[graph] Simple sparse graph implementation, essentially a sparse matrix with no values array

src/graph.h

@@ -0,0 +1,90 @@
+/*
+graph.h
+-------
+
+Graph stored as a compressed sparse row (CSR) matrix with no values.
+
+This is a specialization of sparse matrices suitable for cases
+where we only need to know that two nodes are connected and will
+typically be iterating row-by-row (get all edges for vertex v).
+By default it stores bipartite graphs
+
+Essentially this can be viewed as a sparse matrix where all
+of the non-zero values are 1.
+
+See sparse_matrix.h for more details.
+
+Currently we're not implementing edge types, graph traversal, etc.
+*/
+
+#ifndef GRAPH_H
+#define GRAPH_H
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "collections.h"
+#include "file_utils.h"
+#include "vector.h"
+
+typedef enum {
+    GRAPH_DIRECTED,
+    GRAPH_UNDIRECTED,
+    GRAPH_BIPARTITE
+} graph_type_t;
+
+typedef struct {
+    graph_type_t type;
+    uint32_t m;
+    uint32_t n;
+    bool fixed_rows;
+    uint32_array *indptr;
+    uint32_array *indices;
+} graph_t;
+
+
+graph_t *graph_new_dims(graph_type_t type, uint32_t m, uint32_t n, size_t nnz, bool fixed_rows);
+graph_t *graph_new(graph_type_t type);
+void graph_destroy(graph_t *self);
+
+void graph_set_size(graph_t *self);
+
+void graph_clear(graph_t *self);
+
+void graph_append_edge(graph_t *self, uint32_t col);
+void graph_append_edges(graph_t *self, uint32_t *col, size_t n);
+
+void graph_finalize_vertex(graph_t *self);
+
+bool graph_write(graph_t *self, FILE *f);
+graph_t *graph_read(FILE *f);
+
+#define graph_foreach_row(g, row_var, index_var, length_var, code) {            \
+    uint32_t _row_start = 0, _row_end = 0;                                      \
+    uint32_t *_indptr = g->indptr->a;                                           \
+    size_t _m = g->indptr->n - 1;                                               \
+                                                                                \
+    for (uint32_t _i = 0; _i < _m; _i++) {                                      \
+        (row_var) = _i;                                                         \
+        _row_start = _indptr[_i];                                               \
+        _row_end = _indptr[_i + 1];                                             \
+        (index_var) = _row_start;                                               \
+        (length_var) = _row_end - _row_start;                                   \
+        code;                                                                   \
+    }                                                                           \
+}
+
+#define graph_foreach(g, row_var, col_var, code) {                              \
+    uint32_t *_indices = g->indices->a;                                         \
+    uint32_t _index, _length;                                                   \
+    graph_foreach_row(g, row_var, _index, _length, {                            \
+        if (_length == 0) continue;                                             \
+        for (uint32_t _j = _index; _j < _index + _length; _j++) {               \
+            (col_var) = _indices[_j];                                           \
+            code;                                                               \
+        }                                                                       \
+    })                                                                          \
+}   
+
+#endif