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Diffstat (limited to '')
| -rw-r--r-- | ext/lsm1/lsm_varint.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/ext/lsm1/lsm_varint.c b/ext/lsm1/lsm_varint.c new file mode 100644 index 0000000..c550a64 --- /dev/null +++ b/ext/lsm1/lsm_varint.c @@ -0,0 +1,196 @@ + +/* +** 2012-02-08 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** +** SQLite4-compatible varint implementation. +*/ +#include "lsmInt.h" + +/************************************************************************* +** The following is a copy of the varint.c module from SQLite 4. +*/ + +/* +** Decode the varint in z[]. Write the integer value into *pResult and +** return the number of bytes in the varint. +*/ +static int lsmSqlite4GetVarint64(const unsigned char *z, u64 *pResult){ + unsigned int x; + if( z[0]<=240 ){ + *pResult = z[0]; + return 1; + } + if( z[0]<=248 ){ + *pResult = (z[0]-241)*256 + z[1] + 240; + return 2; + } + if( z[0]==249 ){ + *pResult = 2288 + 256*z[1] + z[2]; + return 3; + } + if( z[0]==250 ){ + *pResult = (z[1]<<16) + (z[2]<<8) + z[3]; + return 4; + } + x = (z[1]<<24) + (z[2]<<16) + (z[3]<<8) + z[4]; + if( z[0]==251 ){ + *pResult = x; + return 5; + } + if( z[0]==252 ){ + *pResult = (((u64)x)<<8) + z[5]; + return 6; + } + if( z[0]==253 ){ + *pResult = (((u64)x)<<16) + (z[5]<<8) + z[6]; + return 7; + } + if( z[0]==254 ){ + *pResult = (((u64)x)<<24) + (z[5]<<16) + (z[6]<<8) + z[7]; + return 8; + } + *pResult = (((u64)x)<<32) + + (0xffffffff & ((z[5]<<24) + (z[6]<<16) + (z[7]<<8) + z[8])); + return 9; +} + +/* +** Write a 32-bit unsigned integer as 4 big-endian bytes. +*/ +static void lsmVarintWrite32(unsigned char *z, unsigned int y){ + z[0] = (unsigned char)(y>>24); + z[1] = (unsigned char)(y>>16); + z[2] = (unsigned char)(y>>8); + z[3] = (unsigned char)(y); +} + +/* +** Write a varint into z[]. The buffer z[] must be at least 9 characters +** long to accommodate the largest possible varint. Return the number of +** bytes of z[] used. +*/ +static int lsmSqlite4PutVarint64(unsigned char *z, u64 x){ + unsigned int w, y; + if( x<=240 ){ + z[0] = (unsigned char)x; + return 1; + } + if( x<=2287 ){ + y = (unsigned int)(x - 240); + z[0] = (unsigned char)(y/256 + 241); + z[1] = (unsigned char)(y%256); + return 2; + } + if( x<=67823 ){ + y = (unsigned int)(x - 2288); + z[0] = 249; + z[1] = (unsigned char)(y/256); + z[2] = (unsigned char)(y%256); + return 3; + } + y = (unsigned int)x; + w = (unsigned int)(x>>32); + if( w==0 ){ + if( y<=16777215 ){ + z[0] = 250; + z[1] = (unsigned char)(y>>16); + z[2] = (unsigned char)(y>>8); + z[3] = (unsigned char)(y); + return 4; + } + z[0] = 251; + lsmVarintWrite32(z+1, y); + return 5; + } + if( w<=255 ){ + z[0] = 252; + z[1] = (unsigned char)w; + lsmVarintWrite32(z+2, y); + return 6; + } + if( w<=32767 ){ + z[0] = 253; + z[1] = (unsigned char)(w>>8); + z[2] = (unsigned char)w; + lsmVarintWrite32(z+3, y); + return 7; + } + if( w<=16777215 ){ + z[0] = 254; + z[1] = (unsigned char)(w>>16); + z[2] = (unsigned char)(w>>8); + z[3] = (unsigned char)w; + lsmVarintWrite32(z+4, y); + return 8; + } + z[0] = 255; + lsmVarintWrite32(z+1, w); + lsmVarintWrite32(z+5, y); + return 9; +} + +/* +** End of SQLite 4 code. +*************************************************************************/ + +int lsmVarintPut64(u8 *aData, i64 iVal){ + return lsmSqlite4PutVarint64(aData, (u64)iVal); +} + +int lsmVarintGet64(const u8 *aData, i64 *piVal){ + return lsmSqlite4GetVarint64(aData, (u64 *)piVal); +} + +int lsmVarintPut32(u8 *aData, int iVal){ + return lsmSqlite4PutVarint64(aData, (u64)iVal); +} + +int lsmVarintGet32(u8 *z, int *piVal){ + u64 i; + int ret; + + if( z[0]<=240 ){ + *piVal = z[0]; + return 1; + } + if( z[0]<=248 ){ + *piVal = (z[0]-241)*256 + z[1] + 240; + return 2; + } + if( z[0]==249 ){ + *piVal = 2288 + 256*z[1] + z[2]; + return 3; + } + if( z[0]==250 ){ + *piVal = (z[1]<<16) + (z[2]<<8) + z[3]; + return 4; + } + + ret = lsmSqlite4GetVarint64(z, &i); + *piVal = (int)i; + return ret; +} + +int lsmVarintLen32(int n){ + u8 aData[9]; + return lsmVarintPut32(aData, n); +} + +/* +** The argument is the first byte of a varint. This function returns the +** total number of bytes in the entire varint (including the first byte). +*/ +int lsmVarintSize(u8 c){ + if( c<241 ) return 1; + if( c<249 ) return 2; + return (int)(c - 246); +} |