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194 regels
4.8 KiB
194 regels
4.8 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "util/coding.h"
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namespace leveldb {
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void EncodeFixed32(char* buf, uint32_t value) {
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#if __BYTE_ORDER == __LITTLE_ENDIAN
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memcpy(buf, &value, sizeof(value));
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#else
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buf[0] = value & 0xff;
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buf[1] = (value >> 8) & 0xff;
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buf[2] = (value >> 16) & 0xff;
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buf[3] = (value >> 24) & 0xff;
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#endif
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}
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void EncodeFixed64(char* buf, uint64_t value) {
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#if __BYTE_ORDER == __LITTLE_ENDIAN
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memcpy(buf, &value, sizeof(value));
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#else
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buf[0] = value & 0xff;
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buf[1] = (value >> 8) & 0xff;
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buf[2] = (value >> 16) & 0xff;
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buf[3] = (value >> 24) & 0xff;
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buf[4] = (value >> 32) & 0xff;
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buf[5] = (value >> 40) & 0xff;
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buf[6] = (value >> 48) & 0xff;
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buf[7] = (value >> 56) & 0xff;
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#endif
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}
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void PutFixed32(std::string* dst, uint32_t value) {
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char buf[sizeof(value)];
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EncodeFixed32(buf, value);
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dst->append(buf, sizeof(buf));
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}
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void PutFixed64(std::string* dst, uint64_t value) {
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char buf[sizeof(value)];
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EncodeFixed64(buf, value);
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dst->append(buf, sizeof(buf));
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}
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char* EncodeVarint32(char* dst, uint32_t v) {
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// Operate on characters as unsigneds
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unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
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static const int B = 128;
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if (v < (1<<7)) {
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*(ptr++) = v;
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} else if (v < (1<<14)) {
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*(ptr++) = v | B;
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*(ptr++) = v>>7;
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} else if (v < (1<<21)) {
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*(ptr++) = v | B;
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*(ptr++) = (v>>7) | B;
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*(ptr++) = v>>14;
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} else if (v < (1<<28)) {
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*(ptr++) = v | B;
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*(ptr++) = (v>>7) | B;
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*(ptr++) = (v>>14) | B;
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*(ptr++) = v>>21;
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} else {
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*(ptr++) = v | B;
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*(ptr++) = (v>>7) | B;
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*(ptr++) = (v>>14) | B;
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*(ptr++) = (v>>21) | B;
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*(ptr++) = v>>28;
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}
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return reinterpret_cast<char*>(ptr);
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}
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void PutVarint32(std::string* dst, uint32_t v) {
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char buf[5];
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char* ptr = EncodeVarint32(buf, v);
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dst->append(buf, ptr - buf);
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}
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char* EncodeVarint64(char* dst, uint64_t v) {
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static const int B = 128;
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unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
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while (v >= B) {
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*(ptr++) = (v & (B-1)) | B;
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v >>= 7;
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}
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*(ptr++) = static_cast<unsigned char>(v);
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return reinterpret_cast<char*>(ptr);
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}
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void PutVarint64(std::string* dst, uint64_t v) {
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char buf[10];
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char* ptr = EncodeVarint64(buf, v);
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dst->append(buf, ptr - buf);
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}
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void PutLengthPrefixedSlice(std::string* dst, const Slice& value) {
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PutVarint32(dst, value.size());
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dst->append(value.data(), value.size());
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}
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int VarintLength(uint64_t v) {
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int len = 1;
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while (v >= 128) {
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v >>= 7;
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len++;
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}
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return len;
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}
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const char* GetVarint32PtrFallback(const char* p,
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const char* limit,
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uint32_t* value) {
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uint32_t result = 0;
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for (uint32_t shift = 0; shift <= 28 && p < limit; shift += 7) {
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uint32_t byte = *(reinterpret_cast<const unsigned char*>(p));
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p++;
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if (byte & 128) {
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// More bytes are present
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result |= ((byte & 127) << shift);
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} else {
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result |= (byte << shift);
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*value = result;
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return reinterpret_cast<const char*>(p);
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}
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}
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return NULL;
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}
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bool GetVarint32(Slice* input, uint32_t* value) {
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const char* p = input->data();
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const char* limit = p + input->size();
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const char* q = GetVarint32Ptr(p, limit, value);
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if (q == NULL) {
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return false;
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} else {
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*input = Slice(q, limit - q);
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return true;
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}
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}
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const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* value) {
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uint64_t result = 0;
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for (uint32_t shift = 0; shift <= 63 && p < limit; shift += 7) {
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uint64_t byte = *(reinterpret_cast<const unsigned char*>(p));
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p++;
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if (byte & 128) {
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// More bytes are present
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result |= ((byte & 127) << shift);
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} else {
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result |= (byte << shift);
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*value = result;
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return reinterpret_cast<const char*>(p);
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}
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}
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return NULL;
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}
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bool GetVarint64(Slice* input, uint64_t* value) {
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const char* p = input->data();
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const char* limit = p + input->size();
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const char* q = GetVarint64Ptr(p, limit, value);
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if (q == NULL) {
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return false;
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} else {
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*input = Slice(q, limit - q);
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return true;
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}
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}
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const char* GetLengthPrefixedSlice(const char* p, const char* limit,
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Slice* result) {
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uint32_t len;
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p = GetVarint32Ptr(p, limit, &len);
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if (p == NULL) return NULL;
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if (p + len > limit) return NULL;
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*result = Slice(p, len);
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return p + len;
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}
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bool GetLengthPrefixedSlice(Slice* input, Slice* result) {
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uint32_t len;
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if (GetVarint32(input, &len) &&
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input->size() >= len) {
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*result = Slice(input->data(), len);
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input->remove_prefix(len);
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return true;
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} else {
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return false;
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}
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}
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}
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