开源地址：https://github.com/ethereum/dapp-bin/blob/master/library/iterable_mapping.sol
库代码
/// @dev Models a uint -> uint mapping where it is possible to iterate over all keys.
library IterableMapping
{
struct itmap
{
mapping(uint => IndexValue) data;
KeyFlag[] keys;
uint size;
}
struct IndexValue { uint keyIndex; uint value; }
struct KeyFlag { uint key; bool deleted; }
function insert(itmap storage self, uint key, uint value) returns (bool replaced)
{
uint keyIndex = self.data[key].keyIndex;
self.data[key].value = value;
if (keyIndex > 0)
return true;
else
{
keyIndex = self.keys.length++;
self.data[key].keyIndex = keyIndex + 1;
self.keys[keyIndex].key = key;
self.size++;
return false;
}
}
function remove(itmap storage self, uint key) returns (bool success)
{
uint keyIndex = self.data[key].keyIndex;
if (keyIndex == 0)
return false;
delete self.data[key];
self.keys[keyIndex - 1].deleted = true;
self.size --;
}
function contains(itmap storage self, uint key) returns (bool)
{
return self.data[key].keyIndex > 0;
}
function iterate_start(itmap storage self) returns (uint keyIndex)
{
return iterate_next(self, uint(-1));
}
function iterate_valid(itmap storage self, uint keyIndex) returns (bool)
{
return keyIndex < self.keys.length;
}
function iterate_next(itmap storage self, uint keyIndex) returns (uint r_keyIndex)
{
keyIndex++;
while (keyIndex < self.keys.length && self.keys[keyIndex].deleted)
keyIndex++;
return keyIndex;
}
function iterate_get(itmap storage self, uint keyIndex) returns (uint key, uint value)
{
key = self.keys[keyIndex].key;
value = self.data[key].value;
}
}案例
// How to use it:
contract User
{
// Just a struct holding our data.
IterableMapping.itmap data;
// Insert something
function insert(uint k, uint v) returns (uint size)
{
// Actually calls itmap_impl.insert, auto-supplying the first parameter for us.
IterableMapping.insert(data, k, v);
// We can still access members of the struct - but we should take care not to mess with them.
return data.size;
}
// Computes the sum of all stored data.
function sum() returns (uint s)
{
for (var i = IterableMapping.iterate_start(data); IterableMapping.iterate_valid(data, i); i = IterableMapping.iterate_next(data, i))
{
var (key, value) = IterableMapping.iterate_get(data, i);
s += value;
}
}
}