lib/mp-readline: Refactor to support coroutine/event-driven usage.

readline_process_char() can be fed character by character, for example,
received from external event loop. This will allow to integrate MicroPython
into cooperative multitasking systems.

2 files changed, 199 insertions, 165 deletions

diff --git a/lib/mp-readline/readline.c b/lib/mp-readline/readline.c
index ee2e8ebdae..78380e3170 100644
--- a/lib/mp-readline/readline.c
+++ b/lib/mp-readline/readline.c
@@ -57,190 +57,220 @@ STATIC char *str_dup_maybe(const char *str) {
     return s2;
 }
 
-int readline(vstr_t *line, const char *prompt) {
-    stdout_tx_str(prompt);
-    int orig_line_len = line->len;
-    int escape_seq = ESEQ_NONE;
-    char escape_seq_buf[1] = {0};
-    int hist_cur = -1;
-    int cursor_pos = orig_line_len;
-    for (;;) {
-        int c = stdin_rx_chr();
-        int last_line_len = line->len;
-        int redraw_step_back = 0;
-        bool redraw_from_cursor = false;
-        int redraw_step_forward = 0;
-        if (escape_seq == ESEQ_NONE) {
-            if (CHAR_CTRL_A <= c && c <= CHAR_CTRL_D && vstr_len(line) == orig_line_len) {
-                // control character with empty line
-                return c;
-            } else if (c == CHAR_CTRL_A) {
-                // CTRL-A with non-empty line is go-to-start-of-line
-                goto home_key;
-            } else if (c == CHAR_CTRL_C) {
-                // CTRL-C with non-empty line is cancel
-                return c;
-            } else if (c == CHAR_CTRL_E) {
-                // CTRL-E is go-to-end-of-line
-                goto end_key;
-            } else if (c == '\r') {
-                // newline
-                stdout_tx_str("\r\n");
-                if (line->len > orig_line_len && (MP_STATE_PORT(readline_hist)[0] == NULL || strcmp(MP_STATE_PORT(readline_hist)[0], line->buf + orig_line_len) != 0)) {
-                    // a line which is not empty and different from the last one
-                    // so update the history
-                    char *most_recent_hist = str_dup_maybe(line->buf + orig_line_len);
-                    if (most_recent_hist != NULL) {
-                        for (int i = READLINE_HIST_SIZE - 1; i > 0; i--) {
-                            MP_STATE_PORT(readline_hist)[i] = MP_STATE_PORT(readline_hist)[i - 1];
-                        }
-                        MP_STATE_PORT(readline_hist)[0] = most_recent_hist;
+typedef struct _readline_t {
+    vstr_t *line;
+    int orig_line_len;
+    int escape_seq;
+    int hist_cur;
+    int cursor_pos;
+    char escape_seq_buf[1];
+} readline_t;
+
+readline_t rl;
+
+int readline_process_char(int c) {
+    int last_line_len = rl.line->len;
+    int redraw_step_back = 0;
+    bool redraw_from_cursor = false;
+    int redraw_step_forward = 0;
+    if (rl.escape_seq == ESEQ_NONE) {
+        if (CHAR_CTRL_A <= c && c <= CHAR_CTRL_D && vstr_len(rl.line) == rl.orig_line_len) {
+            // control character with empty line
+            return c;
+        } else if (c == CHAR_CTRL_A) {
+            // CTRL-A with non-empty line is go-to-start-of-line
+            goto home_key;
+        } else if (c == CHAR_CTRL_C) {
+            // CTRL-C with non-empty line is cancel
+            return c;
+        } else if (c == CHAR_CTRL_E) {
+            // CTRL-E is go-to-end-of-line
+            goto end_key;
+        } else if (c == '\r') {
+            // newline
+            stdout_tx_str("\r\n");
+            if (rl.line->len > rl.orig_line_len && (MP_STATE_PORT(readline_hist)[0] == NULL || strcmp(MP_STATE_PORT(readline_hist)[0], rl.line->buf + rl.orig_line_len) != 0)) {
+                // a line which is not empty and different from the last one
+                // so update the history
+                char *most_recent_hist = str_dup_maybe(rl.line->buf + rl.orig_line_len);
+                if (most_recent_hist != NULL) {
+                    for (int i = READLINE_HIST_SIZE - 1; i > 0; i--) {
+                        MP_STATE_PORT(readline_hist)[i] = MP_STATE_PORT(readline_hist)[i - 1];
                     }
+                    MP_STATE_PORT(readline_hist)[0] = most_recent_hist;
                 }
-                return 0;
-            } else if (c == 27) {
-                // escape sequence
-                escape_seq = ESEQ_ESC;
-            } else if (c == 8 || c == 127) {
-                // backspace/delete
-                if (cursor_pos > orig_line_len) {
-                    vstr_cut_out_bytes(line, cursor_pos - 1, 1);
-                    // set redraw parameters
-                    redraw_step_back = 1;
-                    redraw_from_cursor = true;
-                }
-            } else if (32 <= c && c <= 126) {
-                // printable character
-                vstr_ins_char(line, cursor_pos, c);
+            }
+            return 0;
+        } else if (c == 27) {
+            // escape sequence
+            rl.escape_seq = ESEQ_ESC;
+        } else if (c == 8 || c == 127) {
+            // backspace/delete
+            if (rl.cursor_pos > rl.orig_line_len) {
+                vstr_cut_out_bytes(rl.line, rl.cursor_pos - 1, 1);
                 // set redraw parameters
+                redraw_step_back = 1;
                 redraw_from_cursor = true;
-                redraw_step_forward = 1;
-            }
-        } else if (escape_seq == ESEQ_ESC) {
-            switch (c) {
-                case '[':
-                    escape_seq = ESEQ_ESC_BRACKET;
-                    break;
-                case 'O':
-                    escape_seq = ESEQ_ESC_O;
-                    break;
-                default:
-                    DEBUG_printf("(ESC %d)", c);
-                    escape_seq = ESEQ_NONE;
             }
-        } else if (escape_seq == ESEQ_ESC_BRACKET) {
-            if ('0' <= c && c <= '9') {
-                escape_seq = ESEQ_ESC_BRACKET_DIGIT;
-                escape_seq_buf[0] = c;
-            } else {
-                escape_seq = ESEQ_NONE;
-                if (c == 'A') {
-                    // up arrow
-                    if (hist_cur + 1 < READLINE_HIST_SIZE && MP_STATE_PORT(readline_hist)[hist_cur + 1] != NULL) {
-                        // increase hist num
-                        hist_cur += 1;
-                        // set line to history
-                        line->len = orig_line_len;
-                        vstr_add_str(line, MP_STATE_PORT(readline_hist)[hist_cur]);
-                        // set redraw parameters
-                        redraw_step_back = cursor_pos - orig_line_len;
-                        redraw_from_cursor = true;
-                        redraw_step_forward = line->len - orig_line_len;
-                    }
-                } else if (c == 'B') {
-                    // down arrow
-                    if (hist_cur >= 0) {
-                        // decrease hist num
-                        hist_cur -= 1;
-                        // set line to history
-                        vstr_cut_tail_bytes(line, line->len - orig_line_len);
-                        if (hist_cur >= 0) {
-                            vstr_add_str(line, MP_STATE_PORT(readline_hist)[hist_cur]);
-                        }
-                        // set redraw parameters
-                        redraw_step_back = cursor_pos - orig_line_len;
-                        redraw_from_cursor = true;
-                        redraw_step_forward = line->len - orig_line_len;
-                    }
-                } else if (c == 'C') {
-                    // right arrow
-                    if (cursor_pos < line->len) {
-                        redraw_step_forward = 1;
-                    }
-                } else if (c == 'D') {
-                    // left arrow
-                    if (cursor_pos > orig_line_len) {
-                        redraw_step_back = 1;
+        } else if (32 <= c && c <= 126) {
+            // printable character
+            vstr_ins_char(rl.line, rl.cursor_pos, c);
+            // set redraw parameters
+            redraw_from_cursor = true;
+            redraw_step_forward = 1;
+        }
+    } else if (rl.escape_seq == ESEQ_ESC) {
+        switch (c) {
+            case '[':
+                rl.escape_seq = ESEQ_ESC_BRACKET;
+                break;
+            case 'O':
+                rl.escape_seq = ESEQ_ESC_O;
+                break;
+            default:
+                DEBUG_printf("(ESC %d)", c);
+                rl.escape_seq = ESEQ_NONE;
+        }
+    } else if (rl.escape_seq == ESEQ_ESC_BRACKET) {
+        if ('0' <= c && c <= '9') {
+            rl.escape_seq = ESEQ_ESC_BRACKET_DIGIT;
+            rl.escape_seq_buf[0] = c;
+        } else {
+            rl.escape_seq = ESEQ_NONE;
+            if (c == 'A') {
+                // up arrow
+                if (rl.hist_cur + 1 < READLINE_HIST_SIZE && MP_STATE_PORT(readline_hist)[rl.hist_cur + 1] != NULL) {
+                    // increase hist num
+                    rl.hist_cur += 1;
+                    // set line to history
+                    rl.line->len = rl.orig_line_len;
+                    vstr_add_str(rl.line, MP_STATE_PORT(readline_hist)[rl.hist_cur]);
+                    // set redraw parameters
+                    redraw_step_back = rl.cursor_pos - rl.orig_line_len;
+                    redraw_from_cursor = true;
+                    redraw_step_forward = rl.line->len - rl.orig_line_len;
+                }
+            } else if (c == 'B') {
+                // down arrow
+                if (rl.hist_cur >= 0) {
+                    // decrease hist num
+                    rl.hist_cur -= 1;
+                    // set line to history
+                    vstr_cut_tail_bytes(rl.line, rl.line->len - rl.orig_line_len);
+                    if (rl.hist_cur >= 0) {
+                        vstr_add_str(rl.line, MP_STATE_PORT(readline_hist)[rl.hist_cur]);
                     }
-                } else if (c == 'H') {
-                    // home
-                    goto home_key;
-                } else if (c == 'F') {
-                    // end
-                    goto end_key;
-                } else {
-                    DEBUG_printf("(ESC [ %d)", c);
+                    // set redraw parameters
+                    redraw_step_back = rl.cursor_pos - rl.orig_line_len;
+                    redraw_from_cursor = true;
+                    redraw_step_forward = rl.line->len - rl.orig_line_len;
+                }
+            } else if (c == 'C') {
+                // right arrow
+                if (rl.cursor_pos < rl.line->len) {
+                    redraw_step_forward = 1;
+                }
+            } else if (c == 'D') {
+                // left arrow
+                if (rl.cursor_pos > rl.orig_line_len) {
+                    redraw_step_back = 1;
                 }
+            } else if (c == 'H') {
+                // home
+                goto home_key;
+            } else if (c == 'F') {
+                // end
+                goto end_key;
+            } else {
+                DEBUG_printf("(ESC [ %d)", c);
             }
-        } else if (escape_seq == ESEQ_ESC_BRACKET_DIGIT) {
-            if (c == '~') {
-                if (escape_seq_buf[0] == '1' || escape_seq_buf[0] == '7') {
+        }
+    } else if (rl.escape_seq == ESEQ_ESC_BRACKET_DIGIT) {
+        if (c == '~') {
+            if (rl.escape_seq_buf[0] == '1' || rl.escape_seq_buf[0] == '7') {
 home_key:
-                    redraw_step_back = cursor_pos - orig_line_len;
-                } else if (escape_seq_buf[0] == '4' || escape_seq_buf[0] == '8') {
+                redraw_step_back = rl.cursor_pos - rl.orig_line_len;
+            } else if (rl.escape_seq_buf[0] == '4' || rl.escape_seq_buf[0] == '8') {
 end_key:
-                    redraw_step_forward = line->len - cursor_pos;
-                } else {
-                    DEBUG_printf("(ESC [ %c %d)", escape_seq_buf[0], c);
-                }
+                redraw_step_forward = rl.line->len - rl.cursor_pos;
             } else {
-                DEBUG_printf("(ESC [ %c %d)", escape_seq_buf[0], c);
-            }
-            escape_seq = ESEQ_NONE;
-        } else if (escape_seq == ESEQ_ESC_O) {
-            switch (c) {
-                case 'H':
-                    goto home_key;
-                case 'F':
-                    goto end_key;
-                default:
-                    DEBUG_printf("(ESC O %d)", c);
-                    escape_seq = ESEQ_NONE;
+                DEBUG_printf("(ESC [ %c %d)", rl.escape_seq_buf[0], c);
             }
         } else {
-            escape_seq = ESEQ_NONE;
+            DEBUG_printf("(ESC [ %c %d)", rl.escape_seq_buf[0], c);
         }
+        rl.escape_seq = ESEQ_NONE;
+    } else if (rl.escape_seq == ESEQ_ESC_O) {
+        switch (c) {
+            case 'H':
+                goto home_key;
+            case 'F':
+                goto end_key;
+            default:
+                DEBUG_printf("(ESC O %d)", c);
+                rl.escape_seq = ESEQ_NONE;
+        }
+    } else {
+        rl.escape_seq = ESEQ_NONE;
+    }
 
-        // redraw command prompt, efficiently
-        // TODO we can probably use some more sophisticated VT100 commands here
-        if (redraw_step_back > 0) {
-            for (int i = 0; i < redraw_step_back; i++) {
-                stdout_tx_str("\b");
-            }
-            cursor_pos -= redraw_step_back;
+    // redraw command prompt, efficiently
+    // TODO we can probably use some more sophisticated VT100 commands here
+    if (redraw_step_back > 0) {
+        for (int i = 0; i < redraw_step_back; i++) {
+            stdout_tx_str("\b");
         }
-        if (redraw_from_cursor) {
-            if (line->len < last_line_len) {
-                // erase old chars
-                for (int i = cursor_pos; i < last_line_len; i++) {
-                    stdout_tx_str(" ");
-                }
-                // step back
-                for (int i = cursor_pos; i < last_line_len; i++) {
-                    stdout_tx_str("\b");
-                }
+        rl.cursor_pos -= redraw_step_back;
+    }
+    if (redraw_from_cursor) {
+        if (rl.line->len < last_line_len) {
+            // erase old chars
+            for (int i = rl.cursor_pos; i < last_line_len; i++) {
+                stdout_tx_str(" ");
             }
-            // draw new chars
-            stdout_tx_strn(line->buf + cursor_pos, line->len - cursor_pos);
-            // move cursor forward if needed (already moved forward by length of line, so move it back)
-            for (int i = cursor_pos + redraw_step_forward; i < line->len; i++) {
+            // step back
+            for (int i = rl.cursor_pos; i < last_line_len; i++) {
                 stdout_tx_str("\b");
             }
-            cursor_pos += redraw_step_forward;
-        } else if (redraw_step_forward > 0) {
-            // draw over old chars to move cursor forwards
-            stdout_tx_strn(line->buf + cursor_pos, redraw_step_forward);
-            cursor_pos += redraw_step_forward;
+        }
+        // draw new chars
+        stdout_tx_strn(rl.line->buf + rl.cursor_pos, rl.line->len - rl.cursor_pos);
+        // move cursor forward if needed (already moved forward by length of line, so move it back)
+        for (int i = rl.cursor_pos + redraw_step_forward; i < rl.line->len; i++) {
+            stdout_tx_str("\b");
+        }
+        rl.cursor_pos += redraw_step_forward;
+    } else if (redraw_step_forward > 0) {
+        // draw over old chars to move cursor forwards
+        stdout_tx_strn(rl.line->buf + rl.cursor_pos, redraw_step_forward);
+        rl.cursor_pos += redraw_step_forward;
+    }
+
+    return -1;
+}
+
+void readline_note_newline() {
+    rl.orig_line_len = rl.line->len;
+    rl.cursor_pos = rl.orig_line_len;
+}
+
+void readline_init(vstr_t *line) {
+    rl.line = line;
+    rl.orig_line_len = line->len;
+    rl.escape_seq = ESEQ_NONE;
+    rl.escape_seq_buf[0] = 0;
+    rl.hist_cur = -1;
+    rl.cursor_pos = rl.orig_line_len;
+}
+
+int readline(vstr_t *line, const char *prompt) {
+    stdout_tx_str(prompt);
+    readline_init(line);
+    for (;;) {
+        int c = stdin_rx_chr();
+        int r = readline_process_char(c);
+        if (r >= 0) {
+            return r;
         }
     }
 }
diff --git a/lib/mp-readline/readline.h b/lib/mp-readline/readline.h
index d5ce4704ea..51ea4a56d4 100644
--- a/lib/mp-readline/readline.h
+++ b/lib/mp-readline/readline.h
@@ -32,3 +32,7 @@
 
 void readline_init0(void);
 int readline(vstr_t *line, const char *prompt);
+
+void readline_init(vstr_t *line);
+void readline_note_newline();
+int readline_process_char(int c);