add abi stable way to query the size of index_t (#1064)

* add abi stable way to query the size of index_t

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project aspires to adhere to [Semantic Versioning](https://semver.org/s
 
 ## Unreleased
 
+### Added
+#### General
+- Added C++ `int DataType::sizeof_index_t()` and C `int conduit_datatype_sizeof_index_t()` methods to provide a stable ABI to determine configured size (number of bytes) of Conduit's index_t type.
+
 ### Fixed
 
 #### General

src/libs/conduit/c/conduit_datatype.h

@@ -32,6 +32,8 @@ extern "C" {
 struct conduit_datatype_impl;
 typedef struct conduit_datatype_impl  conduit_datatype;
 
+CONDUIT_API int conduit_datatype_sizeof_index_t();
+
 CONDUIT_API conduit_index_t conduit_datatype_id(const conduit_datatype *cdatatype);
 CONDUIT_API char* conduit_datatype_name(const conduit_datatype *cdatatype);
 CONDUIT_API void conduit_datatype_name_destroy(char *name);

src/libs/conduit/c/conduit_datatype_c.cpp

@@ -29,6 +29,11 @@ extern "C" {
 
 using namespace conduit;
 
+int conduit_datatype_sizeof_index_t()
+{
+    return DataType::sizeof_index_t();
+}
+
 conduit_index_t conduit_datatype_id(const conduit_datatype *cdatatype)
 {
     return cpp_datatype_ref(cdatatype).id();

src/libs/conduit/conduit_bitwidth_style_types.h.in

@@ -338,8 +338,10 @@ typedef conduit_int64 conduit_index64_t;
 /// use a 64-bit index, unless CONDUIT_INDEX_32 is defined.
 #ifdef CONDUIT_INDEX_32
 typedef conduit_index32_t conduit_index_t;
+#define CONDUIT_SIZEOF_INDEX_T 4
 #else
 typedef conduit_index64_t conduit_index_t;
+#define CONDUIT_SIZEOF_INDEX_T 8
 #endif 
 
 //-----------------------------------------------------------------------------

src/libs/conduit/conduit_core.cpp

@@ -85,7 +85,18 @@ about(Node &n)
     n["system"] = CONDUIT_SYSTEM_TYPE;
     n["install_prefix"] = CONDUIT_INSTALL_PREFIX;
     n["license"] = CONDUIT_LICENSE_TEXT;
-
+
+    Node &nt = n["index_t_typemap"];
+
+    // index_t
+#ifdef CONDUIT_INDEX_32
+    nt["index_t"] = "int32";
+    nt["sizeof_index_t"] = 4;
+#else
+    nt["index_t"] = "int64";
+    nt["sizeof_index_t"] = 8;
+#endif
+
     // Type Info Map
     Node &nn = n["native_typemap"];
 
@@ -152,6 +163,14 @@ about(Node &n)
     nn["float64"] = "<unmapped>";
 #endif
 
+    // index_t
+#ifdef CONDUIT_INDEX_32
+    nn["index_t"] = CONDUIT_INT32_NATIVE_NAME;
+#else
+    nn["index_t"] = CONDUIT_INT64_NATIVE_NAME;
+#endif
+
+
 }
 
 

src/libs/conduit/conduit_data_type.cpp

@@ -61,24 +61,38 @@ namespace conduit
 {
 
 
+//-----------------------------------------------------------------------------
 DataType 
 DataType::empty()
 {
     return DataType(EMPTY_ID);
 }
 
+//-----------------------------------------------------------------------------
 DataType 
 DataType::object()
 {
     return DataType(OBJECT_ID);
 }
 
+//-----------------------------------------------------------------------------
 DataType 
 DataType::list()
 {
     return DataType(LIST_ID);
 }
 
+//-----------------------------------------------------------------------------
+int
+DataType::sizeof_index_t()
+{
+#ifdef CONDUIT_INDEX_32
+    return 4;
+#else
+    return 8;
+#endif
+}
+
 
 
 //-----------------------------------------------------------------------------

src/libs/conduit/conduit_data_type.hpp

@@ -71,6 +71,15 @@ class CONDUIT_API DataType
         CHAR8_STR_ID = CONDUIT_CHAR8_STR_ID  // char8 string (incore c-string)
     } TypeID;
 
+//-----------------------------------------------------------------------------
+/// DataType::sizeof_index_t() provides an ABI stable way to probe the size
+/// of index_t.
+///
+/// index_t is fundamental to sizes in Conduit's interface,
+/// it is usually 64-bits but there is still a 32-bit option.
+//-----------------------------------------------------------------------------
+    static int sizeof_index_t();
+
 //-----------------------------------------------------------------------------
 // -- begin conduit::DataType Objects Constructor Helpers --
 //-----------------------------------------------------------------------------
@@ -86,7 +95,7 @@ class CONDUIT_API DataType
     static DataType empty();
     static DataType object();
     static DataType list();
-    
+
 //-----------------------------------------------------------------------------
 // -- end conduit::DataType Objects Constructor Helpers --
 //-----------------------------------------------------------------------------

src/tests/conduit/c/CMakeLists.txt

@@ -9,7 +9,8 @@
 set(C_TESTS
     t_c_conduit_smoke
     t_c_conduit_node
-    t_c_conduit_node_set)
+    t_c_conduit_node_set
+    t_c_conduit_datatype)
 
 ################################
 # Add our tests

src/tests/conduit/c/t_c_conduit_datatype.cpp

@@ -0,0 +1,28 @@
+// Copyright (c) Lawrence Livermore National Security, LLC and other Conduit
+// Project developers. See top-level LICENSE AND COPYRIGHT files for dates and
+// other details. No copyright assignment is required to contribute to Conduit.
+
+//-----------------------------------------------------------------------------
+///
+/// file: t_c_conduit_datatype.cpp
+///
+//-----------------------------------------------------------------------------
+
+#include "conduit.h"
+
+#include <stdio.h>
+#include "gtest/gtest.h"
+
+//-----------------------------------------------------------------------------
+TEST(c_conduit_datatype, sizeof_index_t)
+{
+    int sz_it = conduit_datatype_sizeof_index_t();
+
+#ifdef CONDUIT_INDEX_32
+    EXPECT_EQ(sz_it,4);
+#else
+    EXPECT_EQ(sz_it,8);
+#endif
+
+}
+

src/tests/conduit/t_conduit_datatype_tests.cpp

@@ -737,3 +737,36 @@ TEST(dtype_tests,dtype_comparison_checks)
         }
     }
 }
+
+
+//-----------------------------------------------------------------------------
+TEST(dtype_tests,sizeof_index_t)
+{
+    int sz_it = DataType::sizeof_index_t();
+
+#ifdef CONDUIT_INDEX_32
+    EXPECT_EQ(sz_it,4);
+#else
+    EXPECT_EQ(sz_it,8);
+#endif
+
+    EXPECT_EQ(sz_it,CONDUIT_SIZEOF_INDEX_T);
+
+    // also check about entries
+    Node n_about;
+    conduit::about(n_about);
+
+
+    Node &n_it_info = n_about["index_t_typemap"];
+    EXPECT_EQ(sz_it,n_it_info["sizeof_index_t"].to_int());
+
+    if(sz_it == 4)
+    {
+        EXPECT_EQ(n_it_info["index_t"].as_string(),"int32");
+    }
+    else // if(sz_it == 8)
+    {
+        EXPECT_EQ(n_it_info["index_t"].as_string(),"int64");
+    }
+
+}