implement precision, so we can print fixed-length non-null-terminated name/version strings

1 files changed, 82 insertions, 24 deletions

diff --git a/printf.c b/printf.c
index a6153d8..5a15d12 100644
--- a/printf.c
+++ b/printf.c
@@ -28,7 +28,7 @@ flag:	-	left justify, pad right w/ blanks	DONE
 

 width:		(field width)				DONE

 

-prec:		(precision)				no

+prec:		(precision)				DONE

 

 conv:	d,i	decimal int				DONE

 	u	decimal unsigned			DONE

@@ -43,7 +43,7 @@ mod:	N	near ptr				DONE
 	F	far ptr					no

 	h	short (16-bit) int			DONE

 	l	long (32-bit) int			DONE

-	L	long long (64-bit) int			no

+	L/ll	long long (64-bit) int			no

 *****************************************************************************/

 #include <string.h> /* strlen() */

 #include <stdio.h> /* stdout, putchar(), fputs() (but not printf() :) */

@@ -64,6 +64,10 @@ mod:	N	near ptr				DONE
 2^64-1 in base 8 has 22 digits (add 2 for trailing NUL and for slop) */

 #define	PR_BUFLEN	24

 

+#ifndef max

+#define max(a,b) ((a > b) ? a : b)

+#endif

+

 typedef int (*fnptr_t)(unsigned c, void **helper);

 /*****************************************************************************

 name:	do_printf

@@ -73,12 +77,12 @@ returns:total number of characters output
 *****************************************************************************/

 int do_printf(const char *fmt, va_list args, fnptr_t fn, void *ptr)

 {

-	unsigned flags, actual_wd, count, given_wd;

+        unsigned flags, length, count, width, precision;

 	unsigned char *where, buf[PR_BUFLEN];

 	unsigned char state, radix;

 	long num;

 

-	state = flags = count = given_wd = 0;

+	state = flags = count = width = precision = 0;

 /* begin scanning format specifier list */

 	for(; *fmt; fmt++)

 	{

@@ -102,13 +106,13 @@ int do_printf(const char *fmt, va_list args, fnptr_t fn, void *ptr)
 			{

 				fn(*fmt, &ptr);

 				count++;

-				state = flags = given_wd = 0;

+				state = flags = width = precision = 0;

 				break;

 			}

 			if(*fmt == '-')

 			{

 				if(flags & PR_LJ)/* %-- is illegal */

-					state = flags = given_wd = 0;

+					state = flags = width = precision = 0;

 				else

 					flags |= PR_LJ;

 				break;

@@ -126,15 +130,26 @@ int do_printf(const char *fmt, va_list args, fnptr_t fn, void *ptr)
 		case 2:

 			if(*fmt >= '0' && *fmt <= '9')

 			{

-				given_wd = 10 * given_wd +

-					(*fmt - '0');

+				width = 10 * width + (*fmt - '0');

 				break;

 			}

-/* not field width: advance state to check if it's a modifier */

+/* not a field width: advance state to check if it's field precision */

 			state++;

 			/* FALL THROUGH */

-/* STATE 3: AWAITING MODIFIER CHARS (FNlh) */

+/* STATE 3: AWAITING (NUMERIC) FIELD PRECISION */

 		case 3:

+			if(*fmt == '.')

+				++fmt;

+			if(*fmt >= '0' && *fmt <= '9')

+			{

+				precision = 10 * precision + (*fmt - '0');

+				break;

+			}

+/* not field precision: advance state to check if it's a modifier */

+			state++;

+			/* FALL THROUGH */

+/* STATE 4: AWAITING MODIFIER CHARS (FNlh) */

+		case 4:

 			if(*fmt == 'F')

 			{

 				flags |= PR_FP;

@@ -155,8 +170,8 @@ int do_printf(const char *fmt, va_list args, fnptr_t fn, void *ptr)
 /* not modifier: advance state to check if it's a conversion char */

 			state++;

 			/* FALL THROUGH */

-/* STATE 4: AWAITING CONVERSION CHARS (Xxpndiuocs) */

-		case 4:

+/* STATE 5: AWAITING CONVERSION CHARS (Xxpndiuocs) */

+		case 5:

 			where = buf + PR_BUFLEN - 1;

 			*where = '\0';

 			switch(*fmt)

@@ -225,22 +240,36 @@ OK, I found my mistake. The math here is _always_ unsigned */
 					num = (unsigned long)num / radix;

 				}

 				while(num != 0);

+/* for integers, precision functions like width, but pads with zeros */

+				if (precision != 0)

+				{

+					width = max(width, precision);

+					if (precision > strlen(where))

+						flags |= PR_LZ;

+					precision = 0;

+				}

 				goto EMIT;

 			case 'c':

 /* disallow pad-left-with-zeroes for %c */

 				flags &= ~PR_LZ;

 				where--;

 				*where = (unsigned char)va_arg(args, int);

-				actual_wd = 1;

+				length = 1;

 				goto EMIT2;

 			case 's':

 /* disallow pad-left-with-zeroes for %s */

 				flags &= ~PR_LZ;

 				where = va_arg(args, unsigned char *);

 EMIT:

-				actual_wd = strlen((const char *)where);

+				length = strlen((const char *)where);

+/* if string is longer than precision, truncate */

+				if ((precision != 0) && (precision < length))

+				{

+					length = precision;

+					precision = 0;

+				}

 				if(flags & PR_WS)

-					actual_wd++;

+					length++;

 /* if we pad left with ZEROES, do the sign now */

 				if((flags & (PR_WS | PR_LZ)) ==

 					(PR_WS | PR_LZ))

@@ -251,12 +280,12 @@ EMIT:
 /* pad on left with spaces or zeroes (for right justify) */

 EMIT2:				if((flags & PR_LJ) == 0)

 				{

-					while(given_wd > actual_wd)

+					while(width > length)

 					{

 						fn(flags & PR_LZ ?

 							'0' : ' ', &ptr);

 						count++;

-						given_wd--;

+						width--;

 					}

 				}

 /* if we pad left with SPACES, do the sign now */

@@ -266,16 +295,17 @@ EMIT2:				if((flags & PR_LJ) == 0)
 					count++;

 				}

 /* emit string/char/converted number */

-				while(*where != '\0')

+				for(int i = (flags & PR_WS) ? 1 : 0;

+				    i < length; ++i)

 				{

 					fn(*where++, &ptr);

 					count++;

 				}

 /* pad on right with spaces (for left justify) */

-				if(given_wd < actual_wd)

-					given_wd = 0;

-				else given_wd -= actual_wd;

-				for(; given_wd; given_wd--)

+				if(width < length)

+					width = 0;

+				else width -= length;

+				for(; width; width--)

 				{

 					fn(' ', &ptr);

 					count++;

@@ -285,7 +315,7 @@ EMIT2:				if((flags & PR_LJ) == 0)
 				break;

 			}

 		default:

-			state = flags = given_wd = 0;

+			state = flags = width = precision = 0;

 			break;

 		}

 	}

@@ -369,7 +399,35 @@ int main(void)
 

 	printf("<%-8s> and <%8s> justified strings\n", "left", "right");

 

-	printf("short signed: %hd, short unsigned: %hu\n", -1, -1);

+	printf("short signed: %hd, short unsigned: %hu\n\n", -1, -1);

+

+    char str[] = "abcdefghijklmnopqrstuvwxyz";

+    printf("%8s\n", str);	/* abcdefghijklmnopqrstuvwxyz */

+    printf("%8.32s\n", str);	/* abcdefghijklmnopqrstuvwxyz */

+    printf("%8.16s\n", str);	/* abcdefghijklmnop */

+    printf("%8.8s\n", str);	/* abcdefgh */

+    printf("%8.4s\n", str);	/*     abcd */

+    printf("%4.8s\n", str);	/* abcdefgh */

+    printf("%.8s\n", str);	/* abcdefgh */

+    printf("%8s\n", "abcd");	/*     abcd */

+    printf("%8.8s\n", "abcd");	/*     abcd */

+    printf("%4.8s\n", "abcd");	/* abcd */

+    printf("%.8s\n", "abcd");	/* abcd */

+    printf("%.0s\n", str);	/* */

+    printf("\n");

+

+    int num = 123456;

+    printf("%016d\n", num);	/* 0000000000123456 */

+    printf("%16d\n", num);	/*           123456 */

+    printf("%8d\n", num);	/*   123456 */

+    printf("%8.16d\n", num);	/* 0000000000123456 */

+    printf("%8.8d\n", num);	/* 00123456 */

+    printf("%8.4d\n", num);	/*   123456 */

+    printf("%4.4d\n", num);	/* 123456 */

+    printf("%.16d\n", num);	/* 0000000000123456 */ 

+    printf("%.8d\n", num);	/* 00123456 */

+    printf("%.4d\n", num);	/* 123456 */

+

 	return 0;

 }

 #else