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ircd::db: Add reverse long int comparator; fix reverse string comparator; cleanup.

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This commit is contained in:
Jason Volk 2017-09-23 20:37:44 -07:00
parent f4682522a8
commit a65a033c3b
1 changed files with 51 additions and 26 deletions
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77
include/ircd/db/comparator.h
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@ -28,6 +28,8 @@ namespace ircd::db
struct comparator; struct comparator;
struct cmp_int64_t; struct cmp_int64_t;
struct reverse_cmp_int64_t;
struct cmp_string_view; struct cmp_string_view;
struct reverse_cmp_string_view; struct reverse_cmp_string_view;
} }
@ -39,24 +41,6 @@ struct ircd::db::comparator
std::function<bool (const string_view &, const string_view &)> equal; std::function<bool (const string_view &, const string_view &)> equal;
}; };
struct ircd::db::reverse_cmp_string_view
:db::comparator
{
static bool less(const string_view &a, const string_view &b)
{
return std::memcmp(a.data(), b.data(), std::min(a.size(), b.size())) > 0;
}
static bool equal(const string_view &a, const string_view &b)
{
return a == b;
}
reverse_cmp_string_view()
:db::comparator{"reverse_string_view", &less, &equal}
{}
};
struct ircd::db::cmp_string_view struct ircd::db::cmp_string_view
:db::comparator :db::comparator
{ {
@ -75,24 +59,47 @@ struct ircd::db::cmp_string_view
{} {}
}; };
struct ircd::db::reverse_cmp_string_view
:db::comparator
{
static bool less(const string_view &a, const string_view &b)
{
/// RocksDB sez things will not work correctly unless a shorter string
/// result returns less than a longer string even if one intends some
/// reverse ordering
if(a.size() < b.size())
return true;
/// Furthermore, b.size() < a.size() returning false from this function
/// appears to not be correct. The reversal also has to also come in
/// the form of a bytewise forward iteration.
return std::memcmp(a.data(), b.data(), std::min(a.size(), b.size())) > 0;
}
static bool equal(const string_view &a, const string_view &b)
{
return a == b;
}
reverse_cmp_string_view()
:db::comparator{"reverse_string_view", &less, &equal}
{}
};
struct ircd::db::cmp_int64_t struct ircd::db::cmp_int64_t
:db::comparator :db::comparator
{ {
static bool less(const string_view &sa, const string_view &sb) static bool less(const string_view &sa, const string_view &sb)
{ {
assert(sa.size() == sizeof(int64_t)); assert(sa.size() == sizeof(int64_t) && sb.size() == sizeof(int64_t));
assert(sb.size() == sizeof(int64_t)); const byte_view<int64_t> a{sa}, b{sb};
const byte_view<int64_t> a{sa};
const byte_view<int64_t> b{sb};
return a < b; return a < b;
} }
static bool equal(const string_view &sa, const string_view &sb) static bool equal(const string_view &sa, const string_view &sb)
{ {
assert(sa.size() == sizeof(int64_t)); assert(sa.size() == sizeof(int64_t) && sb.size() == sizeof(int64_t));
assert(sb.size() == sizeof(int64_t)); const byte_view<int64_t> a{sa}, b{sb};
const byte_view<int64_t> a{sa};
const byte_view<int64_t> b{sb};
return a == b; return a == b;
} }
@ -100,3 +107,21 @@ struct ircd::db::cmp_int64_t
:db::comparator{"int64_t", &less, &equal} :db::comparator{"int64_t", &less, &equal}
{} {}
}; };
struct ircd::db::reverse_cmp_int64_t
:db::comparator
{
static bool less(const string_view &a, const string_view &b)
{
return !cmp_int64_t::less(a, b);
}
static bool equal(const string_view &a, const string_view &b)
{
return cmp_int64_t::equal(a, b);
}
reverse_cmp_int64_t()
:db::comparator{"reverse_int64_t", &less, &equal}
{}
};