1 files changed, 152 insertions, 0 deletions
diff --git a/src/km-rand-path.c b/src/km-rand-path.c
new file mode 100644
index 0000000..6597038
--- /dev/null
+++ b/src/km-rand-path.c
@@ -0,0 +1,152 @@
+#include <stdbool.h> // bool
+#include <string.h> // memset()
+#include <stdio.h> // fopen()
+#include "util.h"
+#include "km.h"
+
+#define MAX_BUF_ITEMS (1 << 20)
+
+typedef struct {
+  FILE *fh;
+  size_t ofs;
+  uint64_t buf[MAX_BUF_ITEMS];
+} ctx_t;
+
+static inline bool
+refill(
+  ctx_t * const ctx
+) {
+  ctx->ofs = 0;
+  // D("reading %zu bytes", sizeof(ctx->buf));
+  return !!fread(ctx->buf, sizeof(ctx->buf), 1, ctx->fh);
+}
+
+static bool
+next(
+  ctx_t * const ctx,
+  uint64_t * const r
+) {
+  if ((ctx->ofs >= MAX_BUF_ITEMS - 1) && !refill(ctx)) {
+    // return failure
+    return false;
+  }
+
+  // get next value, increment offset
+  *r = ctx->buf[ctx->ofs];
+  ctx->ofs++;
+
+  // return success
+  return true;
+}
+
+// get N get_floats
+static bool
+on_get_floats(
+  km_rand_t * const rs,
+  const size_t num_vals,
+  float * const vals
+) {
+  ctx_t * const ctx = rs->data;
+
+  // generate results
+  for (size_t i = 0; i < num_vals; i++) {
+    uint64_t v;
+
+    if (!next(ctx, &v)) {
+      // return failure
+      return false;
+    }
+
+    // add value
+    vals[i] = 1.0 * v / RAND_MAX;
+  }
+
+  // return success
+  return true;
+}
+
+// fill sizes callback for system random source
+static bool
+on_get_sizes(
+  km_rand_t * const rs,
+  const size_t num_vals,
+  size_t * const vals
+) {
+  ctx_t * const ctx = rs->data;
+
+  // generate results
+  for (size_t i = 0; i < num_vals; i++) {
+    uint64_t v;
+
+    if (!next(ctx, &v)) {
+      // return failure
+      return false;
+    }
+
+    // add value
+    vals[i] = v;
+  }
+
+  // return success
+  return true;
+}
+
+static void
+on_fini(
+  km_rand_t * const rs
+) {
+  ctx_t * const ctx = rs->data;
+
+  // close file
+  fclose(ctx->fh);
+
+  // free context
+  free(ctx);
+
+  rs->data = NULL;
+}
+
+// path random source callbacks
+static const km_rand_cbs_t
+PATH_RAND_CBS = {
+  .get_floats = on_get_floats,
+  .get_sizes  = on_get_sizes,
+  .fini       = on_fini,
+};
+
+// init system random source (uses system rand())
+bool
+km_rand_init_path(
+  km_rand_t * const rs,
+  const char * const path
+) {
+  // open file
+  FILE *fh = fopen(path, "rb");
+  if (!fh) {
+    // return failure
+    return false;
+  }
+
+  // alloc context
+  ctx_t * const ctx = malloc(sizeof(ctx_t));
+  if (!ctx) {
+    // return failure
+    return false;
+  }
+
+  // populate context
+  ctx->fh = fh;
+
+  // fill buffer
+  if (!refill(ctx)) {
+    // return failure
+    return false;
+  }
+
+  // populate random source
+  rs->cbs = &PATH_RAND_CBS;
+  rs->data = ctx;
+
+  // return success
+  return true;
+}