lib: factor out feature name related code.

database.cc is uncomfortably large, and some of the static data
structures do not need to be shared as much as they are.

This is a somewhat small piece to factor out, but it will turn out to
be helpful to further refactoring.

1 files changed, 114 insertions, 0 deletions

diff --git a/lib/features.cc b/lib/features.cc
new file mode 100644
index 00000000..8def2461
--- /dev/null
+++ b/lib/features.cc
@@ -0,0 +1,114 @@
+#include "database-private.h"
+
+static const struct {
+    /* NOTMUCH_FEATURE_* value. */
+    _notmuch_features value;
+    /* Feature name as it appears in the database.  This name should
+     * be appropriate for displaying to the user if an older version
+     * of notmuch doesn't support this feature. */
+    const char *name;
+    /* Compatibility flags when this feature is declared. */
+    const char *flags;
+} feature_names[] = {
+    { NOTMUCH_FEATURE_FILE_TERMS,
+      "multiple paths per message", "rw" },
+    { NOTMUCH_FEATURE_DIRECTORY_DOCS,
+      "relative directory paths", "rw" },
+    /* Header values are not required for reading a database because a
+     * reader can just refer to the message file. */
+    { NOTMUCH_FEATURE_FROM_SUBJECT_ID_VALUES,
+      "from/subject/message-ID in database", "w" },
+    { NOTMUCH_FEATURE_BOOL_FOLDER,
+      "exact folder:/path: search", "rw" },
+    { NOTMUCH_FEATURE_GHOSTS,
+      "mail documents for missing messages", "w" },
+    /* Knowledge of the index mime-types are not required for reading
+     * a database because a reader will just be unable to query
+     * them. */
+    { NOTMUCH_FEATURE_INDEXED_MIMETYPES,
+      "indexed MIME types", "w" },
+    { NOTMUCH_FEATURE_LAST_MOD,
+      "modification tracking", "w" },
+    /* Existing databases will work fine for all queries not involving
+     * 'body:' */
+    { NOTMUCH_FEATURE_UNPREFIX_BODY_ONLY,
+      "index body and headers separately", "w" },
+};
+
+char *
+_notmuch_database_print_features (const void *ctx, unsigned int features)
+{
+    unsigned int i;
+    char *res = talloc_strdup (ctx, "");
+
+    for (i = 0; i < ARRAY_SIZE (feature_names); ++i)
+	if (features & feature_names[i].value)
+	    res = talloc_asprintf_append_buffer (
+		res, "%s\t%s\n", feature_names[i].name, feature_names[i].flags);
+
+    return res;
+}
+
+
+/* Parse a database features string from the given database version.
+ * Returns the feature bit set.
+ *
+ * For version < 3, this ignores the features string and returns a
+ * hard-coded set of features.
+ *
+ * If there are unrecognized features that are required to open the
+ * database in mode (which should be 'r' or 'w'), return a
+ * comma-separated list of unrecognized but required features in
+ * *incompat_out suitable for presenting to the user.  *incompat_out
+ * will be allocated from ctx.
+ */
+_notmuch_features
+_notmuch_database_parse_features (const void *ctx, const char *features, unsigned int version,
+		 char mode, char **incompat_out)
+{
+    _notmuch_features res = static_cast<_notmuch_features>(0);
+    unsigned int namelen, i;
+    size_t llen = 0;
+    const char *flags;
+
+    /* Prior to database version 3, features were implied by the
+     * version number. */
+    if (version == 0)
+	return NOTMUCH_FEATURES_V0;
+    else if (version == 1)
+	return NOTMUCH_FEATURES_V1;
+    else if (version == 2)
+	return NOTMUCH_FEATURES_V2;
+
+    /* Parse the features string */
+    while ((features = strtok_len_c (features + llen, "\n", &llen)) != NULL) {
+	flags = strchr (features, '\t');
+	if (! flags || flags > features + llen)
+	    continue;
+	namelen = flags - features;
+
+	for (i = 0; i < ARRAY_SIZE (feature_names); ++i) {
+	    if (strlen (feature_names[i].name) == namelen &&
+		strncmp (feature_names[i].name, features, namelen) == 0) {
+		res |= feature_names[i].value;
+		break;
+	    }
+	}
+
+	if (i == ARRAY_SIZE (feature_names) && incompat_out) {
+	    /* Unrecognized feature */
+	    const char *have = strchr (flags, mode);
+	    if (have && have < features + llen) {
+		/* This feature is required to access this database in
+		 * 'mode', but we don't understand it. */
+		if (! *incompat_out)
+		    *incompat_out = talloc_strdup (ctx, "");
+		*incompat_out = talloc_asprintf_append_buffer (
+		    *incompat_out, "%s%.*s", **incompat_out ? ", " : "",
+		    namelen, features);
+	    }
+	}
+    }
+
+    return res;
+}