Update documentation

This commit is contained in:
Petteri Aimonen
2013-03-02 16:27:31 +02:00
parent 0e3053894f
commit f8a143fdfe
3 changed files with 35 additions and 35 deletions

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@@ -36,23 +36,26 @@ Features and limitations
**Features**
#) Pure C runtime
#) Small code size (210 kB depending on processor)
#) Small ram usage (typically 200 bytes)
#) Small code size (210 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.
#) 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
===============
@@ -104,10 +107,3 @@ 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.