libbb: make history saving/loading concurrent-safe
* all history writers always append (not overwrite) history files * they reload history if they detect that file length has changed since last write * they trim history file only when it grows 4 times longer than MAXLINES * they do this atomically by creating new file and renaming it to old Unfortunately, this comes at a price: function old new delta load_history - 346 +346 read_line_input 3155 3358 +203 new_line_input_t 17 31 +14 ...irrelevant small jitter... ------------------------------------------------------------------------------ (add/remove: 1/0 grow/shrink: 5/5 up/down: 573/-13) Total: 560 bytes
This commit is contained in:
Denis Vlasenko
parent
3fd1046300
commit
57abf9e947
@ -1187,9 +1187,9 @@ unsigned long long bb_makedev(unsigned int major, unsigned int minor) FAST_FUNC;
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#if ENABLE_FEATURE_EDITING
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/* It's NOT just ENABLEd or disabled. It's a number: */
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#ifdef CONFIG_FEATURE_EDITING_HISTORY
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#define MAX_HISTORY (CONFIG_FEATURE_EDITING_HISTORY + 0)
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# define MAX_HISTORY (CONFIG_FEATURE_EDITING_HISTORY + 0)
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#else
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#define MAX_HISTORY 0
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# define MAX_HISTORY 0
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#endif
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typedef struct line_input_t {
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int flags;
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@ -1197,7 +1197,11 @@ typedef struct line_input_t {
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#if MAX_HISTORY
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int cnt_history;
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int cur_history;
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USE_FEATURE_EDITING_SAVEHISTORY(const char *hist_file;)
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#if ENABLE_FEATURE_EDITING_SAVEHISTORY
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unsigned cnt_history_in_file;
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off_t last_history_end;
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const char *hist_file;
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#endif
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char *history[MAX_HISTORY + 1];
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#endif
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} line_input_t;
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142
libbb/lineedit.c
142
libbb/lineedit.c
@ -990,64 +990,141 @@ static int get_next_history(void)
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}
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#if ENABLE_FEATURE_EDITING_SAVEHISTORY
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/* We try to ensure that concurrent additions to the history
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* do not overwrite each other, and that additions to the history
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* by one user are noticed by others.
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* Otherwise shell users get unhappy.
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*
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* History file is trimmed lazily, when it grows several times longer
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* than configured MAX_HISTORY lines.
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*/
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/* state->flags is already checked to be nonzero */
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static void load_history(const char *fromfile)
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static void load_history(void)
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{
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char *temp_h[MAX_HISTORY];
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char *line;
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FILE *fp;
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int hi;
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unsigned idx, i, line_len;
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/* NB: do not trash old history if file can't be opened */
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fp = fopen_for_read(fromfile);
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fp = fopen_for_read(state->hist_file);
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if (fp) {
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/* clean up old history */
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for (hi = state->cnt_history; hi > 0;) {
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hi--;
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free(state->history[hi]);
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state->history[hi] = NULL;
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for (idx = state->cnt_history; idx > 0;) {
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idx--;
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free(state->history[idx]);
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state->history[idx] = NULL;
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}
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for (hi = 0; hi < MAX_HISTORY;) {
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char *hl = xmalloc_fgetline(fp);
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int l;
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if (!hl)
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break;
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l = strlen(hl);
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if (l >= MAX_LINELEN)
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hl[MAX_LINELEN-1] = '\0';
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if (l == 0) {
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free(hl);
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/* fill temp_h[], retaining only last MAX_HISTORY lines */
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memset(temp_h, 0, sizeof(temp_h));
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state->cnt_history_in_file = idx = 0;
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while ((line = xmalloc_fgetline(fp)) != NULL) {
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if (line[0] == '\0') {
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free(line);
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continue;
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}
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state->history[hi++] = hl;
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free(temp_h[idx]);
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temp_h[idx] = line;
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state->cnt_history_in_file++;
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idx++;
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if (idx == MAX_HISTORY)
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idx = 0;
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}
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state->last_history_end = lseek(fileno(fp), 0, SEEK_CUR);
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fclose(fp);
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state->cnt_history = hi;
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/* find first non-NULL temp_h[], if any */
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if (state->cnt_history_in_file) {
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while (temp_h[idx] == NULL) {
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idx++;
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if (idx == MAX_HISTORY)
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idx = 0;
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}
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}
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/* copy temp_h[] to state->history[] */
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for (i = 0; i < MAX_HISTORY;) {
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line = temp_h[idx];
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if (!line)
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break;
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idx++;
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if (idx == MAX_HISTORY)
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idx = 0;
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line_len = strlen(line);
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if (line_len >= MAX_LINELEN)
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line[MAX_LINELEN-1] = '\0';
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state->history[i++] = line;
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}
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state->cnt_history = i;
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}
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}
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/* state->flags is already checked to be nonzero */
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static void save_history(const char *tofile)
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static void save_history(char *str)
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{
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FILE *fp;
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off_t end;
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int fd;
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int len;
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fp = fopen_for_write(tofile);
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if (fp) {
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int i;
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len = strlen(str);
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again:
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fd = open(state->hist_file, O_WRONLY | O_CREAT | O_APPEND, 0666);
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if (fd < 0)
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return;
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for (i = 0; i < state->cnt_history; i++) {
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fprintf(fp, "%s\n", state->history[i]);
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end = lseek(fd, 0, SEEK_END);
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if (str) {
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str[len] = '\n';
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full_write(fd, str, len + 1);
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str[len] = '\0';
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str = NULL;
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state->cnt_history_in_file++;
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}
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close(fd);
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/* if it was not a 1st write */
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if (state->last_history_end >= 0) {
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/* did someone else write anything there? */
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if (state->last_history_end != end) {
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load_history(); /* note: updates cnt_history_in_file */
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state->last_history_end = -1;
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goto again;
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}
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fclose(fp);
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}
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state->last_history_end = end + len + 1;
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/* did we write so much that history file needs trimming? */
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if (state->cnt_history_in_file > MAX_HISTORY * 4) {
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FILE *fp;
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char *new_name;
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new_name = xasprintf("%s.new", state->hist_file);
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fp = fopen_for_write(new_name);
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if (fp) {
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int i;
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for (i = 0; i < state->cnt_history; i++) {
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fprintf(fp, "%s\n", state->history[i]);
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}
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state->cnt_history_in_file = i; /* == cnt_history */
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state->last_history_end = lseek(fileno(fp), 0, SEEK_CUR);
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fclose(fp);
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/* replace hist_file atomically */
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rename(new_name, state->hist_file);
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}
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free(new_name);
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}
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}
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#else
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#define load_history(a) ((void)0)
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#define load_history() ((void)0)
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#define save_history(a) ((void)0)
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#endif /* FEATURE_COMMAND_SAVEHISTORY */
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static void remember_in_history(const char *str)
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static void remember_in_history(char *str)
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{
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int i;
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@ -1078,7 +1155,7 @@ static void remember_in_history(const char *str)
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state->cnt_history = i;
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#if ENABLE_FEATURE_EDITING_SAVEHISTORY
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if ((state->flags & SAVE_HISTORY) && state->hist_file)
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save_history(state->hist_file);
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save_history(str);
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#endif
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USE_FEATURE_EDITING_FANCY_PROMPT(num_ok_lines++;)
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}
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@ -1413,7 +1490,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
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state = st ? st : (line_input_t*) &const_int_0;
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#if ENABLE_FEATURE_EDITING_SAVEHISTORY
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if ((state->flags & SAVE_HISTORY) && state->hist_file)
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load_history(state->hist_file);
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load_history();
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#endif
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if (state->flags & DO_HISTORY)
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state->cur_history = state->cnt_history;
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@ -1875,6 +1952,7 @@ line_input_t* FAST_FUNC new_line_input_t(int flags)
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{
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line_input_t *n = xzalloc(sizeof(*n));
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n->flags = flags;
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n->last_history_end = -1;
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return n;
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}
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