leveldb::crc32c Namespace Reference

Classes
class	CRC

Functions
static uint32_t	LE_LOAD32 (const uint8_t *p)
uint32_t	Extend (uint32_t crc, const char *buf, size_t size)
uint32_t	Value (const char *data, size_t n)
uint32_t	Mask (uint32_t crc)
uint32_t	Unmask (uint32_t masked_crc)
	TEST (CRC, StandardResults)
	TEST (CRC, Values)
	TEST (CRC, Extend)
	TEST (CRC, Mask)

Variables
static const uint32_t	table0_ [256]
static const uint32_t	table1_ [256]
static const uint32_t	table2_ [256]
static const uint32_t	table3_ [256]
static const uint32_t	kMaskDelta = 0xa282ead8ul

---

Class Documentation

leveldb::crc32c::CRC

class leveldb::crc32c::CRC

Definition at line 11 of file crc32c_test.cc.

Function Documentation

Extend()

uint32_t leveldb::crc32c::Extend	(	uint32_t	crc,
		const char *	buf,
		size_t	size
	)

Definition at line 286 of file crc32c.cc.

                                                            {
  const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
  const uint8_t *e = p + size;
  uint32_t l = crc ^ 0xffffffffu;

#define STEP1 do {                              \
    int c = (l & 0xff) ^ *p++;                  \
    l = table0_[c] ^ (l >> 8);                  \
} while (0)
#define STEP4 do {                              \
    uint32_t c = l ^ LE_LOAD32(p);              \
    p += 4;                                     \
    l = table3_[c & 0xff] ^                     \
        table2_[(c >> 8) & 0xff] ^              \
        table1_[(c >> 16) & 0xff] ^             \
        table0_[c >> 24];                       \
} while (0)

  // Point x at first 4-byte aligned byte in string.  This might be
  // just past the end of the string.
  const uintptr_t pval = reinterpret_cast<uintptr_t>(p);
  const uint8_t* x = reinterpret_cast<const uint8_t*>(((pval + 3) >> 2) << 2);
  if (x <= e) {
    // Process bytes until finished or p is 4-byte aligned
    while (p != x) {
      STEP1;
    }
  }
  // Process bytes 16 at a time
  while ((e-p) >= 16) {
    STEP4; STEP4; STEP4; STEP4;
  }
  // Process bytes 4 at a time
  while ((e-p) >= 4) {
    STEP4;
  }
  // Process the last few bytes
  while (p != e) {
    STEP1;
  }
#undef STEP4
#undef STEP1
  return l ^ 0xffffffffu;
}

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LE_LOAD32()

static uint32_t leveldb::crc32c::LE_LOAD32 ( const uint8_t *  p )

inlinestatic

Definition at line 282 of file crc32c.cc.

                                                   {
  return DecodeFixed32(reinterpret_cast<const char*>(p));
}

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Mask()

uint32_t leveldb::crc32c::Mask ( uint32_t  crc )

inline

Definition at line 31 of file crc32c.h.

                                   {
  // Rotate right by 15 bits and add a constant.
  return ((crc >> 15) | (crc << 17)) + kMaskDelta;
}

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TEST() [1/4]

leveldb::crc32c::TEST	(	CRC	,
		StandardResults
	)

Definition at line 13 of file crc32c_test.cc.

                           {
  // From rfc3720 section B.4.
  char buf[32];

  memset(buf, 0, sizeof(buf));
  ASSERT_EQ(0x8a9136aa, Value(buf, sizeof(buf)));

  memset(buf, 0xff, sizeof(buf));
  ASSERT_EQ(0x62a8ab43, Value(buf, sizeof(buf)));

  for (int i = 0; i < 32; i++) {
    buf[i] = i;
  }
  ASSERT_EQ(0x46dd794e, Value(buf, sizeof(buf)));

  for (int i = 0; i < 32; i++) {
    buf[i] = 31 - i;
  }
  ASSERT_EQ(0x113fdb5c, Value(buf, sizeof(buf)));

  unsigned char data[48] = {
    0x01, 0xc0, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x14, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x04, 0x00,
    0x00, 0x00, 0x00, 0x14,
    0x00, 0x00, 0x00, 0x18,
    0x28, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x02, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
  };
  ASSERT_EQ(0xd9963a56, Value(reinterpret_cast<char*>(data), sizeof(data)));
}

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TEST() [2/4]

leveldb::crc32c::TEST	(	CRC	,
		Values
	)

Definition at line 50 of file crc32c_test.cc.

                  {
  ASSERT_NE(Value("a", 1), Value("foo", 3));
}

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TEST() [3/4]

leveldb::crc32c::TEST	(	CRC	,
		Extend
	)

Definition at line 54 of file crc32c_test.cc.

                  {
  ASSERT_EQ(Value("hello world", 11),
            Extend(Value("hello ", 6), "world", 5));
}

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TEST() [4/4]

leveldb::crc32c::TEST	(	CRC	,
		Mask
	)

Definition at line 59 of file crc32c_test.cc.

                {
  uint32_t crc = Value("foo", 3);
  ASSERT_NE(crc, Mask(crc));
  ASSERT_NE(crc, Mask(Mask(crc)));
  ASSERT_EQ(crc, Unmask(Mask(crc)));
  ASSERT_EQ(crc, Unmask(Unmask(Mask(Mask(crc)))));
}

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Unmask()

uint32_t leveldb::crc32c::Unmask ( uint32_t  masked_crc )

inline

Definition at line 37 of file crc32c.h.

                                            {
  uint32_t rot = masked_crc - kMaskDelta;
  return ((rot >> 17) | (rot << 15));
}

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Value()

uint32_t leveldb::crc32c::Value ( const char *  data, size_t  n  )

inline

Definition at line 20 of file crc32c.h.

                                                  {
  return Extend(0, data, n);
}

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Variable Documentation

kMaskDelta

const uint32_t leveldb::crc32c::kMaskDelta = 0xa282ead8ul

static

Definition at line 24 of file crc32c.h.

table0_

const uint32_t leveldb::crc32c::table0_[256]

static

Definition at line 16 of file crc32c.cc.

table1_

const uint32_t leveldb::crc32c::table1_[256]

static

Definition at line 82 of file crc32c.cc.

table2_

const uint32_t leveldb::crc32c::table2_[256]

static

Definition at line 148 of file crc32c.cc.

table3_

const uint32_t leveldb::crc32c::table3_[256]

static

Definition at line 214 of file crc32c.cc.