X-Git-Url: https://gerrit.automotivelinux.org/gerrit/gitweb?a=blobdiff_plain;f=docs%2Findex.rst;h=31d781ea74d64d62033b0c1d7eaad59b4b420985;hb=b36a1a259ac065fcd21f4871c8c1e1db429e32bb;hp=f2f8dcfd4f46113d95754fa19c6693c15a302cdd;hpb=5a9f85b87615078868d3b394370a30b550186cce;p=apps%2Fagl-service-can-low-level.git

diff --git a/docs/index.rst b/docs/index.rst
index f2f8dcfd..31d781ea 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -13,20 +13,22 @@ Overall structure
 =================
 
 For the runtime program, you always need *pb.h* for type declarations.
-Depending on whether you want to encode, decode or both, you also need *pb_encode.h/c* or *pb_decode.h/c*.
+Depending on whether you want to encode, decode, or both, you also need *pb_encode.h/c* or *pb_decode.h/c*.
 
-The high-level encoding and decoding functions take an array of *pb_field_t* structures, which describes the fields of a message structure. Usually you want these autogenerated from a *.proto* file. The tool string *nanopb_generator.py* accomplishes this.
+The high-level encoding and decoding functions take an array of *pb_field_t* structures, which describes the fields of a message structure. Usually you want these autogenerated from a *.proto* file. The tool script *nanopb_generator.py* accomplishes this.
+
+.. image:: generator_flow.png
 
 So a typical project might include these files:
 
 1) Nanopb runtime library:
     - pb.h
-    - pb_decode.h and pb_decode.c
-    - pb_encode.h and pb_encode.c
+    - pb_decode.h and pb_decode.c (needed for decoding messages)
+    - pb_encode.h and pb_encode.c (needed for encoding messages)
 2) Protocol description (you can have many):
-    - person.proto
-    - person.c (autogenerated, contains initializers for const arrays)
-    - person.h (autogenerated, contains type declarations)
+    - person.proto (just an example)
+    - person.pb.c (autogenerated, contains initializers for const arrays)
+    - person.pb.h (autogenerated, contains type declarations)
 
 Features and limitations
 ========================
@@ -37,7 +39,7 @@ Features and limitations
 #) Small code size (2–10 kB depending on processor)
 #) Small ram usage (typically 200 bytes)
 #) Allows specifying maximum size for strings and arrays, so that they can be allocated statically.
-#) No malloc needed: everything is stored on the stack.
+#) No malloc needed: everything can be allocated statically or on the stack.
 #) You can use either encoder or decoder alone to cut the code size in half.
 
 **Limitations**
@@ -48,6 +50,9 @@ Features and limitations
 #) The deprecated Protocol Buffers feature called "groups" is not supported.
 #) Fields in the generated structs are ordered by the tag number, instead of the natural ordering in .proto file.
 #) Unknown fields are not preserved when decoding and re-encoding a message.
+#) Reflection (runtime introspection) is not supported. E.g. you can't request a field by giving its name in a string.
+#) Numeric arrays are always encoded as packed, even if not marked as packed in .proto. This causes incompatibility with decoders that do not support packed format.
+#) Cyclic references between messages are not supported. They could be supported in callback-mode if there was an option in the generator to set the mode.
 
 Getting started
 ===============
@@ -58,12 +63,12 @@ For starters, consider this simple message::
     required int32 value = 1;
  }
 
-Save this in *example.proto* and compile it::
+Save this in *message.proto* and compile it::
 
     user@host:~$ protoc -omessage.pb message.proto
-    user@host:~$ python ../generator/nanopb_generator.py message.pb
+    user@host:~$ python nanopb/generator/nanopb_generator.py message.pb
 
-You should now have in *example.h*::
+You should now have in *message.pb.h*::
 
  typedef struct {
     int32_t value;
@@ -80,7 +85,26 @@ Now in your main program do this to encode a message::
 
 After that, buffer will contain the encoded message.
 The number of bytes in the message is stored in *stream.bytes_written*.
-You can feed the message to *protoc --decode=Example example.proto* to verify its validity.
+You can feed the message to *protoc --decode=Example message.proto* to verify its validity.
+
+For complete examples of the simple cases, see *tests/test_decode1.c* and *tests/test_encode1.c*. For an example with network interface, see the *example* subdirectory.
+
+Compiler requirements
+=====================
+Nanopb should compile with most ansi-C compatible compilers. It however requires a few header files to be available:
+
+#) *string.h*, with these functions: *strlen*, *memcpy*, *memset*
+#) *stdint.h*, for definitions of *int32_t* etc.
+#) *stddef.h*, for definition of *size_t*
+#) *stdbool.h*, for definition of *bool*
+
+If these header files do not come with your compiler, you should be able to find suitable replacements online. Mostly the requirements are very simple, just a few basic functions and typedefs.
+
+Debugging and testing
+=====================
+Extensive unittests are included under the *tests* folder. Just type *make* there to run the tests.
+
+This also generates a file called *breakpoints* which includes all lines returning *false* in nanopb. You can use this in gdb by typing *source breakpoints*, after which gdb will break on first nanopb error.
 
 Wishlist
 ========