lib/printfmt.c

   1 // Stripped-down primitive printf-style formatting routines,
   2 // used in common by printf, sprintf, fprintf, etc.
   3 // This code is also used by both the kernel and user programs.
   4
   5 #include <inc/types.h>
   6 #include <inc/stdio.h>
   7 #include <inc/string.h>
   8 #include <inc/stdarg.h>
   9 #include <inc/error.h>
  10
  11 /*
  12  * Space or zero padding and a field width are supported for the numeric
  13  * formats only.
  14  *
  15  * The special format %e takes an integer error code
  16  * and prints a string describing the error.
  17  * The integer may be positive or negative,
  18  * so that -E_NO_MEM and E_NO_MEM are equivalent.
  19  */
  20
  21 static const char * const error_string[MAXERROR + 1] =
  22 {
  23         NULL,
  24         "unspecified error",
  25         "bad environment",
  26         "invalid parameter",
  27         "out of memory",
  28         "out of environments",
  29         "segmentation fault",
  30         "env is not recving",
  31         "unexpected end of file",
  32 };
  33
  34 /*
  35  * Print a number (base <= 16) in reverse order,
  36  * using specified putch function and associated pointer putdat.
  37  */
  38 static void
  39 printnum(void (*putch)(int, void*), void *putdat,
  40          unsigned long long num, unsigned base, int width, int padc)
  41 {
  42         // first recursively print all preceding (more significant) digits
  43         if (num >= base) {
  44                 printnum(putch, putdat, num / base, base, width - 1, padc);
  45         } else {
  46                 // print any needed pad characters before first digit
  47                 while (--width > 0)
  48                         putch(padc, putdat);
  49         }
  50
  51         // then print this (the least significant) digit
  52         putch("0123456789abcdef"[num % base], putdat);
  53 }
  54
  55 // Get an unsigned int of various possible sizes from a varargs list,
  56 // depending on the lflag parameter.
  57 static unsigned long long
  58 getuint(va_list *ap, int lflag)
  59 {
  60         if (lflag >= 2)
  61                 return va_arg(*ap, unsigned long long);
  62         else if (lflag)
  63                 return va_arg(*ap, unsigned long);
  64         else
  65                 return va_arg(*ap, unsigned int);
  66 }
  67
  68 // Same as getuint but signed - can't use getuint
  69 // because of sign extension
  70 static long long
  71 getint(va_list *ap, int lflag)
  72 {
  73         if (lflag >= 2)
  74                 return va_arg(*ap, long long);
  75         else if (lflag)
  76                 return va_arg(*ap, long);
  77         else
  78                 return va_arg(*ap, int);
  79 }
  80
  81
  82 // Main function to format and print a string.
  83 void printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...);
  84
  85 void
  86 vprintfmt(void (*putch)(int, void*), void *putdat, const char *fmt, va_list ap)
  87 {
  88         register const char *p;
  89         register int ch, err;
  90         unsigned long long num;
  91         int base, lflag, width, precision, altflag;
  92         char padc;
  93
  94         while (1) {
  95                 while ((ch = *(unsigned char *) fmt++) != '%') {
  96                         if (ch == '\0')
  97                                 return;
  98                         putch(ch, putdat);
  99                 }
 100
 101                 // Process a %-escape sequence
 102                 padc = ' ';
 103                 width = -1;
 104                 precision = -1;
 105                 lflag = 0;
 106                 altflag = 0;
 107         reswitch:
 108                 switch (ch = *(unsigned char *) fmt++) {
 109
 110                 // flag to pad on the right
 111                 case '-':
 112                         padc = '-';
 113                         goto reswitch;
 114
 115                 // flag to pad with 0's instead of spaces
 116                 case '0':
 117                         padc = '0';
 118                         goto reswitch;
 119
 120                 // width field
 121                 case '1':
 122                 case '2':
 123                 case '3':
 124                 case '4':
 125                 case '5':
 126                 case '6':
 127                 case '7':
 128                 case '8':
 129                 case '9':
 130                         for (precision = 0; ; ++fmt) {
 131                                 precision = precision * 10 + ch - '0';
 132                                 ch = *fmt;
 133                                 if (ch < '0' || ch > '9')
 134                                         break;
 135                         }
 136                         goto process_precision;
 137
 138                 case '*':
 139                         precision = va_arg(ap, int);
 140                         goto process_precision;
 141
 142                 case '.':
 143                         if (width < 0)
 144                                 width = 0;
 145                         goto reswitch;
 146
 147                 case '#':
 148                         altflag = 1;
 149                         goto reswitch;
 150
 151                 process_precision:
 152                         if (width < 0)
 153                                 width = precision, precision = -1;
 154                         goto reswitch;
 155
 156                 // long flag (doubled for long long)
 157                 case 'l':
 158                         lflag++;
 159                         goto reswitch;
 160
 161                 // character
 162                 case 'c':
 163                         putch(va_arg(ap, int), putdat);
 164                         break;
 165
 166                 // error message
 167                 case 'e':
 168                         err = va_arg(ap, int);
 169                         if (err < 0)
 170                                 err = -err;
 171                         if (err > MAXERROR || (p = error_string[err]) == NULL)
 172                                 printfmt(putch, putdat, "error %d", err);
 173                         else
 174                                 printfmt(putch, putdat, "%s", p);
 175                         break;
 176
 177                 // string
 178                 case 's':
 179                         if ((p = va_arg(ap, char *)) == NULL)
 180                                 p = "(null)";
 181                         if (width > 0 && padc != '-')
 182                                 for (width -= strnlen(p, precision); width > 0; width--)
 183                                         putch(padc, putdat);
 184                         for (; (ch = *p++) != '\0' && (precision < 0 || --precision >= 0); width--)
 185                                 if (altflag && (ch < ' ' || ch > '~'))
 186                                         putch('?', putdat);
 187                                 else
 188                                         putch(ch, putdat);
 189                         for (; width > 0; width--)
 190                                 putch(' ', putdat);
 191                         break;
 192
 193                 // (signed) decimal
 194                 case 'd':
 195                         num = getint(&ap, lflag);
 196                         if ((long long) num < 0) {
 197                                 putch('-', putdat);
 198                                 num = -(long long) num;
 199                         }
 200                         base = 10;
 201                         goto number;
 202
 203                 // unsigned decimal
 204                 case 'u':
 205                         num = getuint(&ap, lflag);
 206                         base = 10;
 207                         goto number;
 208
 209                 // (unsigned) octal
 210                 case 'o':
 211                         // Replace this with your code.
 212                         num = getuint(&ap, lflag);
 213                         base = 8;
 214                         goto number;
 215
 216                 // pointer
 217                 case 'p':
 218                         putch('0', putdat);
 219                         putch('x', putdat);
 220                         num = (unsigned long long)
 221                                 (uintptr_t) va_arg(ap, void *);
 222                         base = 16;
 223                         goto number;
 224
 225                 // (unsigned) hexadecimal
 226                 case 'x':
 227                         num = getuint(&ap, lflag);
 228                         base = 16;
 229                 number:
 230                         printnum(putch, putdat, num, base, width, padc);
 231                         break;
 232
 233                 // escaped '%' character
 234                 case '%':
 235                         putch(ch, putdat);
 236                         break;
 237
 238                 // unrecognized escape sequence - just print it literally
 239                 default:
 240                         putch('%', putdat);
 241                         for (fmt--; fmt[-1] != '%'; fmt--)
 242                                 /* do nothing */;
 243                         break;
 244                 }
 245         }
 246 }
 247
 248 void
 249 printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...)
 250 {
 251         va_list ap;
 252
 253         va_start(ap, fmt);
 254         vprintfmt(putch, putdat, fmt, ap);
 255         va_end(ap);
 256 }
 257
 258 struct sprintbuf {
 259         char *buf;
 260         char *ebuf;
 261         int cnt;
 262 };
 263
 264 static void
 265 sprintputch(int ch, struct sprintbuf *b)
 266 {
 267         b->cnt++;
 268         if (b->buf < b->ebuf)
 269                 *b->buf++ = ch;
 270 }
 271
 272 int
 273 vsnprintf(char *buf, int n, const char *fmt, va_list ap)
 274 {
 275         struct sprintbuf b = {buf, buf+n-1, 0};
 276
 277         if (buf == NULL || n < 1)
 278                 return -E_INVAL;
 279
 280         // print the string to the buffer
 281         vprintfmt((void*)sprintputch, &b, fmt, ap);
 282
 283         // null terminate the buffer
 284         *b.buf = '\0';
 285
 286         return b.cnt;
 287 }
 288
 289 int
 290 snprintf(char *buf, int n, const char *fmt, ...)
 291 {
 292         va_list ap;
 293         int rc;
 294
 295         va_start(ap, fmt);
 296         rc = vsnprintf(buf, n, fmt, ap);
 297         va_end(ap);
 298
 299         return rc;
 300 }
 301
 302