+------------------------------------------------------------------------
+r60 | snappy.mirrorbot@gmail.com | 2012-02-23 18:00:36 +0100 (Thu, 23 Feb 2012) | 57 lines
+
+For 32-bit platforms, do not try to accelerate multiple neighboring
+32-bit loads with a 64-bit load during compression (it's not a win).
+
+The main target for this optimization is ARM, but 32-bit x86 gets
+a small gain, too, although there is noise in the microbenchmarks.
+It's a no-op for 64-bit x86. It does not affect decompression.
+
+Microbenchmark results on a Cortex-A9 1GHz, using g++ 4.6.2 (from
+Ubuntu/Linaro), -O2 -DNDEBUG -Wa,-march=armv7a -mtune=cortex-a9
+-mthumb-interwork, minimum 1000 iterations:
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ ---------------------------------------------------
+ BM_ZFlat/0 1158277 1160000 1000 84.2MB/s html (23.57 %) [ +4.3%]
+ BM_ZFlat/1 14861782 14860000 1000 45.1MB/s urls (50.89 %) [ +1.1%]
+ BM_ZFlat/2 393595 390000 1000 310.5MB/s jpg (99.88 %) [ +0.0%]
+ BM_ZFlat/3 650583 650000 1000 138.4MB/s pdf (82.13 %) [ +3.1%]
+ BM_ZFlat/4 4661480 4660000 1000 83.8MB/s html4 (23.55 %) [ +4.3%]
+ BM_ZFlat/5 491973 490000 1000 47.9MB/s cp (48.12 %) [ +2.0%]
+ BM_ZFlat/6 193575 192678 1038 55.2MB/s c (42.40 %) [ +9.0%]
+ BM_ZFlat/7 62343 62754 3187 56.5MB/s lsp (48.37 %) [ +2.6%]
+ BM_ZFlat/8 17708468 17710000 1000 55.5MB/s xls (41.34 %) [ -0.3%]
+ BM_ZFlat/9 3755345 3760000 1000 38.6MB/s txt1 (59.81 %) [ +8.2%]
+ BM_ZFlat/10 3324217 3320000 1000 36.0MB/s txt2 (64.07 %) [ +4.2%]
+ BM_ZFlat/11 10139932 10140000 1000 40.1MB/s txt3 (57.11 %) [ +6.4%]
+ BM_ZFlat/12 13532109 13530000 1000 34.0MB/s txt4 (68.35 %) [ +5.0%]
+ BM_ZFlat/13 4690847 4690000 1000 104.4MB/s bin (18.21 %) [ +4.1%]
+ BM_ZFlat/14 830682 830000 1000 43.9MB/s sum (51.88 %) [ +1.2%]
+ BM_ZFlat/15 84784 85011 2235 47.4MB/s man (59.36 %) [ +1.1%]
+ BM_ZFlat/16 1293254 1290000 1000 87.7MB/s pb (23.15 %) [ +2.3%]
+ BM_ZFlat/17 2775155 2780000 1000 63.2MB/s gaviota (38.27 %) [+12.2%]
+
+Core i7 in 32-bit mode (only one run and 100 iterations, though, so noisy):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ ---------------------------------------------------
+ BM_ZFlat/0 227582 223464 3043 437.0MB/s html (23.57 %) [ +7.4%]
+ BM_ZFlat/1 2982430 2918455 233 229.4MB/s urls (50.89 %) [ +2.9%]
+ BM_ZFlat/2 46967 46658 15217 2.5GB/s jpg (99.88 %) [ +0.0%]
+ BM_ZFlat/3 115298 114864 5833 783.2MB/s pdf (82.13 %) [ +1.5%]
+ BM_ZFlat/4 913440 899743 778 434.2MB/s html4 (23.55 %) [ +0.3%]
+ BM_ZFlat/5 110302 108571 7000 216.1MB/s cp (48.12 %) [ +0.0%]
+ BM_ZFlat/6 44409 43372 15909 245.2MB/s c (42.40 %) [ +0.8%]
+ BM_ZFlat/7 15713 15643 46667 226.9MB/s lsp (48.37 %) [ +2.7%]
+ BM_ZFlat/8 2625539 2602230 269 377.4MB/s xls (41.34 %) [ +1.4%]
+ BM_ZFlat/9 808884 811429 875 178.8MB/s txt1 (59.81 %) [ -3.9%]
+ BM_ZFlat/10 709532 700000 1000 170.5MB/s txt2 (64.07 %) [ +0.0%]
+ BM_ZFlat/11 2177682 2162162 333 188.2MB/s txt3 (57.11 %) [ -1.4%]
+ BM_ZFlat/12 2849640 2840000 250 161.8MB/s txt4 (68.35 %) [ -1.4%]
+ BM_ZFlat/13 849760 835476 778 585.8MB/s bin (18.21 %) [ +1.2%]
+ BM_ZFlat/14 165940 164571 4375 221.6MB/s sum (51.88 %) [ +1.4%]
+ BM_ZFlat/15 20939 20571 35000 196.0MB/s man (59.36 %) [ +2.1%]
+ BM_ZFlat/16 239209 236544 2917 478.1MB/s pb (23.15 %) [ +4.2%]
+ BM_ZFlat/17 616206 610000 1000 288.2MB/s gaviota (38.27 %) [ -1.6%]
+
+R=sanjay
+
+------------------------------------------------------------------------
+r59 | snappy.mirrorbot@gmail.com | 2012-02-21 18:02:17 +0100 (Tue, 21 Feb 2012) | 107 lines
+
+Enable the use of unaligned loads and stores for ARM-based architectures
+where they are available (ARMv7 and higher). This gives a significant
+speed boost on ARM, both for compression and decompression.
+It should not affect x86 at all.
+
+There are more changes possible to speed up ARM, but it might not be
+that easy to do without hurting x86 or making the code uglier.
+Also, we de not try to use NEON yet.
+
+Microbenchmark results on a Cortex-A9 1GHz, using g++ 4.6.2 (from Ubuntu/Linaro),
+-O2 -DNDEBUG -Wa,-march=armv7a -mtune=cortex-a9 -mthumb-interwork:
+
+Benchmark Time(ns) CPU(ns) Iterations
+---------------------------------------------------
+BM_UFlat/0 524806 529100 378 184.6MB/s html [+33.6%]
+BM_UFlat/1 5139790 5200000 100 128.8MB/s urls [+28.8%]
+BM_UFlat/2 86540 84166 1901 1.4GB/s jpg [ +0.6%]
+BM_UFlat/3 215351 210176 904 428.0MB/s pdf [+29.8%]
+BM_UFlat/4 2144490 2100000 100 186.0MB/s html4 [+33.3%]
+BM_UFlat/5 194482 190000 1000 123.5MB/s cp [+36.2%]
+BM_UFlat/6 91843 90175 2107 117.9MB/s c [+38.6%]
+BM_UFlat/7 28535 28426 6684 124.8MB/s lsp [+34.7%]
+BM_UFlat/8 9206600 9200000 100 106.7MB/s xls [+42.4%]
+BM_UFlat/9 1865273 1886792 106 76.9MB/s txt1 [+32.5%]
+BM_UFlat/10 1576809 1587301 126 75.2MB/s txt2 [+32.3%]
+BM_UFlat/11 4968450 4900000 100 83.1MB/s txt3 [+32.7%]
+BM_UFlat/12 6673970 6700000 100 68.6MB/s txt4 [+32.8%]
+BM_UFlat/13 2391470 2400000 100 203.9MB/s bin [+29.2%]
+BM_UFlat/14 334601 344827 522 105.8MB/s sum [+30.6%]
+BM_UFlat/15 37404 38080 5252 105.9MB/s man [+33.8%]
+BM_UFlat/16 535470 540540 370 209.2MB/s pb [+31.2%]
+BM_UFlat/17 1875245 1886792 106 93.2MB/s gaviota [+37.8%]
+BM_UValidate/0 178425 179533 1114 543.9MB/s html [ +2.7%]
+BM_UValidate/1 2100450 2000000 100 334.8MB/s urls [ +5.0%]
+BM_UValidate/2 1039 1044 172413 113.3GB/s jpg [ +3.4%]
+BM_UValidate/3 59423 59470 3363 1.5GB/s pdf [ +7.8%]
+BM_UValidate/4 760716 766283 261 509.8MB/s html4 [ +6.5%]
+BM_ZFlat/0 1204632 1204819 166 81.1MB/s html (23.57 %) [+32.8%]
+BM_ZFlat/1 15656190 15600000 100 42.9MB/s urls (50.89 %) [+27.6%]
+BM_ZFlat/2 403336 410677 487 294.8MB/s jpg (99.88 %) [+16.5%]
+BM_ZFlat/3 664073 671140 298 134.0MB/s pdf (82.13 %) [+28.4%]
+BM_ZFlat/4 4961940 4900000 100 79.7MB/s html4 (23.55 %) [+30.6%]
+BM_ZFlat/5 500664 501253 399 46.8MB/s cp (48.12 %) [+33.4%]
+BM_ZFlat/6 217276 215982 926 49.2MB/s c (42.40 %) [+25.0%]
+BM_ZFlat/7 64122 65487 3054 54.2MB/s lsp (48.37 %) [+36.1%]
+BM_ZFlat/8 18045730 18000000 100 54.6MB/s xls (41.34 %) [+34.4%]
+BM_ZFlat/9 4051530 4000000 100 36.3MB/s txt1 (59.81 %) [+25.0%]
+BM_ZFlat/10 3451800 3500000 100 34.1MB/s txt2 (64.07 %) [+25.7%]
+BM_ZFlat/11 11052340 11100000 100 36.7MB/s txt3 (57.11 %) [+24.3%]
+BM_ZFlat/12 14538690 14600000 100 31.5MB/s txt4 (68.35 %) [+24.7%]
+BM_ZFlat/13 5041850 5000000 100 97.9MB/s bin (18.21 %) [+32.0%]
+BM_ZFlat/14 908840 909090 220 40.1MB/s sum (51.88 %) [+22.2%]
+BM_ZFlat/15 86921 86206 1972 46.8MB/s man (59.36 %) [+42.2%]
+BM_ZFlat/16 1312315 1315789 152 86.0MB/s pb (23.15 %) [+34.5%]
+BM_ZFlat/17 3173120 3200000 100 54.9MB/s gaviota (38.27%) [+28.1%]
+
+
+The move from 64-bit to 32-bit operations for the copies also affected 32-bit x86;
+positive on the decompression side, and slightly negative on the compression side
+(unless that is noise; I only ran once):
+
+Benchmark Time(ns) CPU(ns) Iterations
+-----------------------------------------------------
+BM_UFlat/0 86279 86140 7778 1.1GB/s html [ +7.5%]
+BM_UFlat/1 839265 822622 778 813.9MB/s urls [ +9.4%]
+BM_UFlat/2 9180 9143 87500 12.9GB/s jpg [ +1.2%]
+BM_UFlat/3 35080 35000 20000 2.5GB/s pdf [+10.1%]
+BM_UFlat/4 350318 345000 2000 1.1GB/s html4 [ +7.0%]
+BM_UFlat/5 33808 33472 21212 701.0MB/s cp [ +9.0%]
+BM_UFlat/6 15201 15214 46667 698.9MB/s c [+14.9%]
+BM_UFlat/7 4652 4651 159091 762.9MB/s lsp [ +7.5%]
+BM_UFlat/8 1285551 1282528 538 765.7MB/s xls [+10.7%]
+BM_UFlat/9 282510 281690 2414 514.9MB/s txt1 [+13.6%]
+BM_UFlat/10 243494 239286 2800 498.9MB/s txt2 [+14.4%]
+BM_UFlat/11 743625 740000 1000 550.0MB/s txt3 [+14.3%]
+BM_UFlat/12 999441 989717 778 464.3MB/s txt4 [+16.1%]
+BM_UFlat/13 412402 410076 1707 1.2GB/s bin [ +7.3%]
+BM_UFlat/14 54876 54000 10000 675.3MB/s sum [+13.0%]
+BM_UFlat/15 6146 6100 100000 660.8MB/s man [+14.8%]
+BM_UFlat/16 90496 90286 8750 1.2GB/s pb [ +4.0%]
+BM_UFlat/17 292650 292000 2500 602.0MB/s gaviota [+18.1%]
+BM_UValidate/0 49620 49699 14286 1.9GB/s html [ +0.0%]
+BM_UValidate/1 501371 500000 1000 1.3GB/s urls [ +0.0%]
+BM_UValidate/2 232 227 3043478 521.5GB/s jpg [ +1.3%]
+BM_UValidate/3 17250 17143 43750 5.1GB/s pdf [ -1.3%]
+BM_UValidate/4 198643 200000 3500 1.9GB/s html4 [ -0.9%]
+BM_ZFlat/0 227128 229415 3182 425.7MB/s html (23.57 %) [ -1.4%]
+BM_ZFlat/1 2970089 2960000 250 226.2MB/s urls (50.89 %) [ -1.9%]
+BM_ZFlat/2 45683 44999 15556 2.6GB/s jpg (99.88 %) [ +2.2%]
+BM_ZFlat/3 114661 113136 6364 795.1MB/s pdf (82.13 %) [ -1.5%]
+BM_ZFlat/4 919702 914286 875 427.2MB/s html4 (23.55%) [ -1.3%]
+BM_ZFlat/5 108189 108422 6364 216.4MB/s cp (48.12 %) [ -1.2%]
+BM_ZFlat/6 44525 44000 15909 241.7MB/s c (42.40 %) [ -2.9%]
+BM_ZFlat/7 15973 15857 46667 223.8MB/s lsp (48.37 %) [ +0.0%]
+BM_ZFlat/8 2677888 2639405 269 372.1MB/s xls (41.34 %) [ -1.4%]
+BM_ZFlat/9 800715 780000 1000 186.0MB/s txt1 (59.81 %) [ -0.4%]
+BM_ZFlat/10 700089 700000 1000 170.5MB/s txt2 (64.07 %) [ -2.9%]
+BM_ZFlat/11 2159356 2138365 318 190.3MB/s txt3 (57.11 %) [ -0.3%]
+BM_ZFlat/12 2796143 2779923 259 165.3MB/s txt4 (68.35 %) [ -1.4%]
+BM_ZFlat/13 856458 835476 778 585.8MB/s bin (18.21 %) [ -0.1%]
+BM_ZFlat/14 166908 166857 4375 218.6MB/s sum (51.88 %) [ -1.4%]
+BM_ZFlat/15 21181 20857 35000 193.3MB/s man (59.36 %) [ -0.8%]
+BM_ZFlat/16 244009 239973 2917 471.3MB/s pb (23.15 %) [ -1.4%]
+BM_ZFlat/17 596362 590000 1000 297.9MB/s gaviota (38.27%) [ +0.0%]
+
+R=sanjay
+
+------------------------------------------------------------------------
+r58 | snappy.mirrorbot@gmail.com | 2012-02-11 23:11:22 +0100 (Sat, 11 Feb 2012) | 9 lines
+
+Lower the size allocated in the "corrupted input" unit test from 256 MB
+to 2 MB. This fixes issues with running the unit test on platforms with
+little RAM (e.g. some ARM boards).
+
+Also, reactivate the 2 MB test for 64-bit platforms; there's no good
+reason why it shouldn't be.
+
+R=sanjay
+
+------------------------------------------------------------------------
+r57 | snappy.mirrorbot@gmail.com | 2012-01-08 18:55:48 +0100 (Sun, 08 Jan 2012) | 2 lines
+
+Minor refactoring to accomodate changes in Google's internal code tree.
+
+------------------------------------------------------------------------
+r56 | snappy.mirrorbot@gmail.com | 2012-01-04 14:10:46 +0100 (Wed, 04 Jan 2012) | 19 lines
+
+Fix public issue r57: Fix most warnings with -Wall, mostly signed/unsigned
+warnings. There are still some in the unit test, but the main .cc file should
+be clean. We haven't enabled -Wall for the default build, since the unit test
+is still not clean.
+
+This also fixes a real bug in the open-source implementation of
+ReadFileToStringOrDie(); it would not detect errors correctly.
+
+I had to go through some pains to avoid performance loss as the types
+were changed; I think there might still be some with 32-bit if and only if LFS
+is enabled (ie., size_t is 64-bit), but for regular 32-bit and 64-bit I can't
+see any losses, and I've diffed the generated GCC assembler between the old and
+new code without seeing any significant choices. If anything, it's ever so
+slightly faster.
+
+This may or may not enable compression of very large blocks (>2^32 bytes)
+when size_t is 64-bit, but I haven't checked, and it is still not a supported
+case.
+
+------------------------------------------------------------------------
+r55 | snappy.mirrorbot@gmail.com | 2012-01-04 11:46:39 +0100 (Wed, 04 Jan 2012) | 6 lines
+
+Add a framing format description. We do not have any implementation of this at
+the current point, but there seems to be enough of a general interest in the
+topic (cf. public bug #34).
+
+R=csilvers,sanjay
+
+------------------------------------------------------------------------
+r54 | snappy.mirrorbot@gmail.com | 2011-12-05 22:27:26 +0100 (Mon, 05 Dec 2011) | 81 lines
+
+Speed up decompression by moving the refill check to the end of the loop.
+
+This seems to work because in most of the branches, the compiler can evaluate
+“ip_limit_ - ip” in a more efficient way than reloading ip_limit_ from memory
+(either by already having the entire expression in a register, or reconstructing
+it from “avail”, or something else). Memory loads, even from L1, are seemingly
+costly in the big picture at the current decompression speeds.
+
+Microbenchmarks (64-bit, opt mode):
+
+Westmere (Intel Core i7):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ --------------------------------------------
+ BM_UFlat/0 74492 74491 187894 1.3GB/s html [ +5.9%]
+ BM_UFlat/1 712268 712263 19644 940.0MB/s urls [ +3.8%]
+ BM_UFlat/2 10591 10590 1000000 11.2GB/s jpg [ -6.8%]
+ BM_UFlat/3 29643 29643 469915 3.0GB/s pdf [ +7.9%]
+ BM_UFlat/4 304669 304667 45930 1.3GB/s html4 [ +4.8%]
+ BM_UFlat/5 28508 28507 490077 823.1MB/s cp [ +4.0%]
+ BM_UFlat/6 12415 12415 1000000 856.5MB/s c [ +8.6%]
+ BM_UFlat/7 3415 3415 4084723 1039.0MB/s lsp [+18.0%]
+ BM_UFlat/8 979569 979563 14261 1002.5MB/s xls [ +5.8%]
+ BM_UFlat/9 230150 230148 60934 630.2MB/s txt1 [ +5.2%]
+ BM_UFlat/10 197167 197166 71135 605.5MB/s txt2 [ +4.7%]
+ BM_UFlat/11 607394 607390 23041 670.1MB/s txt3 [ +5.6%]
+ BM_UFlat/12 808502 808496 17316 568.4MB/s txt4 [ +5.0%]
+ BM_UFlat/13 372791 372788 37564 1.3GB/s bin [ +3.3%]
+ BM_UFlat/14 44541 44541 313969 818.8MB/s sum [ +5.7%]
+ BM_UFlat/15 4833 4833 2898697 834.1MB/s man [ +4.8%]
+ BM_UFlat/16 79855 79855 175356 1.4GB/s pb [ +4.8%]
+ BM_UFlat/17 245845 245843 56838 715.0MB/s gaviota [ +5.8%]
+
+Clovertown (Intel Core 2):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ --------------------------------------------
+ BM_UFlat/0 107911 107890 100000 905.1MB/s html [ +2.2%]
+ BM_UFlat/1 1011237 1011041 10000 662.3MB/s urls [ +2.5%]
+ BM_UFlat/2 26775 26770 523089 4.4GB/s jpg [ +0.0%]
+ BM_UFlat/3 48103 48095 290618 1.8GB/s pdf [ +3.4%]
+ BM_UFlat/4 437724 437644 31937 892.6MB/s html4 [ +2.1%]
+ BM_UFlat/5 39607 39600 358284 592.5MB/s cp [ +2.4%]
+ BM_UFlat/6 18227 18224 768191 583.5MB/s c [ +2.7%]
+ BM_UFlat/7 5171 5170 2709437 686.4MB/s lsp [ +3.9%]
+ BM_UFlat/8 1560291 1559989 8970 629.5MB/s xls [ +3.6%]
+ BM_UFlat/9 335401 335343 41731 432.5MB/s txt1 [ +3.0%]
+ BM_UFlat/10 287014 286963 48758 416.0MB/s txt2 [ +2.8%]
+ BM_UFlat/11 888522 888356 15752 458.1MB/s txt3 [ +2.9%]
+ BM_UFlat/12 1186600 1186378 10000 387.3MB/s txt4 [ +3.1%]
+ BM_UFlat/13 572295 572188 24468 855.4MB/s bin [ +2.1%]
+ BM_UFlat/14 64060 64049 218401 569.4MB/s sum [ +4.1%]
+ BM_UFlat/15 7264 7263 1916168 555.0MB/s man [ +1.4%]
+ BM_UFlat/16 108853 108836 100000 1039.1MB/s pb [ +1.7%]
+ BM_UFlat/17 364289 364223 38419 482.6MB/s gaviota [ +4.9%]
+
+Barcelona (AMD Opteron):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ --------------------------------------------
+ BM_UFlat/0 103900 103871 100000 940.2MB/s html [ +8.3%]
+ BM_UFlat/1 1000435 1000107 10000 669.5MB/s urls [ +6.6%]
+ BM_UFlat/2 24659 24652 567362 4.8GB/s jpg [ +0.1%]
+ BM_UFlat/3 48206 48193 291121 1.8GB/s pdf [ +5.0%]
+ BM_UFlat/4 421980 421850 33174 926.0MB/s html4 [ +7.3%]
+ BM_UFlat/5 40368 40357 346994 581.4MB/s cp [ +8.7%]
+ BM_UFlat/6 19836 19830 708695 536.2MB/s c [ +8.0%]
+ BM_UFlat/7 6100 6098 2292774 581.9MB/s lsp [ +9.0%]
+ BM_UFlat/8 1693093 1692514 8261 580.2MB/s xls [ +8.0%]
+ BM_UFlat/9 365991 365886 38225 396.4MB/s txt1 [ +7.1%]
+ BM_UFlat/10 311330 311238 44950 383.6MB/s txt2 [ +7.6%]
+ BM_UFlat/11 975037 974737 14376 417.5MB/s txt3 [ +6.9%]
+ BM_UFlat/12 1303558 1303175 10000 352.6MB/s txt4 [ +7.3%]
+ BM_UFlat/13 517448 517290 27144 946.2MB/s bin [ +5.5%]
+ BM_UFlat/14 66537 66518 210352 548.3MB/s sum [ +7.5%]
+ BM_UFlat/15 7976 7974 1760383 505.6MB/s man [ +5.6%]
+ BM_UFlat/16 103121 103092 100000 1097.0MB/s pb [ +8.7%]
+ BM_UFlat/17 391431 391314 35733 449.2MB/s gaviota [ +6.5%]
+
+R=sanjay
+
+------------------------------------------------------------------------
+r53 | snappy.mirrorbot@gmail.com | 2011-11-23 12:14:17 +0100 (Wed, 23 Nov 2011) | 88 lines
+
+Speed up decompression by making the fast path for literals faster.
+
+We do the fast-path step as soon as possible; in fact, as soon as we know the
+literal length. Since we usually hit the fast path, we can then skip the checks
+for long literals and available input space (beyond what the fast path check
+already does).
+
+Note that this changes the decompression Writer API; however, it does not
+change the ABI, since writers are always templatized and as such never
+cross compilation units. The new API is slightly more general, in that it
+doesn't hard-code the value 16. Note that we also take care to check
+for len <= 16 first, since the other two checks almost always succeed
+(so we don't want to waste time checking for them until we have to).
+
+The improvements are most marked on Nehalem, but are generally positive
+on other platforms as well. All microbenchmarks are 64-bit, opt.
+
+Clovertown (Core 2):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ --------------------------------------------
+ BM_UFlat/0 110226 110224 100000 886.0MB/s html [ +1.5%]
+ BM_UFlat/1 1036523 1036508 10000 646.0MB/s urls [ -0.8%]
+ BM_UFlat/2 26775 26775 522570 4.4GB/s jpg [ +0.0%]
+ BM_UFlat/3 49738 49737 280974 1.8GB/s pdf [ +0.3%]
+ BM_UFlat/4 446790 446792 31334 874.3MB/s html4 [ +0.8%]
+ BM_UFlat/5 40561 40562 350424 578.5MB/s cp [ +1.3%]
+ BM_UFlat/6 18722 18722 746903 568.0MB/s c [ +1.4%]
+ BM_UFlat/7 5373 5373 2608632 660.5MB/s lsp [ +8.3%]
+ BM_UFlat/8 1615716 1615718 8670 607.8MB/s xls [ +2.0%]
+ BM_UFlat/9 345278 345281 40481 420.1MB/s txt1 [ +1.4%]
+ BM_UFlat/10 294855 294855 47452 404.9MB/s txt2 [ +1.6%]
+ BM_UFlat/11 914263 914263 15316 445.2MB/s txt3 [ +1.1%]
+ BM_UFlat/12 1222694 1222691 10000 375.8MB/s txt4 [ +1.4%]
+ BM_UFlat/13 584495 584489 23954 837.4MB/s bin [ -0.6%]
+ BM_UFlat/14 66662 66662 210123 547.1MB/s sum [ +1.2%]
+ BM_UFlat/15 7368 7368 1881856 547.1MB/s man [ +4.0%]
+ BM_UFlat/16 110727 110726 100000 1021.4MB/s pb [ +2.3%]
+ BM_UFlat/17 382138 382141 36616 460.0MB/s gaviota [ -0.7%]
+
+Westmere (Core i7):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ --------------------------------------------
+ BM_UFlat/0 78861 78853 177703 1.2GB/s html [ +2.1%]
+ BM_UFlat/1 739560 739491 18912 905.4MB/s urls [ +3.4%]
+ BM_UFlat/2 9867 9866 1419014 12.0GB/s jpg [ +3.4%]
+ BM_UFlat/3 31989 31986 438385 2.7GB/s pdf [ +0.2%]
+ BM_UFlat/4 319406 319380 43771 1.2GB/s html4 [ +1.9%]
+ BM_UFlat/5 29639 29636 472862 791.7MB/s cp [ +5.2%]
+ BM_UFlat/6 13478 13477 1000000 789.0MB/s c [ +2.3%]
+ BM_UFlat/7 4030 4029 3475364 880.7MB/s lsp [ +8.7%]
+ BM_UFlat/8 1036585 1036492 10000 947.5MB/s xls [ +6.9%]
+ BM_UFlat/9 242127 242105 57838 599.1MB/s txt1 [ +3.0%]
+ BM_UFlat/10 206499 206480 67595 578.2MB/s txt2 [ +3.4%]
+ BM_UFlat/11 641635 641570 21811 634.4MB/s txt3 [ +2.4%]
+ BM_UFlat/12 848847 848769 16443 541.4MB/s txt4 [ +3.1%]
+ BM_UFlat/13 384968 384938 36366 1.2GB/s bin [ +0.3%]
+ BM_UFlat/14 47106 47101 297770 774.3MB/s sum [ +4.4%]
+ BM_UFlat/15 5063 5063 2772202 796.2MB/s man [ +7.7%]
+ BM_UFlat/16 83663 83656 167697 1.3GB/s pb [ +1.8%]
+ BM_UFlat/17 260224 260198 53823 675.6MB/s gaviota [ -0.5%]
+
+Barcelona (Opteron):
+
+ Benchmark Time(ns) CPU(ns) Iterations
+ --------------------------------------------
+ BM_UFlat/0 112490 112457 100000 868.4MB/s html [ -0.4%]
+ BM_UFlat/1 1066719 1066339 10000 627.9MB/s urls [ +1.0%]
+ BM_UFlat/2 24679 24672 563802 4.8GB/s jpg [ +0.7%]
+ BM_UFlat/3 50603 50589 277285 1.7GB/s pdf [ +2.6%]
+ BM_UFlat/4 452982 452849 30900 862.6MB/s html4 [ -0.2%]
+ BM_UFlat/5 43860 43848 319554 535.1MB/s cp [ +1.2%]
+ BM_UFlat/6 21419 21413 653573 496.6MB/s c [ +1.0%]
+ BM_UFlat/7 6646 6645 2105405 534.1MB/s lsp [ +0.3%]
+ BM_UFlat/8 1828487 1827886 7658 537.3MB/s xls [ +2.6%]
+ BM_UFlat/9 391824 391714 35708 370.3MB/s txt1 [ +2.2%]
+ BM_UFlat/10 334913 334816 41885 356.6MB/s txt2 [ +1.7%]
+ BM_UFlat/11 1042062 1041674 10000 390.7MB/s txt3 [ +1.1%]
+ BM_UFlat/12 1398902 1398456 10000 328.6MB/s txt4 [ +1.7%]
+ BM_UFlat/13 545706 545530 25669 897.2MB/s bin [ -0.4%]
+ BM_UFlat/14 71512 71505 196035 510.0MB/s sum [ +1.4%]
+ BM_UFlat/15 8422 8421 1665036 478.7MB/s man [ +2.6%]
+ BM_UFlat/16 112053 112048 100000 1009.3MB/s pb [ -0.4%]
+ BM_UFlat/17 416723 416713 33612 421.8MB/s gaviota [ -2.0%]
+
+R=sanjay
+
+------------------------------------------------------------------------
+r52 | snappy.mirrorbot@gmail.com | 2011-11-08 15:46:39 +0100 (Tue, 08 Nov 2011) | 5 lines
+
+Fix public issue #53: Update the README to the API we actually open-sourced
+with.
+
+R=sanjay
+
+------------------------------------------------------------------------
+r51 | snappy.mirrorbot@gmail.com | 2011-10-05 14:27:12 +0200 (Wed, 05 Oct 2011) | 5 lines
+
+In the format description, use a clearer example to emphasize that varints are
+stored in little-endian. Patch from Christian von Roques.
+
+R=csilvers
+
+------------------------------------------------------------------------
+r50 | snappy.mirrorbot@gmail.com | 2011-09-15 21:34:06 +0200 (Thu, 15 Sep 2011) | 4 lines
+
+Release Snappy 1.0.4.
+
+R=sanjay
+
------------------------------------------------------------------------
r49 | snappy.mirrorbot@gmail.com | 2011-09-15 11:50:05 +0200 (Thu, 15 Sep 2011) | 5 lines
state of ip_ after decompression (or attempted decompresion) is
completely irrelevant, so we don't need the trailer.
-Performance is, as expected, mostly flat -- there's a curious ~3–5%
-loss in the “lsp” test, but that test case is so short it is hard to say
+Performance is, as expected, mostly flat -- there's a curious ~3-5%
+loss in the "lsp" test, but that test case is so short it is hard to say
anything definitive about why (most likely, it's some sort of
unrelated effect).
before it saves ip_ back and returns. (Note that Step() was already inlined,
so it is not the manual inlining that buys the performance here.)
-The wins are about 3–6% for Core 2, 6–13% on Core i7 and 5–12% on Opteron
+The wins are about 3-6% for Core 2, 6-13% on Core i7 and 5-12% on Opteron
(for plain array-to-array decompression, in 64-bit opt mode).
There is a tiny difference in the behavior here; if an invalid literal is
+Snappy v1.0.5, February 24th 2012:
+
+ * More speed improvements. Exactly how big will depend on
+ the architecture:
+
+ - 3–10% faster decompression for the base case (x86-64).
+
+ - ARMv7 and higher can now use unaligned accesses,
+ and will see about 30% faster decompression and
+ 20–40% faster compression.
+
+ - 32-bit platforms (ARM and 32-bit x86) will see 2–5%
+ faster compression.
+
+ These are all cumulative (e.g., ARM gets all three speedups).
+
+ * Fixed an issue where the unit test would crash on system
+ with less than 256 MB address space available,
+ e.g. some embedded platforms.
+
+ * Added a framing format description, for use over e.g. HTTP,
+ or for a command-line compressor. We do not have any
+ implementations of this at the current point, but there seems
+ to be enough of a general interest in the topic.
+ Also make the format description slightly clearer.
+
+ * Remove some compile-time warnings in -Wall
+ (mostly signed/unsigned comparisons), for easier embedding
+ into projects that use -Wall -Werror.
+
+
Snappy v1.0.4, September 15th 2011:
* Speeded up the decompressor somewhat; typically about 2–8%
There are many ways to call Snappy, but the simplest possible is
- snappy::Compress(input, &output);
+ snappy::Compress(input.data(), input.size(), &output);
and similarly
- snappy::Uncompress(input, &output);
+ snappy::Uncompress(input.data(), input.size(), &output);
where "input" and "output" are both instances of std::string.
Snappy compressed format description
-Last revised: 2011-08-09
+Last revised: 2011-10-05
This is not a formal specification, but should suffice to explain most
stored as a little-endian varint. Varints consist of a series of bytes,
where the lower 7 bits are data and the upper bit is set iff there are
more bytes to be read. In other words, an uncompressed length of 64 would
-be stored as 0x40, and an uncompressed length of 2097151 (0x1FFFFF)
-would be stored as 0xFF 0xFF 0x7F.
+be stored as 0x40, and an uncompressed length of 2097150 (0x1FFFFE)
+would be stored as 0xFE 0xFF 0x7F.
2. The compressed stream itself
--- /dev/null
+Snappy framing format description
+Last revised: 2011-12-15
+
+This format decribes a framing format for Snappy, allowing compressing to
+files or streams that can then more easily be decompressed without having
+to hold the entire stream in memory. It also provides data checksums to
+help verify integrity. It does not provide metadata checksums, so it does
+not protect against e.g. all forms of truncations.
+
+Implementation of the framing format is optional for Snappy compressors and
+decompressor; it is not part of the Snappy core specification.
+
+
+1. General structure
+
+The file consists solely of chunks, lying back-to-back with no padding
+in between. Each chunk consists first a single byte of chunk identifier,
+then a two-byte little-endian length of the chunk in bytes (from 0 to 65535,
+inclusive), and then the data if any. The three bytes of chunk header is not
+counted in the data length.
+
+The different chunk types are listed below. The first chunk must always
+be the stream identifier chunk (see section 4.1, below). The stream
+ends when the file ends -- there is no explicit end-of-file marker.
+
+
+2. File type identification
+
+The following identifiers for this format are recommended where appropriate.
+However, note that none have been registered officially, so this is only to
+be taken as a guideline. We use "Snappy framed" to distinguish between this
+format and raw Snappy data.
+
+ File extension: .sz
+ MIME type: application/x-snappy-framed
+ HTTP Content-Encoding: x-snappy-framed
+
+
+3. Checksum format
+
+Some chunks have data protected by a checksum (the ones that do will say so
+explicitly). The checksums are always masked CRC-32Cs.
+
+A description of CRC-32C can be found in RFC 3720, section 12.1, with
+examples in section B.4.
+
+Checksums are not stored directly, but masked, as checksumming data and
+then its own checksum can be problematic. The masking is the same as used
+in Apache Hadoop: Rotate the checksum by 15 bits, then add the constant
+0xa282ead8 (using wraparound as normal for unsigned integers). This is
+equivalent to the following C code:
+
+ uint32_t mask_checksum(uint32_t x) {
+ return ((x >> 15) | (x << 17)) + 0xa282ead8;
+ }
+
+Note that the masking is reversible.
+
+The checksum is always stored as a four bytes long integer, in little-endian.
+
+
+4. Chunk types
+
+The currently supported chunk types are described below. The list may
+be extended in the future.
+
+
+4.1. Stream identifier (chunk type 0xff)
+
+The stream identifier is always the first element in the stream.
+It is exactly six bytes long and contains "sNaPpY" in ASCII. This means that
+a valid Snappy framed stream always starts with the bytes
+
+ 0xff 0x06 0x00 0x73 0x4e 0x61 0x50 0x70 0x59
+
+The stream identifier chunk can come multiple times in the stream besides
+the first; if such a chunk shows up, it should simply be ignored, assuming
+it has the right length and contents. This allows for easy concatenation of
+compressed files without the need for re-framing.
+
+
+4.2. Compressed data (chunk type 0x00)
+
+Compressed data chunks contain a normal Snappy compressed bitstream;
+see the compressed format specification. The compressed data is preceded by
+the CRC-32C (see section 3) of the _uncompressed_ data.
+
+Note that the data portion of the chunk, i.e., the compressed contents,
+can be at most 65531 bytes (2^16 - 1, minus the checksum).
+However, we place an additional restriction that the uncompressed data
+in a chunk must be no longer than 32768 bytes. This allows consumers to
+easily use small fixed-size buffers.
+
+
+4.3. Uncompressed data (chunk type 0x01)
+
+Uncompressed data chunks allow a compressor to send uncompressed,
+raw data; this is useful if, for instance, uncompressible or
+near-incompressible data is detected, and faster decompression is desired.
+
+As in the compressed chunks, the data is preceded by its own masked
+CRC-32C (see section 3).
+
+An uncompressed data chunk, like compressed data chunks, should contain
+no more than 32768 data bytes, so the maximum legal chunk length with the
+checksum is 32772.
+
+
+4.4. Reserved unskippable chunks (chunk types 0x02-0x7f)
+
+These are reserved for future expansion. A decoder that sees such a chunk
+should immediately return an error, as it must assume it cannot decode the
+stream correctly.
+
+Future versions of this specification may define meanings for these chunks.
+
+
+4.5. Reserved skippable chunks (chunk types 0x80-0xfe)
+
+These are also reserved for future expansion, but unlike the chunks
+described in 4.4, a decoder seeing these must skip them and continue
+decoding.
+
+Future versions of this specification may define meanings for these chunks.
// The default implementation always returns the scratch buffer.
virtual char* GetAppendBuffer(size_t length, char* scratch);
+
private:
// No copying
Sink(const Sink&);
// version (anyone who wants to regenerate it can just do the call
// themselves within main()).
#define DEFINE_bool(flag_name, default_value, description) \
- bool FLAGS_ ## flag_name = default_value;
+ bool FLAGS_ ## flag_name = default_value
#define DECLARE_bool(flag_name) \
- extern bool FLAGS_ ## flag_name;
-#define REGISTER_MODULE_INITIALIZER(name, code)
+ extern bool FLAGS_ ## flag_name
namespace snappy {
// Potentially unaligned loads and stores.
+// x86 and PowerPC can simply do these loads and stores native.
+
#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__)
#define UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p))
#define UNALIGNED_STORE32(_p, _val) (*reinterpret_cast<uint32 *>(_p) = (_val))
#define UNALIGNED_STORE64(_p, _val) (*reinterpret_cast<uint64 *>(_p) = (_val))
+// ARMv7 and newer support native unaligned accesses, but only of 16-bit
+// and 32-bit values (not 64-bit); older versions either raise a fatal signal,
+// do an unaligned read and rotate the words around a bit, or do the reads very
+// slowly (trip through kernel mode). There's no simple #define that says just
+// “ARMv7 or higher”, so we have to filter away all ARMv5 and ARMv6
+// sub-architectures.
+//
+// This is a mess, but there's not much we can do about it.
+
+#elif defined(__arm__) && \
+ !defined(__ARM_ARCH_5__) && \
+ !defined(__ARM_ARCH_5T__) && \
+ !defined(__ARM_ARCH_5TE__) && \
+ !defined(__ARM_ARCH_5TEJ__) && \
+ !defined(__ARM_ARCH_6__) && \
+ !defined(__ARM_ARCH_6J__) && \
+ !defined(__ARM_ARCH_6K__) && \
+ !defined(__ARM_ARCH_6Z__) && \
+ !defined(__ARM_ARCH_6ZK__) && \
+ !defined(__ARM_ARCH_6T2__)
+
+#define UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p))
+#define UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32 *>(_p))
+
+#define UNALIGNED_STORE16(_p, _val) (*reinterpret_cast<uint16 *>(_p) = (_val))
+#define UNALIGNED_STORE32(_p, _val) (*reinterpret_cast<uint32 *>(_p) = (_val))
+
+// TODO(user): NEON supports unaligned 64-bit loads and stores.
+// See if that would be more efficient on platforms supporting it,
+// at least for copies.
+
+inline uint64 UNALIGNED_LOAD64(const void *p) {
+ uint64 t;
+ memcpy(&t, p, sizeof t);
+ return t;
+}
+
+inline void UNALIGNED_STORE64(void *p, uint64 v) {
+ memcpy(p, &v, sizeof v);
+}
+
#else
// These functions are provided for architectures that don't support
#endif
+// This can be more efficient than UNALIGNED_LOAD64 + UNALIGNED_STORE64
+// on some platforms, in particular ARM.
+inline void UnalignedCopy64(const void *src, void *dst) {
+ if (sizeof(void *) == 8) {
+ UNALIGNED_STORE64(dst, UNALIGNED_LOAD64(src));
+ } else {
+ const char *src_char = reinterpret_cast<const char *>(src);
+ char *dst_char = reinterpret_cast<char *>(dst);
+
+ UNALIGNED_STORE32(dst_char, UNALIGNED_LOAD32(src_char));
+ UNALIGNED_STORE32(dst_char + 4, UNALIGNED_LOAD32(src_char + 4));
+ }
+}
+
// The following guarantees declaration of the byte swap functions.
#ifdef WORDS_BIGENDIAN
#define SNAPPY_MAJOR 1
#define SNAPPY_MINOR 0
-#define SNAPPY_PATCHLEVEL 4
+#define SNAPPY_PATCHLEVEL 5
#define SNAPPY_VERSION \
((SNAPPY_MAJOR << 16) | (SNAPPY_MINOR << 8) | SNAPPY_PATCHLEVEL)
// compression.
err = deflate(&comp_stream_, flush_mode);
- const uLong source_bytes_consumed = *sourceLen - comp_stream_.avail_in;
*sourceLen = comp_stream_.avail_in;
if ((err == Z_STREAM_END || err == Z_OK)
int ZLib::Compress(Bytef *dest, uLongf *destLen,
const Bytef *source, uLong sourceLen) {
int err;
- const uLongf orig_destLen = *destLen;
if ( (err=CompressChunkOrAll(dest, destLen, source, sourceLen,
Z_FINISH)) != Z_OK )
return err;
while (!feof(fp)) {
char buf[4096];
size_t ret = fread(buf, 1, 4096, fp);
- if (ret == -1) {
+ if (ret == 0 && ferror(fp)) {
perror("fread");
exit(1);
}
static inline void IncrementalCopyFastPath(const char* src, char* op, int len) {
while (op - src < 8) {
- UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));
+ UnalignedCopy64(src, op);
len -= op - src;
op += op - src;
}
while (len > 0) {
- UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));
+ UnalignedCopy64(src, op);
src += 8;
op += 8;
len -= 8;
// - The output will always have 32 spare bytes (see
// MaxCompressedLength).
if (allow_fast_path && len <= 16) {
- UNALIGNED_STORE64(op, UNALIGNED_LOAD64(literal));
- UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(literal + 8));
+ UnalignedCopy64(literal, op);
+ UnalignedCopy64(literal + 8, op + 8);
return op + len;
}
} else {
return op + len;
}
-static inline char* EmitCopyLessThan64(char* op, int offset, int len) {
+static inline char* EmitCopyLessThan64(char* op, size_t offset, int len) {
DCHECK_LE(len, 64);
DCHECK_GE(len, 4);
DCHECK_LT(offset, 65536);
if ((len < 12) && (offset < 2048)) {
- int len_minus_4 = len - 4;
+ size_t len_minus_4 = len - 4;
assert(len_minus_4 < 8); // Must fit in 3 bits
*op++ = COPY_1_BYTE_OFFSET | ((len_minus_4) << 2) | ((offset >> 8) << 5);
*op++ = offset & 0xff;
return op;
}
-static inline char* EmitCopy(char* op, int offset, int len) {
+static inline char* EmitCopy(char* op, size_t offset, int len) {
// Emit 64 byte copies but make sure to keep at least four bytes reserved
while (len >= 68) {
op = EmitCopyLessThan64(op, offset, 64);
// compression, and if the input is short, we won't need that
// many hash table entries anyway.
assert(kMaxHashTableSize >= 256);
- int htsize = 256;
+ size_t htsize = 256;
while (htsize < kMaxHashTableSize && htsize < input_size) {
htsize <<= 1;
}
}
} // end namespace internal
-// For 0 <= offset <= 4, GetUint32AtOffset(UNALIGNED_LOAD64(p), offset) will
+// For 0 <= offset <= 4, GetUint32AtOffset(GetEightBytesAt(p), offset) will
// equal UNALIGNED_LOAD32(p + offset). Motivation: On x86-64 hardware we have
// empirically found that overlapping loads such as
// UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2)
// are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to uint32.
+//
+// We have different versions for 64- and 32-bit; ideally we would avoid the
+// two functions and just inline the UNALIGNED_LOAD64 call into
+// GetUint32AtOffset, but GCC (at least not as of 4.6) is seemingly not clever
+// enough to avoid loading the value multiple times then. For 64-bit, the load
+// is done when GetEightBytesAt() is called, whereas for 32-bit, the load is
+// done at GetUint32AtOffset() time.
+
+#ifdef ARCH_K8
+
+typedef uint64 EightBytesReference;
+
+static inline EightBytesReference GetEightBytesAt(const char* ptr) {
+ return UNALIGNED_LOAD64(ptr);
+}
+
static inline uint32 GetUint32AtOffset(uint64 v, int offset) {
- DCHECK(0 <= offset && offset <= 4) << offset;
+ DCHECK_GE(offset, 0);
+ DCHECK_LE(offset, 4);
return v >> (LittleEndian::IsLittleEndian() ? 8 * offset : 32 - 8 * offset);
}
+#else
+
+typedef const char* EightBytesReference;
+
+static inline EightBytesReference GetEightBytesAt(const char* ptr) {
+ return ptr;
+}
+
+static inline uint32 GetUint32AtOffset(const char* v, int offset) {
+ DCHECK_GE(offset, 0);
+ DCHECK_LE(offset, 4);
+ return UNALIGNED_LOAD32(v + offset);
+}
+
+#endif
+
// Flat array compression that does not emit the "uncompressed length"
// prefix. Compresses "input" string to the "*op" buffer.
//
CHECK_LE(input_size, kBlockSize);
CHECK_EQ(table_size & (table_size - 1), 0) << ": table must be power of two";
const int shift = 32 - Bits::Log2Floor(table_size);
- DCHECK_EQ(kuint32max >> shift, table_size - 1);
+ DCHECK_EQ(static_cast<int>(kuint32max >> shift), table_size - 1);
const char* ip_end = input + input_size;
const char* base_ip = ip;
// Bytes in [next_emit, ip) will be emitted as literal bytes. Or
// [next_emit, ip_end) after the main loop.
const char* next_emit = ip;
- const int kInputMarginBytes = 15;
+ const size_t kInputMarginBytes = 15;
if (PREDICT_TRUE(input_size >= kInputMarginBytes)) {
const char* ip_limit = input + input_size - kInputMarginBytes;
// though we don't yet know how big the literal will be. We handle that
// by proceeding to the next iteration of the main loop. We also can exit
// this loop via goto if we get close to exhausting the input.
- uint64 input_bytes = 0;
+ EightBytesReference input_bytes;
uint32 candidate_bytes = 0;
do {
const char* base = ip;
int matched = 4 + FindMatchLength(candidate + 4, ip + 4, ip_end);
ip += matched;
- int offset = base - candidate;
+ size_t offset = base - candidate;
DCHECK_EQ(0, memcmp(base, candidate, matched));
op = EmitCopy(op, offset, matched);
// We could immediately start working at ip now, but to improve
if (PREDICT_FALSE(ip >= ip_limit)) {
goto emit_remainder;
}
- input_bytes = UNALIGNED_LOAD64(insert_tail);
+ input_bytes = GetEightBytesAt(insert_tail);
uint32 prev_hash = HashBytes(GetUint32AtOffset(input_bytes, 0), shift);
table[prev_hash] = ip - base_ip - 1;
uint32 cur_hash = HashBytes(GetUint32AtOffset(input_bytes, 1), shift);
// bool CheckLength() const;
//
// // Called repeatedly during decompression
-// bool Append(const char* ip, uint32 length, bool allow_fast_path);
-// bool AppendFromSelf(uint32 offset, uint32 length);
-// };
+// bool Append(const char* ip, size_t length);
+// bool AppendFromSelf(uint32 offset, size_t length);
//
-// "allow_fast_path" is a parameter that says if there is at least 16
-// readable bytes in "ip". It is currently only used by SnappyArrayWriter.
+// // The difference between TryFastAppend and Append is that TryFastAppend
+// // is allowed to read up to <available> bytes from the input buffer,
+// // whereas Append is allowed to read <length>.
+// //
+// // Also, TryFastAppend is allowed to return false, declining the append,
+// // without it being a fatal error -- just "return false" would be
+// // a perfectly legal implementation of TryFastAppend. The intention
+// // is for TryFastAppend to allow a fast path in the common case of
+// // a small append.
+// //
+// // NOTE(user): TryFastAppend must always return decline (return false)
+// // if <length> is 61 or more, as in this case the literal length is not
+// // decoded fully. In practice, this should not be a big problem,
+// // as it is unlikely that one would implement a fast path accepting
+// // this much data.
+// bool TryFastAppend(const char* ip, size_t available, size_t length);
+// };
// -----------------------------------------------------------------------
// Lookup table for decompression code. Generated by ComputeTable() below.
CHECK_EQ(dst[i], char_table[i]);
}
}
-REGISTER_MODULE_INITIALIZER(snappy, ComputeTable());
#endif /* !NDEBUG */
// Helper class for decompression
template <class Writer>
void DecompressAllTags(Writer* writer) {
const char* ip = ip_;
- for ( ;; ) {
- if (ip_limit_ - ip < 5) {
- ip_ = ip;
- if (!RefillTag()) return;
- ip = ip_;
- }
+ // We could have put this refill fragment only at the beginning of the loop.
+ // However, duplicating it at the end of each branch gives the compiler more
+ // scope to optimize the <ip_limit_ - ip> expression based on the local
+ // context, which overall increases speed.
+ #define MAYBE_REFILL() \
+ if (ip_limit_ - ip < 5) { \
+ ip_ = ip; \
+ if (!RefillTag()) return; \
+ ip = ip_; \
+ }
+
+ MAYBE_REFILL();
+ for ( ;; ) {
const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip++));
if ((c & 0x3) == LITERAL) {
- uint32 literal_length = c >> 2;
- if (PREDICT_FALSE(literal_length >= 60)) {
+ size_t literal_length = (c >> 2) + 1u;
+ if (writer->TryFastAppend(ip, ip_limit_ - ip, literal_length)) {
+ DCHECK_LT(literal_length, 61);
+ ip += literal_length;
+ MAYBE_REFILL();
+ continue;
+ }
+ if (PREDICT_FALSE(literal_length >= 61)) {
// Long literal.
- const uint32 literal_length_length = literal_length - 59;
+ const size_t literal_length_length = literal_length - 60;
literal_length =
- LittleEndian::Load32(ip) & wordmask[literal_length_length];
+ (LittleEndian::Load32(ip) & wordmask[literal_length_length]) + 1;
ip += literal_length_length;
}
- ++literal_length;
- uint32 avail = ip_limit_ - ip;
+ size_t avail = ip_limit_ - ip;
while (avail < literal_length) {
- if (!writer->Append(ip, avail, false)) return;
+ if (!writer->Append(ip, avail)) return;
literal_length -= avail;
reader_->Skip(peeked_);
size_t n;
if (avail == 0) return; // Premature end of input
ip_limit_ = ip + avail;
}
- bool allow_fast_path = (avail >= 16);
- if (!writer->Append(ip, literal_length, allow_fast_path)) {
+ if (!writer->Append(ip, literal_length)) {
return;
}
ip += literal_length;
+ MAYBE_REFILL();
} else {
const uint32 entry = char_table[c];
const uint32 trailer = LittleEndian::Load32(ip) & wordmask[entry >> 11];
if (!writer->AppendFromSelf(copy_offset + trailer, length)) {
return;
}
+ MAYBE_REFILL();
}
}
+
+#undef MAYBE_REFILL
}
};
SnappyDecompressor decompressor(r);
uint32 uncompressed_len = 0;
if (!decompressor.ReadUncompressedLength(&uncompressed_len)) return false;
+ return InternalUncompressAllTags(
+ &decompressor, writer, uncompressed_len, max_len);
+}
+
+template <typename Writer>
+static bool InternalUncompressAllTags(SnappyDecompressor* decompressor,
+ Writer* writer,
+ uint32 uncompressed_len,
+ uint32 max_len) {
// Protect against possible DoS attack
if (static_cast<uint64>(uncompressed_len) > max_len) {
return false;
writer->SetExpectedLength(uncompressed_len);
// Process the entire input
- decompressor.DecompressAllTags(writer);
- return (decompressor.eof() && writer->CheckLength());
+ decompressor->DecompressAllTags(writer);
+ return (decompressor->eof() && writer->CheckLength());
}
bool GetUncompressedLength(Source* source, uint32* result) {
size_t Compress(Source* reader, Sink* writer) {
size_t written = 0;
- int N = reader->Available();
+ size_t N = reader->Available();
char ulength[Varint::kMax32];
char* p = Varint::Encode32(ulength, N);
writer->Append(ulength, p-ulength);
size_t fragment_size;
const char* fragment = reader->Peek(&fragment_size);
DCHECK_NE(fragment_size, 0) << ": premature end of input";
- const int num_to_read = min(N, kBlockSize);
+ const size_t num_to_read = min(N, kBlockSize);
size_t bytes_read = fragment_size;
- int pending_advance = 0;
+ size_t pending_advance = 0;
if (bytes_read >= num_to_read) {
// Buffer returned by reader is large enough
pending_advance = num_to_read;
return op_ == op_limit_;
}
- inline bool Append(const char* ip, uint32 len, bool allow_fast_path) {
+ inline bool Append(const char* ip, size_t len) {
char* op = op_;
- const int space_left = op_limit_ - op;
- if (allow_fast_path && len <= 16 && space_left >= 16) {
- // Fast path, used for the majority (about 90%) of dynamic invocations.
- UNALIGNED_STORE64(op, UNALIGNED_LOAD64(ip));
- UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(ip + 8));
- } else {
- if (space_left < len) {
- return false;
- }
- memcpy(op, ip, len);
+ const size_t space_left = op_limit_ - op;
+ if (space_left < len) {
+ return false;
}
+ memcpy(op, ip, len);
op_ = op + len;
return true;
}
- inline bool AppendFromSelf(uint32 offset, uint32 len) {
+ inline bool TryFastAppend(const char* ip, size_t available, size_t len) {
char* op = op_;
- const int space_left = op_limit_ - op;
+ const size_t space_left = op_limit_ - op;
+ if (len <= 16 && available >= 16 && space_left >= 16) {
+ // Fast path, used for the majority (about 95%) of invocations.
+ UnalignedCopy64(ip, op);
+ UnalignedCopy64(ip + 8, op + 8);
+ op_ = op + len;
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+ inline bool AppendFromSelf(size_t offset, size_t len) {
+ char* op = op_;
+ const size_t space_left = op_limit_ - op;
if (op - base_ <= offset - 1u) { // -1u catches offset==0
return false;
}
if (len <= 16 && offset >= 8 && space_left >= 16) {
// Fast path, used for the majority (70-80%) of dynamic invocations.
- UNALIGNED_STORE64(op, UNALIGNED_LOAD64(op - offset));
- UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(op - offset + 8));
+ UnalignedCopy64(op - offset, op);
+ UnalignedCopy64(op - offset + 8, op + 8);
} else {
if (space_left >= len + kMaxIncrementCopyOverflow) {
IncrementalCopyFastPath(op - offset, op, len);
inline bool CheckLength() const {
return expected_ == produced_;
}
- inline bool Append(const char* ip, uint32 len, bool allow_fast_path) {
+ inline bool Append(const char* ip, size_t len) {
produced_ += len;
return produced_ <= expected_;
}
- inline bool AppendFromSelf(uint32 offset, uint32 len) {
+ inline bool TryFastAppend(const char* ip, size_t available, size_t length) {
+ return false;
+ }
+ inline bool AppendFromSelf(size_t offset, size_t len) {
if (produced_ <= offset - 1u) return false; // -1u catches offset==0
produced_ += len;
return produced_ <= expected_;
// decompression code should not rely on this guarantee since older
// compression code may not obey it.
static const int kBlockLog = 15;
- static const int kBlockSize = 1 << kBlockLog;
+ static const size_t kBlockSize = 1 << kBlockLog;
static const int kMaxHashTableBits = 14;
- static const int kMaxHashTableSize = 1 << kMaxHashTableBits;
+ static const size_t kMaxHashTableSize = 1 << kMaxHashTableBits;
} // end namespace snappy
reinterpret_cast<const Bytef*>(compressed.data()),
compressed.size());
CHECK_EQ(Z_OK, ret);
- CHECK_EQ(destlen, size);
+ CHECK_EQ(static_cast<uLongf>(size), destlen);
break;
}
#endif // ZLIB_VERSION
&destlen,
NULL);
CHECK_EQ(LZO_E_OK, ret);
- CHECK_EQ(destlen, size);
+ CHECK_EQ(static_cast<lzo_uint>(size), destlen);
break;
}
#endif // LZO_VERSION
// Another security check; check a crazy big length can't DoS us with an
// over-allocation.
// Currently this is done only for 32-bit builds. On 64-bit builds,
- // where 3GBytes might be an acceptable allocation size, Uncompress()
+ // where 3 GB might be an acceptable allocation size, Uncompress()
// attempts to decompress, and sometimes causes the test to run out of
// memory.
dest[0] = dest[1] = dest[2] = dest[3] = 0xff;
- // This decodes to a really large size, i.e., 3221225471 bytes
+ // This decodes to a really large size, i.e., about 3 GB.
dest[4] = 'k';
CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
CHECK(!Uncompress(TypeParam(dest), &uncmp));
- dest[0] = dest[1] = dest[2] = 0xff;
- dest[3] = 0x7f;
- CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
- CHECK(!Uncompress(TypeParam(dest), &uncmp));
} else {
LOG(WARNING) << "Crazy decompression lengths not checked on 64-bit build";
}
+ // This decodes to about 2 MB; much smaller, but should still fail.
+ dest[0] = dest[1] = dest[2] = 0xff;
+ dest[3] = 0x00;
+ CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
+ CHECK(!Uncompress(TypeParam(dest), &uncmp));
+
// try reading stuff in from a bad file.
for (int i = 1; i <= 3; ++i) {
string data = ReadTestDataFile(StringPrintf("baddata%d.snappy", i).c_str());
projects / apitrace / commitdiff