Ensure at least the specified ringbuffer size is writable

Previously, all but one of the specified size could be written (so for a size
of n, only n-1 was guaranteed writable). All users pretty much compensated for
this, but it makes more sense to fix it at the source.

1 files changed, 8 insertions, 26 deletions

diff --git a/Alc/ringbuffer.c b/Alc/ringbuffer.c
index 02fa857c..6c419cf8 100644
--- a/Alc/ringbuffer.c
+++ b/Alc/ringbuffer.c
@@ -46,8 +46,6 @@ struct ll_ringbuffer {
     alignas(16) char buf[];
 };
 
-/* Create a new ringbuffer to hold at least `sz' elements of `elem_sz' bytes.
- * The number of elements is rounded up to the next power of two. */
 ll_ringbuffer_t *ll_ringbuffer_create(size_t sz, size_t elem_sz, int limit_writes)
 {
     ll_ringbuffer_t *rb;
@@ -55,7 +53,7 @@ ll_ringbuffer_t *ll_ringbuffer_create(size_t sz, size_t elem_sz, int limit_write
 
     if(sz > 0)
     {
-        power_of_two = sz - 1;
+        power_of_two = sz;
         power_of_two |= power_of_two>>1;
         power_of_two |= power_of_two>>2;
         power_of_two |= power_of_two>>4;
@@ -79,13 +77,11 @@ ll_ringbuffer_t *ll_ringbuffer_create(size_t sz, size_t elem_sz, int limit_write
     return rb;
 }
 
-/* Free all data associated with the ringbuffer `rb'. */
 void ll_ringbuffer_free(ll_ringbuffer_t *rb)
 {
     al_free(rb);
 }
 
-/* Reset the read and write pointers to zero. This is not thread safe. */
 void ll_ringbuffer_reset(ll_ringbuffer_t *rb)
 {
     ATOMIC_STORE(&rb->write_ptr, 0, almemory_order_release);
@@ -93,16 +89,14 @@ void ll_ringbuffer_reset(ll_ringbuffer_t *rb)
     memset(rb->buf, 0, (rb->size_mask+1)*rb->elem_size);
 }
 
-/* Return the number of elements available for reading. This is the number of
- * elements in front of the read pointer and behind the write pointer. */
+
 size_t ll_ringbuffer_read_space(const ll_ringbuffer_t *rb)
 {
     size_t w = ATOMIC_LOAD(&CONST_CAST(ll_ringbuffer_t*,rb)->write_ptr, almemory_order_acquire);
     size_t r = ATOMIC_LOAD(&CONST_CAST(ll_ringbuffer_t*,rb)->read_ptr, almemory_order_acquire);
     return (w-r) & rb->size_mask;
 }
-/* Return the number of elements available for writing. This is the number of
- * elements in front of the write pointer and behind the read pointer. */
+
 size_t ll_ringbuffer_write_space(const ll_ringbuffer_t *rb)
 {
     size_t w = ATOMIC_LOAD(&CONST_CAST(ll_ringbuffer_t*,rb)->write_ptr, almemory_order_acquire);
@@ -111,8 +105,7 @@ size_t ll_ringbuffer_write_space(const ll_ringbuffer_t *rb)
     return (w > rb->size) ? rb->size : w;
 }
 
-/* The copying data reader. Copy at most `cnt' elements from `rb' to `dest'.
- * Returns the actual number of elements copied. */
+
 size_t ll_ringbuffer_read(ll_ringbuffer_t *rb, char *dest, size_t cnt)
 {
     size_t read_ptr;
@@ -151,9 +144,6 @@ size_t ll_ringbuffer_read(ll_ringbuffer_t *rb, char *dest, size_t cnt)
     return to_read;
 }
 
-/* The copying data reader w/o read pointer advance. Copy at most `cnt'
- * elements from `rb' to `dest'. Returns the actual number of elements copied.
- */
 size_t ll_ringbuffer_peek(ll_ringbuffer_t *rb, char *dest, size_t cnt)
 {
     size_t free_cnt;
@@ -190,8 +180,6 @@ size_t ll_ringbuffer_peek(ll_ringbuffer_t *rb, char *dest, size_t cnt)
     return to_read;
 }
 
-/* The copying data writer. Copy at most `cnt' elements to `rb' from `src'.
- * Returns the actual number of elements copied. */
 size_t ll_ringbuffer_write(ll_ringbuffer_t *rb, const char *src, size_t cnt)
 {
     size_t write_ptr;
@@ -230,22 +218,19 @@ size_t ll_ringbuffer_write(ll_ringbuffer_t *rb, const char *src, size_t cnt)
     return to_write;
 }
 
-/* Advance the read pointer `cnt' places. */
+
 void ll_ringbuffer_read_advance(ll_ringbuffer_t *rb, size_t cnt)
 {
     ATOMIC_ADD(&rb->read_ptr, cnt, almemory_order_acq_rel);
 }
 
-/* Advance the write pointer `cnt' places. */
 void ll_ringbuffer_write_advance(ll_ringbuffer_t *rb, size_t cnt)
 {
     ATOMIC_ADD(&rb->write_ptr, cnt, almemory_order_acq_rel);
 }
 
-/* The non-copying data reader. `vec' is an array of two places. Set the values
- * at `vec' to hold the current readable data at `rb'. If the readable data is
- * in one segment the second segment has zero length. */
-void ll_ringbuffer_get_read_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data_t * vec)
+
+void ll_ringbuffer_get_read_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data_t vec[2])
 {
     size_t free_cnt;
     size_t cnt2;
@@ -277,10 +262,7 @@ void ll_ringbuffer_get_read_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data
     }
 }
 
-/* The non-copying data writer. `vec' is an array of two places. Set the values
- * at `vec' to hold the current writeable data at `rb'. If the writeable data
- * is in one segment the second segment has zero length. */
-void ll_ringbuffer_get_write_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data_t *vec)
+void ll_ringbuffer_get_write_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data_t vec[2])
 {
     size_t free_cnt;
     size_t cnt2;