postio.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 *
 * POSTBEGIN, if it's not NULL, is some PostScript code that's sent to the printer
 * before any of the input files. It's not terribly important since the same thing
 * can be accomplished in other ways, but this approach is convenient. POSTBEGIN
 * is initialized so as to disable job timeouts. The string can also be set on the
 * command line using the -P option.
 *
 */

#define POSTBEGIN	"statusdict /waittimeout 0 put\n"

/*
 *
 * The following help determine where postio is when it's running - either in the
 * START, SEND, or DONE states. Primarily controls what's done in getstatus().
 * RADIAN occasionally had problems with two way conversations. Anyway this stuff
 * can be used to prevent status queries while we're transmitting a job. Enabled
 * by the -q option.
 *
 */

#define NOTCONNECTED	0
#define START		1
#define SEND		2
#define DONE		3

/*
 *
 * Previous versions of postio only ran as a single process. That was (and still
 * is) convenient, but meant we could only flow control one direction. Data coming
 * back from the printer occasionally got lost, but that didn't often hurt (except
 * for lost error messages). Anyway I've added code that lets you split the program
 * into separate read and write processes, thereby helping to prevent data loss in
 * both directions. It should be particularly useful when you're sending a job that
 * you expect will be returning useful data over the communications line.
 *
 * The next three definitions control what's done with data on communications line.
 * The READ flag means the line can be read, while the WRITE flag means it can be
 * written. When we're running as a single process both flags are set. I tried to
 * overlay the separate read/write process code on what was there and working for
 * one process. The implementation isn't as good as it could be, but should be
 * safe. The single process version still works, and remains the default.
 *
 */

#define READ		1
#define WRITE		2
#define READWRITE	3

/*
 *
 * Messages generated on the printer and returned over the communications line
 * look like,
 *
 *	%%[ status: idle; source: serial 25 ]%%
 *	%%[ status: waiting; source: serial 25 ]%%
 *	%%[ status: initializing; source: serial 25 ]%%
 *	%%[ status: busy; source: serial 25 ]%%
 *	%%[ status: printing; source: serial 25 ]%%
 *	%%[ status: PrinterError: out of paper; source: serial 25 ]%%
 *	%%[ status: PrinterError: no paper tray; source: serial 25 ]%%
 *
 *	%%[ PrinterError: out of paper; source: serial 25 ]%%
 *	%%[ PrinterError: no paper tray; source: serial 25 ]%%
 *
 *	%%[ Error: undefined; OffendingCommand: xxx ]%%
 *	%%[ Flushing: rest of job (to end-of-file) will be ignored ]%%
 *
 * although the list isn't meant to be complete.
 *
 * The following constants are used to classify the recognized printer states.
 * readline() reads complete lines from ttyi and stores them in array mesg[].
 * getstatus() looks for the "%%[ " and " ]%%" delimiters that bracket printer
 * messages and if found it tries to parse the enclosed message. After the lookup
 * one of the following numbers is returned as an indication of the existence or
 * content of the printer message. The return value is used in start(), send(),
 * and done() to figure out what's happening and what can be done next.
 *
 */

#define BUSY		0		/* processing data already sent */
#define WAITING		1		/* printer wants more data */
#define PRINTING	2		/* printing a page */
#define IDLE		3		/* ready to start the next job */
#define ENDOFJOB	4		/* readline() builds this up on EOF */
#define PRINTERERROR	5		/* PrinterError - eg. out of paper */
#define ERROR		6		/* some kind of PostScript error */
#define FLUSHING	7		/* throwing out the rest of the job */
#define INITIALIZING	8		/* printer is booting */
#define DISCONNECT	9		/* from Datakit! */
#define UNKNOWN		10		/* in case we missed anything */
#define NOSTATUS	11		/* no response from the printer */

#define WRITEPROCESS	12		/* dummy states for write process */
#define INTERACTIVE	13		/* and interactive mode */

/*
 *
 * An array of type Status is used, in getstatus(), to figure out the printer's
 * current state. Just helps convert strings representing the current state into
 * integer codes that other routines use.
 *
 */

typedef struct {
	char	*state;			/* printer's current status */
	int	val;			/* value returned by getstatus() */
} Status;

/*
 *
 * STATUS is used to initialize an array of type Status that translates the ASCII
 * strings returned by the printer into appropriate codes that can be used later
 * on in the program. getstatus() converts characters to lower case, so if you
 * add any entries make them lower case and put them in before the UNKNOWN entry.
 * The lookup terminates when we get a match or when an entry with a NULL state
 * is found.
 *
 */

#define STATUS								\
									\
	{								\
	    "busy", BUSY,						\
	    "waiting", WAITING,						\
	    "printing", PRINTING,					\
	    "idle", IDLE,						\
	    "endofjob", ENDOFJOB,					\
	    "printererror", PRINTERERROR,				\
	    "error", ERROR,						\
	    "flushing", FLUSHING,					\
	    "initializing", INITIALIZING,				\
	    NULL, UNKNOWN						\
	}

/*
 *
 * The baud rate can be set on the command line using the -b option. If you omit
 * it BAUDRATE will be used.
 *
 */

#define BAUDRATE	B9600

/*
 *
 * An array of type Baud is used, in routine getbaud(), to translate ASCII strings
 * into termio values that represent the requested baud rate.
 *
 */

typedef struct {
	char	*rate;			/* string identifying the baud rate */
	short	val;			/* and its termio.h value */
} Baud;

/*
 *
 * BAUDTABLE initializes the array that's used to translate baud rate requests
 * into termio values. It needs to end with an entry that has NULL assigned to
 * the rate field.
 *
 */

#define BAUDTABLE							\
									\
	{								\
	    "9600", B9600,						\
	    "B9600", B9600,						\
	    "19200", EXTA,						\
	    "19.2", EXTA,						\
	    "B19200", EXTA,						\
	    "EXTA", EXTA,						\
	    "1200", B1200,						\
	    "B1200", B1200,						\
	    "2400", B2400,						\
	    "B2400", B2400,						\
	    "B4800", B4800,						\
	    "4800", B4800,						\
	    "38400", EXTB,						\
	    "38.4", EXTB,						\
	    "B38400", EXTB,						\
	    "EXTB", EXTB,						\
	    NULL, B9600							\
	}

/*
 *
 * A few miscellaneous definitions. BLOCKSIZE is the default size of the buffer
 * used for reading the input files (changed with the -B option). MESGSIZE is the
 * size of the character array used to store printer status lines - don't make it
 * too small!
 *
 */

#define BLOCKSIZE	2048
#define MESGSIZE	512

/*
 *
 * Some of the non-integer valued functions used in postio.c.
 *
 */

char	*find();

char	*malloc();
char	*strtok();