hphp/util/channeled-json-decompressor.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-2014 Facebook, Inc. (http://www.facebook.com)     |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16 #ifndef incl_HPHP_JSON_CHANNELED_DECOMPRESSOR_H_
  17 #define incl_HPHP_JSON_CHANNELED_DECOMPRESSOR_H_
  18
  19 #include <vector>
  20 #include <map>
  21
  22 #include "folly/dynamic.h"
  23 #include "folly/FBString.h"
  24 #include "folly/FBVector.h"
  25 #include "folly/io/Cursor.h"
  26
  27 #include "hphp/util/gen-cpp/channeled_json_compressor_types.h"
  28
  29 namespace HPHP {
  30 ///////////////////////////////////////////////////////////////////////////////
  31
  32 /**
  33 A class that compresses json files according to channels
  34 */
  35 class ChanneledJsonDecompressor {
  36
  37 public:
  38   ChanneledJsonDecompressor();
  39   ~ChanneledJsonDecompressor();
  40
  41   // Reads the data into channels
  42   void readChannels(folly::io::Cursor& cursor);
  43
  44   // Read an object from the underlying channels
  45   void read(folly::dynamic* outObj);
  46
  47 private:
  48   // Read a variable length integer into from the given channels
  49   int64_t readVarInt(Channel channel);
  50
  51   // Read a type (The type is not Type because there are intermediate values)
  52   uint8_t readType();
  53
  54   // read a map
  55   void readMap(int64_t length, folly::dynamic* outMapObj);
  56
  57   // write an array
  58   void readArray(int64_t length, folly::dynamic* outArrayObj);
  59
  60   // write a string
  61   void readString(int64_t length, Channel channel,
  62     folly::dynamic* outStringObj);
  63
  64   // write a double
  65   void readDouble(folly::dynamic* outDoubleObj);
  66
  67 private:
  68
  69   // Maintains the channel's state
  70   struct ChannelState {
  71     const folly::fbstring channel_;
  72     uint32_t pos_;
  73
  74     // Contructor
  75     explicit ChannelState(const folly::fbstring& channel);
  76
  77     // Get the data pointer, advance the position
  78     const char* read(uint32_t length);
  79   };
  80
  81   // output channels (implemented as strings).
  82   // see this discussion of stringstream here: https://fburl.com/16088028
  83   folly::fbvector<ChannelState> channels_;
  84
  85   // memoised strings
  86   std::map<uint32_t, folly::fbstring> memoStrings_;
  87   uint32_t memoStringsNext_;
  88
  89   //memoised keys
  90   std::map<uint32_t, folly::fbstring> memoKeys_;
  91   uint32_t memoKeysNext_;
  92 };
  93
  94 } // namespace HPHP
  95
  96 #endif