lib: Add missing modulo calculation

Adds a missing modulo calculation that would result in index -1 being
returned instead of zero when the ringbuffer skipped back to the
beginning.

3 files changed, 12 insertions, 13 deletions

diff --git a/src/ipcpd/shim-udp/main.c b/src/ipcpd/shim-udp/main.c
index e3f7fcdd..0802583c 100644
--- a/src/ipcpd/shim-udp/main.c
+++ b/src/ipcpd/shim-udp/main.c
@@ -204,8 +204,7 @@ static int port_id_to_fd(int port_id)
 
 static ssize_t ipcp_udp_flow_write(int fd, void * buf, size_t count)
 {
-        /* the AP chooses the amount of headspace and tailspace */
-        size_t index;
+        ssize_t index;
         struct rb_entry e;
 
         rw_lock_rdlock(&_ipcp->state_lock);
diff --git a/src/lib/dev.c b/src/lib/dev.c
index 9b29b992..c365a17b 100644
--- a/src/lib/dev.c
+++ b/src/lib/dev.c
@@ -531,7 +531,7 @@ int flow_cntl(int fd, int cmd, int oflags)
 
 ssize_t flow_write(int fd, void * buf, size_t count)
 {
-        size_t index;
+        ssize_t index;
         struct rb_entry e;
 
         if (buf == NULL)
diff --git a/src/lib/shm_du_map.c b/src/lib/shm_du_map.c
index 7099b265..a7ec5ac9 100644
--- a/src/lib/shm_du_map.c
+++ b/src/lib/shm_du_map.c
@@ -227,11 +227,11 @@ void shm_du_map_destroy(struct shm_du_map * dum)
         free(dum);
 }
 
-int shm_create_du_buff(struct shm_du_map * dum,
-                       size_t              size,
-                       size_t              headspace,
-                       uint8_t *           data,
-                       size_t              len)
+ssize_t shm_create_du_buff(struct shm_du_map * dum,
+                           size_t              size,
+                           size_t              headspace,
+                           uint8_t *           data,
+                           size_t              len)
 {
         struct shm_du_buff * sdb;
         long                 blocks = 0;
@@ -239,7 +239,7 @@ int shm_create_du_buff(struct shm_du_map * dum,
         int                  sz2 = headspace + len + sizeof *sdb;
         uint8_t *            write_pos;
         size_t               copy_len;
-        size_t               index;
+        ssize_t              index;
 
         if (dum == NULL || data == NULL) {
                 LOG_DBGF("Bogus input, bugging out.");
@@ -294,7 +294,7 @@ int shm_create_du_buff(struct shm_du_map * dum,
                 --blocks;
         }
 
-        index = *dum->ptr_head - 1;
+        index = (*dum->ptr_head - 1) & (SHM_BLOCKS_IN_MAP - 1);
 
         pthread_mutex_unlock(dum->shm_mutex);
 
@@ -304,9 +304,9 @@ int shm_create_du_buff(struct shm_du_map * dum,
 /* FIXME: this cannot handle packets stretching beyond the ringbuffer border */
 int shm_du_map_read_sdu(uint8_t **          dst,
                         struct shm_du_map * dum,
-                        size_t              idx)
+                        ssize_t             idx)
 {
-        size_t    len = 0;
+        size_t len = 0;
 
         if (idx > SHM_BLOCKS_IN_MAP)
                 return -1;
@@ -328,7 +328,7 @@ int shm_du_map_read_sdu(uint8_t **          dst,
         return len;
 }
 
-int shm_release_du_buff(struct shm_du_map * dum, size_t idx)
+int shm_release_du_buff(struct shm_du_map * dum, ssize_t idx)
 {
         long sz;
         long blocks = 0;