Add redisConnectFd() and redisFreeKeepFd()

These allows for easier integration of hiredis with external
code that wants to manage its fds, say for instance in a pool.

Closes #223

hiredis.c

@@ -1010,6 +1010,13 @@ void redisFree(redisContext *c) {
     free(c);
 }
 
+int redisFreeKeepFd(redisContext *c) {
+	int fd = c->fd;
+	c->fd = -1;
+	redisFree(c);
+	return fd;
+}
+
 /* Connect to a Redis instance. On error the field error in the returned
  * context will be set to the return value of the error function.
  * When no set of reply functions is given, the default set will be used. */
@@ -1093,6 +1100,18 @@ redisContext *redisConnectUnixNonBlock(const char *path) {
     return c;
 }
 
+redisContext *redisConnectFd(int fd) {
+    redisContext *c;
+
+    c = redisContextInit();
+    if (c == NULL)
+        return NULL;
+
+    c->fd = fd;
+    c->flags |= REDIS_BLOCK | REDIS_CONNECTED;
+    return c;
+}
+
 /* Set read/write timeout on a blocking socket. */
 int redisSetTimeout(redisContext *c, const struct timeval tv) {
     if (c->flags & REDIS_BLOCK)

hiredis.h

@@ -179,9 +179,11 @@ redisContext *redisConnectBindNonBlock(const char *ip, int port, char *source);
 redisContext *redisConnectUnix(const char *path);
 redisContext *redisConnectUnixWithTimeout(const char *path, const struct timeval tv);
 redisContext *redisConnectUnixNonBlock(const char *path);
+redisContext *redisConnectFd(int fd);
 int redisSetTimeout(redisContext *c, const struct timeval tv);
 int redisEnableKeepAlive(redisContext *c);
 void redisFree(redisContext *c);
+int redisFreeKeepFd(redisContext *c);
 int redisBufferRead(redisContext *c);
 int redisBufferWrite(redisContext *c, int *done);
 

test.c

@@ -14,7 +14,8 @@
 
 enum connection_type {
     CONN_TCP,
-    CONN_UNIX
+    CONN_UNIX,
+    CONN_FD
 };
 
 struct config {
@@ -64,7 +65,7 @@ static redisContext *select_database(redisContext *c) {
     return c;
 }
 
-static void disconnect(redisContext *c) {
+static int disconnect(redisContext *c, int keep_fd) {
     redisReply *reply;
 
     /* Make sure we're on DB 9. */
@@ -75,8 +76,11 @@ static void disconnect(redisContext *c) {
     assert(reply != NULL);
     freeReplyObject(reply);
 
-    /* Free the context as well. */
+    /* Free the context as well, but keep the fd if requested. */
+    if (keep_fd)
+        return redisFreeKeepFd(c);
     redisFree(c);
+    return -1;
 }
 
 static redisContext *connect(struct config config) {
@@ -86,6 +90,14 @@ static redisContext *connect(struct config config) {
         c = redisConnect(config.tcp.host, config.tcp.port);
     } else if (config.type == CONN_UNIX) {
         c = redisConnectUnix(config.unix.path);
+    } else if (config.type == CONN_FD) {
+        /* Create a dummy connection just to get an fd to inherit */
+        redisContext *dummy_ctx = redisConnectUnix(config.unix.path);
+        if (dummy_ctx) {
+            int fd = disconnect(dummy_ctx, 1);
+            printf("Connecting to inherited fd %d\n", fd);
+            c = redisConnectFd(fd);
+        }
     } else {
         assert(NULL);
     }
@@ -383,7 +395,7 @@ static void test_blocking_connection(struct config config) {
               strcasecmp(reply->element[1]->str,"pong") == 0);
     freeReplyObject(reply);
 
-    disconnect(c);
+    disconnect(c, 0);
 }
 
 static void test_blocking_io_errors(struct config config) {
@@ -523,7 +535,7 @@ static void test_throughput(struct config config) {
     free(replies);
     printf("\t(%dx LRANGE with 500 elements (pipelined): %.3fs)\n", num, (t2-t1)/1000000.0);
 
-    disconnect(c);
+    disconnect(c, 0);
 }
 
 // static long __test_callback_flags = 0;
@@ -636,6 +648,7 @@ int main(int argc, char **argv) {
         }
     };
     int throughput = 1;
+    int test_inherit_fd = 1;
 
     /* Ignore broken pipe signal (for I/O error tests). */
     signal(SIGPIPE, SIG_IGN);
@@ -654,6 +667,8 @@ int main(int argc, char **argv) {
             cfg.unix.path = argv[0];
         } else if (argc >= 1 && !strcmp(argv[0],"--skip-throughput")) {
             throughput = 0;
+        } else if (argc >= 1 && !strcmp(argv[0],"--skip-inherit-fd")) {
+            test_inherit_fd = 0;
         } else {
             fprintf(stderr, "Invalid argument: %s\n", argv[0]);
             exit(1);
@@ -678,6 +693,12 @@ int main(int argc, char **argv) {
     test_blocking_io_errors(cfg);
     if (throughput) test_throughput(cfg);
 
+    if (test_inherit_fd) {
+        printf("\nTesting against inherited fd (%s):\n", cfg.unix.path);
+        cfg.type = CONN_FD;
+        test_blocking_connection(cfg);
+    }
+
     if (fails) {
         printf("*** %d TESTS FAILED ***\n", fails);
         return 1;