diff --git a/vpxstats.c b/vpxstats.c
new file mode 100644
index 0000000..70cea3e
--- /dev/null
+++ b/vpxstats.c
@@ -0,0 +1,135 @@
+/*
+ *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "./vpxstats.h"
+
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "./tools_common.h"
+
+int stats_open_file(stats_io_t *stats, const char *fpf, int pass) {
+  int res;
+  stats->pass = pass;
+
+  if (pass == 0) {
+    stats->file = fopen(fpf, "wb");
+    stats->buf.sz = 0;
+    stats->buf.buf = NULL;
+    res = (stats->file != NULL);
+  } else {
+#if USE_POSIX_MMAP
+    struct stat stat_buf;
+    int fd;
+
+    fd = open(fpf, O_RDONLY);
+    stats->file = fdopen(fd, "rb");
+    fstat(fd, &stat_buf);
+    stats->buf.sz = stat_buf.st_size;
+    stats->buf.buf = mmap(NULL, stats->buf.sz, PROT_READ, MAP_PRIVATE, fd, 0);
+    res = (stats->buf.buf != NULL);
+#else
+    size_t nbytes;
+
+    stats->file = fopen(fpf, "rb");
+
+    if (fseek(stats->file, 0, SEEK_END))
+      fatal("First-pass stats file must be seekable!");
+
+    stats->buf.sz = stats->buf_alloc_sz = ftell(stats->file);
+    rewind(stats->file);
+
+    stats->buf.buf = malloc(stats->buf_alloc_sz);
+
+    if (!stats->buf.buf)
+      fatal("Failed to allocate first-pass stats buffer (%lu bytes)",
+            (unsigned int)stats->buf_alloc_sz);
+
+    nbytes = fread(stats->buf.buf, 1, stats->buf.sz, stats->file);
+    res = (nbytes == stats->buf.sz);
+#endif  /* USE_POSIX_MMAP */
+  }
+
+  return res;
+}
+
+int stats_open_mem(stats_io_t *stats, int pass) {
+  int res;
+  stats->pass = pass;
+
+  if (!pass) {
+    stats->buf.sz = 0;
+    stats->buf_alloc_sz = 64 * 1024;
+    stats->buf.buf = malloc(stats->buf_alloc_sz);
+  }
+
+  stats->buf_ptr = stats->buf.buf;
+  res = (stats->buf.buf != NULL);
+  return res;
+}
+
+void stats_close(stats_io_t *stats, int last_pass) {
+  if (stats->file) {
+    if (stats->pass == last_pass) {
+#if USE_POSIX_MMAP
+      munmap(stats->buf.buf, stats->buf.sz);
+#else
+      free(stats->buf.buf);
+#endif  /* USE_POSIX_MMAP */
+    }
+
+    fclose(stats->file);
+    stats->file = NULL;
+  } else {
+    if (stats->pass == last_pass)
+      free(stats->buf.buf);
+  }
+}
+
+void stats_write(stats_io_t *stats, const void *pkt, size_t len) {
+  if (stats->file) {
+    (void) fwrite(pkt, 1, len, stats->file);
+  } else {
+    if (stats->buf.sz + len > stats->buf_alloc_sz) {
+      size_t  new_sz = stats->buf_alloc_sz + 64 * 1024;
+      char   *new_ptr = realloc(stats->buf.buf, new_sz);
+
+      if (new_ptr) {
+        stats->buf_ptr = new_ptr + (stats->buf_ptr - (char *)stats->buf.buf);
+        stats->buf.buf = new_ptr;
+        stats->buf_alloc_sz = new_sz;
+      } else {
+        fatal("Failed to realloc firstpass stats buffer.");
+      }
+    }
+
+    memcpy(stats->buf_ptr, pkt, len);
+    stats->buf.sz += len;
+    stats->buf_ptr += len;
+  }
+}
+
+vpx_fixed_buf_t stats_get(stats_io_t *stats) {
+  return stats->buf;
+}
+
+double vp8_mse2psnr(double samples, double peak, double mse) {
+  const int kMaxPSNR = 100;
+  double psnr = kMaxPSNR;
+
+  if (mse > 0.0)
+    psnr = 10.0 * log10(peak * peak * samples / mse);
+
+  if (psnr > kMaxPSNR)
+    psnr = kMaxPSNR;
+
+  return psnr;
+}