Change SkStream.

src/ports/SkOSFile_posix.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkOSFile.h"
+
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+typedef struct {
+    dev_t dev;
+    ino_t ino;
+} SkFILEID;
+
+static bool sk_ino(SkFILE* a, SkFILEID* id) {
+    int fd = fileno((FILE*)a);
+    if (fd < 0) {
+        return 0;
+    }
+    struct stat status;
+    if (0 != fstat(fd, &status)) {
+        return 0;
+    }
+    id->dev = status.st_dev;
+    id->ino = status.st_ino;
+    return true;
+}
+
+bool sk_fidentical(SkFILE* a, SkFILE* b) {
+    SkFILEID aID, bID;
+    return sk_ino(a, &aID) && sk_ino(b, &bID)
+           && aID.ino == bID.ino
+           && aID.dev == bID.dev;
+}
+
+void sk_fmunmap(const void* addr, size_t length) {
+    munmap(const_cast<void*>(addr), length);
+}
+
+void* sk_fmmap(SkFILE* f, size_t* size) {
+    size_t fileSize = sk_fgetsize(f);
+    if (0 == fileSize) {
+        return NULL;
+    }
+
+    int fd = fileno((FILE*)f);
+    if (fd < 0) {
+        return NULL;
+    }
+
+    void* addr = mmap(NULL, fileSize, PROT_READ, MAP_PRIVATE, fd, 0);
+    if (MAP_FAILED == addr) {
+        return NULL;
+    }
+
+    *size = fileSize;
+    return addr;
+}