6/15/72 SALLOC (III)
NAME salloc -- string manipulation routines
SYNOPSIS (get size in r0)
jsr pc,allocate
(get source pointer in r0,
destination pointer in r1)
jsr pc,copy
jsr pc,wc
(all following instructions assume r1 contains pointer)
jsr pc,release
(get character in r0)
jsr pc,putchar
jsr pc,lookchar
(character in r0)
jsr pc,getchar
(character in r0)
(get character in r0)
jsr pc,alterchar
(get position in r0)
jsr pc,seekchar
jsr pc,backspace
(character in r0)
(get word in r0)
jsr pc,putword
jsr pc,lookword
(word in r0)
jsr pc,getword
(word in r0)
(get word in r0)
jsr pc,alterword
jsr pc,backword
(word in r0)
jsr pc,length
(length in r0)
jsr pc,position
(position in r0)
jsr pc,rewind
jsr pc,create
jsr pc,fsfile
jsr pc,zero
DESCRIPTION This package is a complete set of routines for
dealing with almost arbitrary length strings of
words and bytes. The strings are stored on a
disk file, so the sum of their lengths can be
considerably larger than the available core.
For each string there is a header of four words,
namely a write pointer, a read pointer and point-
ers to the beginning and end of the block con-
taining the string. Initially the read and write
pointers point to the beginning of the string.
All routines that refer to a string require the
header address in r1. Unless the string is de-
stroyed by the call, upon return r1 will point to
the same string, although the string may have
grown to the extent that it had to be be moved.
allocate obtains a string of the requested size
and returns a pointer to its header in r1.
release releases a string back to free storage.
putchar and putword write a byte or word respec-
tively into the string and advance the write
pointer.
lookchar and lookword read a byte or word respec-
tively from the string but do not advance the
read pointer.
getchar and getword read a byte or word respec-
tively from the string and advance the read
pointer.
alterchar and alterword write a byte or word re-
spectively into the string where the read pointer
is pointing and advance the read pointer.
backspace and backword read the last byte or word
written and decrement the write pointer.
All write operations will automatically get a
larger block if the current block is exceeded.
All read operations return with the error bit set
if attempting to read beyond the write pointer.
seekchar moves the read pointer to the offset
specified in r0.
length returns the current length of the string
(beginning pointer to write pointer) in r0.
position returns the current offset of the read
pointer in r0.
rewind moves the read pointer to the current po-
sition of the write pointer.
create returns the read and write pointers to the
beginning of the string.
fsfile moves the read pointer to the current po-
sition of the read pointer.
zero zeros the whole string and sets the write
pointer to the beginning of the string.
copy copies the string whose header pointer is in
r0 to the string whose header pointer is in r1.
Care should be taken in using the copy instruc-
tion since r1 will be changed if the contents of
the source string is bigger than the destination
string.
wc forces the contents of the internal buffers
and the header blocks to be written on disc.
FILES The allocator is in /usr/llc/alloc/alloca.
The archive /usr/llc/alloc/allocb contains the
individual routines discussed above.
alloc.d is the temporary file used to contain the
strings.
SEE ALSO --
DIAGNOSTICS "error in copy" if a disk write error occurs dur-
ing the execution of the copy instruction. "er-
ror in allocator" if any routine is called with a
bad header pointer. "Cannot open output file" if
file alloc.d cannot be created or opened. "Out
of space" if there's no available block of the
requested size or no headers available for a new
block.
BUGS --
OWNER llc,rhm