C-API: Constify cache functions where possible (#11243)

Summary:
Makes it easier to use generated Rust bindings. Constness of these is already part of the C++ API.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11243

Reviewed By: hx235

Differential Revision: D44840394

Pulled By: ajkr

fbshipit-source-id: bcd1aeb8c959c304148d25b00043bb8c4cd3e0a4

db/c.cc

@@ -4679,7 +4679,7 @@ rocksdb_cache_t* rocksdb_cache_create_lru_with_strict_capacity_limit(
 }
 
 rocksdb_cache_t* rocksdb_cache_create_lru_opts(
-    rocksdb_lru_cache_options_t* opt) {
+    const rocksdb_lru_cache_options_t* opt) {
   rocksdb_cache_t* c = new rocksdb_cache_t;
   c->rep = NewLRUCache(opt->rep);
   return c;
@@ -4726,7 +4726,7 @@ rocksdb_cache_t* rocksdb_cache_create_hyper_clock(
 }
 
 rocksdb_cache_t* rocksdb_cache_create_hyper_clock_opts(
-    rocksdb_hyper_clock_cache_options_t* opts) {
+    const rocksdb_hyper_clock_cache_options_t* opts) {
   rocksdb_cache_t* c = new rocksdb_cache_t;
   c->rep = opts->rep.MakeSharedCache();
   return c;
@@ -4742,15 +4742,15 @@ void rocksdb_cache_set_capacity(rocksdb_cache_t* cache, size_t capacity) {
   cache->rep->SetCapacity(capacity);
 }
 
-size_t rocksdb_cache_get_capacity(rocksdb_cache_t* cache) {
+size_t rocksdb_cache_get_capacity(const rocksdb_cache_t* cache) {
   return cache->rep->GetCapacity();
 }
 
-size_t rocksdb_cache_get_usage(rocksdb_cache_t* cache) {
+size_t rocksdb_cache_get_usage(const rocksdb_cache_t* cache) {
   return cache->rep->GetUsage();
 }
 
-size_t rocksdb_cache_get_pinned_usage(rocksdb_cache_t* cache) {
+size_t rocksdb_cache_get_pinned_usage(const rocksdb_cache_t* cache) {
   return cache->rep->GetPinnedUsage();
 }
 

include/rocksdb/c.h

@@ -2006,7 +2006,7 @@ extern ROCKSDB_LIBRARY_API rocksdb_cache_t* rocksdb_cache_create_lru(
 extern ROCKSDB_LIBRARY_API rocksdb_cache_t*
 rocksdb_cache_create_lru_with_strict_capacity_limit(size_t capacity);
 extern ROCKSDB_LIBRARY_API rocksdb_cache_t* rocksdb_cache_create_lru_opts(
-    rocksdb_lru_cache_options_t*);
+    const rocksdb_lru_cache_options_t*);
 
 extern ROCKSDB_LIBRARY_API void rocksdb_cache_destroy(rocksdb_cache_t* cache);
 extern ROCKSDB_LIBRARY_API void rocksdb_cache_disown_data(
@@ -2014,11 +2014,11 @@ extern ROCKSDB_LIBRARY_API void rocksdb_cache_disown_data(
 extern ROCKSDB_LIBRARY_API void rocksdb_cache_set_capacity(
     rocksdb_cache_t* cache, size_t capacity);
 extern ROCKSDB_LIBRARY_API size_t
-rocksdb_cache_get_capacity(rocksdb_cache_t* cache);
+rocksdb_cache_get_capacity(const rocksdb_cache_t* cache);
 extern ROCKSDB_LIBRARY_API size_t
-rocksdb_cache_get_usage(rocksdb_cache_t* cache);
+rocksdb_cache_get_usage(const rocksdb_cache_t* cache);
 extern ROCKSDB_LIBRARY_API size_t
-rocksdb_cache_get_pinned_usage(rocksdb_cache_t* cache);
+rocksdb_cache_get_pinned_usage(const rocksdb_cache_t* cache);
 extern ROCKSDB_LIBRARY_API size_t
 rocksdb_cache_get_table_address_count(const rocksdb_cache_t* cache);
 extern ROCKSDB_LIBRARY_API size_t
@@ -2046,7 +2046,8 @@ rocksdb_hyper_clock_cache_options_set_memory_allocator(
 extern ROCKSDB_LIBRARY_API rocksdb_cache_t* rocksdb_cache_create_hyper_clock(
     size_t capacity, size_t estimated_entry_charge);
 extern ROCKSDB_LIBRARY_API rocksdb_cache_t*
-rocksdb_cache_create_hyper_clock_opts(rocksdb_hyper_clock_cache_options_t*);
+rocksdb_cache_create_hyper_clock_opts(
+    const rocksdb_hyper_clock_cache_options_t*);
 
 /* DBPath */