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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <mach.h>
include <config.h>
include <syserr.h>
# KREALLOC -- Change the size of a previously allocated buffer, moving the
# buffer if necessary. If there is no old buffer (NULL pointer) simply
# allocate a new buffer. This routine is equivalent to REALLOC except that it
# merely returns ERR as the function value if an error occurs.
#
# Buffer reallocation or resizing can always be implemented by allocating a new
# buffer, copying the contents of the old buffer to the new buffer, and then
# deleting the old buffer. Nonetheless we use a OS entry point to do the actual
# reallocation, because often it will be possible to change the size of a buffer
# without moving it, particularly when decreasing the size of the buffer.
#
# Allowing the OS to move a buffer causes problems due to the difference in
# alignment criteria imposed by the IRAF pointer scheme, which enforces
# stringent alignment criteria, versus OS memory allocation schemes which
# typically only align on word or longword boundaries. Therefore we must
# check the offset of the data area after reallocation, possibly shifting
# the contents of data area up or down a few chars to reestablish alignment
# with Mem.
int procedure krealloc (ptr, a_nelems, a_dtype)
pointer ptr # buffer to be reallocated
int a_nelems # new size of buffer
int a_dtype # buffer datatype
pointer dataptr
int nelems, dtype, nchars, old_fwa, new_fwa
int char_shift, old_char_offset, new_char_offset
int status, locbuf, loc_Mem
int mgtfwa(), sizeof(), kmalloc()
pointer mgdptr(), msvfwa(), coerce()
data loc_Mem /NULL/
begin
# Copy over the number of elements and the data type in case they are
# located in the block of memory we are reallocating.
nelems = a_nelems
dtype = a_dtype
if (ptr == NULL) {
return (kmalloc (ptr, nelems, dtype))
} else {
if (dtype == TY_CHAR)
nchars = nelems + 1 + SZ_INT + SZ_MEMALIGN
else
nchars = nelems * sizeof(dtype) + SZ_INT + SZ_MEMALIGN
old_fwa = mgtfwa (ptr, dtype)
new_fwa = old_fwa
# Change the buffer size; any error is fatal.
call zraloc (new_fwa, nchars * SZB_CHAR, status)
if (status == ERR) {
ptr = NULL
return (ERR)
}
# Compute the char offset of the old data area within the original
# buffer; zraloc() guarantees that the old data will have the same
# offset in the new buffer. Compute the char offset of the new
# data area. These need not be the same due to the OS allocating
# the new buffer to alignment criteria less than those required
# by MEMIO.
call zlocva (Memc[coerce(ptr,dtype,TY_CHAR)], locbuf)
old_char_offset = (locbuf - old_fwa)
# We must compute a pointer to the data area within the new
# buffer before we can compute the char offset of the new data
# area within the new buffer.
if (loc_Mem == NULL)
call zlocva (Memc, loc_Mem)
dataptr = mgdptr (new_fwa, TY_CHAR, SZ_MEMALIGN, loc_Mem)
call zlocva (Memc[dataptr], locbuf)
new_char_offset = (locbuf - new_fwa)
# Shift the old data to satisfy the new alignment criteria,
# if necessary.
char_shift = (new_char_offset - old_char_offset)
if (char_shift != 0) {
call amovc (Memc[dataptr - char_shift], Memc[dataptr],
nelems * sizeof(dtype))
}
# Save the fwa of the OS buffer in the buffer header, and return
# new pointer to user.
ptr = msvfwa (new_fwa, dtype, SZ_MEMALIGN, loc_Mem)
}
return (OK)
end
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