lib: factor out message-id parsing to separate file.

This is really pure C string parsing, and doesn't need to be mixed in
with the Xapian/C++ layer. Although not strictly necessary, it also
makes it a bit more natural to call _parse_message_id from multiple
compilation units.

1 files changed, 96 insertions, 0 deletions

diff --git a/lib/message-id.c b/lib/message-id.c
new file mode 100644
index 00000000..d7541d50
--- /dev/null
+++ b/lib/message-id.c
@@ -0,0 +1,96 @@
+#include "notmuch-private.h"
+
+/* Advance 'str' past any whitespace or RFC 822 comments. A comment is
+ * a (potentially nested) parenthesized sequence with '\' used to
+ * escape any character (including parentheses).
+ *
+ * If the sequence to be skipped continues to the end of the string,
+ * then 'str' will be left pointing at the final terminating '\0'
+ * character.
+ */
+static void
+skip_space_and_comments (const char **str)
+{
+    const char *s;
+
+    s = *str;
+    while (*s && (isspace (*s) || *s == '(')) {
+	while (*s && isspace (*s))
+	    s++;
+	if (*s == '(') {
+	    int nesting = 1;
+	    s++;
+	    while (*s && nesting) {
+		if (*s == '(') {
+		    nesting++;
+		} else if (*s == ')') {
+		    nesting--;
+		} else if (*s == '\\') {
+		    if (*(s+1))
+			s++;
+		}
+		s++;
+	    }
+	}
+    }
+
+    *str = s;
+}
+
+char *
+_notmuch_message_id_parse (void *ctx, const char *message_id, const char **next)
+{
+    const char *s, *end;
+    char *result;
+
+    if (message_id == NULL || *message_id == '\0')
+	return NULL;
+
+    s = message_id;
+
+    skip_space_and_comments (&s);
+
+    /* Skip any unstructured text as well. */
+    while (*s && *s != '<')
+	s++;
+
+    if (*s == '<') {
+	s++;
+    } else {
+	if (next)
+	    *next = s;
+	return NULL;
+    }
+
+    skip_space_and_comments (&s);
+
+    end = s;
+    while (*end && *end != '>')
+	end++;
+    if (next) {
+	if (*end)
+	    *next = end + 1;
+	else
+	    *next = end;
+    }
+
+    if (end > s && *end == '>')
+	end--;
+    if (end <= s)
+	return NULL;
+
+    result = talloc_strndup (ctx, s, end - s + 1);
+
+    /* Finally, collapse any whitespace that is within the message-id
+     * itself. */
+    {
+	char *r;
+	int len;
+
+	for (r = result, len = strlen (r); *r; r++, len--)
+	    if (*r == ' ' || *r == '\t')
+		memmove (r, r+1, len);
+    }
+
+    return result;
+}