#include "SkTemplates.h"
enum ChecksumType {
+ kChecksum_ChecksumType,
kMD5_ChecksumType,
kSHA1_ChecksumType,
kMurmur3_ChecksumType,
protected:
const char* onGetName() override {
switch (fType) {
+ case kChecksum_ChecksumType: return "compute_checksum";
case kMD5_ChecksumType: return "compute_md5";
case kSHA1_ChecksumType: return "compute_sha1";
case kMurmur3_ChecksumType: return "compute_murmur3";
void onDraw(int loops, SkCanvas*) override {
switch (fType) {
+ case kChecksum_ChecksumType: {
+ for (int i = 0; i < loops; i++) {
+ volatile uint32_t result = SkChecksum::Compute(fData, sizeof(fData));
+ sk_ignore_unused_variable(result);
+ }
+ } break;
case kMD5_ChecksumType: {
for (int i = 0; i < loops; i++) {
SkMD5 md5;
///////////////////////////////////////////////////////////////////////////////
+DEF_BENCH( return new ComputeChecksumBench(kChecksum_ChecksumType); )
DEF_BENCH( return new ComputeChecksumBench(kMD5_ChecksumType); )
DEF_BENCH( return new ComputeChecksumBench(kSHA1_ChecksumType); )
DEF_BENCH( return new ComputeChecksumBench(kMurmur3_ChecksumType); )
#include "SkTLogic.h"
#include "SkTypes.h"
+/**
+ * Computes a 32bit checksum from a blob of 32bit aligned data. This is meant
+ * to be very very fast, as it is used internally by the font cache, in
+ * conjuction with the entire raw key. This algorithm does not generate
+ * unique values as well as others (e.g. MD5) but it performs much faster.
+ * Skia's use cases can survive non-unique values (since the entire key is
+ * always available). Clients should only be used in circumstances where speed
+ * over uniqueness is at a premium.
+ */
class SkChecksum : SkNoncopyable {
+private:
+ /*
+ * Our Rotate and Mash helpers are meant to automatically do the right
+ * thing depending if sizeof(uintptr_t) is 4 or 8.
+ */
+ enum {
+ ROTR = 17,
+ ROTL = sizeof(uintptr_t) * 8 - ROTR,
+ HALFBITS = sizeof(uintptr_t) * 4
+ };
+
+ static inline uintptr_t Mash(uintptr_t total, uintptr_t value) {
+ return ((total >> ROTR) | (total << ROTL)) ^ value;
+ }
+
public:
/**
* uint32_t -> uint32_t hash, useful for when you're about to trucate this hash but you
/**
* Calculate 32-bit Murmur hash (murmur3).
+ * This should take 2-3x longer than SkChecksum::Compute, but is a considerably better hash.
* See en.wikipedia.org/wiki/MurmurHash.
*
* @param data Memory address of the data block to be processed.
* @return hash result
*/
static uint32_t Murmur3(const void* data, size_t bytes, uint32_t seed=0);
+
+ /**
+ * Compute a 32-bit checksum for a given data block
+ *
+ * WARNING: this algorithm is tuned for efficiency, not backward/forward
+ * compatibility. It may change at any time, so a checksum generated with
+ * one version of the Skia code may not match a checksum generated with
+ * a different version of the Skia code.
+ *
+ * @param data Memory address of the data block to be processed. Must be
+ * 32-bit aligned.
+ * @param size Size of the data block in bytes. Must be a multiple of 4.
+ * @return checksum result
+ */
+ static uint32_t Compute(const uint32_t* data, size_t size) {
+ // Use may_alias to remind the compiler we're intentionally violating strict aliasing,
+ // and so not to apply strict-aliasing-based optimizations.
+ typedef uint32_t SK_ATTRIBUTE(may_alias) aliased_uint32_t;
+ const aliased_uint32_t* safe_data = (const aliased_uint32_t*)data;
+
+ SkASSERT(SkIsAlign4(size));
+
+ /*
+ * We want to let the compiler use 32bit or 64bit addressing and math
+ * so we use uintptr_t as our magic type. This makes the code a little
+ * more obscure (we can't hard-code 32 or 64 anywhere, but have to use
+ * sizeof()).
+ */
+ uintptr_t result = 0;
+ const uintptr_t* ptr = reinterpret_cast<const uintptr_t*>(safe_data);
+
+ /*
+ * count the number of quad element chunks. This takes into account
+ * if we're on a 32bit or 64bit arch, since we use sizeof(uintptr_t)
+ * to compute how much to shift-down the size.
+ */
+ size_t n4 = size / (sizeof(uintptr_t) << 2);
+ for (size_t i = 0; i < n4; ++i) {
+ result = Mash(result, *ptr++);
+ result = Mash(result, *ptr++);
+ result = Mash(result, *ptr++);
+ result = Mash(result, *ptr++);
+ }
+ size &= ((sizeof(uintptr_t) << 2) - 1);
+
+ safe_data = reinterpret_cast<const aliased_uint32_t*>(ptr);
+ const aliased_uint32_t* stop = safe_data + (size >> 2);
+ while (safe_data < stop) {
+ result = Mash(result, *safe_data++);
+ }
+
+ /*
+ * smash us down to 32bits if we were 64. Note that when uintptr_t is
+ * 32bits, this code-path should go away, but I still got a warning
+ * when I wrote
+ * result ^= result >> 32;
+ * since >>32 is undefined for 32bit ints, hence the wacky HALFBITS
+ * define.
+ */
+ if (8 == sizeof(result)) {
+ result ^= result >> HALFBITS;
+ }
+ return static_cast<uint32_t>(result);
+ }
};
// SkGoodHash should usually be your first choice in hashing data.
}
uint32_t GrResourceKeyHash(const uint32_t* data, size_t size) {
- return SkChecksum::Murmur3(data, size);
+ return SkChecksum::Compute(data, size);
}
//////////////////////////////////////////////////////////////////////////////
int currP = 0;
int currNP = 0;
while (currP < sortedPurgeableResources.count() &&
- currNP < fNonpurgeableResources.count()) {
+ currNP < fNonpurgeableResources.count()) {
uint32_t tsP = sortedPurgeableResources[currP]->cacheAccess().timestamp();
uint32_t tsNP = fNonpurgeableResources[currNP]->cacheAccess().timestamp();
SkASSERT(tsP != tsNP);
// count should be the next timestamp we return.
SkASSERT(fTimestamp == SkToU32(count));
-
+
// The historical timestamps of flushes are now invalid.
this->resetFlushTimestamps();
- }
+ }
}
return fTimestamp++;
}
projects / platform / upstream / libSkiaSharp.git / commitdiff