From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 25 Oct 2014 18:04:31 +0000 (+0100)
Subject: Static buffers: Provide new rotating static buffer macros
X-Git-Tag: proposed.ipv6-polypath-fixes.v1~2
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=commitdiff_plain;h=5e7a63be9a512bf979e5538e6a694d5fd66b9380

Static buffers: Provide new rotating static buffer macros

Provide new macros SBUF_DEFINE and SBUF which replace the open coded
rotating static buffers in ipaddr_getbuf (ipaddr_to_string and
subnet_to_string) and iaddr_to_string.

No functional change.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/ipaddr.c b/ipaddr.c
index 1506ae6..9302925 100644
--- a/ipaddr.c
+++ b/ipaddr.c
@@ -313,17 +313,11 @@ struct subnet_list *ipset_to_subnet_list(struct ipset *is)
     return r;
 }
 
-#define IPADDR_NBUFS_SHIFT 4
-#define IPADDR_NBUFS (1 << IPADDR_NBUFS_SHIFT)
 #define IPADDR_BUFLEN 20
 
 static char *ipaddr_getbuf(void)
 {
-    static int b;
-    static char bufs[IPADDR_NBUFS][IPADDR_BUFLEN];
-
-    b++;
-    b &= IPADDR_NBUFS-1;
+    SBUF_DEFINE(16, IPADDR_BUFLEN);
     return SBUF;
 }
 
diff --git a/util.c b/util.c
index 478d779..59ed427 100644
--- a/util.c
+++ b/util.c
@@ -543,19 +543,13 @@ void string_item_to_iaddr(const item_t *item, uint16_t port, union iaddr *ia,
 #endif /* CONFIG_IPV6 */
 }
 
-#define IADDR_NBUFS_SHIFT 3
-#define IADDR_NBUFS (1 << IADDR_NBUFS_SHIFT)
+#define IADDR_NBUFS 8
 
 const char *iaddr_to_string(const union iaddr *ia)
 {
-    static int b;
-
-    b++;
-    b &= IADDR_NBUFS-1;
-
 #ifndef CONFIG_IPV6
 
-    static char bufs[IADDR_NBUFS][100];
+    SBUF_DEFINE(IADDR_NBUFS, 100);
 
     assert(ia->sa.sa_family == AF_INET);
 
@@ -565,7 +559,7 @@ const char *iaddr_to_string(const union iaddr *ia)
 
 #else /* CONFIG_IPV6 => we have adns_addr2text */
 
-    static char bufs[IADDR_NBUFS][1+ADNS_ADDR2TEXT_BUFLEN+20];
+    SBUF_DEFINE(IADDR_NBUFS, 1+ADNS_ADDR2TEXT_BUFLEN+20);
 
     int port;
 
diff --git a/util.h b/util.h
index d4663db..de1aaa5 100644
--- a/util.h
+++ b/util.h
@@ -89,7 +89,20 @@ void string_item_to_iaddr(const item_t *item, uint16_t port, union iaddr *ia,
 			  const char *desc);
 
 
-#define SBUF (bufs[b]) /* temporary macro */
+/*
+ * SBUF_DEFINE(int nbufs, size_t size);
+ *   // Generates a number of definitions and statements organising
+ *   // nbufs rotating char[size] buffers such that subsequent code
+ *   // may refer to:
+ * char *const SBUF;
+ */
+#define SBUF_DEFINE(nbufs, size)			\
+    static int static_bufs__bufnum;			\
+    static char static_bufs__bufs[(nbufs)][(size)];	\
+    static_bufs__bufnum++;				\
+    static_bufs__bufnum %= (nbufs);			\
+    static_bufs__bufs[static_bufs__bufnum]
+#define SBUF (static_bufs__bufs[static_bufs__bufnum])
 
 /*----- line-buffered asynch input -----*/