Document field extensions support

[apps/agl-service-can-low-level.git] / docs / index.rst

diff --git a/docs/index.rst b/docs/index.rst
index 31d781e..e56ff4c 100644 (file)
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -36,23 +36,26 @@ Features and limitations
 **Features**
 
 #) Pure C runtime
-#) Small code size (2–10 kB depending on processor)
-#) Small ram usage (typically 200 bytes)
+#) Small code size (2–10 kB depending on processor, plus any message definitions)
+#) Small ram usage (typically ~300 bytes, plus any message structs)
 #) Allows specifying maximum size for strings and arrays, so that they can be allocated statically.
 #) 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.
+#) Support for most protobuf features, including: all data types, nested submessages, default values, repeated and optional fields, packed arrays, extension fields.
+#) Callback mechanism for handling messages larger than can fit in available RAM.
+#) Extensive set of tests.
 
 **Limitations**
 
 #) User must provide callbacks when decoding arrays or strings without maximum size. Malloc support could be added as a separate module.
-#) Some speed has been sacrificed for code size. For example varint calculations are always done in 64 bits.
+#) Some speed has been sacrificed for code size.
 #) Encoding is focused on writing to streams. For memory buffers only it could be made more efficient.
 #) 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.
+#) Cyclic references between messages are supported only in callback mode.
 
 Getting started
 ===============
@@ -100,14 +103,9 @@ Nanopb should compile with most ansi-C compatible compilers. It however requires
 
 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.
 
+Alternatively, you can define *PB_SYSTEM_HEADER*, which should be the name of a single header file including all the necessary definitions.
+
 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
-========
-#) A specialized encoder for encoding to a memory buffer. Should serialize in reverse order to avoid having to determine submessage size beforehand.
-#) A cleaner rewrite of the Python-based source generator.
-#) Better performance for 16- and 8-bit platforms: use smaller datatypes where possible.