http://nisl.wayne.edu/Papers/Tech/code-pf-fast09.pdf
Luigi Rizzo is the original author of the fec C library.
I co-maintain zfec (and the Debian package of it) along with Zooko. A new release of zfec is planned to be out soonish.
edit: removing the <> delimiters around the URL. Sorry!
I wrote an MIT-licensed ReedSolomon module for Node [1], with native C++ multi-core throughput. The internal benchmark (node benchmark.js) provides latency and throughput measurements for data=10, parity=4 for a variety of shard sizes, and the number of data/parity shards can be adjusted for comparison.
It's not yet using optimized assembler or SIMD like Klaus Post's implementation, but it is compatible and also based on Backblaze's implementation, as well as including a pure Javascript implementation for browser use.
In my library, the SSSE3 code also has AVX and AVX2 equivalents, providing higher throughput. There are also implementations with specific optimized instructions for ARM NEON, ARM64, PPC64/AltiVec and Power8. All of this in C (with intrinsics), not ASM, so making use of your C compiler's instruction scheduling, loop unrolling,... See https://github.com/NicolasT/reedsolomon/blob/master/cbits/re...
I believe it's compatible with the Java implementation used by Backblaze and others.