| 发表于：2007-07-12 10:11:162楼 得分:10 |
hashtable.pas
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unit hashtable;
interface
uses sysutils, classes;
type
{ thashtable }
pphashitem = ^phashitem;
phashitem = ^thashitem;
thashitem = record
next: phashitem;
key: string;
value: string;
end;
thashtable = class
private
buckets: array of phashitem;
protected
function find（const key: string): pphashitem;
function hashof（const key: string): cardinal; virtual;
public
constructor create（size: integer = 256);
destructor destroy; override;
procedure put（const key: string; value: string);
procedure clear;
procedure remove（const key: string);
function modify（const key: string; value: string): boolean;
function get（const key: string): string;
end;
implementation
{ thashtable }
procedure thashtable.put（const key: string; value: string);
var
hash: integer;
bucket: phashitem;
begin
hash := hashof（key) mod cardinal（length（buckets));
new（bucket);
bucket^.key := key;
bucket^.value := value;
bucket^.next := buckets[hash];
buckets[hash] := bucket;
end;
procedure thashtable.clear;
var
i: integer;
p, n: phashitem;
begin
for i := 0 to length（buckets) - 1 do
begin
p := buckets[i];
while p <> nil do
begin
n := p^.next;
dispose（p);
p := n;
end;
buckets[i] := nil;
end;
end;
constructor thashtable.create（size: integer);
begin
inherited create;
setlength（buckets, size);
end;
destructor thashtable.destroy;
begin
clear;
inherited;
end;
function thashtable.find（const key: string): pphashitem;
var
hash: integer;
begin
hash := hashof（key) mod cardinal（length（buckets));
result := @buckets[hash];
while result^ <> nil do
begin
if result^.key = key then
exit
else
result := @result^.next;
end;
end;
function thashtable.hashof（const key: string): cardinal;
var
i: integer;
begin
result := 0;
for i := 1 to length（key) do
result := （（result shl 2) or （result shr （sizeof（result) * 8 - 2))) xor
ord（key[i]);
end;
function thashtable.modify（const key: string; value: string): boolean;
var
p: phashitem;
begin
p := find（key)^;
if p <> nil then
begin
result := true;
p^.value := value;
end
else
result := false;
end;
procedure thashtable.remove（const key: string);
var
p: phashitem;
prev: pphashitem;
begin
prev := find（key);
p := prev^;
if p <> nil then
begin
prev^ := p^.next;
dispose（p);
end;
end;
function thashtable.get（const key: string): string;
var
p: phashitem;
begin
p := find（key)^;
if p <> nil then
result := p^.value else
result := ' ';
end;
end.
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使用起来就简单了：
hashtable := thashtable.create（); //创建
hashtable.put（key, value); //赋值
value=hashtable.get（key); //取值
hashtable.destroy; //撤消 | | |
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