android源码分析2--5.0 PackageExtractFileFn

// package_extract_file(package_path, destination_path)

//   or

// package_extract_file(package_path)

//   to return the entire contents of the file as the result of this

//   function (the char* returned is actually a FileContents*).

package_extract_file("system.transfer.list")

package_extract_file("patch/boot.img.p")

package_extract_file("META-INF/com/miui/miui_update", "/cache/miui_update");

run_program("/cache/miui_update")

Value* PackageExtractFileFn(const char* name, State* state,

                           int argc, Expr* argv[]) {

// argc就代表脚本中package_extract_file函数的参数个数

    if (argc < 1 || argc > 2) {

        return ErrorAbort(state, "%s() expects 1 or 2 args, got %d",

                          name, argc);

    }

    bool success = false;

  // 在updater开始将updater_info保存到了state->cookie中

UpdaterInfo updater_info;

updater_info.cmd_pipe = cmd_pipe;

updater_info.package_zip = &za;

updater_info.version = atoi(version);

updater_info.package_zip_addr = map.addr;

updater_info.package_zip_len = map.length;

State state;

state.cookie = &updater_info;

    UpdaterInfo* ui = (UpdaterInfo*)(state->cookie);

 

    if (argc == 2) {

        // The two-argument version extracts to a file.

 

        ZipArchive* za = ((UpdaterInfo*)(state->cookie))->package_zip;

 

        char* zip_path;

        char* dest_path;

        if (ReadArgs(state, argv, 2, &zip_path, &dest_path) < 0) return NULL;

 

        const ZipEntry* entry = mzFindZipEntry(za, zip_path);

        if (entry == NULL) {

            printf("%s: no %s in package\n", name, zip_path);

            goto done2;

        }

 

        FILE* f = fopen(dest_path, "wb");

        if (f == NULL) {

            printf("%s: can't open %s for write: %s\n",

                    name, dest_path, strerror(errno));

            goto done2;

        }

        success = mzExtractZipEntryToFile(za, entry, fileno(f));

        fclose(f);

 

      done2:

        free(zip_path);

        free(dest_path);

        return StringValue(strdup(success ? "t" : ""));

    } else {

        // The one-argument version returns the contents of the file

        // as the result.

 

        char* zip_path;

        Value* v = malloc(sizeof(Value));

        v->type = VAL_BLOB;

        v->size = -1;

        v->data = NULL;

 

// 调用ReadArgs从 package_extract_file("system.transfer.list")中取出system.transfer.list作为zip_path

        if (ReadArgs(state, argv, 1, &zip_path) < 0) return NULL;

 

        ZipArchive* za = ((UpdaterInfo*)(state->cookie))->package_zip;

//从映射到内存中的zip压缩包中找到zip_path

        const ZipEntry* entry = mzFindZipEntry(za, zip_path);

        if (entry == NULL) {

            printf("%s: no %s in package\n", name, zip_path);

            goto done1;

        }

 

        v->size = mzGetZipEntryUncompLen(entry);

        v->data = malloc(v->size);

        if (v->data == NULL) {

            printf("%s: failed to allocate %ld bytes for %s\n",

                    name, (long)v->size, zip_path);

            goto done1;

        }

 //将zip_path（system.transfer.list）的内容从zip包中解压缩到v->data中

* Uncompress "pEntry" in "pArchive" to buffer, which must be large

* enough to hold mzGetZipEntryUncomplen(pEntry) bytes.

*/

boolmzExtractZipEntryToBuffer(const ZipArchive *pArchive,

const ZipEntry *pEntry, unsigned char *buffer)

        success = mzExtractZipEntryToBuffer(za, entry,

                                            (unsigned char *)v->data);

 

      done1:

        free(zip_path);

        if (!success) {

            free(v->data);

//如果mzExtractZipEntryToBuffer执行失败就将v->data重新设为空

            v->data = NULL;

            v->size = -1;

        }

        return v;

    }

}