Add the ability to clone and read binary indexes to the C API. (facebookresearch#3318)

Summary:
I noticed we have a pretty decent C API for binary indexes and please correct me if I'm wrong but we seem to be missing a couple of functions, like the ability to clone and read binary indexes. This PR provides those functions.

Pull Request resolved: facebookresearch#3318

Reviewed By: algoriddle

Differential Revision: D55469615

Pulled By: mdouze

fbshipit-source-id: 42e6f827d8b5ad6bc3efe989e47ede3aa06c1810

Author: aalekhpatel07

c_api/clone_index_c.cpp

@@ -14,6 +14,7 @@
 #include "macros_impl.h"
 
 using faiss::Index;
+using faiss::IndexBinary;
 
 int faiss_clone_index(const FaissIndex* idx, FaissIndex** p_out) {
     try {
@@ -22,3 +23,14 @@ int faiss_clone_index(const FaissIndex* idx, FaissIndex** p_out) {
     }
     CATCH_AND_HANDLE
 }
+
+int faiss_clone_index_binary(
+        const FaissIndexBinary* idx,
+        FaissIndexBinary** p_out) {
+    try {
+        auto out = faiss::clone_binary_index(
+                reinterpret_cast<const IndexBinary*>(idx));
+        *p_out = reinterpret_cast<FaissIndexBinary*>(out);
+    }
+    CATCH_AND_HANDLE
+}

c_api/clone_index_c.h

@@ -13,6 +13,7 @@
 #define FAISS_CLONE_INDEX_C_H
 
 #include <stdio.h>
+#include "IndexBinary_c.h"
 #include "Index_c.h"
 #include "faiss_c.h"
 
@@ -25,6 +26,9 @@ extern "C" {
 /** Clone an index. This is equivalent to `faiss::clone_index` */
 int faiss_clone_index(const FaissIndex*, FaissIndex** p_out);
 
+/** Clone a binary index. This is equivalent to `faiss::clone_index_binary` */
+int faiss_clone_index_binary(const FaissIndexBinary*, FaissIndexBinary** p_out);
+
 #ifdef __cplusplus
 }
 #endif

c_api/index_factory_c.cpp

@@ -15,7 +15,7 @@
 
 using faiss::Index;
 
-/** Build and index with the sequence of processing steps described in
+/** Build an index with the sequence of processing steps described in
  *  the string.
  */
 int faiss_index_factory(
@@ -29,3 +29,17 @@ int faiss_index_factory(
     }
     CATCH_AND_HANDLE
 }
+
+/** Build an index with the sequence of processing steps described in
+ *  the string.
+ */
+int faiss_index_binary_factory(
+        FaissIndexBinary** p_index,
+        int d,
+        const char* description) {
+    try {
+        *p_index = reinterpret_cast<FaissIndexBinary*>(
+                faiss::index_binary_factory(d, description));
+    }
+    CATCH_AND_HANDLE
+}

c_api/index_factory_c.h

@@ -11,14 +11,15 @@
 #ifndef FAISS_INDEX_FACTORY_C_H
 #define FAISS_INDEX_FACTORY_C_H
 
+#include "IndexBinary_c.h"
 #include "Index_c.h"
 #include "faiss_c.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/** Build and index with the sequence of processing steps described in
+/** Build an index with the sequence of processing steps described in
  *  the string.
  */
 int faiss_index_factory(
@@ -27,6 +28,14 @@ int faiss_index_factory(
         const char* description,
         FaissMetricType metric);
 
+/** Build a binary index with the sequence of processing steps described in
+ *  the string.
+ */
+int faiss_index_binary_factory(
+        FaissIndexBinary** p_index,
+        int d,
+        const char* description);
+
 #ifdef __cplusplus
 }
 #endif