fsck_util: improve fsck output format

Now the built-in fsck handler and `bookmarkctl fsck` produces
output that is both parsable and human-readable.

Also document the output format in the user manual.

doc/bookmarkfs.texi

@@ -603,6 +603,9 @@ bookmarkctl fsck @var{pathname}
 Path to the directory to perform checks on.
 @end table
 
+The output shares the same format with the built-in fsck handler.
+@xref{Filesystem-Check Output Format}.
+
 For the full fsck functionalities, @pxref{fsck.bookmarkfs}.
 
 @item xattr-list
@@ -3235,6 +3238,30 @@ Defaults to @samp{_}.
 For each bookmark entry, the built-in handler prints a message
 to standard output explaining why the bookmark name is invalid.
 
+@anchor{Filesystem-Check Output Format}
+@cindex Filesystem-Check Output Format
+Output format (with an ASCII HT character separating each item):
+
+@example
+@var{id} @var{why} @var{extra} @var{name}
+@end example
+
+@table @var
+@item why
+Name of the result code, without the @samp{BOOKMARKFS_FSCK_RESULT_} prefix.
+
+@xref{Filesystem-Check Result Code}.
+
+@item id
+@itemx extra
+@itemx name
+Information of this entry.
+@xref{Filesystem-Check Data}.
+
+Integers are printed in decimal format.
+ASCII control characters in @var{name} are replaced with @samp{?}.
+@end table
+
 When the @option{-o repair} option is given, the handler renames the bookmark
 according to the following rules:
 

src/bookmarkctl.c

@@ -157,7 +157,7 @@ subcmd_fsck (
             log_printf("ioctl(): %s", strerror(errno));
             break;
         }
-        if (0 != explain_fsck_result(status, &fsck_data)) {
+        if (0 != print_fsck_result(status, &fsck_data)) {
             break;
         }
     } while (status != BOOKMARKFS_FSCK_RESULT_END);

src/fsck_handler_simple.c

@@ -282,7 +282,7 @@ handle_entry (
     }
 
     struct bookmarkfs_fsck_data *entry_data = &entry->data;
-    if (0 != explain_fsck_result(why, entry_data)) {
+    if (0 != print_fsck_result(why, entry_data)) {
         return -1;
     }
 

src/fsck_util.c

@@ -34,46 +34,34 @@
 #include "xstd.h"
 
 int
-explain_fsck_result (
+print_fsck_result (
     enum bookmarkfs_fsck_result        result,
     struct bookmarkfs_fsck_data const *data
 ) {
-    char name_buf[sizeof(data->name)];
-    translit_control_chars(name_buf, sizeof(name_buf), data->name, '?');
-
-#define PRINT_FSCK_RESULT(s, ...)  \
-    printf("bookmark %" PRIu64 " name '%.*s' " s "\n", data->id,  \
-            (int)sizeof(name_buf), name_buf, __VA_ARGS__);
+    char *result_str;
     switch (result) {
       case BOOKMARKFS_FSCK_RESULT_END:
-        break;
+        return 0;
 
-      case BOOKMARKFS_FSCK_RESULT_NAME_DUPLICATE:
-        PRINT_FSCK_RESULT("duplicates with %" PRIu64, data->extra);
-        break;
-
-      case BOOKMARKFS_FSCK_RESULT_NAME_BADCHAR:
-        PRINT_FSCK_RESULT("contains a bad character at offset %" PRIu64,
-                data->extra);
-        break;
-
-      case BOOKMARKFS_FSCK_RESULT_NAME_BADLEN:
-        PRINT_FSCK_RESULT("has invalid length %" PRIu64, data->extra);
-        break;
-
-      case BOOKMARKFS_FSCK_RESULT_NAME_DOTDOT:
-        PRINT_FSCK_RESULT("%s", "is invalid (must not be '.' or '..')");
-        break;
-
-      case BOOKMARKFS_FSCK_RESULT_NAME_INVALID:
-        PRINT_FSCK_RESULT("is invalid (reason number %" PRIu64 ")",
-                data->extra);
+#define FSCK_RESULT(result)                  \
+      case BOOKMARKFS_FSCK_RESULT_##result:  \
+        result_str = #result;                \
         break;
+      FSCK_RESULT(NAME_DUPLICATE)
+      FSCK_RESULT(NAME_BADCHAR)
+      FSCK_RESULT(NAME_BADLEN)
+      FSCK_RESULT(NAME_DOTDOT)
+      FSCK_RESULT(NAME_INVALID)
 
       default:
         log_printf("unknown fsck result code: %d", result);
         return -1;
     }
+
+    char name_buf[sizeof(data->name)];
+    translit_control_chars(name_buf, sizeof(name_buf), data->name, '?');
+    printf("%" PRIu64 "\t%s\t%" PRIu64 "\t%.*s\n", data->id, result_str,
+            data->extra, (int)sizeof(name_buf), name_buf);
     return 0;
 }
 

src/fsck_util.h

@@ -28,7 +28,7 @@
 #include "common.h"
 
 int
-explain_fsck_result (
+print_fsck_result (
     enum bookmarkfs_fsck_result        result,
     struct bookmarkfs_fsck_data const *data
 );