NAME
salloc - string allocation and manipulation
SYNOPSIS
(get size in r0)
jsr pc,allocate
(header address in r1)
(get source header address in r0,
destination header address in r1)
jsr pc,copy
jsr pc,wc
(all following routines assume r1 contains header address)
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)
1
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. It
lives in /lib/libs.a. The strings are stored on a disk
file, so the sum of their lengths can be considerably larger
than the available core. A small buffer cache makes for
reasonable speed.
For each string there is a header of four words, namely a
write pointer, a read pointer and pointers to the beginning
and end of the block containing 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 destroyed 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 respectively into
the string and advance the write pointer.
Lookchar and lookword read a byte or word respectively from
the string but do not advance the read pointer.
Getchar and getword read a byte or word respectively from
the string and advance the read pointer.
Alterchar and alterword write a byte or word respectively
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
2
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 beginning of the
string.
Create returns the read and write pointers to the beginning
of the string.
Fsfile moves the read pointer to the current position of the
write 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 instruction since r1 will be changed if
the contents of the source string is bigger than the desti-
nation string.
Wc forces the contents of the internal buffers and the
header blocks to be written on disc.
An in-core version of this allocator exists in dc (I), and a
permanent-file version exists in form and fed (VI).
FILES
/lib/libs.a library, accessed by ld ... -ls
alloc.d temporary file for string storage
SEE ALSO
alloc (III)
DIAGNOSTICS
`error in copy' - disk write error encountered in copy.
`error in allocator' - routine called with bad header
pointer.
`cannot open output file' - temp file alloc.d cannot be cre-
ated or opened.
`out of space' - no sufficiently large block or no header is
available for a new or growing block.
BUGS
3