1 files changed, 152 insertions, 0 deletions
diff --git a/03-refactor/src/printf.c b/03-refactor/src/printf.c
new file mode 100644
index 0000000..fa7f519
--- /dev/null
+++ b/03-refactor/src/printf.c
@@ -0,0 +1,152 @@
+#include "printf.h"
+
+enum PRINTF_TYPE {
+  PRINTF_TYPE_STRING = 0,
+  PRINTF_TYPE_INT = 1,
+  PRINTF_TYPE_PERCENT = 2,
+  PRINTF_TYPE_UNKNOWN = 999
+};
+
+static enum PRINTF_TYPE get_printf_type(const char* cur)
+{
+  while (*cur >= 0x30 && *cur < 0x3a) ++ cur;
+
+  if (*cur == 's') {
+    return PRINTF_TYPE_STRING;
+  } else if (*cur == 'd' || *cur == 'x' || *cur == 'X' || *cur == 'u') {
+    return PRINTF_TYPE_INT;
+  }
+
+  return PRINTF_TYPE_UNKNOWN;
+}
+
+static const char* printf_handle_string(
+  const char* fmt,
+  const char* next,
+  printf_callback_t callback,
+  volatile void* closure)
+{
+  const char* cur = next;
+  for (; *cur != 0; ++ cur) {
+    callback(closure, *cur);
+  }
+
+  return fmt;
+}
+
+static char printf_toupper(char ch)
+{
+  if (ch <= 0x7a && ch > 0x60) {
+    return ch - 0x20;
+  }
+  return ch;
+}
+
+static const char* parse_fmt(
+    const char* fmt,
+    int* out_padding,
+    char* out_pad_char)
+{
+  if (*fmt == '0') {
+    *out_pad_char = '0';
+    ++ fmt;
+  } else {
+    *out_pad_char = ' ';
+  }
+  int padding = 0;
+  while (*fmt < 0x3a && *fmt >= 0x30) {
+    padding *= 10;
+    padding += (*fmt ++) - 0x30;
+  }
+
+  *out_padding = padding;
+  return fmt;
+}
+
+static const char* mapping = "0123456789abcdef";
+static const char* printf_handle_int(
+  const char* fmt, unsigned int next, printf_callback_t callback, volatile void* closure)
+{
+  int base = 10;
+  char chars[32];
+  int pos = 31;
+  int upper = 0;
+  char pad_char;
+  int padding;
+  int is_unsigned = 0;
+
+  fmt = parse_fmt(fmt, &padding, &pad_char);
+
+  if (*fmt == 'x' || *fmt == 'X') {
+    base = 16;
+    is_unsigned = 1;
+  } else if (*fmt == 'u') {
+    is_unsigned = 1;
+  }
+
+  upper = *fmt == 'X';
+
+  int next_i = (int) next;
+  if (next_i < 0 && !is_unsigned) {
+    callback(closure, '-');
+    next_i *= -1;
+    next = (unsigned) next_i;
+  }
+
+  if (next == 0) {
+    callback(closure, '0');
+  } else {
+    while (next > 0) {
+      char next_ch = mapping[next % base];
+      if (upper) next_ch = printf_toupper(next_ch);
+      chars[pos --] = next_ch;
+      padding --;
+      next /= base;
+    }
+
+    while ((padding--) > 0) {
+      chars[pos --] = pad_char;
+    }
+
+    for (++ pos; pos < 32; ++ pos) {
+      callback(closure, chars[pos]);
+    }
+  }
+
+  return fmt;
+}
+
+void printf_format(
+    const char* fmt,
+    printf_callback_t callback,
+    volatile void* closure,
+    va_list ap) 
+{
+  const char* cur = fmt;
+
+  const char* next_string;
+  int next_int;
+
+  for (; *cur != 0; ++ cur) {
+    if (*cur == '%') {
+      // Handle the formatting here.
+      ++ cur;
+      enum PRINTF_TYPE printf_type = get_printf_type(cur);
+
+      switch (printf_type) {
+      case PRINTF_TYPE_PERCENT:
+        callback(closure, '%');
+        break;
+      case PRINTF_TYPE_STRING:
+        next_string = va_arg(ap, const char*);
+        cur = printf_handle_string(cur, next_string, callback, closure);
+        break;
+      case PRINTF_TYPE_INT:
+        next_int = va_arg(ap, int);
+        cur = printf_handle_int(cur, next_int, callback, closure);
+      }
+    } else {
+      callback(closure, *cur);
+    }
+  }
+}