+#define ARRAY_SIZE(arr) (sizeof (arr) / sizeof (arr[0]))
+
+typedef struct {
+ const char *name;
+ const char *prefix;
+} prefix_t;
+
+/* With these prefix values we follow the conventions published here:
+ *
+ * http://xapian.org/docs/omega/termprefixes.html
+ *
+ * as much as makes sense. Note that I took some liberty in matching
+ * the reserved prefix values to notmuch concepts, (for example, 'G'
+ * is documented as "newsGroup (or similar entity - e.g. a web forum
+ * name)", for which I think the thread is the closest analogue in
+ * notmuch. This in spite of the fact that we will eventually be
+ * storing mailing-list messages where 'G' for "mailing list name"
+ * might be even a closer analogue. I'm treating the single-character
+ * prefixes preferentially for core notmuch concepts (which will be
+ * nearly universal to all mail messages).
+ */
+
+prefix_t BOOLEAN_PREFIX_INTERNAL[] = {
+ { "type", "T" },
+ { "thread", "G" },
+ { "ref", "XREFERENCE" },
+ { "timestamp", "XTIMESTAMP" },
+};
+
+prefix_t BOOLEAN_PREFIX_EXTERNAL[] = {
+ { "tag", "K" },
+ { "id", "Q" }
+};
+
+const char *
+_find_prefix (const char *name)
+{
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE (BOOLEAN_PREFIX_INTERNAL); i++)
+ if (strcmp (name, BOOLEAN_PREFIX_INTERNAL[i].name) == 0)
+ return BOOLEAN_PREFIX_INTERNAL[i].prefix;
+
+ for (i = 0; i < ARRAY_SIZE (BOOLEAN_PREFIX_EXTERNAL); i++)
+ if (strcmp (name, BOOLEAN_PREFIX_EXTERNAL[i].name) == 0)
+ return BOOLEAN_PREFIX_EXTERNAL[i].prefix;
+
+ fprintf (stderr, "Internal error: No prefix exists for '%s'\n", name);
+ exit (1);
+
+ return "";
+}
+