Updating the Database
Reading this in 2026. These are my study notes from around 2017, when the 32-bit C (pil32) and 64-bit assembly (pil64) implementations were current. Since 2020 PicoLisp is pil21, written in PicoLisp itself and compiled through LLVM; the language, libraries and examples are largely the same, so the ideas here still apply, but file names and internals differ. See Pil Sources and software-lab.de.
upd is the default syncronization function
(upd sym ..) -> lst
Synchronizes the internal state of all passed (external) symbols by passing them to wipe. upd is the standard function passed to commit during database transactions.
(commit ‘upd) # Commit changes, informing all sister processes
(wipe ‘sym|lst) -> sym|lst
- Clears the VAL and the property list of sym, or of all symbols in the list lst.
- When a symbol is an external symbol, its state is also set to “not loaded”.
- Does nothing when sym is an external symbol that has been modified or deleted (“dirty”).
: (setq A (1 2 3 4))
-> (1 2 3 4)
: (put 'A 'a 1)
-> 1
: (put 'A 'b 2)
-> 2
: (show 'A)
A (1 2 3 4)
b 2
a 1
-> A
: (wipe 'A)
-> A
: (show 'A)
A NIL
-> A
Definitions
(de upd Lst
(wipe Lst) )
# (wipe 'sym|lst) -> sym|lst
(code 'doWipe 2)
push X
ld X E
ld E ((E CDR)) # Get arg
eval # Eval it
cmp E Nil # NIL?
if ne # No
atom E # List?
if nz # No
call wipeEX # Wipe it
else
push E # Save
ld C E # Get list
do
ld E (C) # Next symbol
call wipeEX # Wipe it
ld C (C CDR)
atom C # More?
until nz # No
pop E
end
end
pop X
ret
# (commit ['any] [exe1] [exe2]) -> T
(code 'doCommit 2)
push X
push Y
push Z
ld X E
ld Y (E CDR) # Y on args
ld E (Y) # Eval 'any'
eval
link
push E # <L I> 'any'
link
null (DbLog) # Transaction log?
if z # No
inc (EnvProtect) # Protect the operation
end
call wrLockDb # Write lock DB
null (DbJnl) # Journal?
if nz # Yes
call lockJnl # Write lock journal
end
null (DbLog) # Transaction log?
if nz # Yes
ld E (DbFiles) # Iterate DB files
ld C (DBs) # Count
do
set (E (+ IV 1)) 0 # Clear dirty flag
ld (E VII) 0 # and 'fluse'
add E VIII # Increment by sizeof(dbFile)
sub C VIII # Done?
until z # Yes
push X
push Y
ld X (Extern) # Iterate external symbol tree
ld Y 0 # Clear TOS
do
do
ld A (X CDR) # Get subtrees
atom (A) # Left subtree?
while z # Yes
ld C X # Go left
ld X (A) # Invert tree
ld (A) Y # TOS
ld Y C
loop
do
ld A ((X) TAIL) # Get external symbol's tail
call nameA_A # Get name
rxl A 1 # Dirty or deleted?
if x # Yes
push Y
rxr A 1
ld Y A # Name in Y
call dbFileBlkY_AC # Get file and block index
cmp A (DBs) # Local file?
if lt # Yes
call setBlockAC_Z # Set up block env
call rdBlockZ_Z # Read first block
do
call logBlock # Write to transaction log
null (BlkLink) # More blocks?
while nz # Yes
call rdBlockLinkZ_Z # Read next block
loop
ld C (DbFile)
set (C (+ IV 1)) 1 # Set dirty flag
rxl Y 2 # Deleted?
if nx # No
inc (C VII) # Increment 'fluse'
end
end
pop Y
end
ld A (X CDR) # Right subtree?
atom (A CDR)
if z # Yes
ld C X # Go right
ld X (A CDR) # Invert tree
ld (A CDR) Y # TOS
or C SYM # First visit
ld Y C
break T
end
do
ld A Y # TOS
null A # Empty?
jeq 20 # Done
sym A # Second visit?
if z # Yes
ld C (A CDR) # Nodes
ld Y (C) # TOS on up link
ld (C) X
ld X A
break T
end
off A SYM # Set second visit
ld C (A CDR) # Nodes
ld Y (C CDR)
ld (C CDR) X
ld X A
loop
loop
loop
20 ld X (DbFiles) # Iterate DB files
ld Y (DBs) # Count
do
ld A (X VII) # Get 'fluse'
null A # Any?
if nz # Yes
push A # Save as count
ld A X
ld C 0 # Save Block 0 and free list
call setBlkAC_Z # Set up block env
call rdBlockZ_Z # Read first block
do
call logBlock # Write to transaction log
null (BlkLink) # More blocks?
while nz # Yes
sub (S) 1 # Decrement count
while nb
call rdBlockLinkZ_Z # Read next block
loop
add S I # Drop count
end
add X VIII # Increment by sizeof(dbFile)
sub Y VIII # Done?
until z # Yes
cc putc_unlocked((hex "FF") (DbLog)) # Write end marker
cc putc_unlocked((hex "FF") (DbLog))
cc fflush((DbLog)) # Flush Transaction log
call logFileno_A # Sync log file to disk
cc fsync(A)
nul4 # OK?
js trSyncErrX # No
pop Y
pop X
end
ld Y (Y CDR) # Eval pre-expression
ld E (Y)
eval
cmp (L I) Nil # 'any'?
if eq # No
push 0 # <L -I> No notification
else
ld A (Tell)
or A (Children)
push A # <L -I> Notify flag
if nz
push A # <L -II> Tell's buffer pointer
push (TellBuf) # <L -III> Save current 'tell' env
sub S PIPE_BUF # <L - III - PIPE_BUF> New 'tell' buffer
ld Z S # Buffer pointer
call tellBegZ_Z # Start 'tell' message
ld E (L I) # Get 'any'
call prTellEZ # Print to 'tell'
ld (L -II) Z # Save buffer pointer
end
end
push X
push Y
ld X (Extern) # Iterate external symbol tree
ld Y 0 # Clear TOS
do
do
ld A (X CDR) # Get subtrees
atom (A) # Left subtree?
while z # Yes
ld C X # Go left
ld X (A) # Invert tree
ld (A) Y # TOS
ld Y C
loop
do
lea C ((X) TAIL) # Get external symbol's tail
ld A (C)
num A # Any properties?
if z # Yes
off A SYM # Clear 'extern' tag
do
lea C (A CDR) # Skip property
ld A (C)
num A # Find name
until nz
end
rxl A 1 # Dirty?
if x # Yes
push Y
rxl A 1 # Deleted?
if nx # No
setx # Set "loaded"
rxr A 1
shr A 1
ld (C) A # in status/name
ld Y A # Name in Y
call dbFileBlkY_AC # Get file and block index
cmp A (DBs) # Local file?
if lt # Yes
call setBlockAC_Z # Set up block env
call rdBlockZ_Z # Read first block
ld B 1 # First block in object (might be a new object)
or (Z (- BLK)) B # Set in tag byte
ld (PutBinBZ) putBlockBZ # Set binary print function
ld Y (X) # Get external symbol
ld E (Y) # Print value
ld (Extn) 0 # Set external symbol offset to zero
call binPrintEZ
ld Y (Y TAIL) # Get tail
off Y SYM # Clear 'extern' tag
do
num Y # Properties?
while z # Yes
atom (Y) # Flag?
if z # No
ld E ((Y) CDR) # Get key
cmp E Nil # Volatile property?
if ne # No
call binPrintEZ # Print key
ld E ((Y)) # Print value
call binPrintEZ
end
else
ld E (Y) # Get key
cmp E Nil # Volatile property?
if ne # No
call binPrintEZ # Print key
ld E TSym # Print 'T'
call binPrintEZ
end
end
ld Y (Y CDR)
loop
ld B NIX
call putBlockBZ # Output NIX
ld Z (DbBlock) # Block buffer in Z again
ld B (Z) # Lowest byte of link field
and B BLKTAG # Clear link
zxt
call setAdrAZ # Store in last block
call wrBlockZ # Write block
ld Y (BlkLink) # More blocks?
null Y
if nz # Yes
call cleanUpY # Clean up
end
null (L -I) # Notify?
if nz # Yes
ld Z (L -II) # Get buffer pointer
lea A ((TellBuf) (- PIPE_BUF 10)) # Space for EXTERN+<8>+END?
cmp Z A
if ge # No
ld A 0 # Send to all PIDs
call tellEndAZ # Close 'tell'
lea Z (L (- (+ III PIPE_BUF))) # Reset buffer pointer
call tellBegZ_Z # Start new 'tell' message
ld E (L I) # Get 'any'
call prTellEZ # Print to 'tell'
end
ld E (X) # Get external symbol
call prTellEZ # Print to 'tell'
ld (L -II) Z # Save buffer pointer
end
end
else # Deleted
shr A 2 # Set "not loaded"
ld (C) A # in status/name
ld Y A # Name in Y
call dbFileBlkY_AC # Get file and block index
cmp A (DBs) # Local file?
if lt # Yes
add A (DbFiles) # Get DB file
ld (DbFile) A # Set current
ld Y C
call cleanUpY # Clean up
null (L -I) # Notify?
if nz # Yes
ld Z (L -II) # Get buffer pointer
lea A ((TellBuf) (- PIPE_BUF 10)) # Space for EXTERN+<8>+END?
cmp Z A
if ge # No
ld A 0 # Send to all PIDs
call tellEndAZ # Close 'tell'
lea Z (L (- (+ III PIPE_BUF))) # Reset buffer pointer
call tellBegZ_Z # Start new 'tell' message
ld E (L I) # Get 'any'
call prTellEZ # Print to 'tell'
end
ld E (X) # Get external symbol
call prTellEZ # Print to 'tell'
ld (L -II) Z # Save buffer pointer
end
end
end
pop Y
end
ld A (X CDR) # Right subtree?
atom (A CDR)
if z # Yes
ld C X # Go right
ld X (A CDR) # Invert tree
ld (A CDR) Y # TOS
or C SYM # First visit
ld Y C
break T
end
do
ld A Y # TOS
null A # Empty?
jeq 40 # Done
sym A # Second visit?
if z # Yes
ld C (A CDR) # Nodes
ld Y (C) # TOS on up link
ld (C) X
ld X A
break T
end
off A SYM # Set second visit
ld C (A CDR) # Nodes
ld Y (C CDR)
ld (C CDR) X
ld X A
loop
loop
loop
40 pop Y
pop X
null (L -I) # Notify?
if nz # Yes
ld A 0 # Send to all PIDs
ld Z (L -II) # Get buffer pointer
call tellEndAZ # Close 'tell'
add S PIPE_BUF # Drop 'tell' buffer
pop (TellBuf)
end
ld Y (Y CDR) # Eval post-expression
ld E (Y)
eval
null (DbJnl) # Journal?
if nz # Yes
call unLockJnl # Unlock journal
end
ld Y (Zap) # Objects to delete?
atom Y
if z # Yes
push (OutFile) # Save output channel
sub S (+ III BUFSIZ) # <S> Local buffer with sizeof(outFile)
ld E (Y CDR) # Get zap file pathname
call pathStringE_SZ # Write to stack buffer
cc open(S (| O_APPEND O_CREAT O_WRONLY) (oct "0666")) # Open zap file
nul4 # OK?
js openErrEX # No
ld S Z # Drop buffer
ld (S) A # Store 'fd' in outFile
ld (S I) 0 # Clear 'ix'
ld (S II) 0 # and 'tty'
ld (OutFile) S # Set OutFile
ld (PutBinBZ) putStdoutB # Set binary print function
ld Y (Y) # Get zap list
do
atom Y # More symbols?
while z # Yes
ld E (Y) # Get next
ld (Extn) 0 # Set external symbol offset to zero
call binPrintEZ # Print it
ld Y (Y CDR)
loop
ld A S # Flush file
call flushA_F
ld A S # Close file
call closeAX
ld ((Zap)) Nil # Clear zap list
add S (+ III BUFSIZ) # Drop buffer
pop (OutFile) # Restore output channel
end
null (DbLog) # Transaction log?
if nz # Yes
call fsyncDB # Sync DB files to disk
call truncLog # Truncate log file
end
ld A 0 # Length
call rwUnlockDbA # Unlock all
call unsync # Release sync
null (DbLog) # Transaction log?
if z # No
dec (EnvProtect) # Unprotect
end
ld E (DbFiles) # Iterate DB files
ld C (DBs) # Count
do
ld (E VII) -1 # Init 'fluse'
add E VIII # Increment by sizeof(dbFile)
sub C VIII # Done?
until z # Yes
drop
pop Z
pop Y
pop X
ld E TSym # Return T
ret