kilo.c

#define _DEFAULT_SOURCE
#define _BSD_SOURCE
#define _GNU_SOURCE
/**************** includes ****************/
#include <asm-generic/errno-base.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <stdlib.h> // atexit
#include <sys/ioctl.h> // get window size
#include <sys/types.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>

/**************** defines ****************/
#define KILO_VERSION "0.0.1"
#define KILO_TAB_STOP 8
#define KILO_QUIT_TIMES 3

// 0x1f == 0001_1111
#define CTRL_KEY(k) ((k)&0x1f)

enum editorKey {
  BACKSPACE = 127,
  ARROW_LEFT = 1000,
  ARROW_RIGHT,
  ARROW_UP,
  ARROW_DOWN,
  DEL_KEY,
  HOME_KEY,
  END_KEY,
  PAGE_UP,
  PAGE_DOWN,
};

// 定义不同的高亮模式返回相应的颜色
enum editorHighlight {
  HL_NORMAL = 0,
  HL_COMMENT,
  HL_MLCOMMENT,
  HL_KEYWORD1,
  HL_KEYWORD2,
  HL_STRING,
  HL_NUMBER,
  HL_MATCH
};

#define HL_HIGHLIGHT_NUMBERS (1 << 0)
#define HL_HIGHLIGHT_STRINGS (1 << 1)

/**************** data ****************/
// 编辑器层面的语法高亮参数
struct editorSyntax {
  char *filetype; // 根据文件类型来匹配高亮的设置
  char **filematch;
  char **keywords;
  char *singleline_comment_start;
  char *multiline_comment_start;
  char *multiline_comment_end;
  int flags;
};

// erow : editor row
typedef struct erow {
  int idx;
  int size;  // 当前行的大小
  int rsize; // 当前行渲染后的大小
  char *chars; // 当前行的原始数据
  char *render; // 当前行的渲染数据
  unsigned char *hl; // hl : highlight
  int hl_open_comment; 
} erow;

struct editorConfig {
  int cx, cy; // 当前光标的位置
  int rx;
  int rowoff; // 行偏移
  int coloff; // 列偏移
  int screenrows; // 当前屏幕的行数
  int screencols; // 当前屏幕的列数
  int numrows;    // 当前打开的文件的总行数
  erow *row;      // 文件对应的所有内容，使用 erow 表示
  int dirty;      // 表示当前的文件是否被修改了
  char *filename; // 文件名
  char statusmsg[80];
  time_t statusmsg_time; 
  struct editorSyntax *syntax; // 语法高亮
  struct termios orig_termios; // 终端模式参数，用于退出编辑器时恢复终端模式
};

struct editorConfig E;

char *C_HL_extensions[] = { ".c", ".h", ".cpp", NULL };
char *C_HL_keywords[] = {
  "switch", "if", "while", "for", "break", "continue", "return", "else",
  "struct", "union", "typedef", "static", "enum", "class", "case",
  "int|", "long|", "double|", "float|", "char|", "unsigned|", "signed|",
  "void|", NULL
};

struct editorSyntax HLDB[] = {
  {
    "c",
    C_HL_extensions,
    C_HL_keywords,
    "//", "/*", "*/",
    HL_HIGHLIGHT_NUMBERS | HL_HIGHLIGHT_STRINGS
  },
};

#define HLDB_ENTRIES (sizeof(HLDB) / sizeof(HLDB[0]))

/************* prototypes **********/
void editorRefreshScreen();
char *editorPrompt(char *prompt, void (*callback)(char *, int));

void editorSetStatusMessage(const char* fmt, ...) {
  // 将内容打印到状态缓冲区中:statusmsg
  va_list ap;
  va_start(ap, fmt);
  vsnprintf(E.statusmsg, sizeof(E.statusmsg), fmt, ap);
  va_end(ap);
  E.statusmsg_time = time(NULL);
}

/**************** terminal ****************/
// struct termios orig_termios;

void die(const char *s) {
  perror(s);
  exit(1);
}

void disableRawMode() {
  // 程序打开的时候会记录之前的 orig_termios 的信息，退出的时候恢复原先的状态
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == -1)
    die("tcgetattr");
}

void enableRawMode() {
  if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1)
    die("tcgetattr");
  atexit(disableRawMode); // 退出的时候调用这个函数

  // ECHO 特性就是回显，当我输入什么的时候，屏幕上就会显式什么
  // 当你使用 sudo 输入密码的时候就不会回显，就是这个效果
  struct termios raw = E.orig_termios;
  // 注意，注意这个需要设置在 lflag，lflag 的含义是 local flag，可以理解为混杂的
  // flag 其他的还有 iflag(input flag) oflag(output flag) cflag (control flag)
  // ISIG : 关闭 Ctrl + C 的 SIGINT 信号和 Ctrl + Z 的 SIGSTP 信号
  // IEXTEN : 关闭 Ctrl + V 信号
  raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
  // IXON : 关闭 Ctrl + S 和 Ctrl + Q 信号，Ctrl + S 是停止数据被传输到 terminal
  // ICRNL : 修复  Ctrl + M
  raw.c_iflag &= ~(IXON | ICRNL);
  // BRKINT 会使得 break 条件 SIGINT 发送给程序
  // INPAK 使能奇偶校验，对于termial 不需要
  // ISTRIP 会使得输入的字节的第8位被去掉，设置为 0，不需要该功能
  raw.c_iflag &= ~(BRKINT | INPCK | ISTRIP);
  // 关闭输出处理, O 代表 output ，POST 代表 post-processing of output
  raw.c_oflag &= ~(OPOST);
  // CS8 不是一个 flag，而是 bit mask，设置为每个字符为每字节 8 位
  raw.c_cflag |= (CS8);

  // 设置读取超时,cc代表的是 control character
  raw.c_cc[VMIN] = 0; // VMIN 表示的当 read 返回的时候的最小字节数，设置为 0
                      // ，表示让 read 尽快返回
  raw.c_cc[VTIME] = 1; // 设置的是超时返回的时间，单位是 1/10
                       // 秒，设置为1，表示的超时时间是 1 * 1/10 秒

  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1)
    die("tcsetattr");
}

// 处理读取输入的键盘值
int editorReadKey() {
  int nread = -1;
  char c;
  while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
    if (nread == -1 && errno != EAGAIN)
      die("read");
  }

  if (c == '\x1b') { // 控制类的按键都是 \x1b 字符开头的
    char seq[3];
    if (read(STDIN_FILENO, &seq[0], 1) != 1) return '\x1b';
    if (read(STDIN_FILENO, &seq[1], 1) != 1) return '\x1b';

    if (seq[0] == '[') {
      if (seq[1] >= '0' && seq[1] <= '9') {
        if (read(STDIN_FILENO, &seq[2], 1) != 1) return '\x1b';
        if (seq[2] == '~') {
          switch (seq[1]) {
            case '1': return HOME_KEY;
            case '3': return DEL_KEY;
            case '4': return END_KEY;
            case '5': return PAGE_UP;
            case '6': return PAGE_DOWN;
            case '7': return HOME_KEY;
            case '8': return END_KEY;
          }
        }
      }
      switch (seq[1]) {
        case 'A': return ARROW_UP;
        case 'B': return ARROW_DOWN;
        case 'C': return ARROW_RIGHT;
        case 'D': return ARROW_LEFT;
        case 'H': return HOME_KEY;
        case 'F': return END_KEY;
      }
    } else if (seq[0] == 'O') {
      switch (seq[1])
      {
      case 'H': return HOME_KEY;
      case 'F': return END_KEY;
      }
    }
    return '\x1b';
  }

  return c;
}

// 读取当前光标的位置信息
int getCursorPosition(int *rows, int *cols) {
  char buf[32];
  unsigned int i = 0;
  
  // 写入获取光标位置的命令
  if (write(STDOUT_FILENO, "\x1b[6n", 4) != 4) return -1;

  // 得到的结果是一个 escape 序列，形如：27 [ 24;80R
  while (i < sizeof(buf) - 1) {
    if (read(STDIN_FILENO, &buf[i], 1) != 1) break;
    if (buf[i] == 'R') break;
    i++;
  }
  buf[i] = '\0';

  // 得到相应的屏幕长宽数据信息
  if (buf[0] != '\x1b' || buf[1] != '[') return -1;
  if (sscanf(&buf[2], "%d;%d", rows, cols) != 2) return -1;

  return 0;
}

int getWindowSize(int *rows, int* cols) {
  struct winsize ws;
  // ioctl 函数不能保证在所有的系统中正确获得窗口的大小，所以需要提供一个fallback机制回退获取window大小
  if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
    // 如果 ioctl 失败的话采用的方式就是将光标移动到右下角的边界，然后通过获取光标的位置得到屏幕的大小
    if (write(STDOUT_FILENO, "\x1b[999C\x1b[999B", 12) != 12) return -1;
    return getCursorPosition(rows, cols);
  } else {
    *cols = ws.ws_col;
    *rows = ws.ws_row;
    return 0;
  }
}

/************ syntax highlighting **********/
int is_seprator(int c) {
  return isspace(c) || c == '\0' || strchr(",.()+-/*=~%<>[];", c) != NULL;
}

// 更新语法高亮
void editorUpdateSyntax(erow *row) {
  row->hl = realloc(row->hl, row->rsize); // 分配语法高亮的空间
  memset(row->hl, HL_NORMAL, row->rsize);

  if (E.syntax == NULL) return;

  char **keywords = E.syntax->keywords;

  char *scs = E.syntax->singleline_comment_start; // scs: single comment start
  char *mcs = E.syntax->multiline_comment_start;  // mcs: multiline comment start
  char *mce = E.syntax->multiline_comment_end;    // mce: multiline comment end

  int scs_len = scs ? strlen(scs) : 0;
  int mcs_len = mcs ? strlen(mcs) : 0;
  int mce_len = mce ? strlen(mce) : 0;

  int prev_sep = 1; // 这里设置为 true 表示行的开头的就是分隔符，也就是 seprator
  int in_string = 0;
  int in_comment = (row->idx > 0 && E.row[row->idx - 1].hl_open_comment);

  // 遍历处理所有的 render line 信息
  int i = 0; // 初始化非常重要
  while (i < row->rsize) {
    char c = row->render[i];
    unsigned char prev_hl = (i > 0) ? row->hl[i-1] : HL_NORMAL;

    // 如果单行的注释
    if (scs_len && !in_string && !in_comment) {
      if (!strncmp(&row->render[i], scs, scs_len)) {
        memset(&row->hl[i], HL_COMMENT, row->rsize - i);
        break;
      }
    }

    if (mcs_len && mce_len && !in_string) {
      if (in_comment) {
        row->hl[i] = HL_MLCOMMENT;
        if (!strncmp(&row->render[i], mce, mce_len)) {
          memset(&row->hl[i], HL_MLCOMMENT, mce_len);
          i += mce_len;
          in_comment = 0;
          prev_sep = 1;
          continue;
        } else {
          i++;
          continue;
        }
      } else if (!strncmp(&row->render[i], mcs, mcs_len)) {
        memset(&row->hl[i], HL_MLCOMMENT, mcs_len);
        i += mcs_len;
        in_comment = 1;
        continue;
      }
    }

    if (E.syntax->flags & HL_HIGHLIGHT_STRINGS) {
      if (in_string) {
        row->hl[i] = HL_STRING;
        if (c == '\\' && i + 1 < row->size) {
          row->hl[i+1] = HL_STRING;
          i+=2;
          continue;
        }
        if (c == in_string) in_string = 0;
        i++;
        prev_sep = 1;
        continue;
      } else {
        if (c == '"' || c == '\'') {
          in_string = c;
          row->hl[i] = HL_STRING;
          i++;
          continue;
        }
      }
    }

    if (E.syntax->flags & HL_HIGHLIGHT_NUMBERS) {
      if ((isdigit(c) && (prev_sep || prev_hl == HL_NUMBER)) ||
          (c == '.' && prev_hl == HL_NUMBER)) {
        row->hl[i] = HL_NUMBER;
        i++;
        prev_sep = 0;
        continue;
      }
    }

    if (prev_sep) {
      int j;
      for (j = 0; keywords[j]; j++) {
        int klen = strlen(keywords[j]);
        int kw2 = keywords[j][klen - 1] == '|';
        if (kw2) klen--;
        if (!strncmp(&row->render[i], keywords[j], klen) && is_seprator(row->render[i+klen])) {
          memset(&row->hl[i], kw2 ? HL_KEYWORD2 : HL_KEYWORD1, klen);
          i += klen;
          break;
        }
        if (keywords[j] != NULL) {
          prev_sep = 0;
          continue;
        }
      }
    }

    prev_sep = is_seprator(c);
    i++;
  }

  int changed = (row->hl_open_comment != in_comment);
  row->hl_open_comment = in_comment;
  if (changed && row->idx + 1 < E.numrows) 
    editorUpdateSyntax(&E.row[row->idx + 1]);
}

int editorSyntaxToColor(int hl) {
  switch (hl) {
    case HL_COMMENT:
    case HL_MLCOMMENT: return 36;
    case HL_KEYWORD1: return 33;
    case HL_KEYWORD2: return 32;
    case HL_STRING: return 35;
    case HL_NUMBER: return 31;
    case HL_MATCH: return 34;
    default: return 37;
  }
}

void editorSelectSyntaxHighlight() {
  E.syntax = NULL;
  if (E.filename == NULL) return;
  
  char *ext = strchr(E.filename, '.');

  for (unsigned int j = 0; j < HLDB_ENTRIES; j++) {
    struct editorSyntax *s = &HLDB[j];
    unsigned int i = 0;
    while (s->filematch[i]) {
      int is_ext = (s->filematch[i][0] == '.');
      if ((is_ext && ext && !strcmp(ext, s->filematch[i])) ||
        (!is_ext && strstr(E.filename, s->filematch[i]))) {
          E.syntax = s;

          int filerow;
          for (filerow = 0; filerow < E.numrows; filerow++) {
            editorUpdateSyntax(&E.row[filerow]);
          }

          return;
        }
        i++;
    }
  }

}

/********** row operations ***********/
int editorRowCxToRx(erow *row, int cx) {
  int rx = 0;
  int j;
  for (j = 0; j < cx; j++) {
    if (row->chars[j] == '\t')
      rx += (KILO_TAB_STOP - 1) - (rx % KILO_TAB_STOP);
    rx++;
  }
  return rx;
}

int editorRowRxToCx(erow *row, int rx) {
    int cur_rx = 0;
    int cx;
    for (cx = 0; cx < row->size; cx++) {
        if (row->chars[cx] == '\t')
            cur_rx += (KILO_TAB_STOP - 1) - (cur_rx % KILO_TAB_STOP);
        cur_rx++;

        if (cur_rx > rx) return cx;
    }
    return cx;
}

void editorUpdateRow(erow *row) {
  int tabs = 0;
  int j;
  for (j = 0; j < row->size; j++) {
    if (row->chars[j] == '\t') tabs++;
  }

  free(row->render);
  row->render = malloc(row->size + tabs*(KILO_TAB_STOP - 1)+ 1);

  int idx = 0;
  for (j = 0; j < row->size; j++) {
    if (row->chars[j] == '\t') {
      row->render[idx++] = ' ';
      while (idx % KILO_TAB_STOP != 0) row->render[idx++] = ' ';
    } else {
      row->render[idx++] = row->chars[j];
    }
  }
  row->render[idx] = '\0';
  row->rsize = idx;

  editorUpdateSyntax(row);
}

void editorAppendRow(char *s, size_t len) {
  E.row = realloc(E.row, sizeof(erow) * (E.numrows + 1));

  int at = E.numrows;
  E.row[at].size = len;
  E.row[at].chars = malloc(len + 1);
  memcpy(E.row[at].chars, s, len);
  E.row[at].chars[len] = '\0';

  E.row[at].rsize = 0;
  E.row[at].render = NULL;
  editorUpdateRow(&E.row[at]);

  E.numrows++;
  E.dirty++;
}

void editorRowInsertChar(erow *row, int at, int c) {
  if (at < 0 || at > row->size) at = row->size;
  row->chars = realloc(row->chars, row->size + 2);
  memmove(&row->chars[at + 1], &row->chars[at], row->size - at + 1);
  row->size++;
  row->chars[at] = c;
  editorUpdateRow(row);
  E.dirty++;
}

void editorRowDelChar(erow *row, int at) {
  if (at < 0 || at >= row->size) return;
  memmove(&row->chars[at], &row->chars[at+1], row->size - at);
  row->size--;
  editorUpdateRow(row);
  E.dirty++;
}

void editorFreeRow(erow *row) {
  free(row->render);
  free(row->chars);
  free(row->hl);
}

void editorDelRow(int at) {
  if (at < 0 || at >= E.numrows) return;
  editorFreeRow(&E.row[at]);
  memmove(&E.row[at], &E.row[at + 1], sizeof(erow) * (E.numrows - at - 1));
  for (int j = at; j < E.numrows - 1; j++) E.row[j].idx--;
  E.numrows--;
  E.dirty++;
}

void editorRowAppendString(erow *row, char *s, size_t len) {
  row->chars = realloc(row->chars, row->size + len + 1);
  memcpy(&row->chars[row->size], s, len);
  row->size += len;
  row->chars[row->size] = '\0';
  editorUpdateRow(row);
  E.dirty++;
}

void editorInsertRow(int at, char *s, size_t len) {
  if (at < 0 || at > E.numrows) return;

  E.row = realloc(E.row, sizeof(erow) * (E.numrows + 1));
  memmove(&E.row[at + 1], &E.row[at], sizeof(erow) * (E.numrows - at));
  for (int j = at + 1; j <= E.numrows; j++) E.row[j].idx++;

  E.row[at].idx = at;

  E.row[at].size = len;
  E.row[at].chars = malloc(len + 1);
  memcpy(E.row[at].chars, s, len);
  E.row[at].chars[len] = '\0';

  E.row[at].rsize = 0;
  E.row[at].render = NULL;
  E.row[at].hl = NULL;
  E.row[at].hl_open_comment = 0;
  editorUpdateRow(&E.row[at]);

  E.numrows++;
  E.dirty++;
}
/*********** editor operations ************/
void editorInsertChar(int c) {
  if (E.cy == E.numrows) {
    editorInsertRow(E.numrows, "", 0);
  }
  editorRowInsertChar(&E.row[E.cy], E.cx, c);
  E.cx++;
}

// 插入新行
void editorInsertNewline() {
  if (E.cx == 0) { // 当前光标在开头位置，插入一个空白行
    editorInsertRow(E.cy, "", 0);
  } else { // 光标处于行中间
    erow *row = &E.row[E.cy];
    editorInsertRow(E.cy + 1, &row->chars[E.cx], row->size - E.cx);
    row = &E.row[E.cy];
    row->size = E.cx;
    row->chars[row->size] = '\0';
    editorUpdateRow(row);
  }
  E.cy++;
  E.cx = 0;
}

void editorDelChar() {
  if (E.cy == E.numrows) return;
  if (E.cx == 0 && E.cy == 0) return;

  erow *row = &E.row[E.cy];
  if (E.cx > 0) {
    editorRowDelChar(row, E.cx - 1);
    E.cx--;
  } else {
    E.cx = E.row[E.cy - 1].size;
    editorRowAppendString(&E.row[E.cy-1], row->chars, row->size);
    editorDelRow(E.cy);
    E.cy--;
  }
}
/********** file i/o ***********/
void editorOpen(char *filename) {
  free(E.filename);
  E.filename = strdup(filename);

  editorSelectSyntaxHighlight();

  FILE *fp = fopen(filename, "r");
  if (!fp) die("fopen");

  char *line = NULL;
  size_t linecap = 0;
  ssize_t linelen;
  while ((linelen = getline(&line, &linecap, fp)) != -1) {
    while (linelen > 0 && (line[linelen - 1] == '\n' ||
                           line[linelen - 1] == '\r'))
      linelen--;
    editorInsertRow(E.numrows, line, linelen);
  }
  free(line);
  fclose(fp);
  E.dirty = 0;
}

char *editorRowsToString(int *buflen) {
  int totlen = 0;
  int j;
  for (j = 0; j < E.numrows; j++) {
    totlen += E.row[j].size + 1;
  }
  *buflen = totlen;
  
  char *buf = malloc(totlen);
  char *p = buf;
  for (j = 0; j < E.numrows; j++) {
    memcpy(p, E.row[j].chars, E.row[j].size);
    p+=E.row[j].size;
    *p = '\n';
    p++;
  }
  return buf;
}

void editorSave() {
  if (E.filename == NULL) {
    E.filename = editorPrompt("Save as: %s (ESC to cancel)", NULL);
    if (E.filename == NULL) {
      editorSetStatusMessage("Save aborted");
      return;
    }
    editorSelectSyntaxHighlight();
  }

  int len;
  char *buf = editorRowsToString(&len);
  int fd = open(E.filename, O_RDWR | O_CREAT, 0644);
  if (fd != -1) {
    if (ftruncate(fd, len) != -1) {
      if (write(fd, buf, len) == len) {
        close(fd);
        free(buf);
        E.dirty = 0;
        editorSetStatusMessage("%d bytes written to disk", len);
        return;
      }
    }
    close(fd);
  }
  free(buf);
  editorSetStatusMessage("Can't save! I/O error:%s", strerror(errno));
}
/********* find *******/
void editorFindCallback(char *query, int key) {
  static int last_match = -1;
  static int direction = 1;

  static int saved_hl_line;
  static char *saved_hl = NULL;

  if (saved_hl) {
    memcpy(E.row[saved_hl_line].hl, saved_hl, E.row[saved_hl_line].rsize);
    free(saved_hl);
    saved_hl = NULL;
  }
  
  if (key == '\r' || key == '\x1b') {
    last_match = -1;
    direction = 1;
    return;
  } else if (key == ARROW_RIGHT || key == ARROW_DOWN) {
    direction = 1;
  } else if (key == ARROW_LEFT || key == ARROW_UP) {
    direction = -1;
  } else {
    last_match = -1;
    direction = 1;
  }

  if (last_match == -1) direction = 1;
  int current = last_match;
  int i;
  for (i = 0; i < E.numrows; i++) {
    current += direction;
    if (current == -1) current = E.numrows - 1;
    else if (current == E.numrows) current = 0;

    erow *row = &E.row[current];
    char *match = strstr(row->render, query);
    if (match) {
      last_match = current;
      E.cy = current;
      E.cx = editorRowRxToCx(row, match - row->render);
      E.rowoff = E.numrows;

      saved_hl_line = current;
      saved_hl = malloc(row->rsize);
      memcpy(saved_hl, row->hl, row->rsize);
      memset(&row->hl[match - row->render], HL_MATCH, strlen(query));
      break;
    }
  }
}

void editorFind() {
  int saved_cx = E.cx;
  int saved_cy = E.cy;
  int saved_coloff = E.coloff;
  int saved_rowoff = E.rowoff;

  char *query = editorPrompt("Search:%s (Use ESC/Arrows/Enter)", editorFindCallback);
  
  if (query) {
    free(query);
  } else {
    E.cx = saved_cx;
    E.cy = saved_cy;
    E.coloff = saved_coloff;
    E.rowoff = saved_rowoff;
  }
}

/******** append buffer *******/
// 将所有要渲染的数据放到一块内容中进行存储，一次性刷新到屏幕上
struct abuf {
  char *b;
  int len;
};

#define ABUF_INIT {NULL, 0}

void abAppend(struct abuf *ab, const char *s, int len) {
  char* new = realloc(ab->b, ab->len + len);
  if (new == NULL) return;
  memcpy(&new[ab->len], s, len);
  ab->b = new;
  ab->len += len;
}

void abFree(struct abuf *ab) {
  free(ab->b);
}

/******** input *******/
char *editorPrompt(char *prompt, void (*callback)(char *, int)) {
  size_t bufsize = 128;
  char *buf = malloc(bufsize);

  size_t buflen = 0;
  buf[0] = '\0';

  // 进入到 Prompt 处理流程中，是处在一个while循环的
  while (1) {
    editorSetStatusMessage(prompt, buf);
    editorRefreshScreen();

    int c = editorReadKey();
    if (c == DEL_KEY || c == CTRL_KEY('h') || c == BACKSPACE) {
      if (buflen != 0) buf[--buflen] = '\0';
    } else if (c == '\x1b') {
      editorSetStatusMessage("");
      if (callback) callback(buf, c);
      free(buf);
      return NULL;
    } else if (c == '\r') {
      if (buflen != 0) {
        editorSetStatusMessage("");
        if (callback) callback(buf, c);
        return buf;
      }
    } else if (!iscntrl(c) && c < 128) {
      if (buflen == bufsize - 1) {
        bufsize *= 2;
        buf = realloc(buf, bufsize);
      }
      buf[buflen++] = c;
      buf[buflen] = '\0';
    }
    if (callback) callback(buf, c);
  }
}

void editorMoveCursor(int key) {
  erow *row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
  switch (key)
  {
  case ARROW_LEFT:
    if (E.cx != 0) {
      E.cx--;
    } else if (E.cy > 0) {
      E.cy--;
      E.cx = E.row[E.cy].size;
    }
    break;
  case ARROW_RIGHT:
      if (row && E.cx < row->size) {
        E.cx++;
      } else if (row && E.cx == row->size) {
        E.cy++;
        E.cx = 0;
      }
    break;
  case ARROW_UP:
    if (E.cy != 0 ) {
      E.cy--;
    }
    break;
  case ARROW_DOWN:
    if (E.cy < E.numrows) {
      E.cy++;
    }
    break;
  }
  row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
  int rowlen = row ? row->size : 0;
  if (E.cx > rowlen) {
    E.cx = rowlen;
  }
}

// 处理用户的按键输入，根据不同的输入按键调用不同的处理函数
void editorProcessKeypress() {
  static int quit_times = KILO_QUIT_TIMES;
  int c = editorReadKey();
  switch (c) {
  case '\r':
    editorInsertNewline();
    break;

  case CTRL_KEY('q'):
    if (E.dirty && quit_times > 0) {
      editorSetStatusMessage("WARNING!!! File has unsaved changes. "
      "Press Ctrl+Q %d more times to quit.", quit_times);
      quit_times--;
      return;
    }
    // 退出的时候，清空屏幕内容
    write(STDOUT_FILENO, "\x1b[2J", 4);
    write(STDOUT_FILENO, "\x1b[H", 3);
    exit(0);
    break;

  case CTRL_KEY('s'):
    editorSave();
    break;

  case HOME_KEY:
    E.cx = 0;
    break;
  case END_KEY:
    if (E.cy < E.numrows)
      E.cx = E.row[E.cy].size;
    break;

  case CTRL_KEY('f'):
    editorFind();
    break;

  case BACKSPACE:
  case CTRL_KEY('h'):
  case DEL_KEY:
    if (c == DEL_KEY) editorMoveCursor(ARROW_RIGHT);
    editorDelChar();
    break;

  // 处理翻页功能
  case PAGE_UP:
  case PAGE_DOWN:
    {
      if (c == PAGE_UP) {
        E.cy = E.rowoff;
      } else if (c == PAGE_DOWN) {
        E.cy = E.rowoff + E.screenrows - 1;
        if (E.cy > E.numrows) E.cy = E.numrows;
      }

      int times = E.screenrows;
      while (times--) {
        editorMoveCursor(c == PAGE_UP ? ARROW_UP : ARROW_DOWN);
      }
    }
    break;

  case ARROW_UP:
  case ARROW_DOWN:
  case ARROW_LEFT:
  case ARROW_RIGHT:
    editorMoveCursor(c);
    break;
  
  case CTRL_KEY('l'):
  case '\x1b':
    break;

  default:
    editorInsertChar(c);
    break;
  }
  quit_times = KILO_QUIT_TIMES;
}
/**************** output ****************/
void editorScroll() {
  E.rx = 0;
  if (E.cy < E.numrows) {
    E.rx = editorRowCxToRx(&E.row[E.cy], E.cx);
  }

  E.rx = E.cx;
  if (E.cy < E.rowoff) {
    E.rowoff = E.cy;
  }
  if (E.cy >= E.rowoff + E.screenrows) {
    E.rowoff = E.cy - E.screenrows + 1;
  }
  if (E.rx < E.coloff) {
    E.coloff = E.rx;
  }
  if (E.rx >= E.coloff + E.screencols) {
    E.coloff = E.rx - E.screencols + 1;
  }
}

void editorDrawRows(struct abuf *ab) {
  int y;
  // 输出类似 vim 打开文件最左侧一列的 ~ 符号
  for (y = 0; y < E.screenrows; y++) {
    int filerow = y + E.rowoff;
    if (filerow >= E.numrows) {
      if (E.numrows == 0 && y == E.screenrows / 3) {
        char welcome[80];
        int welcomelen = snprintf(welcome, sizeof(welcome), "Kilo editor -- version %s", KILO_VERSION);
        if (welcomelen > E.screencols) welcomelen = E.screencols;
        // 将编辑器的版本信息字符串居中
        int padding = (E.screencols - welcomelen) / 2;
        if (padding) {
          abAppend(ab, "~", 1);
          padding -= 1;
        }
        while(padding--) abAppend(ab, " ", 1);
        abAppend(ab, welcome, welcomelen);
      } else {
        abAppend(ab, "~", 1);
      }
    } else {
      int len = E.row[filerow].size - E.coloff;
      if (len < 0) len = 0;
      if (len > E.screencols) len = E.screencols;
      char *c = &E.row[filerow].render[E.coloff];
      unsigned char *hl = &E.row[filerow].hl[E.coloff];
      int current_color = -1;
      int j;
      for (j = 0; j < len; j++) {
        if (iscntrl(c[j])) {
          char sym = (c[j] <= 26) ? '@' + c[j] : '?';
          abAppend(ab, "\x1b[7m", 4);
          abAppend(ab, &sym, 1);
          abAppend(ab, "\x1b[m", 3);
          if (current_color != -1) {
            char buf[16];
            int clen = snprintf(buf, sizeof(buf), "\x1b[%dm", current_color);
            abAppend(ab, buf, clen);
          }
        } else if (hl[j] == HL_NORMAL) {
          if (current_color != -1) {
            abAppend(ab, "\x1b[39m", 5);
            current_color = -1;
          }
          abAppend(ab, &c[j], 1);
        } else {
          int color = editorSyntaxToColor(hl[j]);
          if (color != current_color) {
            current_color = color;
            char buf[16];
            int clen = snprintf(buf, sizeof(buf), "\x1b[%dm", color);
            abAppend(ab, buf, clen);
          }
          abAppend(ab, &c[j], 1);
        }
      }
      abAppend(ab, "\x1b[39m", 5);
    }
    abAppend(ab, "\x1b[K", 3); // 清空当前行余下的全部内容
    // if (y < E.screenrows - 1) {
    abAppend(ab, "\r\n", 2);
  }
}

void editorDrawStatusBar(struct abuf *ab) {
  abAppend(ab, "\x1b[7m", 4);
  char status[80], rstatus[80];
  int len = snprintf(status, sizeof(status), "%.20s - %d lines %s",
    E.filename ? E.filename : "[No Name]", E.numrows,
    E.dirty ? "(modified)" : "");
  int rlen = snprintf(rstatus, sizeof(rstatus), "%s %d/%d",
    E.syntax ? E.syntax->filetype : "no ft", E.cy + 1, E.numrows);

  if (len > E.screencols) len = E.screencols;
  abAppend(ab, status, len);
  while (len < E.screencols) {
    if (E.screencols - len == rlen) {
      abAppend(ab, rstatus, rlen);
      break;
    } else {
      abAppend(ab, " ", 1);
      len++;
    }
  }
  abAppend(ab, "\x1b[m", 3);
  abAppend(ab, "\r\n", 2);
}

void editorDrawMessageBar(struct abuf *ab) {
  abAppend(ab, "\x1b[K", 3);
  int msglen = strlen(E.statusmsg);
  if (msglen > E.screencols) msglen = E.screencols;
  if (msglen && time(NULL) - E.statusmsg_time < 5)
    abAppend(ab, E.statusmsg, msglen);
}

// 这里的实现有一个问题，因为这个函数是在 while 循环中调用的
// 每次进行 abuf 的内存分配和释放，会导致过多的内存分配操作，效率不是很高
void editorRefreshScreen() {
  editorScroll();

  struct abuf ab = ABUF_INIT;

  // 刷新屏幕之前隐藏光标
  abAppend(&ab, "\x1b[?25l", 6);
  
  // 清空屏幕输出内容
  // 1b 对应的十进制是 27，是 ESC 的键盘值
  // 所以这里写入的是 escape 序列，后面三个字符是 [2J
  // J 命令是清空屏幕的命令，前面的数值表示的是参数
  // 2 表示清空所有屏幕内容
  // abAppend(&ab, "\x1b[2J", 4); // 这一行是清空整个屏幕

  // 重置输入的光标位置
  abAppend(&ab, "\x1b[H", 3);

  editorDrawRows(&ab);
  editorDrawStatusBar(&ab);
  editorDrawMessageBar(&ab);

  // 重置光标的位置
  char buf[32];
  snprintf(buf, sizeof(buf), "\x1b[%d;%dH", E.cy - E.rowoff + 1, E.rx - E.coloff + 1);
  abAppend(&ab, buf, strlen(buf));

  // 重新显示光标
  abAppend(&ab, "\x1b[?25h", 6);
  write(STDOUT_FILENO, ab.b, ab.len);
  abFree(&ab);
}

/**************** init ****************/
void initEditor() {
  E.cx = 0;
  E.cy = 0;
  E.rx = 0;
  E.rowoff = 0;
  E.coloff = 0;
  E.numrows = 0;
  E.row = NULL;
  E.dirty = 0;
  E.filename = NULL;
  E.statusmsg[0] = '\0';
  E.statusmsg_time = 0;
  E.syntax = NULL;

  if (getWindowSize(&E.screenrows, &E.screencols) == -1) die("getWindowSize");
  E.screenrows -= 2; // 留下一行作为状态栏
}

int main(int argc, char *argv[]) {
  enableRawMode();
  initEditor();
  
  if (argc >= 2) {
    editorOpen(argv[1]);
  }

  editorSetStatusMessage("HELP: Ctrl-S = save | Ctrl-Q = quit | Ctrl-F = find");

  while (1) {
    /*char c = '\0';
    if (read(STDIN_FILENO, &c, 1) == -1 && errno != EAGAIN)
      die("read");
    // iscntrl 函数是在 ctype.h 文件中，测试一个字符是否是控制字符
    // ASCII code 中 0 - 31 是控制字符，127 也是一个控制字符，32 - 126
    // 是可打印的字符 printf 函数是在 stdio.h 文件中
    // 这个时候进行测试会得到一些有意思的结论：
    // 1. 方向键的输入是 3 or 4 个字节的，以 27 '['
    // 开头，后面跟一个或两个字节，27 其实是 esc 的 ASCII
    // 2. backspace 是 127，delete 是一个四字节的序列
    // 3. Enter 键是 10，也就是 \n
    // 4. Ctrl + A 是 1，Ctrl + B 是 2，以此类推。
    // 5. Ctrl + S 是会让终端冻结住，也就是停止输出字符，Ctrl + Q 是恢复输出
    // 6. Ctrl + Z，是将进程停止到后台，使用命令 fg 可以将其调回前台
    if (iscntrl(c)) {
      // 关闭输出预处理之后，需要自己添加 \r\n
      printf("%d\r\n", c);
    } else {
      printf("%d ('%c')\r\n", c, c);
    }
    if (c == CTRL_KEY('q'))
      break;
      */
    editorRefreshScreen(); // 
    editorProcessKeypress();
  }
  return 0;
}