Julia 0.5.0 公布了,此番更新富含了无数新的语言特征。

Inside OTA Packages

The system builds the updater binary from bootable/recovery/updater
and uses it in an OTA package.

The package itself is a .zip file (ota_update.zip,
incremental_ota_update.zip) that contains the executable binary
META-INF/com/google/android/update-binary.

Updater contains several builtin functions and an interpreter for an
extensible scripting language (edify) that supports commands for
typical update-related tasks. Updater looks in the package .zip file for
a script in the file META-INF/com/google/android/updater-script.

Note: Using the edify script and/or builtin functions is not a
common activity, but can be helpful if you need to debug the update
file.

Julia是叁个新的高品质动态高档编程语言。语法和任何编制程序语言形似,易于其余语言顾客学习。Julia拥有丰硕的函数库,提供了数字精度、精致的升幅器(sophisticated
amplifier)和布满式并行运生势势。大旨函数库等大大多库是由Julia编写,但也用成熟的C和FORTRAN库来处理线性代数、随机数发生和字
符串管理等主题素材。Julia语言可定义函数並且依据客户自定义的参数类型组合再张开重载。

Edify syntax


An edify script is a single expression in which all values are strings.
Empty strings are false in a Boolean context and all other strings are
true. Edify supports the following operators (with the usual
meanings):

(expr )
 expr + expr  # string concatenation, not integer addition
 expr == expr
 expr != expr
 expr && expr
 expr || expr
 ! expr
 if expr then expr endif
 if expr then expr else expr endif
 function_name(expr, expr,...)
 expr; expr

Any string of the characters a-z, A-Z, 0-9, _, :, /, . that isn’t a
reserved word is considered a string literal. (Reserved words are if
else
then endif.) String literals may also appear in
double-quotes; this is how to create values with whitespace and other
characters not in the above set. n, t, “, and \ serve as
escapes within quoted strings, as does x##.

The && and || operators are short-circuiting; the right side is not
evaluated if the logical result is determined by the left side. The
following are equivalent:

e1 && e2
if e1 then e2 endif

The ; operator is a sequence point; it means to evaluate first the left
side and then the right side. Its value is the value of the right-side
expression. A semicolon can also appear after an expression, so the
effect simulates C-style statements:

prepare();
do_other_thing("argument");
finish_up();

局地更新内容如下:

Built-in functions


Most update functionality is contained in the functions available for
execution by scripts. (Strictly speaking these are macros rather than
functions in the Lisp sense, since they need not evaluate all of their
arguments.) Unless otherwise noted, functions return true on success
and false on error. If you want errors to abort execution of the
script, use the abort() and/or assert() functions. The set of
functions available in updater can also be extended to provide
device-specific
functionality.

abort([msg])
Aborts execution of the script immediately, with the optional msg. If
the user has turned on text display, msg appears in the recovery log
and on-screen.

assert(expr[, expr, ...])
Evaluates each expr in turn. If any is false, immediately aborts
execution with the message “assert failed” and the source text of the
failed expression.

apply_patch(src_file, tgt_file, tgt_sha1, tgt_size, patch1_sha1, patch1_blob, [...])
Applies a binary patch to the src_file to produce the tgt_file .
If the desired target is the same as the source, pass “-” for
tgt_file . tgt_sha1 and tgt_size are the expected final SHA1
hash and size of the target file. The remaining arguments must come in
pairs: a SHA1 hash (a 40-character hex string) and a blob. The blob is
the patch to be applied when the source file’s current contents have the
given SHA1.

The patching is done in a safe manner that guarantees the target file
either has the desired SHA1 hash and size, or it is untouched—it will
not be left in an unrecoverable intermediate state. If the process is
interrupted during patching, the target file may be in an intermediate
state; a copy exists in the cache partition so restarting the update can
successfully update the file.

Special syntax is supported to treat the contents of Memory Technology
Device (MTD) partitions as files, allowing patching of raw partitions
such as boot. To read an MTD partition, you must know how much data you
want to read since the partition does not have an end-of-file notion.
You can use the string “MTD:partition:size_1:sha1_1:size_2:
sha1_2” as a filename to read the given partition. You must specify
at least one (size, sha-1) pair; you can specify more than one if
there are multiple possibilities for what you expect to read.

apply_patch_check(filename, sha1[, sha1, ...])
Returns true if the contents of filename or the temporary copy in the
cache partition (if present) have a SHA1 checksum equal to one of the
given sha1 values. sha1 values are specified as 40 hex digits. This
function differs from sha1_check(read_file(filename), sha1 [, ...]) in
that it knows to check the cache partition copy, so
apply_patch_check() will succeed even if the file was corrupted by an
interrupted apply_patch() update.

apply_patch_space(bytes)
Returns true if at least bytes of scratch space is available for
applying binary patches.

concat(expr[, expr, ...])
Evaluates each expression and concatenates them. The + operator is
syntactic sugar for this function in the special case of two arguments
(but the function form can take any number of expressions). The
expressions must be strings; it can’t concatenate blobs.

delete([filename, ...])
Deletes all the filenames listed. Returns the number of files
successfully deleted.

delete_recursive([dirname, ...])
Recursively deletes dirnames and all their contents. Returns the
number of directories successfully deleted.

file_getprop(filename, key)
Reads the given filename, interprets it as a properties file (e.g.
/system/build.prop), and returns the value of the given key , or the
empty string if key is not present.

format(fs_type, partition_type, location, fs_size, mount_point)
Reformats a given partition. Supported partition types:

  • fs_type=”yaffs2″ and partition_type=”MTD”. Location must be the
    name of the MTD partition; an empty yaffs2 filesystem is constructed
    there. Remaining arguments are unused.
  • fs_type=”ext4″ and partition_type=”EMMC”. Location must be the
    device file for the partition. An empty ext4 filesystem is
    constructed there. If fs_size is zero, the filesystem takes up
    the entire partition. If fs_size is a positive number, the
    filesystem takes the first fs_size bytes of the partition. If
    fs_size is a negative number, the filesystem takes all except the
    last |fs_size| bytes of the partition.
  • fs_type=”f2fs” and partition_type=”EMMC”. Location must be the
    device file for the partition. fs_size must be a non-negative
    number. If fs_size is zero, the filesystem takes up the entire
    partition. If fs_size is a positive number, the filesystem takes
    the first fs_size bytes of the partition.
  • mount_point should be the future mount point for the filesystem.

getprop(key)
Returns the value of system property key (or the empty string, if it’s
not defined). The system property values defined by the recovery
partition are not necessarily the same as those of the main system. This
function returns the value in recovery.

greater_than_int(a, b)
Returns true if and only if (iff) a (interpreted as an integer) is
greater than b (interpreted as an integer).

ifelse(cond, e1[, e2])
Evaluates cond, and if it is true evaluates and returns the value of
e1, otherwise it evaluates and returns e2 (if present). The “if …
else … then … endif” construct is just syntactic sugar for this
function.

is_mounted(mount_point)
Returns true iff there is a filesystem mounted at mount_point.

is_substring(needle, haystack)
Returns true iff needle is a substring of haystack.

less_than_int(a, b)
Returns true iff a (interpreted as an integer) is less than b
(interpreted as an integer).

mount(fs_type, partition_type, name, mount_point)
Mounts a filesystem of fs_type at mount_point. partition_type
must be one of:

  • MTD. Name is the name of an MTD partition (e.g., system,
    userdata; see /proc/mtd on the device for a complete list).
  • EMMC.

Recovery does not mount any filesystems by default (except the SD card
if the user is doing a manual install of a package from the SD card);
your script must mount any partitions it needs to modify.

package_extract_dir(package_dir, dest_dir)
Extracts all files from the package underneath package_dir and writes
them to the corresponding tree beneath dest_dir. Any existing files
are overwritten.

package_extract_file(package_file[, dest_file])
Extracts a single package_file from the update package and writes it
to dest_file, overwriting existing files if necessary. Without the
dest_file argument, returns the contents of the package file as a
binary blob.

read_file(filename)
Reads filename and returns its contents as a binary blob.

rename(src_filename, tgt_filename)
Renames src_filename to tgt_filename. It automatically creates the
necessary directories for the tgt_filename. Example:
rename("system/app/Hangouts/Hangouts.apk", "system/priv-app/Hangouts/Hangouts.apk").

run_program(path[, arg, ...])
Executes the binary at path, passing args. Returns the program’s
exit status.

set_metadata(filename, key1, value1[, key2 , value2, ...])
Sets the keys of the given filename to values. For example:
set_metadata("/system/bin/netcfg", "uid", 0, "gid", 3003, "mode", 02750, "selabel", "u:object_r:system_file:s0", "capabilities", 0x0).

set_metadata_recursive(dirname, key1, value1[, key2, value2, ...])
Recursively sets the keys of the given dirname and all its children to
values. For example:
set_metadata_recursive("/system", "uid", 0, "gid", 0, "fmode", 0644, "dmode", 0755, "selabel", "u:object_r:system_file:s0", "capabilities", 0x0).

set_progress(frac)
Sets the position of the progress meter within the chunk defined by the
most recent show_progress() call. frac must be in the range [0.0,
1.0]. The progress meter never moves backwards; attempts to make it do
so are ignored.

sha1_check(blob[, sha1])
The blob argument is a blob of the type returned by read_file() or
the one-argument form of package_extract_file(). With no sha1
arguments, this function returns the SHA1 hash of the blob (as a
40-digit hex string). With one or more sha1 arguments, this function
returns the SHA1 hash if it equals one of the arguments, or the empty
string if it does not equal any of them.

show_progress(frac, secs)
Advances the progress meter over the next frac of its length over the
secs seconds (must be an integer). secs may be 0, in which case the
meter is not advanced automatically but by use of the set_progress()
function defined above.

sleep(secs)
Sleeps for secs seconds (must be an integer).

stdout(expr[, expr, ...])
Evaluates each expression and dumps its value to stdout. Useful for
debugging.

symlink(target[, source, ...])
Creates all sources as symlinks to target.

tune2fs(device[, arg, …])
Adjusts tunable parameters args on device.

ui_print([text, ...])
Concatenates all text arguments and prints the result to the UI (where
it will be visible if the user has turned on the text display).

unmount(mount_point)
Unmounts the filesystem mounted at mount_point.

wipe_block_device(block_dev, len)
Wipes the len bytes of the given block device block_dev.

wipe_cache()
Causes the cache partition to be wiped at the end of a successful
installation.

write_raw_image(filename_or_blob, partition)
Writes the image in filename_or_blob to the MTD partition.
filename_or_blob can be a string naming a local file or a
blob-valued argument containing the data to write. To copy a file from
the OTA package to a partition, use:
write_raw_image(package_extract_file("zip_filename"), "partition_name");

Note: Prior to Android 4.1, only filenames were accepted, so to
accomplish this the data first had to be unzipped into a temporary local
file.

  • Generator expressions: `f(i) for i in 1:n` ([#4470]). This
    returns an iterator that computes the specified values on demand.
    This is useful for computing, e.g.

  • `sum(f(i) for i in 1:n)` without creating an intermediate array of
    values.

  • Generators and comprehensions support filtering using `if`
    ([#550]) and nested iteration using multiple `for` keywords
    ([#4867]).

  • Fused broadcasting syntax: “f.(args…)“ is equivalent to
    “broadcast(f, args…)“ ([#15032]), and nested
    `f.(g.(args…))` calls are fused into a single `broadcast` loop
    ([#17300]).

  • Similarly, the syntax `x .= …` is equivalent to a
    `broadcast!(identity, x, …)`call and fuses with nested “dot”
    calls; also, `x .+= y` and similar is now equivalent to `x .= x
    .+ y`, rather than `x = x .+ y` ([#17510]).

  • Macro expander functions are now generic, so macros can have
    multiple definitions(e.g. for different numbers of arguments, or
    optional arguments) ([#8846], [#9627]).

  • However note that the argument types refer to the syntax tree
    representation, and not to the types of run time values.

  • Varargs functions like `foo{T}(x::T…)` may now restrict the
    number of such arguments using `foo{T,N}(x::Vararg{T,N})`
    ([#11242]).

  • `x ∈ X` is now a synonym for `x in X` in `for` loops and
    comprehensions, as it already was in comparisons ([#13824]).

  • The `PROGRAM_FILE` global is now available for determining the
    name of the running script ([#14114]).

  • The syntax `x.:sym` (e.g. `Base.:+`) is now supported, while
    using `x.(:sym)` or `x.(i)` for field access are deprecated in
    favor of `getfield` ([#15032]).

  • Function return type syntax `function f()::T` has been added
    ([#1090]). Values returned from a function with such a
    declaration will be converted to the specified type `T`.

  • Many more operators now support `.` prefixes (e.g. `.≤`)
    ([#17393]).  However, users are discouraged from overloading
    these, since they are mainly parsed in order to implement backwards
    compatibility with planned automatic broadcasting of dot operators
    in Julia 0.6 ([#16285]).  Explicitly qualified operator names
    like `Base.≤` should now use `Base.:≤` (prefixed by
    `@compat` if you need 0.4 compatibility via the `Compat`
    package).

  • User-extensible bounds check elimination is now possible with the
    new `@boundscheck` macro ([#14474]). This macro marks bounds
    checking code blocks, which the compiler may remove when encountered
    inside an `@inbounds` call.

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