shmlog: store meta information in the buffer itself, store path as X11 atom

This makes i3-dump-log completely independent of a running i3 instance.

i3-config-wizard/main.c

@@ -410,7 +410,7 @@ int main(int argc, char *argv[]) {
     unlink(config_path);
 
     if (socket_path == NULL)
-        socket_path = socket_path_from_x11();
+        socket_path = root_atom_contents("I3_SOCKET_PATH");
 
     if (socket_path == NULL)
         socket_path = "/tmp/i3-ipc.sock";

i3-dump-log/main.c

@@ -25,16 +25,14 @@
 #include <sys/stat.h>
 
 #include "libi3.h"
+#include "shmlog.h"
 #include <i3/ipc.h>
 
 int main(int argc, char *argv[]) {
-    char *socket_path = getenv("I3SOCK");
     int o, option_index = 0;
-    int message_type = I3_IPC_MESSAGE_TYPE_GET_LOG_MARKERS;
     bool verbose = false;
 
     static struct option long_options[] = {
-        {"socket", required_argument, 0, 's'},
         {"version", no_argument, 0, 'v'},
         {"verbose", no_argument, 0, 'V'},
         {"help", no_argument, 0, 'h'},
@@ -44,11 +42,7 @@ int main(int argc, char *argv[]) {
     char *options_string = "s:vVh";
 
     while ((o = getopt_long(argc, argv, options_string, long_options, &option_index)) != -1) {
-        if (o == 's') {
+        if (o == 'v') {
-            if (socket_path != NULL)
-                free(socket_path);
-            socket_path = sstrdup(optarg);
-        } else if (o == 'v') {
             printf("i3-dump-log " I3_VERSION "\n");
             return 0;
         } else if (o == 'V') {
@@ -60,86 +54,40 @@ int main(int argc, char *argv[]) {
         }
     }
 
-    if (socket_path == NULL)
+    char *shmname = root_atom_contents("I3_SHMLOG_PATH");
-        socket_path = socket_path_from_x11();
+    if (shmname == NULL)
-
+        errx(EXIT_FAILURE, "Cannot get I3_SHMLOG_PATH atom contents. Is i3 running on this display?");
-    /* Fall back to the default socket path */
-    if (socket_path == NULL)
-        socket_path = sstrdup("/tmp/i3-ipc.sock");
-
-    int sockfd = socket(AF_LOCAL, SOCK_STREAM, 0);
-    if (sockfd == -1)
-        err(EXIT_FAILURE, "Could not create socket");
-
-    struct sockaddr_un addr;
-    memset(&addr, 0, sizeof(struct sockaddr_un));
-    addr.sun_family = AF_LOCAL;
-    strncpy(addr.sun_path, socket_path, sizeof(addr.sun_path) - 1);
-    if (connect(sockfd, (const struct sockaddr*)&addr, sizeof(struct sockaddr_un)) < 0)
-        err(EXIT_FAILURE, "Could not connect to i3");
-
-    if (ipc_send_message(sockfd, 0, message_type, NULL) == -1)
-        err(EXIT_FAILURE, "IPC: write()");
-
-    uint32_t reply_length;
-    uint8_t *reply;
-    int ret;
-    if ((ret = ipc_recv_message(sockfd, message_type, &reply_length, &reply)) != 0) {
-        if (ret == -1)
-            err(EXIT_FAILURE, "IPC: read()");
-        exit(1);
-    }
-    char *buffer = NULL;
-    sasprintf(&buffer, "%.*s", reply_length, reply);
-    /* The reply will look like this:
-     * {"offset_next_write":1729,"offset_last_wrap":1996,"size":2048,"shmname":"/i3-log-399"}
-     * IMO, it’s not worth linking a JSON parser in just for this. If the
-     * structure changes in the future, this decision needs to be re-evaluated
-     * :). */
-    int offset_next_write, offset_last_wrap, logbuffer_size;
-    char *next_write_str = strstr(buffer, "offset_next_write"),
-         *last_wrap_str = strstr(buffer, "offset_last_wrap"),
-         *size_str = strstr(buffer, "size"),
-         *shmname = strstr(buffer, "shmname");
-    if (!next_write_str ||
-        !last_wrap_str ||
-        !size_str ||
-        !shmname ||
-        sscanf(next_write_str, "offset_next_write\":%d", &offset_next_write) != 1 ||
-        sscanf(last_wrap_str, "offset_last_wrap\":%d", &offset_last_wrap) != 1 ||
-        sscanf(size_str, "size\":%d", &logbuffer_size) != 1)
-        errx(EXIT_FAILURE, "invalid IPC reply: %s\n", buffer);
-
-    shmname += strlen("shmname\":\"");
-    char *quote = strchr(shmname, '"');
-    if (!quote)
-        errx(EXIT_FAILURE, "invalid IPC reply: %s\n", buffer);
-    *quote = '\0';
-
-    if (verbose)
-        printf("next_write = %d, last_wrap = %d, logbuffer_size = %d, shmname = %s\n",
-               offset_next_write, offset_last_wrap, logbuffer_size, shmname);
 
     if (*shmname == '\0')
         errx(EXIT_FAILURE, "Cannot dump log: SHM logging is disabled in i3.");
 
+    struct stat statbuf;
+
     int logbuffer_shm = shm_open(shmname, O_RDONLY, 0);
     if (logbuffer_shm == -1)
         err(EXIT_FAILURE, "Could not shm_open SHM segment for the i3 log (%s)", shmname);
 
-    char *logbuffer = mmap(NULL, logbuffer_size, PROT_READ, MAP_SHARED, logbuffer_shm, 0);
+    if (fstat(logbuffer_shm, &statbuf) != 0)
+        err(EXIT_FAILURE, "stat(%s)", shmname);
+
+    char *logbuffer = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, logbuffer_shm, 0);
     if (logbuffer == MAP_FAILED)
         err(EXIT_FAILURE, "Could not mmap SHM segment for the i3 log");
 
+    i3_shmlog_header *header = (i3_shmlog_header*)logbuffer;
+
+    if (verbose)
+        printf("next_write = %d, last_wrap = %d, logbuffer_size = %d, shmname = %s\n",
+               header->offset_next_write, header->offset_last_wrap, header->size, shmname);
     int chars;
-    char *walk = logbuffer + offset_next_write;
+    char *walk = logbuffer + header->offset_next_write;
     /* Skip the first line, it very likely is mangled. Not a problem, though,
      * the log is chatty enough to have plenty lines left. */
     while (*walk != '\0')
         walk++;
 
     /* Print the oldest log lines. We use printf("%s") to stop on \0. */
-    while (walk < (logbuffer + offset_last_wrap)) {
+    while (walk < (logbuffer + header->offset_last_wrap)) {
         chars = printf("%s", walk);
         /* Shortcut: If there are two consecutive \0 bytes, this part of the
          * buffer was never touched. To not call printf() for every byte of the
@@ -150,8 +98,8 @@ int main(int argc, char *argv[]) {
     }
 
     /* Then start from the beginning and print the newer lines */
-    walk = logbuffer;
+    walk = logbuffer + sizeof(i3_shmlog_header);
-    while (walk < (logbuffer + offset_next_write)) {
+    while (walk < (logbuffer + header->offset_next_write)) {
         chars = printf("%s", walk);
         walk += (chars > 0 ? chars : 1);
     }

i3-input/main.c

@@ -342,7 +342,7 @@ int main(int argc, char *argv[]) {
     printf("using format \"%s\"\n", format);
 
     if (socket_path == NULL)
-        socket_path = socket_path_from_x11();
+        socket_path = root_atom_contents("I3_SOCKET_PATH");
 
     if (socket_path == NULL)
         socket_path = "/tmp/i3-ipc.sock";

i3-msg/main.c

@@ -73,11 +73,9 @@ int main(int argc, char *argv[]) {
                 message_type = I3_IPC_MESSAGE_TYPE_GET_MARKS;
             else if (strcasecmp(optarg, "get_bar_config") == 0)
                 message_type = I3_IPC_MESSAGE_TYPE_GET_BAR_CONFIG;
-            else if (strcasecmp(optarg, "get_log_markers") == 0)
-                message_type = I3_IPC_MESSAGE_TYPE_GET_LOG_MARKERS;
             else {
                 printf("Unknown message type\n");
-                printf("Known types: command, get_workspaces, get_outputs, get_tree, get_marks, get_bar_config, get_log_markers\n");
+                printf("Known types: command, get_workspaces, get_outputs, get_tree, get_marks, get_bar_config\n");
                 exit(EXIT_FAILURE);
             }
         } else if (o == 'q') {
@@ -93,7 +91,7 @@ int main(int argc, char *argv[]) {
     }
 
     if (socket_path == NULL)
-        socket_path = socket_path_from_x11();
+        socket_path = root_atom_contents("I3_SOCKET_PATH");
 
     /* Fall back to the default socket path */
     if (socket_path == NULL)

include/atoms.xmacro

@@ -26,3 +26,4 @@ xmacro(WM_WINDOW_ROLE)
 xmacro(I3_SOCKET_PATH)
 xmacro(I3_CONFIG_PATH)
 xmacro(I3_SYNC)
+xmacro(I3_SHMLOG_PATH)

include/i3/ipc.h

@@ -40,9 +40,6 @@
 /** Request the configuration for a specific 'bar' */
 #define I3_IPC_MESSAGE_TYPE_GET_BAR_CONFIG      6
 
-/** Request the SHM debug log start/wrap markers */
-#define I3_IPC_MESSAGE_TYPE_GET_LOG_MARKERS     7
-
 /*
  * Messages from i3 to clients
  *
@@ -69,9 +66,6 @@
 /** Bar config reply type */
 #define I3_IPC_REPLY_TYPE_BAR_CONFIG            6
 
-/** Request the SHM debug log start/wrap markers */
-#define I3_IPC_REPLY_TYPE_LOG_MARKERS           7
-
 /*
  * Events from i3 to clients. Events have the first bit set high.
  *

include/libi3.h

@@ -47,13 +47,14 @@ struct Font {
 #endif
 
 /**
- * Try to get the socket path from X11 and return NULL if it doesn’t work.
+ * Try to get the contents of the given atom (for example I3_SOCKET_PATH) from
+ * the X11 root window and return NULL if it doesn’t work.
  *
- * The memory for the socket path is dynamically allocated and has to be
+ * The memory for the contents is dynamically allocated and has to be
  * free()d by the caller.
  *
  */
-char *socket_path_from_x11();
+char *root_atom_contents(const char *atomname);
 
 /**
  * Safe-wrapper around malloc which exits if malloc returns NULL (meaning that

include/log.h

@@ -37,13 +37,6 @@ void init_logging();
  */
 void add_loglevel(const char *level);
 
-/**
- * Returns the offsets for the next write and for the last wrap.
- * Necessary to print the i3 SHM log in the correct order.
- *
- */
-void get_log_markers(int *offset_next_write, int *offset_last_wrap, int *size);
-
 /**
  * Set verbosity of i3. If verbose is set to true, informative messages will
  * be printed to stdout. If verbose is set to false, only errors will be

libi3/root_atom_contents.c

@@ -16,13 +16,14 @@
 #include "libi3.h"
 
 /*
- * Try to get the socket path from X11 and return NULL if it doesn’t work.
+ * Try to get the contents of the given atom (for example I3_SOCKET_PATH) from
+ * the X11 root window and return NULL if it doesn’t work.
  *
- * The memory for the socket path is dynamically allocated and has to be
+ * The memory for the contents is dynamically allocated and has to be
  * free()d by the caller.
  *
  */
-char *socket_path_from_x11() {
+char *root_atom_contents(const char *atomname) {
     xcb_connection_t *conn;
     xcb_intern_atom_cookie_t atom_cookie;
     xcb_intern_atom_reply_t *atom_reply;
@@ -33,7 +34,7 @@ char *socket_path_from_x11() {
         xcb_connection_has_error(conn))
         return NULL;
 
-    atom_cookie = xcb_intern_atom(conn, 0, strlen("I3_SOCKET_PATH"), "I3_SOCKET_PATH");
+    atom_cookie = xcb_intern_atom(conn, 0, strlen(atomname), atomname);
 
     xcb_screen_t *root_screen = xcb_aux_get_screen(conn, screen);
     xcb_window_t root = root_screen->root;

src/ipc.c

@@ -643,48 +643,6 @@ IPC_HANDLER(get_bar_config) {
     y(free);
 }
 
-/*
- * Formats the reply message for a GET_LOG_MARKERS request and sends it to the
- * client.
- *
- */
-IPC_HANDLER(get_log_markers) {
-#if YAJL_MAJOR >= 2
-    yajl_gen gen = yajl_gen_alloc(NULL);
-#else
-    yajl_gen gen = yajl_gen_alloc(NULL, NULL);
-#endif
-
-    int offset_next_write, offset_last_wrap, logsize;
-    get_log_markers(&offset_next_write, &offset_last_wrap, &logsize);
-
-    y(map_open);
-    ystr("offset_next_write");
-    y(integer, offset_next_write);
-
-    ystr("offset_last_wrap");
-    y(integer, offset_last_wrap);
-
-    ystr("shmname");
-    ystr(shmlogname);
-
-    ystr("size");
-    y(integer, logsize);
-
-    y(map_close);
-
-    const unsigned char *payload;
-#if YAJL_MAJOR >= 2
-    size_t length;
-#else
-    unsigned int length;
-#endif
-    y(get_buf, &payload, &length);
-
-    ipc_send_message(fd, length, I3_IPC_REPLY_TYPE_LOG_MARKERS, payload);
-    y(free);
-}
-
 /*
  * Callback for the YAJL parser (will be called when a string is parsed).
  *
@@ -770,7 +728,7 @@ IPC_HANDLER(subscribe) {
 
 /* The index of each callback function corresponds to the numeric
  * value of the message type (see include/i3/ipc.h) */
-handler_t handlers[8] = {
+handler_t handlers[7] = {
     handle_command,
     handle_get_workspaces,
     handle_subscribe,
@@ -778,7 +736,6 @@ handler_t handlers[8] = {
     handle_tree,
     handle_get_marks,
     handle_get_bar_config,
-    handle_get_log_markers
 };
 
 /*

src/log.c

@@ -23,6 +23,7 @@
 #include "log.h"
 #include "i3.h"
 #include "libi3.h"
+#include "shmlog.h"
 
 /* loglevels.h is autogenerated at make time */
 #include "loglevels.h"
@@ -52,6 +53,20 @@ static int logbuffer_size;
 /* File descriptor for shm_open. */
 static int logbuffer_shm;
 
+/*
+ * Writes the offsets for the next write and for the last wrap to the
+ * shmlog_header.
+ * Necessary to print the i3 SHM log in the correct order.
+ *
+ */
+static void store_log_markers() {
+    i3_shmlog_header *header = (i3_shmlog_header*)logbuffer;
+
+    header->offset_next_write = (logwalk - logbuffer);
+    header->offset_last_wrap = (loglastwrap - logbuffer);
+    header->size = logbuffer_size;
+}
+
 /*
  * Initializes logging by creating an error logfile in /tmp (or
  * XDG_RUNTIME_DIR, see get_process_filename()).
@@ -103,8 +118,9 @@ void init_logging() {
             logbuffer = NULL;
             return;
         }
-        logwalk = logbuffer;
+        logwalk = logbuffer + sizeof(i3_shmlog_header);
         loglastwrap = logbuffer + logbuffer_size;
+        store_log_markers();
     }
 }
 
@@ -141,17 +157,6 @@ void add_loglevel(const char *level) {
     }
 }
 
-/*
- * Returns the offsets for the next write and for the last wrap.
- * Necessary to print the i3 SHM log in the correct order.
- *
- */
-void get_log_markers(int *offset_next_write, int *offset_last_wrap, int *size) {
-    *offset_next_write = (logwalk - logbuffer);
-    *offset_last_wrap = (loglastwrap - logbuffer);
-    *size = logbuffer_size;
-}
-
 /*
  * Logs the given message to stdout (if print is true) while prefixing the
  * current time to it. Additionally, the message will be saved in the i3 SHM
@@ -208,7 +213,7 @@ static void vlog(const bool print, const char *fmt, va_list args) {
          * beginning again. */
         if ((len+1) >= (logbuffer_size - (logwalk - logbuffer))) {
             loglastwrap = logwalk;
-            logwalk = logbuffer;
+            logwalk = logbuffer + sizeof(i3_shmlog_header);
         }
 
         /* Copy the buffer, terminate it, move the write pointer to the byte after
@@ -217,6 +222,8 @@ static void vlog(const bool print, const char *fmt, va_list args) {
         logwalk[len] = '\0';
         logwalk += len + 1;
 
+        store_log_markers();
+
         if (print)
             fwrite(message, len, 1, stdout);
     }

src/main.c

@@ -335,7 +335,7 @@ int main(int argc, char *argv[]) {
                     break;
                 } else if (strcmp(long_options[option_index].name, "get-socketpath") == 0 ||
                            strcmp(long_options[option_index].name, "get_socketpath") == 0) {
-                    char *socket_path = socket_path_from_x11();
+                    char *socket_path = root_atom_contents("I3_SOCKET_PATH");
                     if (socket_path) {
                         printf("%s\n", socket_path);
                         return 0;
@@ -416,7 +416,7 @@ int main(int argc, char *argv[]) {
             optind++;
         }
         LOG("Command is: %s (%d bytes)\n", payload, strlen(payload));
-        char *socket_path = socket_path_from_x11();
+        char *socket_path = root_atom_contents("I3_SOCKET_PATH");
         if (!socket_path) {
             ELOG("Could not get i3 IPC socket path\n");
             return 1;

src/x.c

@@ -928,6 +928,8 @@ void x_set_i3_atoms() {
                         current_socketpath);
     xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_CONFIG_PATH, A_UTF8_STRING, 8,
                         strlen(current_configpath), current_configpath);
+    xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_SHMLOG_PATH, A_UTF8_STRING, 8,
+                        strlen(shmlogname), shmlogname);
 }
 
 /*