doprnt.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 792 行 · 第 1/2 页

		/* Scan the field width and precision */
		case '.':
			flagword |= DOTSEEN;
			prec = 0;
			goto charswitch;

		case '*':
			if (!(flagword & DOTSEEN)) {
				width = va_arg(args, int);
				if (width < 0) {
					width = -width;
					flagword ^= FMINUS;
				}
			} else {
				prec = va_arg(args, int);
				if (prec < 0)
					prec = 0;
			}
			goto charswitch;

		case '0':	/* obsolescent spec:  leading zero in width */
				/* means pad with leading zeros */
			if (!(flagword & (DOTSEEN | FMINUS)))
				flagword |= PADZERO;
		case '1':
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9':
		      { register num = fcode - '0';
			while (isdigit(fcode = *format)) {
				num = num * 10 + fcode - '0';
				format++;
			}
			if (flagword & DOTSEEN)
				prec = num;
			else
				width = num;
			goto charswitch;
		      }

		/* Scan the length modifier */
		case 'l':
			flagword |= LENGTH;
			/* No break */
		case 'h':
			goto charswitch;

		/*
		 *	The character addressed by format must be
		 *	the format letter -- there is nothing
		 *	left for it to be.
		 *
		 *	The status of the +, -, #, and blank
		 *	flags are reflected in the variable
		 *	"flagword".  "width" and "prec" contain
		 *	numbers corresponding to the digit
		 *	strings before and after the decimal
		 *	point, respectively. If there was no
		 *	decimal point, then flagword & DOTSEEN
		 *	is false and the value of prec is meaningless.
		 *
		 *	The following switch cases set things up
		 *	for printing.  What ultimately gets
		 *	printed will be padding blanks, a
		 *	prefix, left padding zeroes, a value,
		 *	right padding zeroes, a suffix, and
		 *	more padding blanks.  Padding blanks
		 *	will not appear simultaneously on both
		 *	the left and the right.  Each case in
		 *	this switch will compute the value, and
		 *	leave in several variables the informa-
		 *	tion necessary to construct what is to
		 *	be printed.  
		 *
		 *	The prefix is a sign, a blank, "0x",
		 *	"0X", or null, and is addressed by
		 *	"prefix".
		 *
		 *	The suffix is either null or an
		 *	exponent, and is addressed by "suffix".
		 *	If there is a suffix, the flagword bit
		 *	SUFFIX will be set.
		 *
		 *	The value to be printed starts at "bp"
		 *	and continues up to and not including
		 *	"p".
		 *
		 *	"lzero" and "rzero" will contain the
		 *	number of padding zeroes required on
		 *	the left and right, respectively.
		 *	The flagword bits LZERO and RZERO tell
		 *	whether padding zeros are required.
		 *
		 *	The number of padding blanks, and
		 *	whether they go on the left or the
		 *	right, will be computed on exit from
		 *	the switch.
		 */



		
		/*
		 *	decimal fixed point representations
		 *
		 *	HIBITL is 100...000
		 *	binary, and is equal to	the maximum
		 *	negative number.
		 *	We assume a 2's complement machine
		 */

		case 'd':
			/* Fetch the argument to be printed */
			if (flagword & LENGTH)
				val = va_arg(args, long);
			else
				val = va_arg(args, int);

			/* Set buffer pointer to last digit */
			p = bp = buf + MAXDIGS;

			/* If signed conversion, make sign */
			if (val < 0) {
				prefix = "-";
				prefixlength = 1;
				/*
				 * Negate, checking in
				 * advance for possible
				 * overflow.
				 */
				if (val != HIBITL)
					val = -val;
				else     /* number is -HIBITL; convert last */
					 /* digit now and get positive number */
					*--bp = _lowdigit(&val);
			} else if (flagword & FPLUS) {
				prefix = "+";
				prefixlength = 1;
			} else if (flagword & FBLANK) {
				prefix = " ";
				prefixlength = 1;
			}

		decimal:
			{ register long qval = val;
				if (qval <= 9) {
					if (qval != 0 || !(flagword & DOTSEEN))
						*--bp = qval + '0';
				} else {
					do {
						n = qval;
						qval /= 10;
						*--bp = n - qval * 10 + '0';
					} while (qval > 9);
					*--bp = qval + '0';
				}
			}

			/* Calculate minimum padding zero requirement */
			if (flagword & DOTSEEN) {
				register leadzeroes = prec - (p - bp);
				if (leadzeroes > 0) {
					otherlength = lzero = leadzeroes;
					flagword |= LZERO;
				}
			}

			break;

		case 'u':
			/* Fetch the argument to be printed */
			if (flagword & LENGTH)
				val = va_arg(args, long);
			else
				val = va_arg(args, unsigned);

			p = bp = buf + MAXDIGS;

			if (val & HIBITL)
				*--bp = _lowdigit(&val);

			goto decimal;

		/*
		 *	non-decimal fixed point representations
		 *	for radix equal to a power of two
		 *
		 *	"mradix" is one less than the radix for the conversion.
		 *	"lradix" is one less than the base 2 log
		 *	of the radix for the conversion. Conversion is unsigned.
		 *	HIBITL is 100...000
		 *	binary, and is equal to	the maximum
		 *	negative number.
		 *	We assume a 2's complement machine
		 */

		case 'o':
			mradix = 7;
			lradix = 2;
			goto fixed;

		case 'X':
		case 'x':
			mradix = 15;
			lradix = 3;

		fixed:
			/* Fetch the argument to be printed */
			if (flagword & LENGTH)
				val = va_arg(args, long);
			else
				val = va_arg(args, unsigned);

			/* Set translate table for digits */
			tab = (fcode == 'X') ?
			    "0123456789ABCDEF" : "0123456789abcdef";

			/* Develop the digits of the value */
			p = bp = buf + MAXDIGS;
			{ register long qval = val;
				if (qval == 0) {
					if (!(flagword & DOTSEEN)) {
						otherlength = lzero = 1;
						flagword |= LZERO;
					}
				} else
					do {
						*--bp = tab[qval & mradix];
						qval = ((qval >> 1) & ~HIBITL)
								 >> lradix;
					} while (qval != 0);
			}

			/* Calculate minimum padding zero requirement */
			if (flagword & DOTSEEN) {
				register leadzeroes = prec - (p - bp);
				if (leadzeroes > 0) {
					otherlength = lzero = leadzeroes;
					flagword |= LZERO;
				}
			}

			/* Handle the # flag */
			if (flagword & FSHARP && val != 0)
				switch (fcode) {
				case 'o':
					if (!(flagword & LZERO)) {
						otherlength = lzero = 1;
						flagword |= LZERO;
					}
					break;
				case 'x':
					prefix = "0x";
					prefixlength = 2;
					break;
				case 'X':
					prefix = "0X";
					prefixlength = 2;
					break;
				}

			break;

		case '%':
			buf[0] = fcode;
			goto c_merge;

		case 'c':
			buf[0] = va_arg(args, int);
		c_merge:
			p = (bp = &buf[0]) + 1;
			break;

		case 's':
			bp = va_arg(args, char *);
			if (bp == NULL) {	/* DAG -- robustness addition */
				bp = "(null)";
				flagword &= ~DOTSEEN;
			}
			if (!(flagword & DOTSEEN))
				p = bp + strlen(bp);
			else { /* a strnlen function would  be useful here! */
				register char *qp = bp;
				while (*qp++ != '\0' && --prec >= 0)
					;
				p = qp - 1;
			}
			break;

		default: /* this is technically an error; what we do is to */
			/* back up the format pointer to the offending char */
			/* and continue with the format scan */
			format--;
			continue;

		}

		/* Calculate number of padding blanks */
		k = (n = p - bp) + prefixlength + otherlength;
		if (width <= k)
			count += k;
		else {
			count += width;

			/* Set up for padding zeroes if requested */
			/* Otherwise emit padding blanks unless output is */
			/* to be left-justified.  */

			if (flagword & PADZERO) {
				if (!(flagword & LZERO)) {
					flagword |= LZERO;
					lzero = width - k;
				}
				else
					lzero += width - k;
				k = width; /* cancel padding blanks */
			} else
				/* Blanks on left if required */
				if (!(flagword & FMINUS))
					blankpad(width - k);
		}

		/* Prefix, if any */
		if (prefixlength != 0)
			PUT(prefix, prefixlength);

		/* Zeroes on the left */
		if (flagword & LZERO)
			zeropad(lzero);
		
		/* The value itself */
		if (n > 0)
			PUT(bp, n);

		if (flagword & (RZERO | SUFFIX | FMINUS)) {
			/* Zeroes on the right */
			if (flagword & RZERO)
				zeropad(rzero);

			/* The suffix */
			if (flagword & SUFFIX)
				PUT(suffix, suffixlength);

			/* Blanks on the right if required */
			if (flagword & FMINUS && width > k)
				blankpad(width - k);
		}
	}
}

/*
 * Padding was done very naively before. It assumed no more than 20
 * characters of padding. csh needs 21 in one place and maybe more.
 *
 * The routines below handle all cases.
 */

static
blankpad(n)
int n;
{

	static char *blanks = "                    ";	/* 20 blanks	*/

	while (n >= 20) {
		PUT(blanks, 20);
		n -= 20;
	}

	if (n > 0) {
		PUT(blanks, n);
	}
}

static
zeropad(n)
int n;
{

	static char *zeros = "00000000000000000000";	/* 20 zeros	*/

	while (n >= 20) {
		PUT(zeros, 20);
		n -= 20;
	}

	if (n > 0) {
		PUT(zeros, n);
	}
}