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Use as much of the low buffer as possible with a single memcopy before going fine grained byte by byte.

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Con Kolivas 2012-03-08 09:01:31 +11:00
parent 30bfe06f1a
commit cf8567e314
1 changed files with 9 additions and 6 deletions
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15
rzip.c
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@ -190,7 +190,7 @@ static uchar *single_get_sb(__maybe_unused rzip_control *control, struct sliding
/* Since the sliding get_sb only allows us to access one byte at a time, we /* Since the sliding get_sb only allows us to access one byte at a time, we
* do the same as we did with get_sb with the memcpy since one memcpy is much * do the same as we did with get_sb with the memcpy since one memcpy is much
* faster than numerous memcpys 1 byte at a time */ * faster than numerous memcpys 1 byte at a time */
static void single_mcpy(__maybe_unused rzip_control *control, unsigned char *buf, i64 offset, i64 len) static void single_mcpy(rzip_control *control, unsigned char *buf, i64 offset, i64 len)
{ {
memcpy(buf, control->sb.buf_low + offset, len); memcpy(buf, control->sb.buf_low + offset, len);
} }
@ -198,16 +198,19 @@ static void single_mcpy(__maybe_unused rzip_control *control, unsigned char *buf
static void sliding_mcpy(rzip_control *control, unsigned char *buf, i64 offset, i64 len) static void sliding_mcpy(rzip_control *control, unsigned char *buf, i64 offset, i64 len)
{ {
struct sliding_buffer *sb = &control->sb; struct sliding_buffer *sb = &control->sb;
i64 i; i64 i, offdiff = offset - sb->offset_low;
/* See if we fit in the low buffer first and use the faster function /* See if we fit in the low buffer first and use the faster function
* where possible */ * where possible */
if (offset >= sb->offset_low && offset + len < sb->offset_low + sb->size_low) { if (offdiff >= 0 && offdiff < sb->size_low) {
single_mcpy(control, buf, offset - sb->offset_low, len); i64 minlen = MIN(len, sb->size_low - offdiff);
return;
memcpy(buf, control->sb.buf_low + offdiff, minlen);
len -= minlen;
} }
/* We have no choice but to go fine-grained since we will be paging */ /* We have no choice but to go fine-grained if there's any len left
* since we will be paging */
for (i = 0; i < len; i++) for (i = 0; i < len; i++)
memcpy(buf + i, sliding_get_sb(control, &control->sb, offset + i), 1); memcpy(buf + i, sliding_get_sb(control, &control->sb, offset + i), 1);
} }