freywaros/src/kernel/vga.c

#include "src/kernel/vga.h"
#include "src/kernel/panic.h"
#include "src/kernel/util.h"
#include "src/lib/memory.h"

static uint16_t *vga = (uint16_t *)0xFFFFFFFF800B8000;
static uint16_t color = (uint16_t)0x0F << 8;
static uint16_t offset = 0;

static void set_char(char c) {
  vga[offset] = color | (uint16_t)c;
}

static void set_cursor() {
  outb(0x3D4, 0x0F);
  outb(0x3D5, offset & 0xFF);
  outb(0x3D4, 0x0E);
  outb(0x3D5, (offset >> 8) & 0xFF);
}

static void scroll() {
  memory_move(vga + VGA_WIDTH, 2 * VGA_WIDTH * (VGA_HEIGHT - 1), vga);
  for (offset = VGA_WIDTH * (VGA_HEIGHT - 1); offset < VGA_WIDTH * VGA_HEIGHT; offset++) {
    set_char(' ');
  }
  offset = VGA_WIDTH * (VGA_HEIGHT - 1);
}

static void advance() {
  offset++;
  if (offset >= VGA_WIDTH * VGA_HEIGHT) {
    scroll();
  }
}

static void clear() {
  uint16_t *ptr = vga;
  uint16_t fill = 0x0F20;
  uint32_t count = VGA_WIDTH * VGA_HEIGHT;
  __asm__ volatile("rep stosw" : "=D"(ptr), "=c"(count) : "D"(ptr), "a"(fill), "c"(count) : "memory");

  offset = 0;
  set_cursor();
}

typedef enum {
  PARSE_NORMAL,
  PARSE_ESC,
  PARSE_CSI,
} parse_state_t;

static parse_state_t parser_state = PARSE_NORMAL;
static char parser_csi_param[8];
static uint8_t parser_csi_len;

static void on_char_received(char c) {
  switch (parser_state) {
  case PARSE_NORMAL:
    switch (c) {
    case '\x1B':
      parser_state = PARSE_ESC;
      break;
    case '\b':
    case '\x7F':
      if (offset > 0) {
        offset--;
        set_cursor();
      }
      break;
    case '\r':
      offset -= offset % VGA_WIDTH;
      set_cursor();
      break;
    case '\n':
      if (offset / VGA_WIDTH == VGA_HEIGHT - 1) {
        scroll();
      } else {
        offset += VGA_WIDTH;
      }
      offset -= offset % VGA_WIDTH;
      set_cursor();
      break;
    default:
      if (c >= '\x01' && c <= '\x1A') {
        set_char('^');
        advance();
        set_char(c + 'A' - 1);
        advance();
        set_cursor();
      } else if (c >= ' ') {
        set_char(c);
        advance();
        set_cursor();
      }
      break;
    }
    break;

  case PARSE_ESC:
    if (c == '[') {
      parser_state = PARSE_CSI;
      parser_csi_len = 0;
    } else {
      parser_state = PARSE_NORMAL;
    }
    break;

  case PARSE_CSI:
    if ((c >= '0' && c <= '9') || c == ';') {
      if (parser_csi_len < sizeof(parser_csi_param) - 1) {
        parser_csi_param[parser_csi_len++] = c;
      }
    } else {
      parser_state = PARSE_NORMAL;
      parser_csi_param[parser_csi_len] = '\0';

      switch (c) {
      case 'C':
        if (offset < VGA_WIDTH * VGA_HEIGHT - 1) {
          offset++;
        }
        set_cursor();
        break;
      case 'D':
        if (offset > 0) {
          offset--;
        }
        set_cursor();
        break;
      case 'H':
        offset -= offset % VGA_WIDTH;
        set_cursor();
        break;
      case 'F':
        offset -= offset % VGA_WIDTH;
        offset += VGA_WIDTH - 1;
        set_cursor();
        break;
      }
    }
    break;
  }
}

static uint64_t stream_write(__attribute__((unused)) stream_t *self, const char *from, uint64_t bytes) {
  uint64_t left = bytes;
  while (left--) {
    on_char_received(*from++);
  }
  return bytes;
}

static uint64_t stream_read(__attribute__((unused)) stream_t *self, __attribute__((unused)) uint64_t max,
                            __attribute__((unused)) char *to) {
  return 0;
}

static uint64_t stream_truncate(__attribute__((unused)) stream_t *self, __attribute__((unused)) uint64_t size) {
  return size;
}

static void stream_close(__attribute__((unused)) stream_t *self) {
}

static stream_t stream = {stream_write, stream_read, stream_truncate, stream_close};

stream_t *vga_init() {
  clear();
  return &stream;
}

void vga_set_string(uint8_t row, uint8_t col, const char *str, uint8_t c) {
  ASSERT(row < VGA_HEIGHT && col < VGA_WIDTH, "vga_set_string: invalid coordinates")
  color = (uint16_t)((uint16_t)c << 8);
  offset = row * VGA_WIDTH + col;
  while (*str) {
    on_char_received(*str++);
  }
}