OSX/libsecurity_utilities/lib/buffers.h

   1 /*
   2  * Copyright (c) 2000-2001,2003-2004,2011,2014 Apple 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 // buffer - simple data buffers with convenience
  27 //
  28 #ifndef _H_BUFFER
  29 #define _H_BUFFER
  30
  31 #include <security_utilities/utilities.h>
  32 #include <cstdarg>
  33 #include <limits.h>
  34
  35
  36 namespace Security {
  37
  38
  39 class Buffer {
  40 public:
  41     Buffer(size_t size);                        // allocate empty buffer
  42     ~Buffer();
  43
  44     static Buffer reader(void *base, size_t size, bool owned = false)
  45     { return Buffer(base, size, true, owned); }
  46     static Buffer writer(void *base, size_t size, bool owned = false)
  47     { return Buffer(base, size, false, owned); }
  48
  49     size_t available(bool heavy = false) const
  50     { return heavy ? ((mTop - mEnd) + (mStart - mBase)): (mTop - mEnd); }
  51     bool isFull(bool heavy = false) const
  52     { return heavy ? (mEnd == mTop && mStart == mBase) : (mEnd == mTop); }
  53     bool isEmpty() const                { return mStart == mEnd; }
  54
  55     size_t length() const               { return mEnd - mStart; }
  56     void *data()                                { assert(mStart == mBase); return mStart; }
  57
  58     void clear()                                { mStart = mEnd = mBase; }
  59
  60 protected:
  61     // private constructor with full flexibility
  62     Buffer(void *base, size_t size, bool filled, bool owned = false);
  63
  64     // perform expensive realignment to coalesce freespace
  65     size_t shuffle(size_t needed = UINT_MAX);
  66
  67     // perform cheap adjustments after data was taken out
  68     void adjustGet()
  69     {
  70         if (isEmpty())  // empty buffer. Reset pointers to base
  71             mStart = mEnd = mBase;
  72     }
  73
  74 public:
  75     // elementary put: copy mode
  76     size_t put(const void *data, size_t length)
  77     {
  78         if (length > available())
  79             length = shuffle(length);
  80         memcpy(mEnd, data, length);
  81         mEnd += length;
  82         return length;
  83     }
  84
  85     // elementary put: locate mode. Remember that each can shuffle memory
  86     template <class T> void locatePut(T * &addr, size_t &length)
  87     {
  88         if (length > available())
  89             length = shuffle(length);
  90         addr = reinterpret_cast<T *>(mEnd);
  91     }
  92
  93     void usePut(size_t length)
  94     {
  95         assert(length <= available());
  96         mEnd += length;
  97     }
  98
  99     // elementary get: locate mode
 100     template <class T> void locateGet(T * &addr, size_t &length)
 101     {
 102         if (length > size_t(mEnd - mStart))
 103             length = mEnd - mStart;
 104         addr = reinterpret_cast<T *>(mStart);
 105     }
 106
 107     void useGet(size_t length)
 108     {
 109         assert(length <= this->length());
 110         mStart += length;
 111         adjustGet();
 112     }
 113
 114     //
 115     // I/O via FileDescoid objects
 116     //
 117     template <class IO>
 118     size_t read(IO &io, size_t length)
 119     {
 120         if (length > available())
 121             length = shuffle(length);
 122         size_t bytesRead = io.read(mEnd, length);
 123         mEnd += bytesRead;
 124         return bytesRead;
 125     }
 126
 127     template <class IO>
 128     size_t write(IO &io, size_t length)
 129     {
 130         length = min(this->length(), length);
 131         size_t bytesWritten = io.write(mStart, length);
 132         mStart += bytesWritten;
 133         adjustGet();
 134         return bytesWritten;
 135     }
 136
 137     template <class IO> size_t read(IO &io, bool heavy = false)
 138     { return read(io, available(heavy)); }
 139
 140     template <class IO> size_t write(IO &io)
 141     { return write(io, length()); }
 142
 143     // printf-style output to a buffer
 144     void printf(const char *format, ...);
 145     void vprintf(const char *format, va_list args);
 146
 147     // memory ownership
 148     void own()          { mOwningMemory = true; }
 149
 150 private:
 151     char *const mBase;                  // base pointer
 152     char *const mTop;                   // end pointer + 1
 153     char *mStart;                               // start of used area
 154     char *mEnd;                                 // end of used area + 1
 155     bool mOwningMemory;                 // true if we own the memory (free on destruction)
 156 };
 157
 158
 159 }       // end namespace Security
 160
 161
 162 #endif //_H_BUFFER