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author | Romain Forlot <romain.forlot@iot.bzh> | 2017-05-02 18:29:37 +0200 |
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committer | Romain Forlot <romain.forlot@iot.bzh> | 2017-05-02 18:29:37 +0200 |
commit | b9e1b4435a406a8a27c078ea05dee1240e51704a (patch) | |
tree | 3bd5e75d001d0c1d57710c47375af5c8ba84c26c /CAN-binder/libs/nanopb/examples/using_union_messages/README.txt | |
parent | 0242c26c2f5dc96387bca7efb118364c800f4ee7 (diff) |
Added external libraries from openXC CMake files.
Now libraries are cleanly included and built.
Change-Id: Iaa85639578b55b2da8357bc438426403e2cca8de
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>
Diffstat (limited to 'CAN-binder/libs/nanopb/examples/using_union_messages/README.txt')
-rw-r--r-- | CAN-binder/libs/nanopb/examples/using_union_messages/README.txt | 52 |
1 files changed, 0 insertions, 52 deletions
diff --git a/CAN-binder/libs/nanopb/examples/using_union_messages/README.txt b/CAN-binder/libs/nanopb/examples/using_union_messages/README.txt deleted file mode 100644 index 7a1e75d4..00000000 --- a/CAN-binder/libs/nanopb/examples/using_union_messages/README.txt +++ /dev/null @@ -1,52 +0,0 @@ -Nanopb example "using_union_messages" -===================================== - -Union messages is a common technique in Google Protocol Buffers used to -represent a group of messages, only one of which is passed at a time. -It is described in Google's documentation: -https://developers.google.com/protocol-buffers/docs/techniques#union - -This directory contains an example on how to encode and decode union messages -with minimal memory usage. Usually, nanopb would allocate space to store -all of the possible messages at the same time, even though at most one of -them will be used at a time. - -By using some of the lower level nanopb APIs, we can manually generate the -top level message, so that we only need to allocate the one submessage that -we actually want. Similarly when decoding, we can manually read the tag of -the top level message, and only then allocate the memory for the submessage -after we already know its type. - - -Example usage -------------- - -Type `make` to run the example. It will build it and run commands like -following: - -./encode 1 | ./decode -Got MsgType1: 42 -./encode 2 | ./decode -Got MsgType2: true -./encode 3 | ./decode -Got MsgType3: 3 1415 - -This simply demonstrates that the "decode" program has correctly identified -the type of the received message, and managed to decode it. - - -Details of implementation -------------------------- - -unionproto.proto contains the protocol used in the example. It consists of -three messages: MsgType1, MsgType2 and MsgType3, which are collected together -into UnionMessage. - -encode.c takes one command line argument, which should be a number 1-3. It -then fills in and encodes the corresponding message, and writes it to stdout. - -decode.c reads a UnionMessage from stdin. Then it calls the function -decode_unionmessage_type() to determine the type of the message. After that, -the corresponding message is decoded and the contents of it printed to the -screen. - |