| commit | 01e08a9faf3548b1aa353fb12719f707eaaed459 | [log] [tgz] |
|---|---|---|
| author | Laurence Lundblade <lgl@island-resort.com> | Sun Oct 28 20:13:12 2018 +0700 |
| committer | Laurence Lundblade <lgl@island-resort.com> | Sun Oct 28 20:13:12 2018 +0700 |
| tree | 5eb457e25eb99e915db5aa9f9bee23cfc1753d60 | |
| parent | b836efbabe89799832793d06689c039744eb8a23 [diff] |
remote TODO: marker that was fixed previously
QCBOR encodes and decodes RFC 7049 CBOR.
Implemented in C with minimal dependecy – Only dependencies are C99, stdint.h, stddef.h, stdbool.h and string.h making it highly portable. There are no #ifdefs.
Focused on C / native data representation – Simpler code because there is no support for encoding/decoding to/from JSON, pretty printing, diagnostic notation... Only encoding from native C representations and decoding to native C representations is supported.
Small simple memory model – Malloc is not needed. The encode context is 136 bytes, decode context is 104 bytes and the description of decoded data item is 56 bytes. Stack use is very light and there is no recursion. The caller supplies the memory to hold the encoded CBOR and encode/decode contexts so caller has full control of memory usage and it is good for embedded implementations that have to run in small fixed memory.
Supports nearly all of RFC 7049 – Only minor, corner-case parts of RFC 7049 are not directly supported (canonicalization, decimal fractions, big floats). Decoding indefinite length strings but requires a string allocator (see documentation). Encoding indefinite length strings is not supported, but is also not necessary or preferred.
Extensible and General – Provides a way to handle data types that are not directly supported.
Secure Coding Style – Uses a construct called UsefulBuf as a discipline for very safe coding the handling of binary data.
Small Code Size – When optimized for size using the compiler -Os option, x86 code is less than 5KB (~2KB encode, 2KB decode, 1KB common).
Clear documented public interface – The public interface is separated from the implementation. It can be put to use without reading the source.
QCBOR was originally developed by Qualcomm. It was open sourced through CAF with a permissive Linux license, September 2018 (thanks Qualcomm!).
This code in Laurence's GitHub has diverged some from the CAF source with some small simplifications and tidying up. The full test suite is not up and running and available in GitHub yet, so some caution is advised. This should be remedies soon.
The following modifications are planned:
These changes may result in some interface changes.
There is a simple makefile for the UNIX style command line binary that compiles everything to run the tests.
The actual non-test source files are these seven:
For most use cases you should just be able to add them to your project. Hopefully the easy portability of this implementation makes this work straight away, whatever your development environment is.
The files ieee754.c and ieee754.h are support for half-precision floating point. The encoding side of the floating point functionality is about 500 bytes. If it is never called because no floating point numbers are ever encoded, all 500 bytes will be dead stripped and not impact code size. The decoding side is about 150 bytes of object code. It is never dead stripped because it directly referenced by the core decoder , however it doesn't add very much to the size.
The test directory includes some tests that are nearly as portable as the main implementation. If your development environment doesn't support UNIX style command line and make, you should be able to make a simple project and add the test files to it. Then just call run_tests() to invole them all.