diff options
Diffstat (limited to 'kernel/std/printf.c')
| -rw-r--r-- | kernel/std/printf.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/kernel/std/printf.c b/kernel/std/printf.c new file mode 100644 index 0000000..0bb5506 --- /dev/null +++ b/kernel/std/printf.c @@ -0,0 +1,199 @@ +#include <limits.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+static bool print(const char* data, size_t length) {
+ const unsigned char* bytes = (const unsigned char*) data;
+ for (size_t i = 0; i < length; i++)
+ if (putchar(bytes[i]) == EOF)
+ return false;
+ return true;
+}
+
+// for %d and %x.
+static const char* itoa(unsigned int num, char* str, unsigned int base) {
+ int cou = 0; // nt
+
+ if (num == 0) { // 0
+ str[cou] = '0';
+ str[++cou] = '\0';
+ return str;
+ }
+
+ while (num)
+ {
+ unsigned int rem = (num % base);
+ // brings the number up to ascii 0 + the digit
+ if (rem > 9) {
+ str[cou] = rem + '7'; // 7 = 55 + 10(A) = 65
+ } else {
+ str[cou] = rem + '0';
+ }
+ num /= base;
+ ++cou;
+ }
+
+ // reverse the string
+ size_t start = 0;
+ size_t end = cou - 1;
+ while (start < end) {
+ char temp = str[start];
+ str[start] = str[end];
+ str[end] = temp;
+ ++start;
+ --end;
+ }
+
+ str[cou] = '\0';
+ return str;
+}
+
+// have no idea if there's a better way to do this. for %lx
+static const char* itoa_u64(unsigned long long num, char* str, int base) {
+ size_t cou = 0; // nt
+
+ if (num == 0) { // 0
+ str[cou] = '0';
+ str[++cou] = '\0';
+ return str;
+ }
+
+ while (num)
+ {
+ unsigned long long rem = num % base;
+ // brings the number up to ascii 0 + the digit
+ if (rem > 9) {
+ str[cou] = rem + '7'; // 7 = 55 + 10(A) = 65
+ } else {
+ str[cou] = rem + '0';
+ }
+ num /= base;
+ ++cou;
+ }
+
+ // reverse the string
+ size_t start = 0;
+ size_t end = cou - 1;
+ while (start < end) {
+ char temp = str[start];
+ str[start] = str[end];
+ str[end] = temp;
+ ++start;
+ --end;
+ }
+
+ str[cou] = '\0';
+ return str;
+}
+
+int printf(const char* restrict format, ...) {
+ va_list parameters;
+ va_start(parameters, format);
+
+ int written = 0;
+
+ while (*format != '\0') {
+ size_t maxrem = INT_MAX - written;
+
+ if (format[0] != '%' || format[1] == '%') {
+ if (format[0] == '%')
+ format++;
+ size_t amount = 1;
+ while (format[amount] && format[amount] != '%')
+ amount++;
+ if (maxrem < amount) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(format, amount))
+ return -1;
+ format += amount;
+ written += amount;
+ continue;
+ }
+
+ const char* format_begun_at = format++;
+
+ if (*format == 'c') {
+ format++;
+ char c = (char) va_arg(parameters, int /* char promotes to int */);
+ if (!maxrem) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(&c, sizeof(c)))
+ return -1;
+ written++;
+ } else if (*format == 'd') {
+ format++;
+ char str[20]; // probably a long enough buffer
+ unsigned int d = va_arg(parameters, unsigned int);
+ itoa(d, str, 10);
+ size_t len = strlen(str);
+ if (maxrem < len) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(str, len))
+ return -1;
+ written += len;
+ } else if (*format == 'x') {
+ format++;
+ char str[20]; // probably a long enough buffer
+ unsigned int d = va_arg(parameters, unsigned int);
+ itoa(d, str, 16);
+ size_t len = strlen(str);
+ if (maxrem < len) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(str, len))
+ return -1;
+ written += len;
+ } else if (*format == 'l') { // for %lx and others that start with l
+ format++;
+ if (*format == 'x') {
+ format++;
+ char str[20]; // probably a long enough buffer
+ unsigned long long d = va_arg(parameters, unsigned long long);
+ itoa_u64(d, str, 16);
+ size_t len = strlen(str);
+ if (maxrem < len) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(str, len))
+ return -1;
+ written += len;
+ }
+ } else if (*format == 's') {
+ format++;
+ const char* str = va_arg(parameters, const char*);
+ size_t len = strlen(str);
+ if (maxrem < len) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(str, len))
+ return -1;
+ written += len;
+ } else {
+ format = format_begun_at;
+ size_t len = strlen(format);
+ if (maxrem < len) {
+ // TODO: Set errno to EOVERFLOW.
+ return -1;
+ }
+ if (!print(format, len))
+ return -1;
+ written += len;
+ format += len;
+ }
+ }
+
+ va_end(parameters);
+ return written;
+}
\ No newline at end of file |