libbb/lineedit: implement optional Ctrl-R history search

function                                             old     new   delta
read_line_input                                     3433    3957    +524
load_string                                           77      90     +13
input_tab                                           1086    1069     -17
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 537/-17)           Total: 520 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 161 insertions, 12 deletions

diff --git a/libbb/Config.src b/libbb/Config.src
index 0ea8f43ab..aa442365a 100644
--- a/libbb/Config.src
+++ b/libbb/Config.src
@@ -94,6 +94,14 @@ config FEATURE_EDITING_SAVEHISTORY
         help
           Enable history saving in shells.
 
+config FEATURE_REVERSE_SEARCH
+        bool "Reverse history search"
+        default y
+        depends on FEATURE_EDITING_SAVEHISTORY
+        help
+          Enable readline-like Ctrl-R combination for reverse history search.
+          Increases code by about 0.5k.
+
 config FEATURE_TAB_COMPLETION
         bool "Tab completion"
         default y
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 4e3bc0ef7..10265192e 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -207,18 +207,21 @@ static void deinit_S(void)
 
 
 #if ENABLE_UNICODE_SUPPORT
-static size_t load_string(const char *src, int maxsize)
+static size_t load_string(const char *src)
 {
         if (unicode_status == UNICODE_ON) {
-                ssize_t len = mbstowcs(command_ps, src, maxsize - 1);
+                ssize_t len = mbstowcs(command_ps, src, S.maxsize - 1);
                 if (len < 0)
                         len = 0;
                 command_ps[len] = BB_NUL;
                 return len;
         } else {
                 unsigned i = 0;
-                while ((command_ps[i] = src[i]) != 0)
+                while (src[i] && i < S.maxsize - 1) {
+                        command_ps[i] = src[i];
                         i++;
+                }
+                command_ps[i] = BB_NUL;
                 return i;
         }
 }
@@ -319,9 +322,9 @@ static wchar_t adjust_width_and_validate_wc(wchar_t wc)
         return wc;
 }
 #else /* !UNICODE */
-static size_t load_string(const char *src, int maxsize)
+static size_t load_string(const char *src)
 {
-        safe_strncpy(command_ps, src, maxsize);
+        safe_strncpy(command_ps, src, S.maxsize);
         return strlen(command_ps);
 }
 # if ENABLE_FEATURE_TAB_COMPLETION
@@ -1224,10 +1227,10 @@ static NOINLINE void input_tab(smallint *lastWasTab)
                         strcpy(match_buf, &command[cursor_mb]);
                         /* where do we want to have cursor after all? */
                         strcpy(&command[cursor_mb], chosen_match + match_pfx_len);
-                        len = load_string(command, S.maxsize);
+                        len = load_string(command);
                         /* add match and tail */
                         sprintf(&command[cursor_mb], "%s%s", chosen_match + match_pfx_len, match_buf);
-                        command_len = load_string(command, S.maxsize);
+                        command_len = load_string(command);
                         /* write out the matched command */
                         /* paranoia: load_string can return 0 on conv error,
                          * prevent passing pos = (0 - 12) to redraw */
@@ -1948,6 +1951,140 @@ static int isrtl_str(void)
 #undef CTRL
 #define CTRL(a) ((a) & ~0x40)
 
+enum {
+        VI_CMDMODE_BIT = 0x40000000,
+        /* 0x80000000 bit flags KEYCODE_xxx */
+};
+
+#if ENABLE_FEATURE_REVERSE_SEARCH
+/* Mimic readline Ctrl-R reverse history search.
+ * When invoked, it shows the following prompt:
+ * (reverse-i-search)'': user_input [cursor pos unchanged by Ctrl-R]
+ * and typing results in search being performed:
+ * (reverse-i-search)'tmp': cd /tmp [cursor under t in /tmp]
+ * Search is performed by looking at progressively older lines in history.
+ * Ctrl-R again searches for the next match in history.
+ * Backspace deletes last matched char.
+ * Control keys exit search and return to normal editing (at current history line).
+ */
+static int32_t reverse_i_search(void)
+{
+        char match_buf[128]; /* for user input */
+        char read_key_buffer[KEYCODE_BUFFER_SIZE];
+        const char *matched_history_line;
+        const char *saved_prompt;
+        int32_t ic;
+
+        matched_history_line = NULL;
+        read_key_buffer[0] = 0;
+        match_buf[0] = '\0';
+
+        /* Save and replace the prompt */
+        saved_prompt = cmdedit_prompt;
+        goto set_prompt;
+
+        while (1) {
+                int h;
+                unsigned match_buf_len = strlen(match_buf);
+
+                fflush_all();
+//FIXME: correct timeout?
+                ic = lineedit_read_key(read_key_buffer, -1);
+
+                switch (ic) {
+                case CTRL('R'): /* searching for the next match */
+                        break;
+
+                case '\b':
+                case '\x7f':
+                        /* Backspace */
+                        if (unicode_status == UNICODE_ON) {
+                                while (match_buf_len != 0) {
+                                        uint8_t c = match_buf[--match_buf_len];
+                                        if ((c & 0xc0) != 0x80) /* start of UTF-8 char? */
+                                                break; /* yes */
+                                }
+                        } else {
+                                if (match_buf_len != 0)
+                                        match_buf_len--;
+                        }
+                        match_buf[match_buf_len] = '\0';
+                        break;
+
+                default:
+                        if (ic < ' '
+                         || (!ENABLE_UNICODE_SUPPORT && ic >= 256)
+                         || (ENABLE_UNICODE_SUPPORT && ic >= VI_CMDMODE_BIT)
+                        ) {
+                                goto ret;
+                        }
+
+                        /* Append this char */
+#if ENABLE_UNICODE_SUPPORT
+                        if (unicode_status == UNICODE_ON) {
+                                mbstate_t mbstate = { 0 };
+                                char buf[MB_CUR_MAX + 1];
+                                int len = wcrtomb(buf, ic, &mbstate);
+                                if (len > 0) {
+                                        buf[len] = '\0';
+                                        if (match_buf_len + len < sizeof(match_buf))
+                                                strcpy(match_buf + match_buf_len, buf);
+                                }
+                        } else
+#endif
+                        if (match_buf_len < sizeof(match_buf) - 1) {
+                                match_buf[match_buf_len] = ic;
+                                match_buf[match_buf_len + 1] = '\0';
+                        }
+                        break;
+                } /* switch (ic) */
+
+                /* Search in history for match_buf */
+                h = state->cur_history;
+                if (ic == CTRL('R'))
+                        h--;
+                while (h >= 0) {
+                        if (state->history[h]) {
+                                char *match = strstr(state->history[h], match_buf);
+                                if (match) {
+                                        state->cur_history = h;
+                                        matched_history_line = state->history[h];
+                                        command_len = load_string(matched_history_line);
+                                        cursor = match - matched_history_line;
+//FIXME: cursor position for Unicode case
+
+                                        free((char*)cmdedit_prompt);
+ set_prompt:
+                                        cmdedit_prompt = xasprintf("(reverse-i-search)'%s': ", match_buf);
+                                        cmdedit_prmt_len = strlen(cmdedit_prompt);
+                                        goto do_redraw;
+                                }
+                        }
+                        h--;
+                }
+
+                /* Not found */
+                match_buf[match_buf_len] = '\0';
+                beep();
+                continue;
+
+ do_redraw:
+                redraw(cmdedit_y, command_len - cursor);
+        } /* while (1) */
+
+ ret:
+        if (matched_history_line)
+                command_len = load_string(matched_history_line);
+
+        free((char*)cmdedit_prompt);
+        cmdedit_prompt = saved_prompt;
+        cmdedit_prmt_len = strlen(cmdedit_prompt);
+        redraw(cmdedit_y, command_len - cursor);
+
+        return ic;
+}
+#endif
+
 /* maxsize must be >= 2.
  * Returns:
  * -1 on read errors or EOF, or on bare Ctrl-D,
@@ -2062,15 +2199,14 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
                  * clutters the big switch a bit, but keeps all the code
                  * in one place.
                  */
-                enum {
-                        VI_CMDMODE_BIT = 0x40000000,
-                        /* 0x80000000 bit flags KEYCODE_xxx */
-                };
                 int32_t ic, ic_raw;
 
                 fflush_all();
                 ic = ic_raw = lineedit_read_key(read_key_buffer, timeout);
 
+#if ENABLE_FEATURE_REVERSE_SEARCH
+ again:
+#endif
 #if ENABLE_FEATURE_EDITING_VI
                 newdelflag = 1;
                 if (vi_cmdmode) {
@@ -2174,6 +2310,11 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
                         while (cursor > 0 && !BB_isspace(command_ps[cursor-1]))
                                 input_backspace();
                         break;
+#if ENABLE_FEATURE_REVERSE_SEARCH
+                case CTRL('R'):
+                        ic = ic_raw = reverse_i_search();
+                        goto again;
+#endif
 
 #if ENABLE_FEATURE_EDITING_VI
                 case 'i'|VI_CMDMODE_BIT:
@@ -2327,7 +2468,7 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
                         /* Rewrite the line with the selected history item */
                         /* change command */
                         command_len = load_string(state->history[state->cur_history] ?
-                                        state->history[state->cur_history] : "", maxsize);
+                                        state->history[state->cur_history] : "");
                         /* redraw and go to eol (bol, in vi) */
                         redraw(cmdedit_y, (state->flags & VI_MODE) ? 9999 : 0);
                         break;