Squashed 'src/rocksdb/' content from commit 224932d

git-subtree-dir: src/rocksdb
git-subtree-split: 224932d4d0b561712107d747c662df181c39644d

util/coding.cc

@@ -0,0 +1,169 @@
+//  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/coding.h"
+
+#include <algorithm>
+#include "rocksdb/slice.h"
+#include "rocksdb/slice_transform.h"
+
+namespace rocksdb {
+
+char* EncodeVarint32(char* dst, uint32_t v) {
+  // Operate on characters as unsigneds
+  unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
+  static const int B = 128;
+  if (v < (1 << 7)) {
+    *(ptr++) = v;
+  } else if (v < (1 << 14)) {
+    *(ptr++) = v | B;
+    *(ptr++) = v >> 7;
+  } else if (v < (1 << 21)) {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = v >> 14;
+  } else if (v < (1 << 28)) {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = (v >> 14) | B;
+    *(ptr++) = v >> 21;
+  } else {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = (v >> 14) | B;
+    *(ptr++) = (v >> 21) | B;
+    *(ptr++) = v >> 28;
+  }
+  return reinterpret_cast<char*>(ptr);
+}
+
+const char* GetVarint32PtrFallback(const char* p, const char* limit,
+                                   uint32_t* value) {
+  uint32_t result = 0;
+  for (uint32_t shift = 0; shift <= 28 && p < limit; shift += 7) {
+    uint32_t byte = *(reinterpret_cast<const unsigned char*>(p));
+    p++;
+    if (byte & 128) {
+      // More bytes are present
+      result |= ((byte & 127) << shift);
+    } else {
+      result |= (byte << shift);
+      *value = result;
+      return reinterpret_cast<const char*>(p);
+    }
+  }
+  return nullptr;
+}
+
+const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* value) {
+  uint64_t result = 0;
+  for (uint32_t shift = 0; shift <= 63 && p < limit; shift += 7) {
+    uint64_t byte = *(reinterpret_cast<const unsigned char*>(p));
+    p++;
+    if (byte & 128) {
+      // More bytes are present
+      result |= ((byte & 127) << shift);
+    } else {
+      result |= (byte << shift);
+      *value = result;
+      return reinterpret_cast<const char*>(p);
+    }
+  }
+  return nullptr;
+}
+
+void BitStreamPutInt(char* dst, size_t dstlen, size_t offset,
+                     uint32_t bits, uint64_t value) {
+  assert((offset + bits + 7)/8 <= dstlen);
+  assert(bits <= 64);
+
+  unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
+
+  size_t byteOffset = offset / 8;
+  size_t bitOffset = offset % 8;
+
+  // This prevents unused variable warnings when compiling.
+#ifndef NDEBUG
+  // Store truncated value.
+  uint64_t origValue = (bits < 64)?(value & (((uint64_t)1 << bits) - 1)):value;
+  uint32_t origBits = bits;
+#endif
+
+  while (bits > 0) {
+    size_t bitsToGet = std::min<size_t>(bits, 8 - bitOffset);
+    unsigned char mask = ((1 << bitsToGet) - 1);
+
+    ptr[byteOffset] = (ptr[byteOffset] & ~(mask << bitOffset)) +
+                      ((value & mask) << bitOffset);
+
+    value >>= bitsToGet;
+    byteOffset += 1;
+    bitOffset = 0;
+    bits -= bitsToGet;
+  }
+
+  assert(origValue == BitStreamGetInt(dst, dstlen, offset, origBits));
+}
+
+uint64_t BitStreamGetInt(const char* src, size_t srclen, size_t offset,
+                         uint32_t bits) {
+  assert((offset + bits + 7)/8 <= srclen);
+  assert(bits <= 64);
+
+  const unsigned char* ptr = reinterpret_cast<const unsigned char*>(src);
+
+  uint64_t result = 0;
+
+  size_t byteOffset = offset / 8;
+  size_t bitOffset = offset % 8;
+  size_t shift = 0;
+
+  while (bits > 0) {
+    size_t bitsToGet = std::min<size_t>(bits, 8 - bitOffset);
+    unsigned char mask = ((1 << bitsToGet) - 1);
+
+    result += (uint64_t)((ptr[byteOffset] >> bitOffset) & mask) << shift;
+
+    shift += bitsToGet;
+    byteOffset += 1;
+    bitOffset = 0;
+    bits -= bitsToGet;
+  }
+
+  return result;
+}
+
+void BitStreamPutInt(std::string* dst, size_t offset, uint32_t bits,
+                     uint64_t value) {
+  assert((offset + bits + 7)/8 <= dst->size());
+
+  const size_t kTmpBufLen = sizeof(value) + 1;
+  char tmpBuf[kTmpBufLen];
+
+  // Number of bytes of tmpBuf being used
+  const size_t kUsedBytes = (offset%8 + bits)/8;
+
+  // Copy relevant parts of dst to tmpBuf
+  for (size_t idx = 0; idx <= kUsedBytes; ++idx) {
+    tmpBuf[idx] = (*dst)[offset/8 + idx];
+  }
+
+  BitStreamPutInt(tmpBuf, kTmpBufLen, offset%8, bits, value);
+
+  // Copy tmpBuf back to dst
+  for (size_t idx = 0; idx <= kUsedBytes; ++idx) {
+    (*dst)[offset/8 + idx] = tmpBuf[idx];
+  }
+
+  // Do the check here too as we are working with a buffer.
+  assert(((bits < 64)?(value & (((uint64_t)1 << bits) - 1)):value) ==
+         BitStreamGetInt(dst, offset, bits));
+}
+
+}  // namespace rocksdb