Initial open sourcing of MuJoCo.

PiperOrigin-RevId: 450374687
Change-Id: Ie3225a46ce095fc28ae8e63c326a640261f562bb

src/engine/engine_file.c

@@ -0,0 +1,80 @@
+// Copyright 2022 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "engine/engine_file.h"
+
+#include <stdio.h>
+#include <limits.h>
+
+#include "engine/engine_util_errmem.h"
+
+void* mju_fileToMemory(const char* filename, int* filesize) {
+  // open file
+  *filesize = 0;
+  FILE* fp = fopen(filename, "rb");
+  if (!fp) {
+    return NULL;
+  }
+
+  // find size
+  if (fseek(fp, 0, SEEK_END) != 0) {
+    fclose(fp);
+    mju_warning_s("Failed to calculate size for '%s'", filename);
+    return NULL;
+  }
+
+  // ensure file size fits in int
+  long long_filesize = ftell(fp);
+  if (long_filesize > INT_MAX) {
+    fclose(fp);
+    mju_warning_s("File size over 2GB is not supported. File: '%s'", filename);
+    return NULL;
+  } else if (long_filesize < 0) {
+    fclose(fp);
+    mju_warning_s("Failed to calculate size for '%s'", filename);
+    return NULL;
+  }
+  *filesize = long_filesize;
+
+  // go back to start of file
+  if (fseek(fp, 0, SEEK_SET) != 0) {
+    fclose(fp);
+    mju_warning_s("Read error while reading '%s'", filename);
+    return NULL;
+  }
+
+  // allocate and read
+  void* buffer = mju_malloc(*filesize);
+  if (!buffer) {
+    mju_error("mjFileToMemory: could not allocate memory");
+  }
+  size_t bytes_read = fread(buffer, 1, *filesize, fp);
+
+  // check that read data matches file size
+  if (bytes_read != *filesize) { // SHOULD NOT OCCUR
+    if (ferror(fp)) {
+      fclose(fp);
+      mju_free(buffer);
+      *filesize = 0;
+      mju_warning_s("Read error while reading '%s'", filename);
+      return NULL;
+    } else if (feof(fp)) {
+      *filesize = bytes_read;
+    }
+  }
+
+  // close file, return contents
+  fclose(fp);
+  return buffer;
+}