## Proposed changes
Hadoop snappycodec source :
https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/src/codec/SnappyCodec.cc
Example:
OriginData(The original data will be divided into several large data
block.) :
large data block1 | large data block2 | large data block3 | ....
The large data block will be divided into several small data block.
Suppose a large data block is divided into three small blocks:
large data block1: | small block1 | small block2 | small block3 |
CompressData: <A [B1 compress(small block1) ] [B2 compress(small block1)
] [B3 compress(small block1)]>
A : original length of the current block of large data block.
sizeof(A) = 4 bytes.
A = length(small block1) + length(small block2) + length(small block3)
Bx : length of small data block bx.
sizeof(Bx) = 4 bytes.
Bx = length(compress(small blockx))
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