diff --git a/components/console/linenoise/linenoise.c b/components/console/linenoise/linenoise.c index 2887995..1449622 100644 --- a/components/console/linenoise/linenoise.c +++ b/components/console/linenoise/linenoise.c @@ -205,47 +205,107 @@ static void flushWrite(void) { /* Use the ESC [6n escape sequence to query the horizontal cursor position * and return it. On error -1 is returned, on success the position of the * cursor. */ -static int getCursorPosition() { - char buf[32]; - int cols, rows; - unsigned int i = 0; +static int getCursorPosition(void) { + char buf[LINENOISE_COMMAND_MAX_LEN] = { 0 }; + int cols = 0; + int rows = 0; + int i = 0; + const int out_fd = fileno(stdout); + const int in_fd = fileno(stdin); + /* The following ANSI escape sequence is used to get from the TTY the + * cursor position. */ + const char get_cursor_cmd[] = "\x1b[6n"; - /* Report cursor location */ - fprintf(stdout, "\x1b[6n"); + /* Send the command to the TTY on the other end of the UART. + * Let's use unistd's write function. Thus, data sent through it are raw + * reducing the overhead compared to using fputs, fprintf, etc... */ + write(out_fd, get_cursor_cmd, sizeof(get_cursor_cmd)); + + /* For USB CDC, it is required to flush the output. */ flushWrite(); - /* Read the response: ESC [ rows ; cols R */ + + /* The other end will send its response which format is ESC [ rows ; cols R + * We don't know exactly how many bytes we have to read, thus, perform a + * read for each byte. + * Stop right before the last character of the buffer, to be able to NULL + * terminate it. */ while (i < sizeof(buf)-1) { - if (fread(buf+i, 1, 1, stdin) != 1) break; - if (buf[i] == 'R') break; - i++; + /* Keep using unistd's functions. Here, using `read` instead of `fgets` + * or `fgets` guarantees us that we we can read a byte regardless on + * whether the sender sent end of line character(s) (CR, CRLF, LF). */ + if (read(in_fd, buf + i, 1) != 1 || buf[i] == 'R') { + /* If we couldn't read a byte from STDIN or if 'R' was received, + * the transmission is finished. */ + break; + } + + /* For some reasons, it is possible that we receive new line character + * after querying the cursor position on some UART. Let's ignore them, + * this will not affect the rest of the program. */ + if (buf[i] != '\n') { + i++; + } } + + /* NULL-terminate the buffer, this is required by `sscanf`. */ buf[i] = '\0'; - /* Parse it. */ - if (buf[0] != ESC || buf[1] != '[') return -1; - if (sscanf(buf+2,"%d;%d",&rows,&cols) != 2) return -1; + + /* Parse the received data to get the position of the cursor. */ + if (buf[0] != ESC || buf[1] != '[' || sscanf(buf+2,"%d;%d",&rows,&cols) != 2) { + return -1; + } return cols; } /* Try to get the number of columns in the current terminal, or assume 80 * if it fails. */ -static int getColumns() { - int start, cols; +static int getColumns(void) { + int start = 0; + int cols = 0; + int written = 0; + char seq[LINENOISE_COMMAND_MAX_LEN] = { 0 }; + const int fd = fileno(stdout); + + /* The following ANSI escape sequence is used to tell the TTY to move + * the cursor to the most-right position. */ + const char move_cursor_right[] = "\x1b[999C"; + const size_t cmd_len = sizeof(move_cursor_right); + + /* This one is used to set the cursor position. */ + const char set_cursor_pos[] = "\x1b[%dD"; /* Get the initial position so we can restore it later. */ start = getCursorPosition(); - if (start == -1) goto failed; + if (start == -1) { + goto failed; + } - /* Go to right margin and get position. */ - if (fwrite("\x1b[999C", 1, 6, stdout) != 6) goto failed; + /* Send the command to go to right margin. Use `write` function instead of + * `fwrite` for the same reasons explained in `getCursorPosition()` */ + if (write(fd, move_cursor_right, cmd_len) != cmd_len) { + goto failed; + } flushWrite(); - cols = getCursorPosition(); - if (cols == -1) goto failed; - /* Restore position. */ + /* After sending this command, we can get the new position of the cursor, + * we'd get the size, in columns, of the opened TTY. */ + cols = getCursorPosition(); + if (cols == -1) { + goto failed; + } + + /* Restore the position of the cursor back. */ if (cols > start) { - char seq[32]; - snprintf(seq,32,"\x1b[%dD",cols-start); - if (fwrite(seq, 1, strlen(seq), stdout) == -1) { + /* Generate the move cursor command. */ + written = snprintf(seq, LINENOISE_COMMAND_MAX_LEN, set_cursor_pos, cols-start); + + /* If `written` is equal or bigger than LINENOISE_COMMAND_MAX_LEN, it + * means that the output has been truncated because the size provided + * is too small. */ + assert (written < LINENOISE_COMMAND_MAX_LEN); + + /* Send the command with `write`, which is not buffered. */ + if (write(fd, seq, written) == -1) { /* Can't recover... */ } flushWrite();