o Adding support for star modifier.

This allows %*s where the leading padding is taken from an extra
argument so that this:

    char buf[] = "0123456789";
    printf("'%*s'", 5, &buf[5]);

yields

    '56789'

Author: trygvis

test/all.c

@@ -21,11 +21,7 @@ void check(const char *expr, int expected_sz, int actual_sz)
     printf("Output     %s", actual_buffer);
   } else {
     failures++;
-    printf("FAIL       %s\n", expr);
-
-    if (!size_pass) {
-      printf("Size fail: expected=%d, actual=%d\n", expected_sz, actual_sz);
-    }
+    printf("FAIL       printf(%s)\n", expr);
 
     if (!content_pass) {
       printf("libc       %s\n", expected_buffer);
@@ -85,7 +81,12 @@ void main()
 
   {
     char buf[] = "0123456789";
-    TPRINTF("%*s", 5, &buf[5]);
+    TPRINTF("%*s", 5, &buf[5]);         /* minimum length, too long string */
+    TPRINTF("%.*s", 5, buf);            /* maximum length, too long string */
+    TPRINTF("%.*s", 5, &buf[8]);        /* maximum length, too short string */
+    TPRINTF("%*.*s", 5, 5, &buf[8]);    /* minimum and maximum, too short string*/
+    TPRINTF("%*.*s", 5, 1, &buf[8]);
+    TPRINTF("%*.*s", 5, 5, buf);
 
     TPRINTF("%-*d", 5, 123);
     TPRINTF("%*d", 5, 123);

tinyprintf.c

@@ -70,15 +70,16 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  * Implementation
  */
 struct param {
-    char l:1;           /**<  Add leading character */
-    char alt:1;         /**<  alternate form */
-    char uc:1;          /**<  Upper case (for base16 only) */
-    char align_left:1;  /**<  0 == align right (default), 1 == align left */
-    char lchr;          /**<  Leading character */
-    unsigned int width; /**<  field width */
-    char sign;          /**<  The sign to display (if any) */
-    unsigned int base;  /**<  number base (e.g.: 8, 10, 16) */
-    char *bf;           /**<  Buffer to output */
+    char l:1;               /**<  Add leading character */
+    char alt:1;             /**<  alternate form */
+    char uc:1;              /**<  Upper case (for base16 only) */
+    char align_left:1;      /**<  0 == align right (default), 1 == align left */
+    char lchr;              /**<  Leading character */
+    unsigned int width;     /**<  field width */
+    unsigned int precision; /**<  field precision */
+    char sign;              /**<  The sign to display (if any) */
+    unsigned int base;      /**<  number base (e.g.: 8, 10, 16) */
+    char *bf;               /**<  Buffer to output */
 };
 
 
@@ -199,14 +200,19 @@ static char a2u(char ch, const char **src, int base, unsigned int *nump)
     return ch;
 }
 
-static void putchw(void *putp, putcf putf, struct param *p)
+static void putchw(void *putp, putcf putf, const struct param *p)
 {
     char ch;
     int n = p->width;
     char *bf = p->bf;
+    unsigned int precision = p->precision;
+
+    if (precision == 0) {
+        precision = n;
+    }
 
     /* Number of filling characters */
-    while (*bf++ && n > 0)
+    while (*bf++ && n > 0 && precision--)
         n--;
     if (p->sign)
         n--;
@@ -241,7 +247,11 @@ static void putchw(void *putp, putcf putf, struct param *p)
 
     /* Put actual buffer */
     bf = p->bf;
-    while ((ch = *bf++))
+    precision = p->precision;
+    if (precision == 0) {
+        precision = n;
+    }
+    while ((ch = *bf++) && precision--)
         putf(putp, ch);
 
     /* Fill with space to align to the left, after string */
@@ -260,6 +270,7 @@ void tfp_format(void *putp, putcf putf, const char *fmt, va_list va)
     char bf[12];  /* int = 32b on some architectures */
 #endif
     char ch;
+    int w;
     p.bf = bf;
 
     while ((ch = *(fmt++))) {
@@ -274,6 +285,7 @@ void tfp_format(void *putp, putcf putf, const char *fmt, va_list va)
             p.lchr = ' ';
             p.alt = 0;
             p.width = 0;
+            p.precision = (unsigned int)-1; /* This turns into a very large number */
             p.align_left = 0;
             p.sign = 0;
 
@@ -292,7 +304,13 @@ void tfp_format(void *putp, putcf putf, const char *fmt, va_list va)
                     p.alt = 1;
                     continue;
                 case '*':
-                    p.width = (unsigned int) va_arg(va, int);
+                    w = va_arg(va, int);
+                    if (w < 0) {
+                        p.align_left = 1;
+                        p.width = (unsigned int) -w;
+                    } else {
+                        p.width = (unsigned int) w;
+                    }
                     continue;
                 default:
                     break;
@@ -319,6 +337,12 @@ void tfp_format(void *putp, putcf putf, const char *fmt, va_list va)
                 if (num > 1) {
                   p.lchr = '0';
                 }
+              } else if (ch == '*') {
+                  ch = *(fmt++);
+                  unsigned int precision = (unsigned int) va_arg(va, int);
+                  if (precision > 0) {
+                      p.precision = precision;
+                  }
               }
             }