hamburglar was here

holey-bytes

@@ -1 +1 @@
-Subproject commit 75995422262a192f2c87713d239856e98c799f41
+Subproject commit 6a444bd29ea6d474ec98edbc11b27030825b86e2

src/vfs.hbasm

@@ -1,12 +1,47 @@
 -- r255 is used as a bump allocator pointer
 -- r254 is -1
 -- r253 is 33 (the number of bytes in an inode other than its name)
+-- r252 is the root inode address
+-- r251 is `/` (47)
+-- r250 is `\` (92)
 
 jal r0, r0, start
 
 start:
     li r255, data
     li r254, -1
+    li r253, 33
+    li r251, 47
+    li r250, 92
+
+    jal r1, r0, create_root
+
+    -- allocate space for the path ("/e")
+    cp r8, r255
+    addi r255, r255, 2
+    li r9, 101
+    -- store the path
+    st r251, r8, 0, 1
+    st r9, r8, 1, 1
+    
+    li r9, 2
+    li r10, 0
+    cp r32, r8  -- copy r8 to use the path again later
+
+    jal r2, r0, create_inode
+
+    cp r33, r8   -- copy r8 to compare against
+
+    -- find `e` in /
+    cp r8, r32
+    addi r8, r8, 1
+    li r9, 1
+    ld r10, r252, 17, 8
+    jal r3, r0, find_inode
+    cp r34, r8
+
+    -- at this point r33 is the address we created /e at, and r34 is the address we found it at
+    ecall
 
 -- Reads the file at the path pointed to by `name_addr`
 -- 
@@ -53,74 +88,80 @@ write:
 --   r8: addr
 -- returns to r1
 mount:
+    jal r0, r1, 0 -- do nothing for now
+
+-- Creates the root inode `/`
+-- This should be run at the start of execution, before any other inodes are made
+-- 
+-- returns to r1
+-- sets 252 to root inode's address
+create_root:
+    cp r252, r255
+    add r255, r255, r253    -- bump allocator past this inode
+    st r0, r252, 0, 8   -- `next`
+    li r8, 2
+    st r8, r252, 8, 1   -- put 2 in `flags`
+    st r0, r252, 9, 8   -- 0 `size` for now
+    st r0, r252, 17, 8  -- 0 `addr` too
+    st r0, r252, 25, 8   -- 0 `name_len`
+    jal r0, r1, 0
 
 -- Creates a new inode with a chosen path
 -- 
 -- inputs:
 --   r8: path_addr
 --   r9: path_len
---   r10: dir
+--   r10: flags
 -- outputs:
 --   r8: addr
+--     1 if the path doesn't begin with a slash
+--     2 if a parent doesn't exist
+--     3 if a parent is a file
 -- returns to r2
 -- modifies r8-r17
+-- indirectly modifies r19-r27
 create_inode:
     cp r16, r9  -- copy `path_len` so we can use r9
-    cp r17, r10 -- same with `dir` and r10
+    cp r17, r10 -- same with `flags` and r10
-    -- r8 will store the address of the next byte
+    -- r8 will store the address of the next bytes
-    li r9, 0    -- r9 will store the parsed length of the current part
-    li r10, data    -- r10 will be used to refer to the current parent inode, so we'll start it at the root
-    cp r11, r8  -- r11 will store the base of the current part
-    li r12, 0   -- r12 will store the total length of the parsed path for comparing to `path_len`
 
-    -- store slash character bytes to compare to
+    -- r9 becomes the address of the end name
-    li r14, 42 -- `/` is ascii 47
+    -- r10 becomes the address of the direct parent, or an error code
-    li r15, 97 -- `\` is ascii 92
+    -- r11 becomes the length of the end name
-
+    jal r4, r0, follow_path
-    create_parse_path:
+    li r24, 10
-        -- we have the start address, now we need the length of the part
+    jltu r10, r24, create_inode_fail
-        -- the next byte goes in r13
-        ld r13, r8, 0, 8
-        -- try to enter the inode if a slash was found
-        jeq r13, r14, create_enter_inode
-        jeq r13, r15, create_enter_inode
-        -- increment the byte pointer and check the next one
-        addi r8, r8, 1
-        addi r9, r9, 1
-        jeq r12, r16, creation  -- create the inode if this is the last part
-        jal r0, r0, create_parse_path
-    
-    create_enter_inode:
-        cp r8, r11  -- for `find_inode` argument
-        jal r3, r0, find_inode  -- this will put the inode address in r8, or 0 if not found
-        jeq r8, r0, create_inode_return     -- return if the inode wasn't found
-        cp r10, r8
-        add r11, r11, r9    -- skip to the next path part
-        addi r11, r10, 1    -- also skip the slash
-        cp r8, r11
-        add r12, r12, r9    -- increase the parsed length
-        addi r12, r12, 1
-        li r9, 0
-        jal r0, r0, create_parse_path
 
     creation:
         cp r8, r255 -- set the base address of this inode
-        add r255, r255, r9  -- 
+        add r255, r255, r253    -- bump allocator past this inode
-        add r255, r255, r253 -- bump allocator past this inode
+        add r255, r255, r9      -- and its name
-        st r9, r8, 0, 8 -- store name_len
+        -- get the first entry under the parent inode
+        addi r24, r10, 17   -- r24 is now at the `addr` field of the parent
+        st r24, r8, 0, 8    -- make this inode's `next` field point to the previous first child
+        st r8, r10, 17, 8   -- point the parent's `addr` to this inode
+        st r17, r8, 8, 1    -- store `flags`
+        st r0, r8, 9, 8     -- store 0 for `size` until something gets added
+        st r0, r8, 17, 8    -- same for `addr`
+        st r9, r8, 25, 8    -- store `name_len`
         -- copy the name into the inode
         cp r24, r11
         cp r25, r9
         cp r26, r8
-        addi r26, r253
+        add r26, r26, r253
+        -- increase the parent's size
+        ld r24, r10, 9, 1
+        addi r24, r24, 1
+        st r24, r10, 9, 1
         jal r4, r0, copy_buf
-        -- get the first entry under the parent inode
-        addi r25, r25,    -- now r25 is at the `addr` field of the parent
-        
 
     create_inode_return:
         jal r0, r2, 0
 
+    create_inode_fail:
+        cp r8, r10
+        jal r0, r2, 0
+
 -- Finds an inode address by name within a parent inode
 -- Returns with 0 in `r8` if there is no inode with the passed name
 -- 
@@ -130,12 +171,20 @@ create_inode:
 --   r10: current_addr
 -- outputs:
 --   r8: addr
+--     1 if the inode doesn't exist
 -- returns to r3
 -- modifies r10 and r19-r27
 find_inode:
     ld r19, r10, 25, 8  -- load the name length to compare
-    ld r20, r27, 0, 8   -- load the `next` field of this inode
+    ld r20, r10, 0, 8   -- load the `next` field of this inode
     jeq r9, r19, find_compare   -- only compare names if they're the same length
+
+    ld r64, r10, 0, 8
+    ld r65, r10, 8, 1
+    ld r66, r10, 9, 24
+    ecall
+
+    jeq r10, r20, find_inode_fail   -- fail if this is the last one
     cp r10, r20
     jal r0, r0, find_inode  -- else try the next inode
 
@@ -157,19 +206,19 @@ find_inode:
             cmp_4:
                 ld r26, r19, 0, 4
                 ld r24, r25, 0, 4
-                add r21, r21, 4
+                addi r21, r21, 4
                 jal r0, r0, cmp_end
 
             cmp_2:
                 ld r26, r19, 0, 2   -- first 2 bytes
                 ld r24, r25, 0, 2
-                add r21, r21, 2
+                addi r21, r21, 2
                 jal r0, r0, cmp_end
 
             cmp_1:
                 ld r26, r19, 0, 1   -- get the byte to compare
                 ld r24, r25, 0, 1   -- and the byte to compare with
-                add r21, r21, 1
+                addi r21, r21, 1
 
             cmp_end:
                 jeq r26, r24, find_compare_loop -- continue if this set matches
@@ -180,6 +229,10 @@ find_inode:
     find_inode_return:
         jal r0, r3, 0
 
+    find_inode_fail:
+        li r8, 1
+        jal r0, r3, 0
+
 -- Copies a buffer
 -- 
 -- inputs:
@@ -199,7 +252,7 @@ copy_buf:
         jeq r27, r0, copy_end
         addi r24, r24, 4
         addi r26, r26, 4
-        addi r25, -4
+        addi r25, r25, -4
         jal r0, r0, copy_buf
     
     copy_2:
@@ -207,7 +260,7 @@ copy_buf:
         jeq r27, r0, copy_end
         addi r24, r24, 2
         addi r26, r26, 2
-        addi r25, -2
+        addi r25, r25, -2
         jal r0, r0, copy_buf
 
     copy_1:
@@ -216,6 +269,72 @@ copy_buf:
     copy_end:
         jal r0, r4, 0
 
+-- Parses a path, returning the address of the direct parent
+-- 
+-- inputs:
+--   r8: path_addr
+--   r16: path_len
+-- outputs:
+--   r9: name_len
+--   r10: parent_addr
+--     1 if the direct parent wasn't found
+--     2 if a parent is a file
+--   r11: name_addr
+-- returns to r4
+-- modifies r12-r13
+follow_path:
+    li r9, 0    -- r9 will store the parsed length of the current part
+    cp r10, r252    -- r10 will be used to refer to the current parent inode, so we'll start it at the root
+    cp r11, r8  -- r11 will store the base of the current part
+    li r12, 0   -- r12 will store the total length of the parsed path for comparing to `path_len`
+
+    -- skip leading slash if it exists
+    ld r13, r8, 0, 1
+    jeq r13, r14, skip_leading
+    jeq r13, r15, skip_leading
+    li r8, 1    -- return with a 1 in r8
+    jal r0, r0, parse_return
+
+    skip_leading:
+        addi r8, r8, 1
+        addi r9, r9, 1
+    
+    parse_loop:
+        -- we have the start address, now we need the length of the part
+        -- the next byte goes in r13
+        ld r13, r8, 0, 1
+        -- try to enter the inode if a slash was found
+        jeq r13, r251, enter_inode
+        jeq r13, r250, enter_inode
+        -- increment the byte pointer and check the next one
+        addi r8, r8, 1
+        addi r9, r9, 1
+        jeq r12, r16, parse_return  -- return inode if this is the last part
+        jal r0, r0, parse_loop
+
+    enter_inode:
+        cp r8, r11  -- for `find_inode` argument
+        jal r3, r0, find_inode  -- this will put the inode address in r8, or 0 if not found
+        jeq r8, r0, parse_fail    -- fail if the inode wasn't found
+        cp r10, r8 
+        add r11, r11, r9    -- skip to the next path part
+        addi r11, r11, 1    -- also skip the slash
+        cp r8, r11
+        add r12, r12, r9    -- increase the parsed length
+        addi r12, r12, 1    -- including the slash
+        li r9, 0
+        jal r0, r0, parse_loop
+    
+    parse_return:
+        jal r0, r4, 0
+
+    parse_fail:
+        li r10, 1
+        jal r0, r4, 0
+    
+    parse_parent_file:
+        li r10, 2
+        jal r0, r4, 0
 
 -- This is where all the VFS and FS data will be stored
 -- VFS comes first, and FS starts at `data + 2048`