Adding documentation on the sync part of the adb protocol previously missing.

In the SERVICES.TXT a missing documentation file is mentioned - SYNC.TXT. This file is supposed to contain all the godie bits of the adb protocol for pushing and pulling files. I've read the source code and documented this in the file SYNC.TXT. I've used my own documentation to create a java implementation to verify the documentation here: https://github.com/vidstige/jadb

Added line breaks at 78 characters. Added comments about remote files might be deleted.

Change-Id: I48c87c2a9fb5b59b85c72679124dfbbfa9a701bc
Signed-off-by: Samuel Carlsson <samuel.carlsson@gmail.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/adb/SYNC.TXT b/adb/SYNC.TXT
new file mode 100644
index 0000000..e74d217
--- /dev/null
+++ b/adb/SYNC.TXT
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+This file tries to document file related requests a client can make
+to the ADB server of an adbd daemon. See the OVERVIEW.TXT document
+to understand what's going on here. See the SERVICES.TXT to learn more
+about the other requests that are possible.
+
+SYNC SERVICES:
+
+
+Requesting the sync service ("sync:") using the protocol as described in
+SERVICES.TXT sets the connection in sync mode. This mode is a binary mode that
+differ from the regular adb protocol. The connection stays in sync mode until
+explicitly terminated (see below).
+
+After the initial "sync:" command is sent the server must respond with either
+"OKAY" or "FAIL" as per usual. 
+
+In sync mode both the server and the client will frequently use eight-byte
+packets to communicate in this document called sync request and sync
+responses. The first four bytes is an id and specifies sync request is
+represented by four utf-8 characters. The last four bytes is a Little-Endian
+integer, with various uses. This number will be called "length" below. In fact
+all binary integers are Little-Endian in the sync mode. Sync mode is
+implicitly exited after each sync request, and normal adb communication
+follows as described in SERVICES.TXT.
+
+The following sync requests are accepted:
+LIST - List the files in a folder
+SEND - Send a file to device
+RECV - Retreive a file from device
+
+Not yet documented:
+STAT - Stat a file
+ULNK - Unlink (remove) a file. (Not currently supported)
+
+For all of the sync request above the must be followed by length number of
+bytes containing an utf-8 string with a remote filename.
+
+LIST:
+Lists files in the directory specified by the remote filename. The server will
+respond with zero or more directory entries or "dents".
+
+The directory entries will be returned in the following form
+1. A four-byte sync response id beeing "DENT"
+2. A four-byte integer representing file mode.
+3. A four-byte integer representing file size.
+4. A four-byte integer representing last modified time.
+5. A four-byte integer representing file name length.
+6. length number of bytes containing an utf-8 string representing the file
+   name.
+
+When an sync response "DONE" is received the listing is done.
+
+SEND:
+The remote file name is split into two parts separated by the last
+comma (","). The first part is the actual path, while the second is a decimal
+encoded file mode containing the permissions of the file on device.
+
+Note that some file types will be deleted before the copying starts, and if
+the transfer fails. Some file types will not be deleted, which allows
+  adb push disk_image /some_block_device
+to work.
+
+After this the actual file is sent in chunks. Each chucks has the following
+format.
+A sync request with id "DATA" and length equal to the chunk size. After
+follows chunk size number of bytes. This is repeated until the file is
+transfered. Each chunk must not be larger than 64k.
+
+When the file is tranfered a sync request "DONE" is sent, where length is set
+to the last modified time for the file. The server responds to this last
+request (but not to chuck requests) with an "OKAY" sync response (length can
+be ignored).
+
+
+RECV:
+Retrieves a file from device to a local file. The remote path is the path to
+the file that will be returned. Just as for the SEND sync request the file
+received is split up into chunks. The sync response id is "DATA" and length is
+the chuck size. After follows chunk size number of bytes. This is repeated
+until the file is transfered. Each chuck will not be larger than 64k.
+
+When the file is transfered a sync resopnse "DONE" is retrieved where the
+length can be ignored.
+