add i3-dump-log, a tool to dump the SHM log

2 files changed, 192 insertions, 0 deletions

diff --git a/i3-dump-log/Makefile b/i3-dump-log/Makefile
new file mode 100644
index 00000000..18076e51
--- /dev/null
+++ b/i3-dump-log/Makefile
@@ -0,0 +1,32 @@
+# Default value so one can compile i3-dump-log standalone
+TOPDIR=..
+
+include $(TOPDIR)/common.mk
+
+CFLAGS += -I$(TOPDIR)/include
+
+# Depend on the object files of all source-files in src/*.c and on all header files
+FILES=$(patsubst %.c,%.o,$(wildcard *.c))
+HEADERS=$(wildcard *.h)
+
+# Depend on the specific file (.c for each .o) and on all headers
+%.o: %.c ${HEADERS}
+	echo "[i3-dump-log] CC $<"
+	$(CC) $(CPPFLAGS) $(CFLAGS) -c -o $@ $<
+
+all: i3-dump-log
+
+i3-dump-log: ${FILES}
+	echo "[i3-dump-log] LINK i3-dump-log"
+	$(CC) $(LDFLAGS) -o i3-dump-log ${FILES} $(LIBS)
+
+install: all
+	echo "[i3-dump-log] INSTALL"
+	$(INSTALL) -d -m 0755 $(DESTDIR)$(PREFIX)/bin
+	$(INSTALL) -m 0755 i3-dump-log $(DESTDIR)$(PREFIX)/bin/
+
+clean:
+	rm -f *.o
+
+distclean: clean
+	rm -f i3-dump-log
diff --git a/i3-dump-log/main.c b/i3-dump-log/main.c
new file mode 100644
index 00000000..68cbdb46
--- /dev/null
+++ b/i3-dump-log/main.c
@@ -0,0 +1,160 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009-2011 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ * i3-dump-log/main.c: Dumps the i3 SHM log to stdout.
+ *
+ */
+#include <stdio.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <err.h>
+#include <stdint.h>
+#include <getopt.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#include "libi3.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'},
+        {0, 0, 0, 0}
+    };
+
+    char *options_string = "s:vVh";
+
+    while ((o = getopt_long(argc, argv, options_string, long_options, &option_index)) != -1) {
+        if (o == 's') {
+            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') {
+            verbose = true;
+        } else if (o == 'h') {
+            printf("i3-dump-log " I3_VERSION "\n");
+            printf("i3-dump-log [-s <socket>]\n");
+            return 0;
+        }
+    }
+
+    if (socket_path == NULL)
+        socket_path = socket_path_from_x11();
+
+    /* 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.");
+
+    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 (logbuffer == MAP_FAILED)
+        err(EXIT_FAILURE, "Could not mmap SHM segment for the i3 log");
+
+    int chars;
+    char *walk = logbuffer + 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)) {
+        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
+         * buffer, we directly exit the loop. */
+        if (*walk == '\0' && *(walk+1) == '\0')
+            break;
+        walk += (chars > 0 ? chars : 1);
+    }
+
+    /* Then start from the beginning and print the newer lines */
+    walk = logbuffer;
+    while (walk < (logbuffer + offset_next_write)) {
+        chars = printf("%s", walk);
+        walk += (chars > 0 ? chars : 1);
+    }
+
+    return 0;
+}