所谓的非标准头文件就是指那些在aosp外不曾见过的文件或者一些库的用法。
string8
这个在aosp中尤其常见，例如:
String8 argv_String;
for (int i = 0; i < argc; ++i) {
argv_String.append("\"");
argv_String.append(argv[i]);
argv_String.append("\" ");
}
ALOGV("app_process main with argv: %s", argv_String.string());
String8 的定义在 system/core/libutils/include/utils/String8.h 中，为什么不用std呢？从我看代码的了解中 看到String8照顾了UTF-8的特性， 而且其UTF-8的值不能超过0x10FFFFF,
处理路径
/*
* Set the filename field to a specific value.
*
* Normalizes the filename, removing a trailing '/' if present.
*/
void setPathName(const char* name);
void setPathName(const char* name, size_t numChars);
/*
* Remove the last (file name) component, leaving just the directory
* name.
*
* "/tmp/foo/bar.c" --> "/tmp/foo"
* "/tmp" --> "" // ????? shouldn't this be "/" ???? XXX
* "bar.c" --> ""
*/
String8 getPathDir(void) const;
/*
* Return the filename extension. This is the last '.' and any number
* of characters that follow it. The '.' is included in case we
* decide to expand our definition of what constitutes an extension.
*
* "/tmp/foo/bar.c" --> ".c"
* "/tmp" --> ""
* "/tmp/foo.bar/baz" --> ""
* "foo.jpeg" --> ".jpeg"
* "foo." --> ""
*/
String8 getPathExtension(void) const;
/*
* Return the path without the extension. Rules for what constitutes
* an extension are described in the comment for getPathExtension().
*
* "/tmp/foo/bar.c" --> "/tmp/foo/bar"
*/
String8 getBasePath(void) const
...
简单摘抄了一点了，可以看出，aosp自己实现了一些有助于操作的函数，尤其对于一个涉及路径文件的字符串操作。