libsecurity_utilities/lib/memstreams.h

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 //
  26 // memstreams - primitive memory block streaming support
  27 //
  28 #ifndef _H_MEMSTREAMS
  29 #define _H_MEMSTREAMS
  30
  31 #include <stdint.h>
  32 #include <security_utilities/memutils.h>
  33 #include <security_utilities/endian.h>
  34 #include <security_utilities/errors.h>
  35
  36
  37 namespace Security
  38 {
  39
  40 //
  41 // Encapsulate these very sharp tools in a separate namespace
  42 //
  43 namespace LowLevelMemoryUtilities
  44 {
  45
  46
  47 //
  48 // A simple utility for incremental creation of a contiguous memory block.
  49 //
  50 // Note that Writer and Writer::Counter go together. They use the same alignment
  51 // and padding rules, so Writer::Counter will correctly calculate total buffer
  52 // size for Writer, *presuming* that they are called in the same order.
  53 //
  54 // This layer allocates no memory; that's up to the caller (you).
  55 //
  56 // WARNING: There is no check for overflow. If you write too much, you will die.
  57 // Writer::Counter can tell you how much you need.
  58 //
  59 class Writer {
  60 private:
  61         void *advance(size_t size)
  62         {
  63                 void *here = alignUp(writePos);
  64                 writePos = increment(here, size);
  65                 return here;
  66         }
  67
  68 public:
  69         Writer() { }
  70         Writer(void *base) : writePos(base) { }
  71         void operator = (void *base) { writePos = base; }
  72
  73         template <class T>
  74         T *operator () (const T &obj)
  75         { T *here = (T *)advance(sizeof(T)); *here = obj; return here; }
  76
  77         void *operator () (const void *addr, size_t size)
  78         { void *here = advance(size); return memcpy(here, addr, size); }
  79
  80         char *operator () (const char *s)
  81         { return (char *)(*this)(s, strlen(s) + 1); }
  82
  83         void countedData(const void *data, size_t length)
  84         {
  85         if (length > uint32_t(~0))
  86             UnixError::throwMe(ERANGE);
  87         Endian<uint32_t> temp = length; (*this)(temp); (*this)(data, length);
  88     }
  89
  90         template <class Data>
  91         void countedData(const Data &data)
  92         { countedData(data.data(), data.length()); }
  93
  94         class Counter;
  95
  96 private:
  97         void *writePos;                 // next byte address
  98 };
  99
 100 class Writer::Counter {
 101 private:
 102         void align() { totalSoFar = alignUp(totalSoFar); }
 103
 104 public:
 105         Counter() : totalSoFar(0) { }
 106         operator size_t () { return totalSoFar; }
 107
 108         template <class T> size_t operator () (const T &) { align(); return totalSoFar += sizeof(T); }
 109         size_t insert(size_t size) { align(); return totalSoFar += size; }
 110         size_t operator () (const char *s) { align(); return totalSoFar += strlen(s) + 1; }
 111
 112         void countedData(const void *, size_t length)
 113         { insert(sizeof(length)); insert(length); }
 114
 115         template <class Data>
 116         void countedData(const Data &data)
 117         { countedData(data.data(), data.length()); }
 118
 119 private:
 120         size_t totalSoFar;      // total size counted so far
 121 };
 122
 123
 124 //
 125 // The Reader counter-part for a Writer.
 126 // Again, Reader and Writer share alignment and representation rules, so what was
 127 // Written shall be Read again, just fine.
 128 //
 129 class Reader {
 130 private:
 131     const void *advance(size_t size = 0)
 132     {
 133         const void *here = alignUp(readPos);
 134         readPos = increment(here, size);
 135         return here;
 136     }
 137
 138 public:
 139     Reader() { }
 140     Reader(const void *base) : readPos(base) { }
 141     void operator = (const void *base) { readPos = base; }
 142
 143     template <class T>
 144     void operator () (T &obj) { obj = *reinterpret_cast<const T *>(advance(sizeof(T))); }
 145     void operator () (void *addr, size_t size)  { memcpy(addr, advance(size), size); }
 146     void operator () (const char * &s)
 147     { s = reinterpret_cast<const char *>(advance()); advance(strlen(s) + 1); }
 148     template <class T>
 149     const T *get(size_t size)
 150         { return reinterpret_cast<const T *>(advance(size)); }
 151
 152         void countedData(const void * &data, size_t &length)
 153         { Endian<uint32_t> temp; (*this)(temp); length = temp; data = advance(length); }
 154
 155 private:
 156         // Explicitly forbid some invocations that are likely to be wrong.
 157         void operator () (char * &s);   // can't get writable string in-place
 158
 159 private:
 160     const void *readPos;        // next byte address
 161 };
 162
 163
 164 } // end namespace LowLevelMemoryUtilities
 165
 166 } // end namespace Security
 167
 168 #endif //_H_MEMUTILS