简介

可以说，前面分析的OTA升级的各部分代码都是在搭一个舞台，而主角现在终于登场，它就是updater. Google的代码架构设计非常好，各部分尽量松耦合。前面介绍升级脚本时，可知有两种类型的脚本，amend& edify. 他们各自对应一个updater. 这里，我们主要关注新的edify的updater.

源码文件

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.
├── Android.mk
├── blockimg.c
├── blockimg.h
├── install.c
├── install.h
├── updater.c
└── updater.h

入口函数 main

  1. 处理version 参数
  2. 获取命令管道

    Set up the pipe for sending commands back to the parent process.

  3. 读入脚本

    mzFindZipEntry(&za, SCRIPT_NAME);

  4. 注册语句处理函数

    Configure edify’s functions.

  5. 解析脚本命令

    Parse the script.

  6. 执行脚本

    核心函数是 Evaluate。它会调用其他callback函数，而这些callback函数又会调用Evaluate去解析不同的脚本片段。

主流程的代码非常简单,因为细节隐藏在那些 callback 函数里。

callback函数

  1. RegisterBuiltins
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void RegisterBuiltins() {
    RegisterFunction("ifelse", IfElseFn);
    RegisterFunction("abort", AbortFn);
    RegisterFunction("assert", AssertFn);
    RegisterFunction("concat", ConcatFn);
    RegisterFunction("is_substring", SubstringFn);
    RegisterFunction("stdout", StdoutFn);
    RegisterFunction("sleep", SleepFn);
    RegisterFunction("less_than_int", LessThanIntFn);
    RegisterFunction("greater_than_int", GreaterThanIntFn);
}

  1. RegisterInstallFunctions

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    void RegisterInstallFunctions() {
        RegisterFunction("mount", MountFn);
        RegisterFunction("is_mounted", IsMountedFn);
        RegisterFunction("unmount", UnmountFn);
        RegisterFunction("format", FormatFn);
        RegisterFunction("show_progress", ShowProgressFn);
        RegisterFunction("set_progress", SetProgressFn);
        RegisterFunction("delete", DeleteFn);
        RegisterFunction("delete_recursive", DeleteFn);
        RegisterFunction("package_extract_dir", PackageExtractDirFn);
        RegisterFunction("package_extract_file", PackageExtractFileFn);
        RegisterFunction("symlink", SymlinkFn);
        // Usage:
        //   set_metadata("filename", "key1", "value1", "key2", "value2", ...)
        // Example:
        //   set_metadata("/system/bin/netcfg", "uid", 0, "gid", 3003, "mode", 02750, "selabel", "u:object_r:system_file:s0", "capabilities", 0x0);
        RegisterFunction("set_metadata", SetMetadataFn);
        // Usage:
        //   set_metadata_recursive("dirname", "key1", "value1", "key2", "value2", ...)
        // Example:
        //   set_metadata_recursive("/system", "uid", 0, "gid", 0, "fmode", 0644, "dmode", 0755, "selabel", "u:object_r:system_file:s0", "capabilities", 0x0);
        RegisterFunction("set_metadata_recursive", SetMetadataFn);
        RegisterFunction("getprop", GetPropFn);
        RegisterFunction("file_getprop", FileGetPropFn);
        RegisterFunction("write_raw_image", WriteRawImageFn);
        RegisterFunction("write_raw_parameter_image", WriteRawParameterImageFn);
        RegisterFunction("clear_misc_command", ClearMiscCommandFn);
        RegisterFunction("apply_patch", ApplyPatchFn);
        RegisterFunction("apply_patch_check", ApplyPatchCheckFn);
        RegisterFunction("apply_patch_space", ApplyPatchSpaceFn);
        RegisterFunction("wipe_block_device", WipeBlockDeviceFn);
        RegisterFunction("read_file", ReadFileFn);
        RegisterFunction("sha1_check", Sha1CheckFn);
        RegisterFunction("rename", RenameFn);
        RegisterFunction("wipe_cache", WipeCacheFn);
        RegisterFunction("ui_print", UIPrintFn);
        RegisterFunction("run_program", RunProgramFn);
        RegisterFunction("reboot_now", RebootNowFn);
        RegisterFunction("get_stage", GetStageFn);
        RegisterFunction("set_stage", SetStageFn);
        RegisterFunction("enable_reboot", EnableRebootFn);
        RegisterFunction("tune2fs", Tune2FsFn);
    }

  2. RegisterBlockImageFunctions

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void RegisterBlockImageFunctions() {
    RegisterFunction("block_image_verify", BlockImageVerifyFn);
    RegisterFunction("block_image_update", BlockImageUpdateFn);
    RegisterFunction("range_sha1", RangeSha1Fn);
}

  1. FinishRegistration

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    void FinishRegistration() {
        qsort(fn_table, fn_entries, sizeof(NamedFunction), fn_entry_compare);
    }