1 files changed, 46 insertions, 0 deletions
diff --git a/libpod/lock/shm/shm_lock.h b/libpod/lock/shm/shm_lock.h
new file mode 100644
index 000000000..8e7e23fb7
--- /dev/null
+++ b/libpod/lock/shm/shm_lock.h
@@ -0,0 +1,46 @@
+#ifndef shm_locks_h_
+#define shm_locks_h_
+
+#include <pthread.h>
+#include <stdint.h>
+
+// Magic number to ensure we open the right SHM segment
+#define MAGIC 0x87D1
+
+// Type for our bitmaps
+typedef uint32_t bitmap_t;
+
+// bitmap size
+#define BITMAP_SIZE (sizeof(bitmap_t) * 8)
+
+// Struct to hold a single bitmap and associated locks
+typedef struct lock_group {
+  bitmap_t        bitmap;
+  pthread_mutex_t locks[BITMAP_SIZE];
+} lock_group_t;
+
+// Struct to hold our SHM locks.
+// Unused is required to be 0 in the current implementation. If we ever make
+// changes to this structure in the future, this will be repurposed as a version
+// field.
+typedef struct shm_struct {
+  uint16_t        magic;
+  uint16_t        unused;
+  pthread_mutex_t segment_lock;
+  uint32_t        num_bitmaps;
+  uint32_t        num_locks;
+  lock_group_t    locks[];
+} shm_struct_t;
+
+static size_t compute_shm_size(uint32_t num_bitmaps);
+static int take_mutex(pthread_mutex_t *mutex);
+static int release_mutex(pthread_mutex_t *mutex);
+shm_struct_t *setup_lock_shm(char *path, uint32_t num_locks, int *error_code);
+shm_struct_t *open_lock_shm(char *path, uint32_t num_locks, int *error_code);
+int32_t close_lock_shm(shm_struct_t *shm);
+int64_t allocate_semaphore(shm_struct_t *shm);
+int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index);
+int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index);
+int32_t unlock_semaphore(shm_struct_t *shm, uint32_t sem_index);
+
+#endif