funky
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README.md
33
README.md
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@ -6,9 +6,15 @@
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// reads the whole file
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// reads the whole file
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pub fn read(file: FileHandle) -> Vec<u8>
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pub fn read(file: FileHandle) -> Vec<u8>
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// reads up to 4096 bytes of the file
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pub fn read_block(file: FileHandle) -> Vec<u8>
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// overwrites the contents of the file
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// overwrites the contents of the file
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pub fn write(file: FileHandle, data: Vec<u8>)
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pub fn write(file: FileHandle, data: Vec<u8>)
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// writes 4096 bytes to the file
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pub fn write_block(file: FileHandle, data: Vec<u8>)
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// opens a file for reading and writing
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// opens a file for reading and writing
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pub fn open(path: Path)
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pub fn open(path: Path)
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@ -48,7 +54,7 @@ All filesystems must expose at least these functions in order to work with the V
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## Structure
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## Structure
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### Mount Point Lookup Entry
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### Mount Point
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```
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```
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path_len: u64
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path_len: u64
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@ -57,17 +63,30 @@ entries: u64
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addr: u64
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addr: u64
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```
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```
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There is one of these for each mount point, stored sequentially within the root directory it belongs to. The list ends when it finds a `path_len` of 0
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There is one of these for each mount point, stored sequentially. The list ends when it finds a path_len of 0
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### Inode
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### Sub Part
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```
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```
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name_len: u64
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name_len: u64
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name: [u8; <name_len>]
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name: [u8; <name_len>]
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dir: u8
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next: u64
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size: u64
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flags: u8
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entries: u64
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addr: u64
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addr: u64
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```
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```
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There can be many of these in a mount point, and they can be nested within eachother. dir is 1 if the part is a directory, or 0 if it's a file. size specifies the number of sub parts within a directory, or the number of bytes within a file
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There can be many of these in a mount point, and they can be nested within eachother. If this is the last entry in the parent, `next` will refer to this inode, otherwise it will be the address of the next inode under the parent. `entries` specifies the number of inodes within a directory
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#### Flags
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| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
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|:---:|:---:|:---:|:---:|:---:|:---:|:---:|:---:|
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| NA | NA | NA | NA | NA | NA | dir | mnt |
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`dir` is set if the inode is a directory, or unset if it's a file.
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`mnt` is set if the inode is a mount point
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#### create_inode
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1. traverse the path until we reach the last element or a nonexistent directory
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2. if any path elements are mount points, request the filesystem belonging to it to create the item and if it succeeds create the inode
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119
src/vfs.hbasm
119
src/vfs.hbasm
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@ -1,14 +1,113 @@
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jmp r0, write
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-- r64 is used as a bump allocator pointer
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jal r0, r0, start
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start:
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li r64, fsdata
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-- Reads the file at the path pointed to by `name_addr`
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--
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-- inputs:
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-- r8: name_addr
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-- r9: name_len
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-- outputs:
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-- r8: data_addr
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-- r9: data_len
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-- returns to r32
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read:
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muli r16, r8, 8
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ld r8, r16, fsdata, 8
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jal r0, r32, 0
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-- Writes `data_len` bytes from `data_addr` to the file at the path pointed to by `name_addr`
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-- This creates the file if it doesn't exist
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--
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-- inputs:
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-- r8: name_addr
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-- r9: name_len
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-- r10: data_addr
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-- r11: data_len
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-- returns to r32
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write:
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write:
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li r8, 64
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muli r16, r8, 8
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-- ctrl-a ctrl-c ctrl-v
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st r10, r16, fsdata, 8
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brc r9, r8, 1
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jal r0, r32, 0
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brc r10, r8, 2
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brc r12, r8, 4
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brc r16, r8, 8
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brc r24, r8, 16
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li r8, 32
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fsdata:
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-- Creates a mount point with the path located at `path_addr`
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--
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-- Structure:
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-- path_len: u64
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-- path: [u8; <path_len>]
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-- entries: u64
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-- fs: u64
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-- addr: u64
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--
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-- inputs:
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-- r8: path_addr
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-- r9: path_len
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-- r10: size
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-- outputs:
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-- r8: addr
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-- returns to r32
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mount:
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-- Creates a new inode with a chosen path
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--
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-- inputs:
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-- r8: path_addr
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-- r9: path_len
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-- r10: dir
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-- outputs:
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-- r8: addr
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-- returns to r34
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create_inode:
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-- back up path arguments
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-- we need to use r8 and r9 as arguments for `find_inode`
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brc r8, r16, 3
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-- r8 will store the address of the next character
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li r9, 0 -- this will be store the length of the current part
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li r10, data -- this will be used to refer to the current parent inode, so we'll start it at the root
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cp r11, r8 -- this will store the base of the current part
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li r12, 0 -- this will store the total length of the parsed path for comparing to `path_len`
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-- store slash characters to compare to
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li r48, 42
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li r49, 97
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jal r0, r0, create_parse_path
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create_parse_path:
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-- we have the start address, now we need the length of the part
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-- this can be found by adding 1 and jumping to `parse_path` if the next character is not a / or \
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-- `/` is 47, and `\` is 92
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-- the next character goes in r24
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ld r24, r8, 0, 8
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-- try to enter the inode if a slash was found
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jeq r24, r48, create_enter_inode
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jeq r24, r49, create_enter_inode
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-- increment the character pointer and check the next one
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addi r8, r8, 1
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jal r0, r0, create_parse_path
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create_enter_inode:
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-- move the base of the part into r8
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cp r8, r11
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jal r36, r0, find_inode
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-- Finds an inode address by name within a parent inode
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-- Returns with 0 in `r8` if there is no inode with the chosen name
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--
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-- inputs:
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-- r8: name_addr
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-- r9: name_len
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-- r10: parent_addr
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-- outputs:
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-- r8: addr
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-- returns to r36
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find_inode:
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// This is where all the VFS and FS data will be stored
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// VFS comes first, and FS starts at `data + 2048`
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data:
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