+struct integer_base
+ {
+ int base; /* Base. */
+ const char *digits; /* Collection of digits. */
+ const char *signifier; /* Prefix used with # flag. */
+ int group; /* Number of digits to group with ' flag. */
+ };
+
+static const struct integer_base base_d = {10, "0123456789", "", 3};
+static const struct integer_base base_o = {8, "01234567", "0", 3};
+static const struct integer_base base_x = {16, "0123456789abcdef", "0x", 4};
+static const struct integer_base base_X = {16, "0123456789ABCDEF", "0X", 4};
+
+static const char *parse_conversion (const char *format,
+ struct printf_conversion *,
+ va_list *);
+static void format_integer (uintmax_t value, bool negative,
+ const struct integer_base *,
+ const struct printf_conversion *,
+ void (*output) (char, void *), void *aux);
+static void output_dup (char ch, size_t cnt,
+ void (*output) (char, void *), void *aux);
+static void format_string (const char *string, size_t length,
+ struct printf_conversion *,
+ void (*output) (char, void *), void *aux);
+static void printf_core (const char *format,
+ void (*output) (char, void *), void *aux, ...);
+
+static void
+vprintf_core (const char *format, va_list args,
+ void (*output) (char, void *), void *aux)
+{
+ for (; *format != '\0'; format++)
+ {
+ struct printf_conversion c;
+
+ /* Literally copy non-conversions to output. */
+ if (*format != '%')
+ {
+ output (*format, aux);
+ continue;
+ }
+ format++;
+
+ /* %% => %. */
+ if (*format == '%')
+ {
+ output ('%', aux);
+ continue;
+ }
+
+ /* Parse conversion specifiers. */
+ format = parse_conversion (format, &c, &args);
+
+ /* Do conversion. */
+ switch (*format)
+ {
+ case 'd':
+ case 'i':
+ {
+ /* Signed integer conversions. */
+ intmax_t value;
+
+ switch (c.type)
+ {
+ case CHAR:
+ value = (signed char) va_arg (args, int);
+ break;
+ case SHORT:
+ value = (short) va_arg (args, int);
+ break;
+ case INT:
+ value = va_arg (args, int);
+ break;
+ case LONG:
+ value = va_arg (args, long);
+ break;
+ case LONGLONG:
+ value = va_arg (args, long long);
+ break;
+ case PTRDIFFT:
+ value = va_arg (args, ptrdiff_t);
+ break;
+ case SIZET:
+ value = va_arg (args, size_t);
+ break;
+ default:
+ NOT_REACHED ();
+ }
+
+ format_integer (value < 0 ? -value : value,
+ value < 0, &base_d, &c, output, aux);
+ }
+ break;
+
+ case 'o':
+ case 'u':
+ case 'x':
+ case 'X':
+ {
+ /* Unsigned integer conversions. */
+ uintmax_t value;
+ const struct integer_base *b;
+
+ switch (c.type)
+ {
+ case CHAR:
+ value = (unsigned char) va_arg (args, unsigned);
+ break;
+ case SHORT:
+ value = (unsigned short) va_arg (args, unsigned);
+ break;
+ case INT:
+ value = va_arg (args, unsigned);
+ break;
+ case LONG:
+ value = va_arg (args, unsigned long);
+ break;
+ case LONGLONG:
+ value = va_arg (args, unsigned long long);
+ break;
+ case PTRDIFFT:
+ value = va_arg (args, ptrdiff_t);
+ break;
+ case SIZET:
+ value = va_arg (args, size_t);
+ break;
+ default:
+ NOT_REACHED ();
+ }
+
+ switch (*format)
+ {
+ case 'o': b = &base_o; break;
+ case 'u': b = &base_d; break;
+ case 'x': b = &base_x; break;
+ case 'X': b = &base_X; break;
+ default: NOT_REACHED ();
+ }
+
+ format_integer (value, false, b, &c, output, aux);
+ }
+ break;
+
+ case 'c':
+ {
+ /* Treat character as single-character string. */
+ char ch = va_arg (args, int);
+ format_string (&ch, 1, &c, output, aux);
+ }
+ break;
+
+ case 's':
+ {
+ /* String conversion. */
+ const char *s = va_arg (args, char *);
+ if (s == NULL)
+ s = "(null)";
+
+ /* Limit string length according to precision.
+ Note: if c.precision == -1 then strnlen() will get
+ SIZE_MAX for MAXLEN, which is just what we want. */
+ format_string (s, strnlen (s, c.precision), &c, output, aux);
+ }
+ break;
+
+ case 'p':
+ {
+ /* Pointer conversion.
+ Format non-null pointers as %#x. */
+ void *p = va_arg (args, void *);
+
+ c.flags = POUND;
+ if (p != NULL)
+ format_integer ((uintptr_t) p, false, &base_x, &c, output, aux);
+ else
+ format_string ("(nil)", 5, &c, output, aux);
+ }
+ break;
+
+ case 'f':
+ case 'e':
+ case 'E':
+ case 'g':
+ case 'G':
+ case 'n':
+ /* We don't support floating-point arithmetic,
+ and %n can be part of a security hole. */
+ printf_core ("<<no %%%c in kernel>>", output, aux, *format);
+ break;
+
+ default:
+ printf_core ("<<no %%%c conversion>>", output, aux, *format);
+ break;
+ }
+ }
+}
+
+/* Parses conversion option characters starting at FORMAT and
+ initializes C appropriately. Returns the character in FORMAT
+ that indicates the conversion (e.g. the `d' in `%d'). Uses
+ *ARGS for `*' field widths and precisions. */