| #include "SkMiniData.h" |
| |
| namespace { |
| |
| // SkMiniData::fRep either stores a LongData* or is punned into a ShortData. |
| // We use the low bits to distinguish the two: all pointers from malloc are at |
| // least 8-byte aligned, leaving those low bits clear when it's a LongData*. |
| |
| static bool is_long(uint64_t rep) { |
| // Even on 32-bit machines, we require the bottom 3 bits from malloc'd pointers are clear. |
| // If any of those bottom 3 bits are set, it's from a ShortData's len. And if no bits are |
| // set anywhere, it's an empty SkMiniData, which also follows the ShortData path. |
| return rep && SkIsAlign8(rep); |
| } |
| |
| // Can be used for any length, but we always use it for >=8. |
| struct LongData { |
| size_t len; |
| uint8_t data[8]; // There are actually len >= 8 bytes here. |
| |
| static uint64_t Create(const void* data, size_t len) { |
| SkASSERT(len > 7); |
| LongData* s = (LongData*)sk_malloc_throw(sizeof(size_t) + len); |
| s->len = len; |
| memcpy(s->data, data, len); |
| |
| uint64_t rep = reinterpret_cast<uint64_t>(s); |
| SkASSERT(is_long(rep)); |
| return rep; |
| } |
| }; |
| |
| // At most 7 bytes fit, but never mallocs. |
| struct ShortData { |
| // Order matters here. len must align with the least signficant bits of a pointer. |
| #ifdef SK_CPU_LENDIAN |
| uint8_t len; |
| uint8_t data[7]; |
| #else // Warning! Only the little-endian path has been tested. |
| uint8_t data[7]; |
| uint8_t len; |
| #endif |
| |
| static uint64_t Create(const void* data, size_t len) { |
| SkASSERT(len <= 7); |
| #ifdef SK_CPU_LENDIAN |
| ShortData s = { (uint8_t)len, {0, 0, 0, 0, 0, 0, 0} }; |
| #else // Warning! Only the little-endian path has been tested. |
| ShortData s = { {0, 0, 0, 0, 0, 0, 0}, (uint8_t)len }; |
| #endif |
| memcpy(s.data, data, len); |
| return *reinterpret_cast<uint64_t*>(&s); |
| } |
| }; |
| |
| } // namespace |
| |
| SkMiniData::SkMiniData(const void* data, size_t len) |
| : fRep(len <= 7 ? ShortData::Create(data, len) |
| : LongData::Create(data, len)) {} |
| |
| SkMiniData::SkMiniData(const SkMiniData& s) |
| : fRep(s.len() <= 7 ? ShortData::Create(s.data(), s.len()) |
| : LongData::Create(s.data(), s.len())) {} |
| |
| SkMiniData::~SkMiniData() { |
| if (is_long(fRep)) { |
| sk_free(reinterpret_cast<void*>(fRep)); |
| } |
| } |
| |
| const void* SkMiniData::data() const { |
| return is_long(fRep) ? reinterpret_cast<const LongData*>( fRep)->data |
| : reinterpret_cast<const ShortData*>(&fRep)->data; |
| } |
| |
| size_t SkMiniData::len() const { |
| return is_long(fRep) ? reinterpret_cast<const LongData*>( fRep)->len |
| : reinterpret_cast<const ShortData*>(&fRep)->len; |
| } |