[graph] Builder for graphs not constructed in vertex-sorted order

src/graph_builder.h

@@ -0,0 +1,53 @@
+/*
+graph_builder.h
+---------------
+
+For graphs it's sometimes impractical to assume that the vertices
+will arrive in sorted order, which is required for constructing a
+compressed sparse row (CSR) matrix. This is simply a coordinate matrix
+(COO) style constructor where the rows/columns do not need to be
+ordered or unique.
+
+*/
+
+#ifndef GRAPH_BUILDER_H
+#define GRAPH_BUILDER_H
+
+#include "collections.h"
+#include "file_utils.h"
+#include "graph.h"
+
+
+typedef struct graph_edge {
+    uint32_t v1;
+    uint32_t v2;
+} graph_edge_t;
+
+VECTOR_INIT(graph_edge_array, graph_edge_t)
+
+
+typedef struct graph_builder {
+    graph_type_t type;
+    size_t m;
+    size_t n;
+    bool fixed_rows;
+    graph_edge_array *edges;
+} graph_builder_t;
+
+graph_builder_t *graph_builder_new(graph_type_t type, bool fixed_rows);
+/*
+Destroy the builder and return a graph.
+
+Note: remove_duplicates=true requires sorting the indices. Can only preserve
+edge ordering if we can guarantee there are no duplicates.
+*/
+graph_t *graph_builder_finalize(graph_builder_t *self, bool sort_edges, bool remove_duplicates);
+
+/*
+Add an edge. Order 
+
+Reflexive edges not allowed.
+*/
+void graph_builder_add_edge(graph_builder_t *self, uint32_t v1, uint32_t v2);
+
+#endif