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Current implementation of random sampling in my fork of frag_find, based on code from bulk_extractor.
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| /* [...] */ | |
| int main(int argc,char **argv) | |
| { | |
| /* [...] */ | |
| //RANDOM SAMPLING START | |
| if(opt_sampling_params.size()>0) set_sampling_parameters(opt_sampling_params); | |
| /* Create a list of blocks to sample */ | |
| srand(time(NULL)); | |
| std::set<uint64_t> blocks_to_sample; | |
| uint64_t nblocks = imagefile.blocks; | |
| int at_pass = 0; | |
| if (sampling()) { | |
| while(at_pass < sampling_passes) { | |
| at_pass++; | |
| while(blocks_to_sample.size() < nblocks * sampling_fraction * at_pass){ | |
| uint64_t blk_high = ((uint64_t)random()) << 32; | |
| uint64_t blk_low = random(); | |
| uint64_t blk = (blk_high | blk_low) % nblocks; | |
| blocks_to_sample.insert(blk); // will be added even if already present | |
| } | |
| } | |
| } | |
| //RANDOM SAMPLING END | |
| for(uint64_t blocknumber=opt_start;blocknumber < opt_end && blocknumber < imagefile.blocks; blocknumber++){ | |
| /* [...] */ | |
| //RANDOM SAMPLING START | |
| /* Limit search to the random samples */ | |
| if (sampling() && blocks_to_sample.find(blocknumber) == blocks_to_sample.end()) continue; | |
| //RANDOM SAMPLING END | |
| /* [...] */ | |
| } | |
| /* [...] */ | |
| } |
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Random sampling for
frag_findThis gist presents the current implementation of random sampling in my fork of
frag_find, based on code frombulk_extractor.Usage
Through
frag_find's option-R <frac>[:<pass>]: use<frac>as random sampling fraction (default is 1) and<pass>as number of passes (default is 1).Integration
In
frag_find.cpp, see commits 1 and 2.Based on
bulk_extractor.cpp.