logcat: Add --max-count option

(cherry pick from commit 6ac498d4bb)

This new option causes logcat to quit after it prints N messages.

Test: New unit test passes
Bug: 27706081
Change-Id: Ie52ddf300160a041e68a6bac0ae7ade68bb28a7c

logcat/logcat.cpp

@@ -79,6 +79,9 @@ static size_t g_outByteCount = 0;
 static int g_printBinary = 0;
 static int g_devCount = 0;                              // >1 means multiple
 static pcrecpp::RE* g_regex;
+// 0 means "infinite"
+static size_t g_maxCount = 0;
+static size_t g_printCount = 0;
 
 __noreturn static void logcat_panic(bool showHelp, const char *fmt, ...) __printflike(2,3);
 
@@ -193,6 +196,8 @@ static void processBuffer(log_device_t* dev, struct log_msg *buf)
         regexOk(entry, buf->id())) {
         bytesWritten = android_log_printLogLine(g_logformat, g_outFD, &entry);
 
+        g_printCount++;
+
         if (bytesWritten < 0) {
             logcat_panic(false, "output error");
         }
@@ -292,6 +297,8 @@ static void show_help(const char *cmd)
                     "  -d              dump the log and then exit (don't block)\n"
                     "  -e <expr>       only print lines where the log message matches <expr>\n"
                     "  --regex <expr>  where <expr> is a regular expression\n"
+                    "  -m <count>      quit after printing <count> lines. This is meant to be\n"
+                    "  --max-count=<count> paired with --regex, but will work on its own.\n"
                     "  -t <count>      print only the most recent <count> lines (implies -d)\n"
                     "  -t '<time>'     print most recent lines since specified time (implies -d)\n"
                     "  -T <count>      print only the most recent <count> lines (does not imply -d)\n"
@@ -542,6 +549,7 @@ int main(int argc, char **argv)
     size_t tail_lines = 0;
     log_time tail_time(log_time::EPOCH);
     size_t pid = 0;
+    bool got_t = false;
 
     signal(SIGPIPE, exit);
 
@@ -568,6 +576,7 @@ int main(int argc, char **argv)
           { "format",        required_argument, NULL,   'v' },
           { "last",          no_argument,       NULL,   'L' },
           { pid_str,         required_argument, NULL,   0 },
+          { "max-count",     required_argument, NULL,   'm' },
           { "prune",         optional_argument, NULL,   'p' },
           { "regex",         required_argument, NULL,   'e' },
           { "rotate_count",  required_argument, NULL,   'n' },
@@ -578,7 +587,7 @@ int main(int argc, char **argv)
           { NULL,            0,                 NULL,   0 }
         };
 
-        ret = getopt_long(argc, argv, ":cdDLt:T:gG:sQf:r:n:v:b:BSpP:e:",
+        ret = getopt_long(argc, argv, ":cdDLt:T:gG:sQf:r:n:v:b:BSpP:m:e:",
                           long_options, &option_index);
 
         if (ret < 0) {
@@ -635,6 +644,7 @@ int main(int argc, char **argv)
             break;
 
             case 't':
+                got_t = true;
                 mode |= ANDROID_LOG_RDONLY | ANDROID_LOG_NONBLOCK;
                 /* FALLTHRU */
             case 'T':
@@ -670,6 +680,15 @@ int main(int argc, char **argv)
                 g_regex = new pcrecpp::RE(optarg);
             break;
 
+            case 'm': {
+                char *end = NULL;
+                if (!getSizeTArg(optarg, &g_maxCount)) {
+                    logcat_panic(false, "-%c \"%s\" isn't an "
+                                 "integer greater than zero\n", ret, optarg);
+                }
+            }
+            break;
+
             case 'g':
                 if (!optarg) {
                     getLogSize = 1;
@@ -946,6 +965,10 @@ int main(int argc, char **argv)
         }
     }
 
+    if (g_maxCount && got_t) {
+        logcat_panic(true, "Cannot use -m (--max-count) and -t together");
+    }
+
     if (!devices) {
         dev = devices = new log_device_t("main", false);
         g_devCount = 1;
@@ -1161,7 +1184,8 @@ int main(int argc, char **argv)
 
     dev = NULL;
     log_device_t unexpected("unexpected", false);
-    while (1) {
+
+    while (!g_maxCount || g_printCount < g_maxCount) {
         struct log_msg log_msg;
         log_device_t* d;
         int ret = android_logger_list_read(logger_list, &log_msg);

logcat/tests/logcat_test.cpp

@@ -986,3 +986,34 @@ TEST(logcat, regex) {
 
     ASSERT_EQ(2, count);
 }
+
+TEST(logcat, maxcount) {
+    FILE *fp;
+    int count = 0;
+
+    char buffer[5120];
+
+    snprintf(buffer, sizeof(buffer), "logcat --pid %d -d --max-count 3", getpid());
+
+    LOG_FAILURE_RETRY(__android_log_print(ANDROID_LOG_WARN, "logcat_test", "logcat_test"));
+    LOG_FAILURE_RETRY(__android_log_print(ANDROID_LOG_WARN, "logcat_test", "logcat_test"));
+    LOG_FAILURE_RETRY(__android_log_print(ANDROID_LOG_WARN, "logcat_test", "logcat_test"));
+    LOG_FAILURE_RETRY(__android_log_print(ANDROID_LOG_WARN, "logcat_test", "logcat_test"));
+
+    // Let the logs settle
+    sleep(1);
+
+    ASSERT_TRUE(NULL != (fp = popen(buffer, "r")));
+
+    while (fgets(buffer, sizeof(buffer), fp)) {
+        if (!strncmp(begin, buffer, sizeof(begin) - 1)) {
+            continue;
+        }
+
+        count++;
+    }
+
+    pclose(fp);
+
+    ASSERT_EQ(3, count);
+}