libsmartcols: add filter support to 'fromfile' sample

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libsmartcols/samples/fromfile.c b/libsmartcols/samples/fromfile.c
index d47ca477c030ac25f9e46e661eb11f7aa175c04e..0875e135016e04570a9e880ca7237c3d0c9355aa 100644 (file)
--- a/libsmartcols/samples/fromfile.c
+++ b/libsmartcols/samples/fromfile.c
@@ -212,6 +212,81 @@ static void compose_tree(struct libscols_table *tb, int parent_col, int id_col)
        scols_free_iter(itr);
 }
 
+static struct libscols_filter *init_filter(
+                       struct libscols_table *tb,
+                       const char *query, int dump)
+{
+       struct libscols_iter *itr;
+       struct libscols_filter *f = scols_new_filter(NULL);
+       const char *name = NULL;
+       int rc = 0;
+
+       if (!f)
+               err(EXIT_FAILURE, "failed to allocate filter");
+       if (scols_filter_parse_string(f, query) != 0)
+               errx(EXIT_FAILURE, "failed to parse filter: %s",
+                               scols_filter_get_errmsg(f));
+
+       itr = scols_new_iter(SCOLS_ITER_FORWARD);
+       if (!itr)
+               err(EXIT_FAILURE, "failed to allocate iterator");
+
+       while (scols_filter_next_holder(f, itr, &name, 0) == 0) {
+               struct libscols_column *col;
+
+               col = scols_table_get_column_by_name(tb, name);
+               if (!col) {
+                       warnx("unknown column '%s' in filter", name);
+                       rc++;
+                       continue;
+               }
+               scols_filter_assign_column(f, itr, name, col);
+       }
+
+       scols_free_iter(itr);
+       if (dump && f)
+               scols_dump_filter(f, stdout);
+       if (rc) {
+               scols_unref_filter(f);
+               err(EXIT_FAILURE, "failed to initialize filter");
+       }
+
+       return f;
+}
+
+/* Note: This is a simple (naive) way to use the filter, employed here for
+ * testing functionality.
+ *
+ * A more effective approach to using the filter is demonstrated in lsblk.c,
+ * where data manipulation is divided into two steps. The initial step prepares
+ * only the data necessary for evaluating the filter, and the remaining data is
+ * gathered later, only if necessary.
+ */
+static void apply_filter(struct libscols_table *tb, struct libscols_filter *fltr)
+{
+       struct libscols_iter *itr = scols_new_iter(SCOLS_ITER_FORWARD);
+       struct libscols_line *ln;
+
+       if (!itr)
+               err(EXIT_FAILURE, "failed to allocate iterator");
+
+       while (scols_table_next_line(tb, itr, &ln) == 0) {
+               int status = 0;
+
+               if (scols_line_apply_filter(ln, fltr, &status) != 0)
+                       err(EXIT_FAILURE, "failed to apply filter");
+               if (status == 0) {
+                       struct libscols_line *x = scols_line_get_parent(ln);
+
+                       if (x)
+                               scols_line_remove_child(x, ln);
+                       scols_table_remove_line(tb, ln);
+                       ln = NULL;
+               }
+       }
+
+       scols_free_iter(itr);
+}
 
 static void __attribute__((__noreturn__)) usage(void)
 {
@@ -230,6 +305,7 @@ static void __attribute__((__noreturn__)) usage(void)
        fputs(" -w, --width <num>              hardcode terminal width\n", out);
        fputs(" -p, --tree-parent-column <n>   parent column\n", out);
        fputs(" -i, --tree-id-column <n>       id column\n", out);
+       fputs(" -Q, --filter <expr>            filter\n", out);
        fputs(" -h, --help                     this help\n", out);
        fputs("\n", out);
 
@@ -241,6 +317,9 @@ int main(int argc, char *argv[])
        struct libscols_table *tb;
        int c, n, nlines = 0;
        int parent_col = -1, id_col = -1;
+       int fltr_dump = 0;
+       const char *fltr_str = NULL;
+       struct libscols_filter *fltr = NULL;
 
        static const struct option longopts[] = {
                { "maxout", 0, NULL, 'm' },
@@ -254,6 +333,8 @@ int main(int argc, char *argv[])
                { "raw",    0, NULL, 'r' },
                { "export", 0, NULL, 'E' },
                { "colsep",  1, NULL, 'C' },
+               { "filter", 1, NULL, 'Q' },
+               { "filter-dump", 0, NULL, 'd' },
                { "help",   0, NULL, 'h' },
                { NULL, 0, NULL, 0 },
        };
@@ -272,7 +353,7 @@ int main(int argc, char *argv[])
        if (!tb)
                err(EXIT_FAILURE, "failed to create output table");
 
-       while((c = getopt_long(argc, argv, "hCc:Ei:JMmn:p:rw:", longopts, NULL)) != -1) {
+       while((c = getopt_long(argc, argv, "hCc:dEi:JMmn:p:Q:rw:", longopts, NULL)) != -1) {
 
                err_exclusive_options(c, longopts, excl, excl_st);
 
@@ -291,6 +372,9 @@ int main(int argc, char *argv[])
                        fclose(f);
                        break;
                }
+               case 'd':
+                       fltr_dump = 1;
+                       break;
                case 'p':
                        parent_col = strtou32_or_err(optarg, "failed to parse tree PARENT column");
                        break;
@@ -319,6 +403,9 @@ int main(int argc, char *argv[])
                case 'n':
                        nlines = strtou32_or_err(optarg, "failed to parse number of lines");
                        break;
+               case 'Q':
+                       fltr_str = optarg;
+                       break;
                case 'w':
                        scols_table_set_termforce(tb, SCOLS_TERMFORCE_ALWAYS);
                        scols_table_set_termwidth(tb, strtou32_or_err(optarg, "failed to parse terminal width"));
@@ -342,6 +429,9 @@ int main(int argc, char *argv[])
                scols_unref_line(ln);
        }
 
+       if (fltr_str)
+               fltr = init_filter(tb, fltr_str, fltr_dump);
+
        n = 0;
 
        while (optind < argc) {
@@ -360,7 +450,12 @@ int main(int argc, char *argv[])
 
        scols_table_enable_colors(tb, isatty(STDOUT_FILENO));
 
+       if (fltr)
+               apply_filter(tb, fltr);
+
        scols_print_table(tb);
+
+       scols_unref_filter(fltr);
        scols_unref_table(tb);
        return EXIT_SUCCESS;
 }