linenoise.c

/* linenoise.c -- guerrilla line editing library against the idea that a
 * line editing lib needs to be 20,000 lines of C code.
 *
 * You can find the latest source code at:
 * 
 *   http://github.com/antirez/linenoise
 *
 * Does a number of crazy assumptions that happen to be true in 99.9999% of
 * the 2010 UNIX computers around.
 *
 * Copyright (c) 2010, Salvatore Sanfilippo <antirez at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * References:
 * - http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
 * - http://www.3waylabs.com/nw/WWW/products/wizcon/vt220.html
 *
 * Todo list:
 * - Switch to gets() if $TERM is something we can't support.
 * - Completion?
 *
 * List of escape sequences used by this program, we do everything just
 * with three sequences. In order to be so cheap we may have some
 * flickering effect with some slow terminal, but the lesser sequences
 * the more compatible.
 *
 * CHA (Cursor Horizontal Absolute)
 *    Sequence: ESC [ n G
 *    Effect: moves cursor to column n
 *
 * EL (Erase Line)
 *    Sequence: ESC [ n K
 *    Effect: if n is 0 or missing, clear from cursor to end of line
 *    Effect: if n is 1, clear from beginning of line to cursor
 *    Effect: if n is 2, clear entire line
 *
 * CUF (CUrsor Forward)
 *    Sequence: ESC [ n C
 *    Effect: moves cursor forward of n chars
 * 
 */

#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <unistd.h>

static struct termios orig_termios; /* in order to restore at exit */
static int rawmode = 0; /* for atexit() function to check if restore is needed*/
static int atexit_registered = 0; /* register atexit just 1 time */
static int history_max_len = 100;
static int history_len = 0;
char **history = NULL;

static void linenoiseAtExit(void);
int linenoiseHistoryAdd(char *line);

static void freeHistory(void) {
    if (history) {
        int j;

        for (j = 0; j < history_len; j++)
            free(history[j]);
        free(history);
    }
}

static int enableRawMode(int fd) {
    struct termios raw;

    if (!isatty(STDIN_FILENO)) goto fatal;
    if (!atexit_registered) {
        atexit(linenoiseAtExit);
        atexit_registered = 1;
    }
    if (tcgetattr(fd,&orig_termios) == -1) goto fatal;

    raw = orig_termios;  /* modify the original mode */
    /* input modes: no break, no CR to NL, no parity check, no strip char,
     * no start/stop output control. */
    raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
    /* output modes - disable post processing */
    raw.c_oflag &= ~(OPOST);
    /* control modes - set 8 bit chars */
    raw.c_cflag |= (CS8);
    /* local modes - choing off, canonical off, no extended functions,
     * no signal chars (^Z,^C) */
    raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
    /* control chars - set return condition: min number of bytes and timer.
     * We want read to return every single byte, without timeout. */
    raw.c_cc[VMIN] = 1; raw.c_cc[VTIME] = 0; /* 1 byte, no timer */

    /* put terminal in raw mode after flushing */
    if (tcsetattr(fd,TCSAFLUSH,&raw) < 0) goto fatal;
    rawmode = 1;
    return 0;

fatal:
    errno = ENOTTY;
    return -1;
}

static void disableRawMode(int fd) {
    /* Don't even check the return value as it's too late. */
    if (rawmode && tcsetattr(fd,TCSAFLUSH,&orig_termios) != -1)
        rawmode = 0;
}

/* At exit we'll try to fix the terminal to the initial conditions. */
static void linenoiseAtExit(void) {
    disableRawMode(STDIN_FILENO);
    freeHistory();
}

static int getColumns(void) {
    struct winsize ws;

    if (ioctl(1, TIOCGWINSZ, &ws) == -1) return 80;
    return ws.ws_col;
}

static void refreshLine(int fd, char *prompt, char *buf, size_t len, size_t pos, size_t cols) {
    char seq[64];
    size_t plen = strlen(prompt);
    
    while((plen+pos) >= cols) {
        buf++;
        len--;
        pos--;
    }
    while (plen+len > cols) {
        len--;
    }

    /* Cursor to left edge */
    snprintf(seq,64,"\x1b[0G");
    if (write(fd,seq,strlen(seq)) == -1) return;
    /* Write the prompt and the current buffer content */
    if (write(fd,prompt,strlen(prompt)) == -1) return;
    if (write(fd,buf,len) == -1) return;
    /* Erase to right */
    snprintf(seq,64,"\x1b[0K");
    if (write(fd,seq,strlen(seq)) == -1) return;
    /* Move cursor to original position. */
    snprintf(seq,64,"\x1b[0G\x1b[%dC", (int)(pos+plen));
    if (write(fd,seq,strlen(seq)) == -1) return;
}

static int linenoisePrompt(int fd, char *buf, size_t buflen, char *prompt) {
    size_t plen = strlen(prompt);
    size_t pos = 0;
    size_t len = 0;
    size_t cols = getColumns();
    int history_index = 0;

    buf[0] = '\0';
    buflen--; /* Make sure there is always space for the nulterm */

    /* The latest history entry is always our current buffer, that
     * initially is just an empty string. */
    linenoiseHistoryAdd("");
    
    if (write(fd,prompt,plen) == -1) return -1;
    while(1) {
        char c;
        int nread;
        char seq[2];

        nread = read(fd,&c,1);
        if (nread <= 0) return len;
        switch(c) {
        case 13:    /* enter */
        case 4:     /* ctrl+d */
            history_len--;
            return len;
        case 3:     /* ctrl+c */
            errno = EAGAIN;
            return -1;
        case 127:   /* backspace */
            if (pos > 0 && len > 0) {
                memmove(buf+pos-1,buf+pos,len-pos);
                pos--;
                len--;
                buf[len] = '\0';
                refreshLine(fd,prompt,buf,len,pos,cols);
            }
            break;
        case 27:    /* escape sequence */
            if (read(fd,seq,2) == -1) break;
            if (seq[0] == 91 && seq[1] == 68) {
                /* left arrow */
                if (pos > 0) {
                    pos--;
                    refreshLine(fd,prompt,buf,len,pos,cols);
                }
            } else if (seq[0] == 91 && seq[1] == 67) {
                /* right arrow */
                if (pos != len) {
                    pos++;
                    refreshLine(fd,prompt,buf,len,pos,cols);
                }
            } else if (seq[0] == 91 && (seq[1] == 65 || seq[1] == 66)) {
                /* up and down arrow: history */
                if (history_len > 1) {
                    /* Update the current history entry before to
                     * overwrite it with tne next one. */
                    free(history[history_len-1-history_index]);
                    history[history_len-1-history_index] = strdup(buf);
                    /* Show the new entry */
                    history_index += (seq[1] == 65) ? 1 : -1;
                    if (history_index < 0)
                        history_index = history_len-1;
                    else if (history_index >= history_len)
                        history_index = 0;
                    strncpy(buf,history[history_len-1-history_index],buflen);
                    buf[buflen] = '\0';
                    len = pos = strlen(buf);
                    refreshLine(fd,prompt,buf,len,pos,cols);
                }
            }
            break;
        default:
            if (len < buflen) {
                if (len == pos) {
                    buf[pos] = c;
                    pos++;
                    len++;
                    buf[len] = '\0';
                    if (plen+len < cols) {
                        /* Avoid a full update of the line in the
                         * trivial case. */
                        if (write(fd,&c,1) == -1) return -1;
                    } else {
                        refreshLine(fd,prompt,buf,len,pos,cols);
                    }
                } else {
                    memmove(buf+pos+1,buf+pos,len-pos);
                    buf[pos] = c;
                    len++;
                    pos++;
                    buf[len] = '\0';
                    refreshLine(fd,prompt,buf,len,pos,cols);
                }
            }
            break;
        case 21: /* Ctrl+u, delete the whole line. */
            buf[0] = '\0';
            pos = len = 0;
            refreshLine(fd,prompt,buf,len,pos,cols);
            break;
        case 11: /* Ctrl+k, delete from current to end of line. */
            buf[pos] = '\0';
            len = pos;
            refreshLine(fd,prompt,buf,len,pos,cols);
            break;
        case 1: /* Ctrl+a, go to the start of the line */
            pos = 0;
            refreshLine(fd,prompt,buf,len,pos,cols);
            break;
        case 5: /* ctrl+e, go to the end of the line */
            pos = len;
            refreshLine(fd,prompt,buf,len,pos,cols);
            break;
        }
    }
    return len;
}

int linenoise(char *buf, size_t buflen, char *prompt) {
    int fd = STDIN_FILENO;
    int count;

    if (buflen == 0) {
        errno = EINVAL;
        return -1;
    }
    if (enableRawMode(fd) == -1) return -1;
    count = linenoisePrompt(fd, buf, buflen, prompt);
    disableRawMode(fd);
    printf("\n");
    return count;
}

/* Using a circular buffer is smarter, but a bit more complex to handle. */
int linenoiseHistoryAdd(char *line) {
    if (history_max_len == 0) return 0;
    if (history == 0) {
        history = malloc(sizeof(char*)*history_max_len);
        if (history == NULL) return 0;
        memset(history,0,(sizeof(char*)*history_max_len));
    }
    line = strdup(line);
    if (!line) return 0;
    if (history_len == history_max_len) {
        memmove(history,history+1,sizeof(char*)*(history_max_len-1));
        history_len--;
    }
    history[history_len] = line;
    history_len++;
    return 1;
}

int linenoiseHistorySetMaxLen(int len) {
    char **new;

    if (len < 1) return 0;
    if (history) {
        int tocopy = history_len;

        new = malloc(sizeof(char*)*len);
        if (new == NULL) return 0;
        if (len < tocopy) tocopy = len;
        memcpy(new,history+(history_max_len-tocopy), sizeof(char*)*tocopy);
        free(history);
        history = new;
    }
    history_max_len = len;
    if (history_len > history_max_len)
        history_len = history_max_len;
    return 1;
}