[Patch v9 04/17] notmuch-tag: factor out double quoting routine

[david at tethera.net]

From: David Bremner <bremner at debian.org>

This could live in tag-util as well, but it is really nothing specific
to tags (although the conventions are arguable specific to Xapian).

The API is changed from "caller-allocates" to "readline-like". The scan for
max tag length is pushed down into the double quoting routine.
---
 notmuch-tag.c      |   52 ++++++++++++++++++----------------------------------
 util/string-util.c |   37 +++++++++++++++++++++++++++++++++++++
 util/string-util.h |    8 ++++++++
 3 files changed, 63 insertions(+), 34 deletions(-)

diff --git a/notmuch-tag.c b/notmuch-tag.c
index 0965ee7..a480215 100644
--- a/notmuch-tag.c
+++ b/notmuch-tag.c
@@ -20,6 +20,7 @@
 
 #include "notmuch-client.h"
 #include "tag-util.h"
+#include "string-util.h"
 
 static volatile sig_atomic_t interrupted;
 
@@ -37,25 +38,6 @@ handle_sigint (unused (int sig))
 }
 
 static char *
-_escape_tag (char *buf, const char *tag)
-{
-    const char *in = tag;
-    char *out = buf;
-
-    /* Boolean terms surrounded by double quotes can contain any
-     * character.  Double quotes are quoted by doubling them. */
-    *out++ = '"';
-    while (*in) {
-	if (*in == '"')
-	    *out++ = '"';
-	*out++ = *in++;
-    }
-    *out++ = '"';
-    *out = 0;
-    return buf;
-}
-
-static char *
 _optimize_tag_query (void *ctx, const char *orig_query_string,
 		     const tag_op_list_t *list)
 {
@@ -67,44 +49,46 @@ _optimize_tag_query (void *ctx, const char *orig_query_string,
      * parenthesize and the exclusion part of the query must not use
      * the '-' operator (though the NOT operator is fine). */
 
-    char *escaped, *query_string;
+    char *escaped = NULL;
+    size_t escaped_len = 0;
+    char *query_string;
     const char *join = "";
     size_t i;
-    unsigned int max_tag_len = 0;
 
     /* Don't optimize if there are no tag changes. */
     if (tag_op_list_size (list) == 0)
 	return talloc_strdup (ctx, orig_query_string);
 
-    /* Allocate a buffer for escaping tags.  This is large enough to
-     * hold a fully escaped tag with every character doubled plus
-     * enclosing quotes and a NUL. */
-    for (i = 0; i < tag_op_list_size (list); i++)
-	if (strlen (tag_op_list_tag (list, i)) > max_tag_len)
-	    max_tag_len = strlen (tag_op_list_tag (list, i));
-
-    escaped = talloc_array (ctx, char, max_tag_len * 2 + 3);
-    if (! escaped)
-	return NULL;
-
     /* Build the new query string */
     if (strcmp (orig_query_string, "*") == 0)
 	query_string = talloc_strdup (ctx, "(");
     else
 	query_string = talloc_asprintf (ctx, "( %s ) and (", orig_query_string);
 
+    /* Boolean terms surrounded by double quotes can contain any
+     * character.  Double quotes are quoted by doubling them. */
+
     for (i = 0; i < tag_op_list_size (list) && query_string; i++) {
+	/* XXX in case of OOM, query_string will be deallocated when
+	 * ctx is, which might be at shutdown */
+	if (double_quote_str (ctx,
+			      tag_op_list_tag (list, i),
+			      &escaped, &escaped_len))
+	    return NULL;
+
 	query_string = talloc_asprintf_append_buffer (
 	    query_string, "%s%stag:%s", join,
 	    tag_op_list_isremove (list, i) ? "" : "not ",
-	    _escape_tag (escaped, tag_op_list_tag (list, i)));
+	    escaped);
 	join = " or ";
     }
 
     if (query_string)
 	query_string = talloc_strdup_append_buffer (query_string, ")");
 
-    talloc_free (escaped);
+    if (escaped)
+	talloc_free (escaped);
+
     return query_string;
 }
 
diff --git a/util/string-util.c b/util/string-util.c
index 44f8cd3..b9039f4 100644
--- a/util/string-util.c
+++ b/util/string-util.c
@@ -20,6 +20,7 @@
 
 
 #include "string-util.h"
+#include "talloc.h"
 
 char *
 strtok_len (char *s, const char *delim, size_t *len)
@@ -32,3 +33,39 @@ strtok_len (char *s, const char *delim, size_t *len)
 
     return *len ? s : NULL;
 }
+
+
+int
+double_quote_str (void *ctx, const char *str,
+		  char **buf, size_t *len)
+{
+    const char *in;
+    char *out;
+    size_t needed = 3;
+
+    for (in = str; *in; in++)
+	needed += (*in == '"') ? 2 : 1;
+
+    if ((*buf == NULL) || (needed > *len)) {
+	*len = 2 * needed;
+	*buf = talloc_realloc (ctx, *buf, char, *len);
+    }
+
+
+    if (! *buf)
+	return 1;
+
+    out = *buf;
+
+    *out++ = '"';
+    in = str;
+    while (*in) {
+	if (*in == '"')
+	    *out++ = '"';
+	*out++ = *in++;
+    }
+    *out++ = '"';
+    *out = '\0';
+
+    return 0;
+}
diff --git a/util/string-util.h b/util/string-util.h
index ac7676c..4fc7942 100644
--- a/util/string-util.h
+++ b/util/string-util.h
@@ -19,4 +19,12 @@
 
 char *strtok_len (char *s, const char *delim, size_t *len);
 
+/* Copy str to dest, surrounding with double quotes.
+ * Any internal double-quotes are doubled, i.e. a"b -> "a""b"
+ *
+ * Output is into buf; it may be talloc_realloced
+ * Return: 0 on success, non-zero on memory allocation failure.
+ */
+int double_quote_str (void *talloc_ctx, const char *str,
+		      char **buf, size_t *len);
 #endif
-- 
1.7.10.4