Support the -e (--existing) option from mlocate.

This can be useful if recently having deleted some files,
and not wanting to do a database rebuild. Note that we don't
support the --nofollow option (--follow is the default),
since it's not clear what it would be useful for, and the mlocate
source code says it “looks like a historical accident”.

diff --git a/io_uring_engine.cpp b/io_uring_engine.cpp
index 116cf85f285ab15b1a85a6a39f59741271422e06..eab5e8d068bdccd99db8e1f5179a31d0dd02969b 100644 (file)
--- a/io_uring_engine.cpp
+++ b/io_uring_engine.cpp
@@ -123,7 +123,7 @@ void IOUringEngine::submit_stat_internal(io_uring_sqe *sqe, char *path, std::fun
        pending->stat.pathname = path;
        pending->stat.buf = new struct statx;
 
-       io_uring_prep_statx(sqe, /*fd=*/-1, pending->stat.pathname, AT_STATX_SYNC_AS_STAT, STATX_MODE, pending->stat.buf);
+       io_uring_prep_statx(sqe, /*fd=*/-1, pending->stat.pathname, AT_STATX_SYNC_AS_STAT | AT_SYMLINK_NOFOLLOW, STATX_MODE, pending->stat.buf);
        io_uring_sqe_set_data(sqe, pending);
        ++pending_reads;
 }

diff --git a/options.h b/options.h
index a372886c71c1f528bfa7dff1ef3e98ebe506bacf..eba4900c08a4b6818718caeadd8d88e9ef238e03 100644 (file)
--- a/options.h
+++ b/options.h
@@ -10,6 +10,7 @@ extern bool use_debug;
 extern bool flush_cache;
 extern bool patterns_are_regex;
 extern bool use_extended_regex;
+extern bool check_existence;
 extern int64_t limit_matches;
 extern int64_t limit_left;  // Not strictly an option.
 extern bool stdout_is_tty;  // Same.

diff --git a/plocate.1 b/plocate.1
index 090fdb9694da0bfb1269297ec5d9ea74f8e3cada..cc0e8430b4a6889c990e26e3dde60e79a399cc2d 100644 (file)
--- a/plocate.1
+++ b/plocate.1
@@ -78,6 +78,15 @@ It is also possible to give multiple databases in one argument, separated by
 .BR : .
 (Any character, including : and \\, can be escaped by prepending a \\.)
 
+.TP
+\fB\-e\fR, \fB\-\-existing\fR
+Print only entries that refer to files existing at the time
+.B locate
+is run. Note that unlike
+.BR mlocate (1),
+symlinks are not followed by default (and indeed, there is no option
+to change this).
+
 .TP
 \fB\-i\fR, \fB\-\-ignore\-case\fR
 Do a case-insensitive match as given by the current locale

diff --git a/plocate.cpp b/plocate.cpp
index 72dbe287434ac848d705f17b02f58929bdd4b16c..7cc4f5a4eb2587f4bb685aaa83155e8951f06dd2 100644 (file)
--- a/plocate.cpp
+++ b/plocate.cpp
@@ -53,6 +53,7 @@ bool flush_cache = false;
 bool patterns_are_regex = false;
 bool use_extended_regex = false;
 bool match_basename = false;
+bool check_existence = false;
 int64_t limit_matches = numeric_limits<int64_t>::max();
 int64_t limit_left = numeric_limits<int64_t>::max();
 bool stdout_is_tty = false;
@@ -152,8 +153,24 @@ size_t Corpus::get_num_filename_blocks() const
        return hdr.num_docids;
 }
 
+template<class T>
+void stat_if_needed(const char *filename, bool access_ok, IOUringEngine *engine, T cb)
+{
+       if (!access_ok || !check_existence) {
+               // Doesn't have access or doesn't care about existence, so no need to stat.
+               cb(access_ok);
+       } else if (engine == nullptr || !engine->get_supports_stat()) {
+               // Do a synchronous stat.
+               struct stat buf;
+               bool ok = lstat(filename, &buf) == 0;
+               cb(ok);
+       } else {
+               engine->submit_stat(filename, cb);
+       }
+}
+
 void scan_file_block(const vector<Needle> &needles, string_view compressed,
-                     AccessRXCache *access_rx_cache, uint64_t seq, ResultReceiver *serializer,
+                     IOUringEngine *engine, AccessRXCache *access_rx_cache, uint64_t seq, ResultReceiver *serializer,
                      atomic<uint64_t> *matched)
 {
        unsigned long long uncompressed_len = ZSTD_getFrameContentSize(compressed.data(), compressed.size());
@@ -182,14 +199,16 @@ void scan_file_block(const vector<Needle> &needles, string_view compressed,
        block[block.size() - 1] = '\0';
 
        auto test_candidate = [&](const char *filename, uint64_t local_seq, uint64_t next_seq) {
-               access_rx_cache->check_access(filename, /*allow_async=*/true, [matched, serializer, local_seq, next_seq, filename{ strdup(filename) }](bool ok) {
-                       if (ok) {
-                               ++*matched;
-                               serializer->print(local_seq, next_seq - local_seq, filename);
-                       } else {
-                               serializer->print(local_seq, next_seq - local_seq, "");
-                       }
-                       free(filename);
+               access_rx_cache->check_access(filename, /*allow_async=*/true, [matched, engine, serializer, local_seq, next_seq, filename{ strdup(filename) }](bool ok) {
+                       stat_if_needed(filename, ok, engine, [matched, serializer, local_seq, next_seq, filename](bool ok) {
+                               if (ok) {
+                                       ++*matched;
+                                       serializer->print(local_seq, next_seq - local_seq, filename);
+                               } else {
+                                       serializer->print(local_seq, next_seq - local_seq, "");
+                               }
+                               free(filename);
+                       });
                });
        };
 
@@ -240,8 +259,8 @@ size_t scan_docids(const vector<Needle> &needles, const vector<uint32_t> &docids
        atomic<uint64_t> matched{ 0 };
        for (size_t i = 0; i < docids.size(); ++i) {
                uint32_t docid = docids[i];
-               corpus.get_compressed_filename_block(docid, [i, &matched, &needles, &access_rx_cache, &docids_in_order](string_view compressed) {
-                       scan_file_block(needles, compressed, &access_rx_cache, i, &docids_in_order, &matched);
+               corpus.get_compressed_filename_block(docid, [i, &matched, &needles, &access_rx_cache, engine, &docids_in_order](string_view compressed) {
+                       scan_file_block(needles, compressed, engine, &access_rx_cache, i, &docids_in_order, &matched);
                });
        }
        engine->finish();
@@ -328,7 +347,7 @@ uint64_t scan_all_docids(const vector<Needle> &needles, int fd, const Corpus &co
        dprintf("Using %u worker threads for linear scan.\n", num_threads);
        unique_ptr<WorkerThread[]> threads(new WorkerThread[num_threads]);
        for (unsigned i = 0; i < num_threads; ++i) {
-               threads[i].t = thread([&threads, &mu, &queue_added, &queue_removed, &work_queue, &done, &offsets, &needles, &access_rx_cache, &matched, i] {
+               threads[i].t = thread([&threads, &mu, &queue_added, &queue_removed, &work_queue, &done, &offsets, &needles, &access_rx_cache, engine{ corpus.engine }, &matched, i] {
                        // regcomp() takes a lock on the regex, so each thread will need its own.
                        const vector<Needle> *use_needles = &needles;
                        vector<Needle> recompiled_needles;
@@ -359,7 +378,7 @@ uint64_t scan_all_docids(const vector<Needle> &needles, int fd, const Corpus &co
                                for (uint32_t docid = io_docid; docid < last_docid; ++docid) {
                                        size_t relative_offset = offsets[docid] - offsets[io_docid];
                                        size_t len = offsets[docid + 1] - offsets[docid];
-                                       scan_file_block(*use_needles, { &compressed[relative_offset], len }, &access_rx_cache, docid, &receiver, &matched);
+                                       scan_file_block(*use_needles, { &compressed[relative_offset], len }, engine, &access_rx_cache, docid, &receiver, &matched);
                                }
                        }
                });
@@ -816,6 +835,7 @@ int main(int argc, char **argv)
                { "count", no_argument, 0, 'c' },
                { "basename", no_argument, 0, 'b' },
                { "database", required_argument, 0, 'd' },
+               { "existing", no_argument, 0, 'e' },
                { "ignore-case", no_argument, 0, 'i' },
                { "limit", required_argument, 0, 'l' },
                { "null", no_argument, 0, '0' },
@@ -832,7 +852,7 @@ int main(int argc, char **argv)
        setlocale(LC_ALL, "");
        for (;;) {
                int option_index = 0;
-               int c = getopt_long(argc, argv, "bcd:hil:n:0rwVD", long_options, &option_index);
+               int c = getopt_long(argc, argv, "bcd:ehil:n:0rwVD", long_options, &option_index);
                if (c == -1) {
                        break;
                }
@@ -846,6 +866,9 @@ int main(int argc, char **argv)
                case 'd':
                        parse_dbpaths(optarg, &dbpaths);
                        break;
+               case 'e':
+                       check_existence = true;
+                       break;
                case 'h':
                        usage();
                        exit(0);