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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <gki.h>
define LEN_DEFIBUF 2048
define ONEWORD SZ_SHORT
define TWOWORDS (2*SZ_SHORT)
# Header fields of a GKI instruction.
define I_BOI Mems[$1+GKI_HDR_BOI-1]
define I_OPCODE Mems[$1+GKI_HDR_OPCODE-1]
define I_LENGTH Mems[$1+GKI_HDR_LENGTH-1]
define I_DATA Mems[$1+GKI_DATAFIELDS-1]
# GKI_FETCH_NEXT_INSTRUCTION -- Fetch the next GKI metacode instruction from the
# input stream. A pointer to a short integer buffer containing the instruction
# is returned as an output argument. EOF is returned as the function value
# when EOF is seen on the input stream. The instruction buffer may be
# deallocated by our caller at any time, if desired. A new buffer will be
# created automatically when next we are called.
int procedure gki_fetch_next_instruction (fd, instruction)
int fd # input file containing metacode
pointer instruction # pointer to instruction (output)
int len_ibuf, nchars
pointer ibuf
int read()
errchk read, malloc, realloc
data ibuf /NULL/
begin
# Allocate a default sized instruction buffer. We can reallocate
# a larger buffer later if necessary.
if (ibuf == NULL) {
call malloc (ibuf, LEN_DEFIBUF, TY_SHORT)
len_ibuf = LEN_DEFIBUF
}
# Advance to the next instruction. Nulls and botched portions of
# instructions are ignored. Read the instruction header to determine
# the length of the instruction, and then read the rest of instruction
# into buffer. If the entire instruction cannot be read we have a
# botched instruction and must try again.
repeat {
repeat {
if (read (fd, I_BOI(ibuf), ONEWORD) == EOF)
return (EOF)
} until (I_BOI(ibuf) == BOI)
if (read (fd, I_OPCODE(ibuf), TWOWORDS) == EOF)
return (EOF)
# Make instruction buffer large enough to hold instruction.
# Compute length of remainder of instruction in chars.
if (I_LENGTH(ibuf) > len_ibuf) {
len_ibuf = I_LENGTH(ibuf)
call realloc (ibuf, len_ibuf, TY_SHORT)
}
nchars = (I_LENGTH(ibuf) - LEN_GKIHDR) * SZ_SHORT
if (nchars == 0)
break
} until (read (fd, I_DATA(ibuf), nchars) == nchars)
instruction = ibuf
# Check for a soft end of file, otherwise return the length of the
# instruction as the function value.
if (I_OPCODE(ibuf) == GKI_EOF)
return (EOF)
else
return (I_LENGTH(ibuf))
end
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