Initial QSfera import

Server/vendor/github.com/blevesearch/go-faiss/index_flat.go

@@ -0,0 +1,56 @@
+package faiss
+
+/*
+#include <faiss/c_api/IndexFlat_c.h>
+#include <faiss/c_api/Index_c.h>
+*/
+import "C"
+import "unsafe"
+
+// IndexFlat is an index that stores the full vectors and performs exhaustive
+// search.
+type IndexFlat struct {
+	Index
+}
+
+// NewIndexFlat creates a new flat index.
+func NewIndexFlat(d int, metric int) (*IndexFlat, error) {
+	var idx faissIndex
+	if c := C.faiss_IndexFlat_new_with(
+		&idx.idx,
+		C.idx_t(d),
+		C.FaissMetricType(metric),
+	); c != 0 {
+		return nil, getLastError()
+	}
+	return &IndexFlat{&idx}, nil
+}
+
+// NewIndexFlatIP creates a new flat index with the inner product metric type.
+func NewIndexFlatIP(d int) (*IndexFlat, error) {
+	return NewIndexFlat(d, MetricInnerProduct)
+}
+
+// NewIndexFlatL2 creates a new flat index with the L2 metric type.
+func NewIndexFlatL2(d int) (*IndexFlat, error) {
+	return NewIndexFlat(d, MetricL2)
+}
+
+// Xb returns the index's vectors.
+// The returned slice becomes invalid after any add or remove operation.
+func (idx *IndexFlat) Xb() []float32 {
+	var size C.size_t
+	var ptr *C.float
+	C.faiss_IndexFlat_xb(idx.cPtr(), &ptr, &size)
+	return (*[1 << 30]float32)(unsafe.Pointer(ptr))[:size:size]
+}
+
+// AsFlat casts idx to a flat index.
+// AsFlat panics if idx is not a flat index.
+func (idx *IndexImpl) AsFlat() *IndexFlat {
+	ptr := C.faiss_IndexFlat_cast(idx.cPtr())
+	if ptr == nil {
+		panic("index is not a flat index")
+	}
+	return &IndexFlat{&faissIndex{ptr}}
+}