] ; file_disk
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add r11, 506
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jmp ryfs_read_whole_file_sector_loop
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ryfs_read_whole_file_last_sector:
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pop r11
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pop r10
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pop r2
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pop r1
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pop r0
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ret
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