+static struct encoding *
+find_duplicate_encoding (struct encoding *encodings, size_t n_encodings,
+ char **utf8_strings, size_t n_strings,
+ unsigned int hash)
+{
+ struct encoding *e;
+
+ for (e = encodings; e < &encodings[n_encodings]; e++)
+ {
+ int i;
+
+ if (e->hash != hash)
+ goto next_encoding;
+
+ for (i = 0; i < n_strings; i++)
+ if (strcmp (utf8_strings[i], e->utf8_strings[i]))
+ goto next_encoding;
+
+ return e;
+ next_encoding:;
+ }
+
+ return NULL;
+}
+
+static bool
+all_equal (const struct encoding *encodings, size_t n_encodings,
+ size_t string_idx)
+{
+ const char *s0;
+ size_t i;
+
+ s0 = encodings[0].utf8_strings[string_idx];
+ for (i = 1; i < n_encodings; i++)
+ if (strcmp (s0, encodings[i].utf8_strings[string_idx]))
+ return false;
+
+ return true;
+}
+
+static int
+equal_prefix (const struct encoding *encodings, size_t n_encodings,
+ size_t string_idx)
+{
+ const char *s0;
+ size_t prefix;
+ size_t i;
+
+ s0 = encodings[0].utf8_strings[string_idx];
+ prefix = strlen (s0);
+ for (i = 1; i < n_encodings; i++)
+ {
+ const char *si = encodings[i].utf8_strings[string_idx];
+ size_t j;
+
+ for (j = 0; j < prefix; j++)
+ if (s0[j] != si[j])
+ {
+ prefix = j;
+ if (!prefix)
+ return 0;
+ break;
+ }
+ }
+
+ while (prefix > 0 && s0[prefix - 1] != ' ')
+ prefix--;
+ return prefix;
+}
+
+static int
+equal_suffix (const struct encoding *encodings, size_t n_encodings,
+ size_t string_idx)
+{
+ const char *s0;
+ size_t s0_len;
+ size_t suffix;
+ size_t i;
+
+ s0 = encodings[0].utf8_strings[string_idx];
+ s0_len = strlen (s0);
+ suffix = s0_len;
+ for (i = 1; i < n_encodings; i++)
+ {
+ const char *si = encodings[i].utf8_strings[string_idx];
+ size_t si_len = strlen (si);
+ size_t j;
+
+ if (si_len < suffix)
+ suffix = si_len;
+ for (j = 0; j < suffix; j++)
+ if (s0[s0_len - j - 1] != si[si_len - j - 1])
+ {
+ suffix = j;
+ if (!suffix)
+ return 0;
+ break;
+ }
+ }
+
+ while (suffix > 0 && s0[s0_len - suffix] != ' ')
+ suffix--;
+ return suffix;
+}
+
+static void
+report_encodings (const struct file_handle *h, struct pool *pool,
+ char **titles, bool *ids, char **strings, size_t n_strings)
+{
+ struct encoding encodings[N_ENCODING_NAMES];
+ size_t n_encodings, n_unique_strings;
+ size_t i, j;
+ struct tab_table *t;
+ size_t row;
+
+ n_encodings = 0;
+ for (i = 0; i < N_ENCODING_NAMES; i++)
+ {
+ char **utf8_strings;
+ struct encoding *e;
+ unsigned int hash;
+
+ utf8_strings = recode_strings (pool, strings, ids, n_strings,
+ encoding_names[i]);
+ if (!utf8_strings)
+ continue;
+
+ /* Hash utf8_strings. */
+ hash = 0;
+ for (j = 0; j < n_strings; j++)
+ hash = hash_string (utf8_strings[j], hash);
+
+ /* If there's a duplicate encoding, just mark it. */
+ e = find_duplicate_encoding (encodings, n_encodings,
+ utf8_strings, n_strings, hash);
+ if (e)
+ {
+ e->encodings |= UINT64_C (1) << i;
+ continue;
+ }
+
+ e = &encodings[n_encodings++];
+ e->encodings = UINT64_C (1) << i;
+ e->utf8_strings = utf8_strings;
+ e->hash = hash;
+ }
+ if (!n_encodings)
+ {
+ msg (SW, _("No valid encodings found."));
+ return;
+ }
+
+ t = tab_create (2, n_encodings + 1);
+ tab_title (t, _("Usable encodings for %s."), fh_get_name (h));
+ tab_caption (t, _("Encodings that can successfully read %s (by specifying "
+ "the encoding name on the GET command's ENCODING "
+ "subcommand). Encodings that yield identical text are "
+ "listed together."), fh_get_name (h));
+ tab_headers (t, 1, 0, 1, 0);
+ tab_box (t, TAL_1, TAL_1, -1, -1, 0, 0, 1, n_encodings);
+ tab_hline (t, TAL_1, 0, 1, 1);
+ tab_text (t, 0, 0, TAB_RIGHT, "#");
+ tab_text (t, 1, 0, TAB_LEFT, _("Encodings"));
+ for (i = 0; i < n_encodings; i++)
+ {
+ struct string s;