print.cpp

#include "print.h"

uint16_t* buffer = (uint16_t*)0xb8000;
int linecount = 0;
int colcount = 0;

void cls() {
  for (uint32_t i = 0; i < HEIGHT*WIDTH; i++) {
    buffer[i] &= 0xFF00;
  }
  linecount = 0;
  colcount = 0;
}
  
void setposc(uint32_t row, uint32_t col, char c) {
  buffer[row * WIDTH + col] = (buffer[row * WIDTH + col] & 0xFF00) | c;
}

void newline() {
  linecount++;
  colcount = 0;
  if (linecount >= HEIGHT) {
    for (int i = 0; i < HEIGHT - 1; i++) {
      for (int j = 0; j < WIDTH; j++) {
	buffer[i * WIDTH + j] = buffer[(i + 1) * WIDTH + j];
      }
    }
    linecount = HEIGHT - 1;
    for (int j = 0; j < WIDTH; j++) {
      setposc(HEIGHT-1, j, ' ');
    }
  }
}

extern "C" void putc(char c) {
  if (c == '\n') {
      newline();
  } else if (c == '\b') {
    if (colcount == 0) {
      colcount = WIDTH - 1;
      linecount--;
    } else {
      colcount--;
    }
    setposc(linecount, colcount, ' ');
  } else {
    if (colcount >= WIDTH) {
      newline();
    }
    setposc(linecount, colcount, c);
    colcount++;
  }
}

extern "C" void printf(char* str) {
  for(uint32_t i = 0; str[i] != '\0'; i++) {
    putc(str[i]);
  }
}

char nib2char(uint8_t nib) {
  nib &= 0xF;
  if (0 <= nib && nib <= 9) {
    return nib + '0';
  } else {
    return nib - 10 + 'A';
  }
}

extern "C" void printh(uint32_t p) {
  char buf[11] = "0x00000000";
  for (int i = 9; i > 1; i--) {
    buf[i] = nib2char(p);
    p = p >> 4;
  }
  printf(buf);
}

// compares to strings until n
extern "C" bool strn_eq(char* str1, char* str2, uint32_t n) {
    for (int i = 0; i < n; i++) {
      if (str1[i] != str2[i]) {
	return false;
      } else if (str1[i] == '\0') {
	return true;
      }
    }
    return true;
}

uint8_t ConsoleStdout::write(uint32_t offset, uint8_t* buf, uint32_t bytes) {
  // TODO how to handle offset?
  // TODO lmao security issue where you can use stdout to write to
  // memory you don't own
  while (bytes != 0) {
    putc(*buf);
    buf++;
    bytes--;
  }
}