I wrote a contract source which is just a FIFO queue below:
pragma solidity ^0.4.0;
contract queue
{
struct Queue {
uint256[] data;
uint256 front;
uint256 back;
}
/// @dev the number of elements stored in the queue.
function length(Queue storage q) constant internal returns (uint256) {
return q.back - q.front;
}
/// @dev the number of elements this queue can hold
function capacity(Queue storage q) constant internal returns (uint256) {
return q.data.length - 1;
}
/// @dev push a new element to the back of the queue
function push(Queue storage q, uint256 data) internal
{
if ((q.back + 1) % q.data.length == q.front)
return; // throw;
q.data[q.back] = data;
q.back = (q.back + 1) % q.data.length;
}
/// @dev remove and return the element at the front of the queue
function pop(Queue storage q) internal returns (uint256 r)
{
if (q.back == q.front)
return; // throw;
r = q.data[q.front];
delete q.data[q.front];
q.front = (q.front + 1) % q.data.length;
return r;
}
Queue requests;
function queue() {
requests.data.length = 200;
}
function addRequest(uint256 d) {
push(requests, d);
}
function popRequest() constant returns (uint256) {
return pop(requests);
}
function queueLength() constant returns (uint256) {
return length(requests);
}
function hello() constant returns(string s){
return 'hello world!';
}
}
and then I compile it on online compiler https://ethereum.github.io/browser-solidity. I got the contents from the Web3 deploy box, which is :
var queue_sol_queueContract = web3.eth.contract([{"constant":true,"inputs":[],"name":"hello","outputs":[{"name":"s","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"d","type":"uint256"}],"name":"addRequest","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"queueLength","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"popRequest","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"inputs":[],"payable":false,"type":"constructor"}]);
var queue_sol_queue = queue_sol_queueContract.new(
{
from: web3.eth.accounts[0],
data: '0x6060604052341561000c57fe5b5b60c860006000018161001f9190610026565b505b610077565b81548183558181151161004d5781836000526020600020918201910161004c9190610052565b5b505050565b61007491905b80821115610070576000816000905550600101610058565b5090565b90565b610339806100866000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff16806319ff1d211461005c5780634ca1fad8146100f5578063ab91c7b014610115578063e4690a0b1461013b575bfe5b341561006457fe5b61006c610161565b60405180806020018281038252838181518152602001915080519060200190808383600083146100bb575b8051825260208311156100bb57602082019150602081019050602083039250610097565b505050905090810190601f1680156100e75780820380516001836020036101000a031916815260200191505b509250505060405180910390f35b34156100fd57fe5b61011360048080359060200190919050506101a6565b005b341561011d57fe5b6101256101b5565b6040518082815260200191505060405180910390f35b341561014357fe5b61014b6101c7565b6040518082815260200191505060405180910390f35b6101696102f9565b604060405190810160405280600c81526020017f68656c6c6f20776f726c6421000000000000000000000000000000000000000081525090505b90565b6101b16000826101d9565b5b50565b60006101c16000610253565b90505b90565b60006101d36000610268565b90505b90565b8160010154826000018054905060018460020154018115156101f757fe5b0614156102035761024f565b8082600001836002015481548110151561021957fe5b906000526020600020900160005b50819055508160000180549050600183600201540181151561024557fe5b0682600201819055505b5050565b6000816001015482600201540390505b919050565b600081600101548260020154141561027f576102f4565b81600001826001015481548110151561029457fe5b906000526020600020900160005b505490508160000182600101548154811015156102bb57fe5b906000526020600020900160005b5060009055816000018054905060018360010154018115156102e757fe5b0682600101819055508090505b919050565b6020604051908101604052806000815250905600a165627a7a7230582052aa3a94b7e1e757a3b8de91244871650c0e29a8114a06384386ab323fae210e0029',
gas: '800000'
}, function (e, contract){
console.log(e, contract);
if (typeof contract.address !== 'undefined') {
console.log('Contract mined! address: ' + contract.address + ' transactionHash: ' + contract.transactionHash);
}
})
Ok, I click the create button to test it and it works well. Then I deploy it on my geth but its response isn't good enough:
> eth.defaultAccount = eth.accounts[0]
"0x047347096a6dc73f8626afb520c383a02efda314"
> queue_sol_queue.addRequest(2)
I0405 16:19:43.308834 internal/ethapi/api.go:1076] Tx(0xc42776310dde4eb79798ba02f33176bcbb0a8283aa3bb4508af0fd30ed34175e) to: 0x1666d22ba16ff64f94d938301f8ec252f88813a3
"0xc42776310dde4eb79798ba02f33176bcbb0a8283aa3bb4508af0fd30ed34175e"
> queue_sol_queue.addRequest.call(2)
[]
> queue_sol_queue.addRequest.call(2)
[]
> queue_sol_queue.addRequest.call(2)
[]
> queue_sol_queue.popRequest()
0
> queue_sol_queue.popRequest.call()
0
it seems that the push can't push any data and pop can't pop any data ,So how do it work like a FIFO queue? thank you very much.
After getting help from some nice people. I have a new question here: How to return the value pushed before with only one function? I read some information about events, so I think it may be a solution, but it doesn't return the exact value pushed before. There is my new source below which added events:
pragma solidity ^0.4.0;
////////////////////////////////////////////////////////////
// This is an example contract hacked together at a meetup.
// It is by far not complete and only used to show some
// features of Solidity.
////////////////////////////////////////////////////////////
contract queue
{
struct Queue {
uint256[] data;
uint256 front;
uint256 back;
}
/// @dev the number of elements stored in the queue.
function length(Queue storage q) constant internal returns (uint256) {
return q.back - q.front;
}
/// @dev the number of elements this queue can hold
function capacity(Queue storage q) constant internal returns (uint256) {
return q.data.length - 1;
}
/// @dev push a new element to the back of the queue
function push(Queue storage q, uint256 data) internal
{
if ((q.back + 1) % q.data.length == q.front)
return; // throw;
q.data[q.back] = data;
q.back = (q.back + 1) % q.data.length;
}
/// @dev remove and return the element at the front of the queue
function pop(Queue storage q) internal returns (uint256 r)
{
if (q.back == q.front)
return; // throw;
r = q.data[q.front];
delete q.data[q.front];
q.front = (q.front + 1) % q.data.length;
return r;
}
Queue requests;
event PopEvent(bool ok); //my event designed by me here.(*^__^*) 嘻嘻……
function queue() {
requests.data.length = 200;
}
function addRequest(uint256 d) {
push(requests, d);
}
function popRequest() returns (uint256) {
PopEvent(true);
return pop(requests);
}
function queueLength() constant returns (uint256) {
return length(requests);
}
function hello() constant returns(string s){
return 'hello world!';
}
}
Hence, can any body help me? thank you!!!
