Algorithm / pseudo-code to create paging links?

Question

Can someome provide code or pseudo-code for how the paging links on StackOverflow are generated?

I keep racking my brain but can\'t think of a decent way to build th

Answer 1

Here is my algorithm. It works really nice:

// Input
total_items   // Number of rows, records etc. from db, file or whatever
per_page      // num items per page
page          // current page
visible_pages // number of visible pages

// Calculations
lastPage = ceil(total_items / per_page);
prevPage = page - 1 < 1 ? 0 : page - 1;
nextPage = page + 1 > lastPage ? 0 : page + 1;
halfpages = ceil(visible_pages / 2);
startPage = page - halfpages < 1 ? 1 : page - halfpages;
endPage = startPage + visible_pages - 1;
if(endPage > lastPage) {
    startPage -= endPage - lastPage;
    startPage = startPage < 1 ? 1 : startPage;
    endPage = startPage + visible_pages > lastPage ? lastPage : startPage + visible_pages - 1;
}

// Output
lastPage    // Total number of pages
prevPage    // Previous page number (if 0 there is no prev page)
nextPage    // Next page number (if 0 there is no next page)
startPage   // First visible page
endPage     // Last visible page

So you can do a pager like this:

if prevPage
    [1] [prevPage] 
endif

[startPage] ... [endPage] 

if nextPage
    [nextPage] [lastPage] 
endif

or customize whatever you like.