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This commit is contained in:
Moinak Ghosh 2012-12-31 23:27:31 +05:30
parent 13d9378acd
commit 43f5acfa2d
1 changed files with 23 additions and 1 deletions
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24
delta2/delta2.c
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@ -96,6 +96,15 @@ static uchar_t strides[NSTRIDES] = {3, 5, 7, 8};
static int delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen, static int delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen,
int rle_thresh, int last_encode, int *hdr_ovr); int rle_thresh, int last_encode, int *hdr_ovr);
/*
* Perform Delta2 encoding of the given data buffer in src. Delta Encoding
* processes data in blocks of 4k. After each call to delta2_encode_real()
* determine if any encoding was done.
* If no delta sequence was found in the block then it is added to the running
* literal span count. If delta was found in the block then the previous literal
* span is copied out. If copying a literal span would overflow the destination
* buffer then delta encoding is aborted.
*/
int int
delta2_encode(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen, int rle_thresh) delta2_encode(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen, int rle_thresh)
{ {
@ -190,6 +199,9 @@ delta2_encode(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen, int
return (0); return (0);
} }
/*
* Process one block of data upto 4K in size.
*/
static int static int
delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen, delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen,
int rle_thresh, int last_encode, int *hdr_ovr) int rle_thresh, int last_encode, int *hdr_ovr)
@ -306,6 +318,11 @@ delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen
vld2 = vl2 - vl1; vld2 = vl2 - vl1;
if (vld1 != vld2) { if (vld1 != vld2) {
if (snum > rle_thresh) { if (snum > rle_thresh) {
/*
* We have a series but there is some pending literal data
* to be copied before the series begins. First copy that
* as a literal sequence.
*/
if (gtot1 > 0) { if (gtot1 > 0) {
gtot1 &= MSB_SETZERO_MASK; gtot1 &= MSB_SETZERO_MASK;
*((uint64_t *)pos2) = LE64(gtot1); *((uint64_t *)pos2) = LE64(gtot1);
@ -317,7 +334,9 @@ delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen
} }
/* /*
* RLE Encode delta series. * RLE Encode delta series. Store total number of bytes,
* stride length, starting value and difference between
* the terms.
*/ */
gtot2 = stride; gtot2 = stride;
gtot2 <<= MSB_SHIFT; gtot2 <<= MSB_SHIFT;
@ -341,6 +360,9 @@ delta2_encode_real(uchar_t *src, uint64_t srclen, uchar_t *dst, uint64_t *dstlen
pos += stride; pos += stride;
} }
/*
* Encode final sequence, if any.
*/
if (snum > 0) { if (snum > 0) {
if (snum > rle_thresh) { if (snum > rle_thresh) {
if (gtot1 > 0) { if (gtot1 > 0) {