[PATCH v2 1/7] cli: allow query to come from stdin

[markwalters1009]

From: Mark Walters <markwalters1009 at gmail.com>

After this series there will be times when a caller will want to pass
a very large query string to notmuch (eg a list of 10,000 message-ids)
and this can exceed the size of ARG_MAX. Hence allow notmuch to take
the query from stdin (if the query is -).
---
 query-string.c |   41 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/query-string.c b/query-string.c
index 6536512..b1fbdeb 100644
--- a/query-string.c
+++ b/query-string.c
@@ -20,6 +20,44 @@
 
 #include "notmuch-client.h"
 
+/* Read a single query string from STDIN, using
+ * 'ctx' as the talloc owner for all allocations.
+ *
+ * This function returns NULL in case of insufficient memory or read
+ * errors.
+ */
+static char *
+query_string_from_stdin (void *ctx)
+{
+    char *query_string;
+    char buf[4096];
+    ssize_t remain;
+
+    query_string = talloc_strdup (ctx, "");
+    if (query_string == NULL)
+	return NULL;
+
+    for (;;) {
+	remain = read (STDIN_FILENO, buf, sizeof(buf) - 1);
+	if (remain == 0)
+	    break;
+	if (remain < 0) {
+	    if (errno == EINTR)
+		continue;
+	    fprintf (stderr, "Error: reading from standard input: %s\n",
+		     strerror (errno));
+	    return NULL;
+	}
+
+	buf[remain] = '\0';
+	query_string = talloc_strdup_append (query_string, buf);
+	if (query_string == NULL)
+	    return NULL;
+    }
+
+    return query_string;
+}
+
 /* Construct a single query string from the passed arguments, using
  * 'ctx' as the talloc owner for all allocations.
  *
@@ -35,6 +73,9 @@ query_string_from_args (void *ctx, int argc, char *argv[])
     char *query_string;
     int i;
 
+    if ((argc == 1) && (strcmp ("-", argv[0]) == 0))
+	return query_string_from_stdin (ctx);
+
     query_string = talloc_strdup (ctx, "");
     if (query_string == NULL)
 	return NULL;
-- 
1.7.9.1