mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-13 18:02:24 +00:00
408 lines
12 KiB
C++
408 lines
12 KiB
C++
#include <string.h>
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#include <random>
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#include <pcg_random.hpp>
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#include <common/likely.h>
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#include <common/Types.h>
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#include <IO/ReadBuffer.h>
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#include <IO/ReadBufferFromFileDescriptor.h>
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#include <IO/WriteBufferFromFileDescriptor.h>
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#include <IO/BufferWithOwnMemory.h>
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#include <Compression/CompressionInfo.h>
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#include <IO/WriteHelpers.h>
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#include <IO/copyData.h>
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#include <Common/PODArray.h>
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/** Quick and dirty implementation of data scrambler.
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*
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* The task is to replace the data with pseudorandom values.
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* But with keeping some probability distributions
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* and with maintaining the same compression ratio.
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*
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* The solution is to operate directly on compressed LZ4 stream.
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* The stream consists of independent compressed blocks.
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* Each block is a stream of "literals" and "matches".
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* Liteal is an instruction to literally put some following bytes,
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* and match is an instruction to copy some bytes that was already seen before.
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*
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* We get literals and apply some scramble operation on it.
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* But we keep literal length and matches without changes.
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*
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* That's how we get pseudorandom data but with keeping
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* all repetitive patterns and maintaining the same compression ratio.
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*
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* Actually, the compression ratio, if you decompress scrambled data and compress again
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* become slightly worse, because LZ4 use simple match finder based on value of hash function,
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* and it can find different matches due to collisions in hash function.
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*
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* Scramble operation replace literals with pseudorandom bytes,
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* but with some heuristics to keep some sort of data structure.
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*
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* It's in question, is it scramble data enough and while is it safe to publish scrambled data.
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* In general, you should assume that it is not safe.
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*/
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#define ML_BITS 4
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#define ML_MASK ((1U<<ML_BITS)-1)
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#define RUN_BITS (8-ML_BITS)
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#define RUN_MASK ((1U<<RUN_BITS)-1)
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#define MINMATCH 4
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#define WILDCOPYLENGTH 8
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#define LASTLITERALS 5
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static UInt8 rand(pcg64 & generator, UInt8 min, UInt8 max)
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{
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return min + generator() % (max + 1 - min);
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}
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static void mutate(pcg64 & generator, void * src, size_t length)
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{
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UInt8 * pos = static_cast<UInt8 *>(src);
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UInt8 * end = pos + length;
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while (pos < end)
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{
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if (pos + strlen("https") <= end && 0 == memcmp(pos, "https", strlen("https")))
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{
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pos += strlen("https");
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continue;
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}
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if (pos + strlen("http") <= end && 0 == memcmp(pos, "http", strlen("http")))
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{
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pos += strlen("http");
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continue;
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}
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if (pos + strlen("www") <= end && 0 == memcmp(pos, "www", strlen("www")))
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{
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pos += strlen("www");
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continue;
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}
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if (*pos >= '1' && *pos <= '9')
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*pos = rand(generator, '1', '9');
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else if (*pos >= 'a' && *pos <= 'z')
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*pos = rand(generator, 'a', 'z');
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else if (*pos >= 'A' && *pos <= 'Z')
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*pos = rand(generator, 'A', 'Z');
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else if (*pos >= 0x80 && *pos <= 0xBF)
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*pos = rand(generator, *pos & 0xF0U, *pos | 0x0FU);
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else if (*pos == '\\')
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++pos;
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++pos;
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}
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pos = static_cast<UInt8 *>(src);
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while (pos < end)
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{
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if (pos + 3 <= end
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&& isAlphaASCII(pos[0])
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&& !isAlphaASCII(pos[1]) && pos[1] != '\\' && pos[1] >= 0x20
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&& isAlphaASCII(pos[2]))
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{
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auto res = rand(generator, 0, 3);
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if (res == 2)
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{
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std::swap(pos[0], pos[1]);
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}
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else if (res == 3)
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std::swap(pos[1], pos[2]);
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pos += 3;
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}
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else if (pos + 5 <= end
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&& pos[0] >= 0xC0 && pos[0] <= 0xDF && pos[1] >= 0x80 && pos[1] <= 0xBF
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&& pos[2] >= 0x20 && pos[2] < 0x80 && !isAlphaASCII(pos[2])
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&& pos[3] >= 0xC0 && pos[3] <= 0xDF && pos[4] >= 0x80 && pos[4] <= 0xBF)
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{
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auto res = rand(generator, 0, 3);
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if (res == 2)
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{
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std::swap(pos[1], pos[2]);
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std::swap(pos[0], pos[1]);
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}
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else if (res == 3)
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{
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std::swap(pos[3], pos[2]);
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std::swap(pos[4], pos[3]);
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}
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pos += 5;
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}
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else
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++pos;
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}
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}
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static void LZ4_copy8(void* dst, const void* src)
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{
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memcpy(dst,src,8);
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}
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/* customized variant of memcpy, which can overwrite up to 8 bytes beyond dstEnd */
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static void LZ4_wildCopy(void* dstPtr, const void* srcPtr, void* dstEnd)
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{
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UInt8* d = (UInt8*)dstPtr;
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const UInt8* s = (const UInt8*)srcPtr;
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UInt8* const e = (UInt8*)dstEnd;
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do { LZ4_copy8(d,s); d+=8; s+=8; } while (d<e);
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}
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static UInt16 LZ4_read16(const void* memPtr)
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{
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UInt16 val; memcpy(&val, memPtr, sizeof(val)); return val;
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}
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static void LZ4_write32(void* memPtr, UInt32 value)
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{
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memcpy(memPtr, &value, sizeof(value));
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}
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int LZ4_decompress_mutate(
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char* const source,
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char* const dest,
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int outputSize)
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{
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pcg64 generator;
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/* Local Variables */
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UInt8* ip = (UInt8*) source;
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UInt8* op = (UInt8*) dest;
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UInt8* const oend = op + outputSize;
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UInt8* cpy;
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const unsigned dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4};
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const int dec64table[] = {0, 0, 0, -1, 0, 1, 2, 3};
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/* Main Loop : decode sequences */
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while (1) {
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size_t length;
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const UInt8* match;
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size_t offset;
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/* get literal length */
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unsigned const token = *ip++;
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if ((length=(token>>ML_BITS)) == RUN_MASK) {
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unsigned s;
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do {
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s = *ip++;
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length += s;
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} while (s==255);
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}
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/* copy literals */
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cpy = op+length;
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if (cpy>oend-WILDCOPYLENGTH)
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{
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if (cpy != oend) goto _output_error; /* Error : block decoding must stop exactly there */
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mutate(generator, ip, length);
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memcpy(op, ip, length);
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ip += length;
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op += length;
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break; /* Necessarily EOF, due to parsing restrictions */
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}
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mutate(generator, ip, cpy - op);
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LZ4_wildCopy(op, ip, cpy);
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ip += length; op = cpy;
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/* get offset */
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offset = LZ4_read16(ip); ip+=2;
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match = op - offset;
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LZ4_write32(op, (UInt32)offset); /* costs ~1%; silence an msan warning when offset==0 */
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/* get matchlength */
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length = token & ML_MASK;
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if (length == ML_MASK) {
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unsigned s;
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do {
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s = *ip++;
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length += s;
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} while (s==255);
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}
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length += MINMATCH;
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/* copy match within block */
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cpy = op + length;
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if (unlikely(offset<8)) {
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const int dec64 = dec64table[offset];
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op[0] = match[0];
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op[1] = match[1];
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op[2] = match[2];
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op[3] = match[3];
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match += dec32table[offset];
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memcpy(op+4, match, 4);
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match -= dec64;
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} else { LZ4_copy8(op, match); match+=8; }
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op += 8;
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if (unlikely(cpy>oend-12)) {
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UInt8* const oCopyLimit = oend-(WILDCOPYLENGTH-1);
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if (cpy > oend-LASTLITERALS) goto _output_error; /* Error : last LASTLITERALS bytes must be literals (uncompressed) */
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if (op < oCopyLimit) {
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LZ4_wildCopy(op, match, oCopyLimit);
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match += oCopyLimit - op;
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op = oCopyLimit;
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}
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while (op<cpy) *op++ = *match++;
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} else {
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LZ4_copy8(op, match);
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if (length>16) LZ4_wildCopy(op+8, match+8, cpy);
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}
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op=cpy; /* correction */
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}
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return (int) (((const char*)ip)-source); /* Nb of input bytes read */
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/* Overflow error detected */
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_output_error:
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return (int) (-(((const char*)ip)-source))-1;
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}
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int UNKNOWN_COMPRESSION_METHOD;
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extern const int TOO_LARGE_SIZE_COMPRESSED;
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extern const int CANNOT_DECOMPRESS;
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}
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class MutatingCompressedReadBufferBase
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{
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protected:
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ReadBuffer * compressed_in;
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/// If 'compressed_in' buffer has whole compressed block - then use it. Otherwise copy parts of data to 'own_compressed_buffer'.
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PODArray<char> own_compressed_buffer;
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/// Points to memory, holding compressed block.
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char * compressed_buffer = nullptr;
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size_t readCompressedData(size_t & size_decompressed, size_t & size_compressed_without_checksum)
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{
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if (compressed_in->eof())
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return 0;
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CityHash_v1_0_2::uint128 checksum;
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compressed_in->readStrict(reinterpret_cast<char *>(&checksum), sizeof(checksum));
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own_compressed_buffer.resize(COMPRESSED_BLOCK_HEADER_SIZE);
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compressed_in->readStrict(&own_compressed_buffer[0], COMPRESSED_BLOCK_HEADER_SIZE);
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UInt8 method = own_compressed_buffer[0]; /// See CompressedWriteBuffer.h
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size_t & size_compressed = size_compressed_without_checksum;
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if (method == static_cast<UInt8>(CompressionMethodByte::LZ4) ||
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method == static_cast<UInt8>(CompressionMethodByte::ZSTD) ||
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method == static_cast<UInt8>(CompressionMethodByte::NONE))
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{
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size_compressed = unalignedLoad<UInt32>(&own_compressed_buffer[1]);
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size_decompressed = unalignedLoad<UInt32>(&own_compressed_buffer[5]);
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}
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else
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throw Exception("Unknown compression method: " + toString(method), ErrorCodes::UNKNOWN_COMPRESSION_METHOD);
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if (size_compressed > DBMS_MAX_COMPRESSED_SIZE)
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throw Exception("Too large size_compressed. Most likely corrupted data.", ErrorCodes::TOO_LARGE_SIZE_COMPRESSED);
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/// Is whole compressed block located in 'compressed_in' buffer?
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if (compressed_in->offset() >= COMPRESSED_BLOCK_HEADER_SIZE &&
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compressed_in->position() + size_compressed - COMPRESSED_BLOCK_HEADER_SIZE <= compressed_in->buffer().end())
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{
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compressed_in->position() -= COMPRESSED_BLOCK_HEADER_SIZE;
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compressed_buffer = compressed_in->position();
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compressed_in->position() += size_compressed;
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}
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else
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{
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own_compressed_buffer.resize(size_compressed);
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compressed_buffer = &own_compressed_buffer[0];
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compressed_in->readStrict(compressed_buffer + COMPRESSED_BLOCK_HEADER_SIZE, size_compressed - COMPRESSED_BLOCK_HEADER_SIZE);
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}
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return size_compressed + sizeof(checksum);
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}
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void decompress(char * to, size_t size_decompressed, size_t size_compressed_without_checksum)
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{
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UInt8 method = compressed_buffer[0]; /// See CompressedWriteBuffer.h
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if (method == static_cast<UInt8>(CompressionMethodByte::LZ4))
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{
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if (LZ4_decompress_mutate(compressed_buffer + COMPRESSED_BLOCK_HEADER_SIZE, to, size_decompressed) < 0)
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throw Exception("Cannot LZ4_decompress_fast", ErrorCodes::CANNOT_DECOMPRESS);
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}
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else
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throw Exception("Unknown compression method: " + toString(method), ErrorCodes::UNKNOWN_COMPRESSION_METHOD);
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}
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public:
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/// 'compressed_in' could be initialized lazily, but before first call of 'readCompressedData'.
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MutatingCompressedReadBufferBase(ReadBuffer * in = nullptr)
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: compressed_in(in), own_compressed_buffer(COMPRESSED_BLOCK_HEADER_SIZE)
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{
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}
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};
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class MutatingCompressedReadBuffer : public MutatingCompressedReadBufferBase, public BufferWithOwnMemory<ReadBuffer>
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{
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private:
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size_t size_compressed = 0;
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bool nextImpl() override
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{
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size_t size_decompressed;
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size_t size_compressed_without_checksum;
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size_compressed = readCompressedData(size_decompressed, size_compressed_without_checksum);
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if (!size_compressed)
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return false;
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memory.resize(size_decompressed);
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working_buffer = Buffer(&memory[0], &memory[size_decompressed]);
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decompress(working_buffer.begin(), size_decompressed, size_compressed_without_checksum);
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return true;
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}
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public:
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MutatingCompressedReadBuffer(ReadBuffer & in_)
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: MutatingCompressedReadBufferBase(&in_), BufferWithOwnMemory<ReadBuffer>(0)
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{
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}
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};
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}
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int main(int, char **)
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try
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{
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DB::ReadBufferFromFileDescriptor in(STDIN_FILENO);
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DB::MutatingCompressedReadBuffer mutating_in(in);
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DB::WriteBufferFromFileDescriptor out(STDOUT_FILENO);
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DB::copyData(mutating_in, out);
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return 0;
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}
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catch (...)
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{
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std::cerr << DB::getCurrentExceptionMessage(true);
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return DB::getCurrentExceptionCode();
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}
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