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rem0rec.ic:

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Do not use short int in rem0rec.ic, since its size is not fixed in ANSI C; improve comments of the relative offset field in a record; use mach_read_from_2() to read the relative offset field to save CPU time, if the compiler does not optimize a more complex access function


innobase/include/rem0rec.ic:
  Do not use short int in rem0rec.ic, since its size is not fixed in ANSI C; improve comments of the relative offset field in a record; use mach_read_from_2() to read the relative offset field to save CPU time, if the compiler does not optimize a more complex access function
This commit is contained in:
unknown 2004-12-18 13:04:34 +02:00
parent e3f1d56252
commit b2474e7ac1
1 changed files with 56 additions and 25 deletions
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81
innobase/include/rem0rec.ic
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@ -40,8 +40,18 @@ most significant bytes and bits are written below less significant.
(1) byte offset (2) bit usage within byte
downward from
origin -> 1 8 bits pointer to next record (relative)
2 8 bits pointer to next record (relative)
origin -> 1 8 bits relative offset of next record
2 8 bits relative offset of next record
the relative offset is an unsigned 16-bit
integer:
(offset_of_next_record
- offset_of_this_record) mod 64Ki,
where mod is the modulo as a non-negative
number;
we can calculate the the offset of the next
record with the formula:
relative_offset + offset_of_this_record
mod UNIV_PAGE_SIZE
3 3 bits status:
000=conventional record
001=node pointer record (inside B-tree)
@ -252,26 +262,37 @@ UNIV_INLINE
ulint
rec_get_next_offs(
/*==============*/
/* out: the page offset of the next chained record */
/* out: the page offset of the next chained record, or
0 if none */
rec_t* rec, /* in: physical record */
ibool comp) /* in: TRUE=compact page format */
{
ulint field_value;
ut_ad(REC_NEXT_MASK == 0xFFFFUL);
ut_ad(REC_NEXT_SHIFT == 0);
field_value = mach_read_from_2(rec - REC_NEXT);
if (comp) {
lint ret = (signed short) rec_get_bit_field_2(rec, REC_NEXT,
REC_NEXT_MASK, REC_NEXT_SHIFT);
#if UNIV_PAGE_SIZE <= 32768
/* with 64 KiB page size, the pointer will "wrap around",
and the following assertions are invalid */
ut_ad(ret + ut_align_offset(rec, UNIV_PAGE_SIZE) <
UNIV_PAGE_SIZE);
/* Note that for 64 KiB pages, field_value can 'wrap around'
and the debug assertion is not valid */
ut_ad((int16_t)field_value
+ ut_align_offset(rec, UNIV_PAGE_SIZE)
< UNIV_PAGE_SIZE);
#endif
return(ret ? ut_align_offset(rec + ret, UNIV_PAGE_SIZE) : 0);
}
else {
ulint ret = rec_get_bit_field_2(rec, REC_NEXT,
REC_NEXT_MASK, REC_NEXT_SHIFT);
ut_ad(ret < UNIV_PAGE_SIZE);
return(ret);
if (field_value == 0) {
return(0);
}
return(ut_align_offset(rec + field_value, UNIV_PAGE_SIZE));
} else {
ut_ad(field_value < UNIV_PAGE_SIZE);
return(field_value);
}
}
@ -284,21 +305,31 @@ rec_set_next_offs(
/*==============*/
rec_t* rec, /* in: physical record */
ibool comp, /* in: TRUE=compact page format */
ulint next) /* in: offset of the next record */
ulint next) /* in: offset of the next record, or 0 if none */
{
ut_ad(rec);
ut_ad(UNIV_PAGE_SIZE > next);
ut_ad(REC_NEXT_MASK == 0xFFFFUL);
ut_ad(REC_NEXT_SHIFT == 0);
if (comp) {
rec_set_bit_field_2(rec, next
? (next - ut_align_offset(rec, UNIV_PAGE_SIZE))
#ifdef UNIV_DEBUG /* avoid an assertion failure */
& (REC_NEXT_MASK >> REC_NEXT_SHIFT)
#endif
: 0, REC_NEXT, REC_NEXT_MASK, REC_NEXT_SHIFT);
ulint field_value;
if (next) {
/* The following two statements calculate
next - offset_of_rec mod 64Ki, where mod is the modulo
as a non-negative number */
field_value = (ulint)((lint)next
- (lint)ut_align_offset(rec, UNIV_PAGE_SIZE));
field_value &= REC_NEXT_MASK;
} else {
field_value = 0;
}
mach_write_to_2(rec - REC_NEXT, field_value);
} else {
rec_set_bit_field_2(rec, next,
REC_NEXT, REC_NEXT_MASK, REC_NEXT_SHIFT);
mach_write_to_2(rec - REC_NEXT, next);
}
}