57abf9e94
Denis Vlasenko
2009-03-22
Subject
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 b
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include/libbb.h+7 -3
| @@ -1187,9 +1187,9 @@ unsigned long long bb_makedev(unsigned int major, unsigned int minor) FAST_FUNC; | |
| #if ENABLE_FEATURE_EDITING | |
| /* It's NOT just ENABLEd or disabled. It's a number: */ | |
| #ifdef CONFIG_FEATURE_EDITING_HISTORY | |
| - | #define MAX_HISTORY (CONFIG_FEATURE_EDITING_HISTORY + 0) |
| + | # define MAX_HISTORY (CONFIG_FEATURE_EDITING_HISTORY + 0) |
| #else | |
| - | #define MAX_HISTORY 0 |
| + | # define MAX_HISTORY 0 |
| #endif | |
| typedef struct line_input_t { | |
| int flags; | |
| @@ -1197,7 +1197,11 @@ typedef struct line_input_t { | |
| #if MAX_HISTORY | |
| int cnt_history; | |
| int cur_history; | |
| - | USE_FEATURE_EDITING_SAVEHISTORY(const char *hist_file;) |
| + | #if ENABLE_FEATURE_EDITING_SAVEHISTORY |
| + | unsigned cnt_history_in_file; |
| + | off_t last_history_end; |
| + | const char *hist_file; |
| + | #endif |
| char *history[MAX_HISTORY + 1]; | |
| #endif | |
| } line_input_t; | |
libbb/lineedit.c+110 -32
| @@ -990,64 +990,141 @@ static int get_next_history(void) | |
| } | |
| #if ENABLE_FEATURE_EDITING_SAVEHISTORY | |
| + | /* We try to ensure that concurrent additions to the history |
| + | * do not overwrite each other, and that additions to the history |
| + | * by one user are noticed by others. |
| + | * Otherwise shell users get unhappy. |
| + | * |
| + | * History file is trimmed lazily, when it grows several times longer |
| + | * than configured MAX_HISTORY lines. |
| + | */ |
| + | |
| /* state->flags is already checked to be nonzero */ | |
| - | static void load_history(const char *fromfile) |
| + | static void load_history(void) |
| { | |
| + | char *temp_h[MAX_HISTORY]; |
| + | char *line; |
| FILE *fp; | |
| - | int hi; |
| + | unsigned idx, i, line_len; |
| /* NB: do not trash old history if file can't be opened */ | |
| - | fp = fopen_for_read(fromfile); |
| + | fp = fopen_for_read(state->hist_file); |
| if (fp) { | |
| /* clean up old history */ | |
| - | for (hi = state->cnt_history; hi > 0;) { |
| - | hi--; |
| - | free(state->history[hi]); |
| - | state->history[hi] = NULL; |
| + | for (idx = state->cnt_history; idx > 0;) { |
| + | idx--; |
| + | free(state->history[idx]); |
| + | state->history[idx] = NULL; |
| } | |
| - | for (hi = 0; hi < MAX_HISTORY;) { |
| - | char *hl = xmalloc_fgetline(fp); |
| - | int l; |
| - | |
| - | if (!hl) |
| - | break; |
| - | l = strlen(hl); |
| - | if (l >= MAX_LINELEN) |
| - | hl[MAX_LINELEN-1] = '\0'; |
| - | if (l == 0) { |
| - | free(hl); |
| + | /* fill temp_h[], retaining only last MAX_HISTORY lines */ |
| + | memset(temp_h, 0, sizeof(temp_h)); |
| + | state->cnt_history_in_file = idx = 0; |
| + | while ((line = xmalloc_fgetline(fp)) != NULL) { |
| + | if (line[0] == '\0') { |
| + | free(line); |
| continue; | |
| } | |
| - | state->history[hi++] = hl; |
| + | free(temp_h[idx]); |
| + | temp_h[idx] = line; |
| + | state->cnt_history_in_file++; |
| + | idx++; |
| + | if (idx == MAX_HISTORY) |
| + | idx = 0; |
| } | |
| + | state->last_history_end = lseek(fileno(fp), 0, SEEK_CUR); |
| fclose(fp); | |
| - | state->cnt_history = hi; |
| + | |
| + | /* find first non-NULL temp_h[], if any */ |
| + | if (state->cnt_history_in_file) { |
| + | while (temp_h[idx] == NULL) { |
| + | idx++; |
| + | if (idx == MAX_HISTORY) |
| + | idx = 0; |
| + | } |
| + | } |
| + | |
| + | /* copy temp_h[] to state->history[] */ |
| + | for (i = 0; i < MAX_HISTORY;) { |
| + | line = temp_h[idx]; |
| + | if (!line) |
| + | break; |
| + | idx++; |
| + | if (idx == MAX_HISTORY) |
| + | idx = 0; |
| + | line_len = strlen(line); |
| + | if (line_len >= MAX_LINELEN) |
| + | line[MAX_LINELEN-1] = '\0'; |
| + | state->history[i++] = line; |
| + | } |
| + | state->cnt_history = i; |
| } | |
| } | |
| /* state->flags is already checked to be nonzero */ | |
| - | static void save_history(const char *tofile) |
| + | static void save_history(char *str) |
| { | |
| - | FILE *fp; |
| + | off_t end; |
| + | int fd; |
| + | int len; |
| - | fp = fopen_for_write(tofile); |
| - | if (fp) { |
| - | int i; |
| + | len = strlen(str); |
| + | again: |
| + | fd = open(state->hist_file, O_WRONLY | O_CREAT | O_APPEND, 0666); |
| + | if (fd < 0) |
| + | return; |
| - | for (i = 0; i < state->cnt_history; i++) { |
| - | fprintf(fp, "%s\n", state->history[i]); |
| + | end = lseek(fd, 0, SEEK_END); |
| + | |
| + | if (str) { |
| + | str[len] = '\n'; |
| + | full_write(fd, str, len + 1); |
| + | str[len] = '\0'; |
| + | str = NULL; |
| + | state->cnt_history_in_file++; |
| + | } |
| + | close(fd); |
| + | |
| + | /* if it was not a 1st write */ |
| + | if (state->last_history_end >= 0) { |
| + | /* did someone else write anything there? */ |
| + | if (state->last_history_end != end) { |
| + | load_history(); /* note: updates cnt_history_in_file */ |
| + | state->last_history_end = -1; |
| + | goto again; |
| } | |
| - | fclose(fp); |
| + | } |
| + | state->last_history_end = end + len + 1; |
| + | |
| + | /* did we write so much that history file needs trimming? */ |
| + | if (state->cnt_history_in_file > MAX_HISTORY * 4) { |
| + | FILE *fp; |
| + | char *new_name; |
| + | |
| + | new_name = xasprintf("%s.new", state->hist_file); |
| + | fp = fopen_for_write(new_name); |
| + | if (fp) { |
| + | int i; |
| + | |
| + | for (i = 0; i < state->cnt_history; i++) { |
| + | fprintf(fp, "%s\n", state->history[i]); |
| + | } |
| + | state->cnt_history_in_file = i; /* == cnt_history */ |
| + | state->last_history_end = lseek(fileno(fp), 0, SEEK_CUR); |
| + | fclose(fp); |
| + | /* replace hist_file atomically */ |
| + | rename(new_name, state->hist_file); |
| + | } |
| + | free(new_name); |
| } | |
| } | |
| #else | |
| - | #define load_history(a) ((void)0) |
| + | #define load_history() ((void)0) |
| #define save_history(a) ((void)0) | |
| #endif /* FEATURE_COMMAND_SAVEHISTORY */ | |
| - | static void remember_in_history(const char *str) |
| + | static void remember_in_history(char *str) |
| { | |
| int i; | |
| @@ -1078,7 +1155,7 @@ static void remember_in_history(const char *str) | |
| state->cnt_history = i; | |
| #if ENABLE_FEATURE_EDITING_SAVEHISTORY | |
| if ((state->flags & SAVE_HISTORY) && state->hist_file) | |
| - | save_history(state->hist_file); |
| + | save_history(str); |
| #endif | |
| USE_FEATURE_EDITING_FANCY_PROMPT(num_ok_lines++;) | |
| } | |
| @@ -1413,7 +1490,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li | |
| state = st ? st : (line_input_t*) &const_int_0; | |
| #if ENABLE_FEATURE_EDITING_SAVEHISTORY | |
| if ((state->flags & SAVE_HISTORY) && state->hist_file) | |
| - | load_history(state->hist_file); |
| + | load_history(); |
| #endif | |
| if (state->flags & DO_HISTORY) | |
| state->cur_history = state->cnt_history; | |
| @@ -1875,6 +1952,7 @@ line_input_t* FAST_FUNC new_line_input_t(int flags) | |
| { | |
| line_input_t *n = xzalloc(sizeof(*n)); | |
| n->flags = flags; | |
| + | n->last_history_end = -1; |
| return n; | |
| } | |