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sys/shell: refactor readline function
This makes the code of `readline()` clearer and shorter. It also fixes a minor artifact of the long line handling. Previously it was not possible to recover from a long line. That is, if too many characters were sent, the line would be invalidated and pressing backspace would not fix it- the only option was to discard the line. It is now possible to bring the line back to size. Note that visual effects when deleting characters will still depend on the host's terminal. The new code is written in a way that all writes to memory are guarded by bounds check, so an assertion was removed. Co-authored-by: Juan Carrano <j.carrano@fu-berlin.de>
This commit is contained in:
Hendrik van Essen
parent
45f898563a
commit
a0a3e6c3a1
@ -237,6 +237,40 @@ static void handle_input_line(const shell_command_t *command_list, char *line)
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}
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}
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static inline void print_prompt(void)
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{
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if (PROMPT_ON) {
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putchar('>');
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putchar(' ');
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}
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flush_if_needed();
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}
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static inline void echo_char(char c)
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{
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if (ECHO_ON) {
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putchar(c);
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}
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}
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static inline void white_tape(void)
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{
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if (ECHO_ON) {
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putchar('\b');
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putchar(' ');
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putchar('\b');
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}
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}
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static inline void new_line(void)
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{
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if (ECHO_ON) {
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putchar('\r');
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putchar('\n');
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}
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}
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/**
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* @brief Read a single line from standard input into a buffer.
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*
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@ -246,6 +280,10 @@ static void handle_input_line(const shell_command_t *command_list, char *line)
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* If the input line is too long, the input will still be consumed until the end
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* to prevent the next line from containing garbage.
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*
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* We allow Unix (\n), DOS (\r\n), and Mac linebreaks (\r).
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* QEMU transmits only a single '\r' == 13 on hitting enter ("-serial stdio").
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* DOS newlines are handled like hitting enter twice.
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*
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* @param buf Buffer where the input will be placed.
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* @param size Size of the buffer. The maximum line length will be one less
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* than size, to accommodate for the null terminator.
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@ -254,7 +292,7 @@ static void handle_input_line(const shell_command_t *command_list, char *line)
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* @return length of the read line, excluding the terminator, if reading was
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* successful.
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* @return EOF, if the end of the input stream was reached.
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* @return ENOBUFS if the buffer size was exceeded.
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* @return -ENOBUFS if the buffer size was exceeded.
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*/
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static int readline(char *buf, size_t size)
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{
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@ -264,85 +302,59 @@ static int readline(char *buf, size_t size)
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assert((size_t) size > 0);
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while (1) {
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/* At the start of the loop, cur_pos should point inside of
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* buf. This ensures the terminator can always fit. */
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assert((size_t) curr_pos < size);
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int c = getchar();
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if (c < 0) {
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return EOF;
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}
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/* We allow Unix linebreaks (\n), DOS linebreaks (\r\n), and Mac
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* linebreaks (\r). QEMU transmits only a single '\r' == 13 on hitting
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* enter ("-serial stdio"). DOS newlines are handled like hitting enter
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* twice, but empty lines are ignored. Ctrl-C cancels the current line.
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*/
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if (c == '\r' || c == '\n' || c == ETX) {
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if (c == ETX) {
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switch (c) {
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case EOF:
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return EOF;
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case ETX:
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/* Ctrl-C cancels the current line. */
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curr_pos = 0;
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length_exceeded = false;
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}
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/* fall-thru */
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case '\r':
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/* fall-thru */
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case '\n':
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buf[curr_pos] = '\0';
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buf[curr_pos] = '\0';
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new_line();
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if (ECHO_ON) {
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putchar('\r');
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putchar('\n');
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}
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return (length_exceeded) ? -ENOBUFS : curr_pos;
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return (length_exceeded) ? -ENOBUFS : curr_pos;
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/* check for backspace: */
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case BS: /* 0x08 (BS) for most terminals */
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/* fall-thru */
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case DEL: /* 0x7f (DEL) when using QEMU */
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if (curr_pos > 0) {
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curr_pos--;
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if ((size_t) curr_pos < size) {
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buf[curr_pos] = '\0';
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length_exceeded = false;
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}
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white_tape();
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}
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break;
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default:
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/* Always consume characters, but do not not always store them */
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if ((size_t) curr_pos < size - 1) {
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buf[curr_pos++] = c;
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}
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else {
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length_exceeded = true;
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}
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echo_char(c);
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break;
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}
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/* check for backspace:
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* 0x7f (DEL) when using QEMU
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* 0x08 (BS) for most terminals */
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if (c == BS || c == DEL) {
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if (curr_pos == 0) {
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/* ignore empty line */
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continue;
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}
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/* after we dropped characters don't edit the line, yet keep the
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* visual effects */
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if (!length_exceeded) {
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buf[--curr_pos] = '\0';
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}
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/* white-tape the character */
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if (ECHO_ON) {
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putchar('\b');
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putchar(' ');
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putchar('\b');
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}
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}
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else {
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/* Always consume characters, but do not not always store them */
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if ((size_t) curr_pos < size - 1) {
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buf[curr_pos++] = c;
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}
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else {
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length_exceeded = true;
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}
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if (ECHO_ON) {
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putchar(c);
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}
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}
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flush_if_needed();
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}
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}
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static inline void print_prompt(void)
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{
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if (PROMPT_ON) {
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putchar('>');
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putchar(' ');
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}
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flush_if_needed();
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}
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void shell_run_once(const shell_command_t *shell_commands,
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char *line_buf, int len)
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{
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