Files
@ r16321:e1d5398db7dc
Branch filter:
Location: cpp/openttd-patchpack/source/src/misc/blob.hpp
r16321:e1d5398db7dc
11.5 KiB
text/x-c++hdr
(svn r21039) -Fix/Cleanup: Remove an unneeded and even wrong test, which is never reached anyway though.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 | /* $Id$ */
/*
* This file is part of OpenTTD.
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file blob.hpp Support for storing random binary data. */
#ifndef BLOB_HPP
#define BLOB_HPP
#include "../core/alloc_func.hpp"
#include "../core/mem_func.hpp"
#include <new>
/**
* Base class for simple binary blobs.
* Item is byte.
* The word 'simple' means:
* - no configurable allocator type (always made from heap)
* - no smart deallocation - deallocation must be called from the same
* module (DLL) where the blob was allocated
* - no configurable allocation policy (how big blocks should be allocated)
* - no extra ownership policy (i.e. 'copy on write') when blob is copied
* - no thread synchronization at all
*
* Internal member layout:
* 1. The only class member is pointer to the first item (see union).
* 2. Allocated block contains the blob header (see BlobHeader) followed by the raw byte data.
* Always, when it allocates memory the allocated size is:
* sizeof(BlobHeader) + <data capacity>
* 3. Two 'virtual' members (items and capacity) are stored in the BlobHeader at beginning
* of the alloated block.
* 4. The pointer of the union pobsize_ts behind the header (to the first data byte).
* When memory block is allocated, the sizeof(BlobHeader) it added to it.
* 5. Benefits of this layout:
* - items are accessed in the simplest possible way - just dereferencing the pointer,
* which is good for performance (assuming that data are accessed most often).
* - sizeof(blob) is the same as the size of any other pointer
* 6. Drawbacks of this layout:
* - the fact, that pointer to the alocated block is adjusted by sizeof(BlobHeader) before
* it is stored can lead to several confusions:
* - it is not common pattern so the implementation code is bit harder to read
* - valgrind can generate warning that allocated block is lost (not accessible)
*/
class ByteBlob {
protected:
/** header of the allocated memory block */
struct BlobHeader {
size_t items; ///< actual blob size in bytes
size_t capacity; ///< maximum (allocated) size in bytes
};
/** type used as class member */
union {
byte *data; ///< ptr to the first byte of data
BlobHeader *header; ///< ptr just after the BlobHeader holding items and capacity
};
private:
/**
* Just to silence an unsilencable GCC 4.4+ warning
* Note: This cannot be 'const' as we do a lot of 'hdrEmpty[0]->items += 0;' and 'hdrEmpty[0]->capacity += 0;'
* after const_casting.
*/
static BlobHeader hdrEmpty[];
public:
static const size_t tail_reserve = 4; ///< four extra bytes will be always allocated and zeroed at the end
static const size_t header_size = sizeof(BlobHeader);
/** default constructor - initializes empty blob */
FORCEINLINE ByteBlob() { InitEmpty(); }
/** copy constructor */
FORCEINLINE ByteBlob(const ByteBlob &src)
{
InitEmpty();
AppendRaw(src);
}
/** move constructor - take ownership of blob data */
FORCEINLINE ByteBlob(BlobHeader * const & src)
{
assert(src != NULL);
header = src;
*const_cast<BlobHeader**>(&src) = NULL;
}
/** destructor */
FORCEINLINE ~ByteBlob()
{
Free();
}
protected:
/** all allocation should happen here */
static FORCEINLINE BlobHeader *RawAlloc(size_t num_bytes)
{
return (BlobHeader*)MallocT<byte>(num_bytes);
}
/**
* Return header pointer to the static BlobHeader with
* both items and capacity containing zero
*/
static FORCEINLINE BlobHeader *Zero()
{
return const_cast<BlobHeader *>(&ByteBlob::hdrEmpty[1]);
}
/** simple allocation policy - can be optimized later */
static FORCEINLINE size_t AllocPolicy(size_t min_alloc)
{
if (min_alloc < (1 << 9)) {
if (min_alloc < (1 << 5)) return (1 << 5);
return (min_alloc < (1 << 7)) ? (1 << 7) : (1 << 9);
}
if (min_alloc < (1 << 15)) {
if (min_alloc < (1 << 11)) return (1 << 11);
return (min_alloc < (1 << 13)) ? (1 << 13) : (1 << 15);
}
if (min_alloc < (1 << 20)) {
if (min_alloc < (1 << 17)) return (1 << 17);
return (min_alloc < (1 << 19)) ? (1 << 19) : (1 << 20);
}
min_alloc = (min_alloc | ((1 << 20) - 1)) + 1;
return min_alloc;
}
/** all deallocations should happen here */
static FORCEINLINE void RawFree(BlobHeader *p)
{
/* Just to silence an unsilencable GCC 4.4+ warning. */
assert(p != ByteBlob::hdrEmpty);
/* In case GCC warns about the following, see GCC's PR38509 why it is bogus. */
free(p);
}
/** initialize the empty blob */
FORCEINLINE void InitEmpty()
{
header = Zero();
}
/** initialize blob by attaching it to the given header followed by data */
FORCEINLINE void Init(BlobHeader *src)
{
header = &src[1];
}
/** blob header accessor - use it rather than using the pointer arithmetics directly - non-const version */
FORCEINLINE BlobHeader& Hdr()
{
return *(header - 1);
}
/** blob header accessor - use it rather than using the pointer arithmetics directly - const version */
FORCEINLINE const BlobHeader& Hdr() const
{
return *(header - 1);
}
/** return reference to the actual blob size - used when the size needs to be modified */
FORCEINLINE size_t& LengthRef()
{
return Hdr().items;
}
public:
/** return true if blob doesn't contain valid data */
FORCEINLINE bool IsEmpty() const
{
return Length() == 0;
}
/** return the number of valid data bytes in the blob */
FORCEINLINE size_t Length() const
{
return Hdr().items;
}
/** return the current blob capacity in bytes */
FORCEINLINE size_t Capacity() const
{
return Hdr().capacity;
}
/** return pointer to the first byte of data - non-const version */
FORCEINLINE byte *Begin()
{
return data;
}
/** return pointer to the first byte of data - const version */
FORCEINLINE const byte *Begin() const
{
return data;
}
/** invalidate blob's data - doesn't free buffer */
FORCEINLINE void Clear()
{
LengthRef() = 0;
}
/** free the blob's memory */
FORCEINLINE void Free()
{
if (Capacity() > 0) {
RawFree(&Hdr());
InitEmpty();
}
}
/** append new bytes at the end of existing data bytes - reallocates if necessary */
FORCEINLINE void AppendRaw(const void *p, size_t num_bytes)
{
assert(p != NULL);
if (num_bytes > 0) {
memcpy(Append(num_bytes), p, num_bytes);
}
}
/** append bytes from given source blob to the end of existing data bytes - reallocates if necessary */
FORCEINLINE void AppendRaw(const ByteBlob& src)
{
if (!src.IsEmpty()) {
memcpy(Append(src.Length()), src.Begin(), src.Length());
}
}
/**
* Reallocate if there is no free space for num_bytes bytes.
* @return pointer to the new data to be added
*/
FORCEINLINE byte *Prepare(size_t num_bytes)
{
size_t new_size = Length() + num_bytes;
if (new_size > Capacity()) SmartAlloc(new_size);
return data + Length();
}
/**
* Increase Length() by num_bytes.
* @return pointer to the new data added
*/
FORCEINLINE byte *Append(size_t num_bytes)
{
byte *pNewData = Prepare(num_bytes);
LengthRef() += num_bytes;
return pNewData;
}
/** reallocate blob data if needed */
void SmartAlloc(size_t new_size)
{
if (Capacity() >= new_size) return;
/* calculate minimum block size we need to allocate
* and ask allocation policy for some reasonable block size */
new_size = AllocPolicy(header_size + new_size + tail_reserve);
/* allocate new block and setup header */
BlobHeader *tmp = RawAlloc(new_size);
tmp->items = Length();
tmp->capacity = new_size - (header_size + tail_reserve);
/* copy existing data */
if (tmp->items != 0) {
memcpy(tmp + 1, data, tmp->items);
}
/* replace our block with new one */
if (Capacity() > 0) {
RawFree(&Hdr());
}
Init(tmp);
}
/** fixing the four bytes at the end of blob data - useful when blob is used to hold string */
FORCEINLINE void FixTail() const
{
if (Capacity() > 0) {
byte *p = &data[Length()];
for (uint i = 0; i < tail_reserve; i++) {
p[i] = 0;
}
}
}
};
/**
* Blob - simple dynamic T array. T (template argument) is a placeholder for any type.
* T can be any integral type, pointer, or structure. Using Blob instead of just plain C array
* simplifies the resource management in several ways:
* 1. When adding new item(s) it automatically grows capacity if needed.
* 2. When variable of type Blob comes out of scope it automatically frees the data buffer.
* 3. Takes care about the actual data size (number of used items).
* 4. Dynamically constructs only used items (as opposite of static array which constructs all items)
*/
template <typename T>
class CBlobT : public ByteBlob {
/* make template arguments public: */
public:
typedef ByteBlob base;
static const size_t type_size = sizeof(T);
struct OnTransfer {
typename base::BlobHeader *header;
OnTransfer(const OnTransfer& src) : header(src.header) {assert(src.header != NULL); *const_cast<typename base::BlobHeader**>(&src.header) = NULL;}
OnTransfer(CBlobT& src) : header(src.header) {src.InitEmpty();}
~OnTransfer() {assert(header == NULL);}
};
/** Default constructor - makes new Blob ready to accept any data */
FORCEINLINE CBlobT()
: base()
{}
/** Take ownership constructor */
FORCEINLINE CBlobT(const OnTransfer& ot)
: base(ot.header)
{}
/** Destructor - ensures that allocated memory (if any) is freed */
FORCEINLINE ~CBlobT()
{
Free();
}
/** Check the validity of item index (only in debug mode) */
FORCEINLINE void CheckIdx(size_t index) const
{
assert(index < Size());
}
/** Return pointer to the first data item - non-const version */
FORCEINLINE T *Data()
{
return (T*)base::Begin();
}
/** Return pointer to the first data item - const version */
FORCEINLINE const T *Data() const
{
return (const T*)base::Begin();
}
/** Return pointer to the index-th data item - non-const version */
FORCEINLINE T *Data(size_t index)
{
CheckIdx(index);
return (Data() + index);
}
/** Return pointer to the index-th data item - const version */
FORCEINLINE const T *Data(size_t index) const
{
CheckIdx(index);
return (Data() + index);
}
/** Return number of items in the Blob */
FORCEINLINE size_t Size() const
{
return (base::Length() / type_size);
}
/** Return total number of items that can fit in the Blob without buffer reallocation */
FORCEINLINE size_t MaxSize() const
{
return (base::Capacity() / type_size);
}
/** Return number of additional items that can fit in the Blob without buffer reallocation */
FORCEINLINE size_t GetReserve() const
{
return ((base::Capacity() - base::Length()) / type_size);
}
/** Grow number of data items in Blob by given number - doesn't construct items */
FORCEINLINE T *GrowSizeNC(size_t num_items)
{
return (T*)base::Append(num_items * type_size);
}
/**
* Ensures that given number of items can be added to the end of Blob. Returns pointer to the
* first free (unused) item
*/
FORCEINLINE T *MakeFreeSpace(size_t num_items)
{
return (T*)base::Prepare(num_items * type_size);
}
FORCEINLINE OnTransfer Transfer()
{
return OnTransfer(*this);
}
};
#endif /* BLOB_HPP */
|