1-----------------------------------------------------------------------------
2-- Little program to download files from URLs
3-- LuaSocket sample files
4-- Author: Diego Nehab
5-----------------------------------------------------------------------------
6local socket = require("socket")
7local http = require("socket.http")
8local ftp = require("socket.ftp")
9local url = require("socket.url")
10local ltn12 = require("ltn12")
11
12-- formats a number of seconds into human readable form
13function nicetime(s)
14    local l = "s"
15    if s > 60 then
16        s = s / 60
17        l = "m"
18        if s > 60 then
19            s = s / 60
20            l = "h"
21            if s > 24 then
22                s = s / 24
23                l = "d" -- hmmm
24            end
25        end
26    end
27    if l == "s" then return string.format("%5.0f%s", s, l)
28    else return string.format("%5.2f%s", s, l) end
29end
30
31-- formats a number of bytes into human readable form
32function nicesize(b)
33    local l = "B"
34    if b > 1024 then
35        b = b / 1024
36        l = "KB"
37        if b > 1024 then
38            b = b / 1024
39            l = "MB"
40            if b > 1024 then
41                b = b / 1024
42                l = "GB" -- hmmm
43            end
44        end
45    end
46    return string.format("%7.2f%2s", b, l)
47end
48
49-- returns a string with the current state of the download
50local remaining_s = "%s received, %s/s throughput, %2.0f%% done, %s remaining"
51local elapsed_s =   "%s received, %s/s throughput, %s elapsed                "
52function gauge(got, delta, size)
53    local rate = got / delta
54    if size and size >= 1 then
55        return string.format(remaining_s, nicesize(got),  nicesize(rate),
56            100*got/size, nicetime((size-got)/rate))
57    else
58        return string.format(elapsed_s, nicesize(got),
59            nicesize(rate), nicetime(delta))
60    end
61end
62
63-- creates a new instance of a receive_cb that saves to disk
64-- kind of copied from luasocket's manual callback examples
65function stats(size)
66    local start = socket.gettime()
67    local last = start
68    local got = 0
69    return function(chunk)
70        -- elapsed time since start
71        local current = socket.gettime()
72        if chunk then
73            -- total bytes received
74            got = got + string.len(chunk)
75            -- not enough time for estimate
76            if current - last > 1 then
77                io.stderr:write("\r", gauge(got, current - start, size))
78                io.stderr:flush()
79                last = current
80            end
81        else
82            -- close up
83            io.stderr:write("\r", gauge(got, current - start), "\n")
84        end
85        return chunk
86    end
87end
88
89-- determines the size of a http file
90function gethttpsize(u)
91    local r, c, h = http.request {method = "HEAD", url = u}
92    if c == 200 then
93        return tonumber(h["content-length"])
94    end
95end
96
97-- downloads a file using the http protocol
98function getbyhttp(u, file)
99    local save = ltn12.sink.file(file or io.stdout)
100    -- only print feedback if output is not stdout
101    if file then save = ltn12.sink.chain(stats(gethttpsize(u)), save) end
102    local r, c, h, s = http.request {url = u, sink = save }
103    if c ~= 200 then io.stderr:write(s or c, "\n") end
104end
105
106-- downloads a file using the ftp protocol
107function getbyftp(u, file)
108    local save = ltn12.sink.file(file or io.stdout)
109    -- only print feedback if output is not stdout
110    -- and we don't know how big the file is
111    if file then save = ltn12.sink.chain(stats(), save) end
112    local gett = url.parse(u)
113    gett.sink = save
114    gett.type = "i"
115    local ret, err = ftp.get(gett)
116    if err then print(err) end
117end
118
119-- determines the scheme
120function getscheme(u)
121    -- this is an heuristic to solve a common invalid url poblem
122    if not string.find(u, "//") then u = "//" .. u end
123    local parsed = url.parse(u, {scheme = "http"})
124    return parsed.scheme
125end
126
127-- gets a file either by http or ftp, saving as <name>
128function get(u, name)
129    local fout = name and io.open(name, "wb")
130    local scheme = getscheme(u)
131    if scheme == "ftp" then getbyftp(u, fout)
132    elseif scheme == "http" then getbyhttp(u, fout)
133    else print("unknown scheme" .. scheme) end
134end
135
136-- main program
137arg = arg or {}
138if #arg < 1 then
139    io.write("Usage:\n  lua get.lua <remote-url> [<local-file>]\n")
140    os.exit(1)
141else get(arg[1], arg[2]) end
142