* libcurl via FFI
@ 2018-05-17 10:11 Henri Menke
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From: Henri Menke @ 2018-05-17 10:11 UTC (permalink / raw)
To: ntg-context@ntg.nl >> mailing list for ConTeXt users
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Dear list,
As announced in another thread, here a better annotated example of using
libcurl via FFI in ConTeXt, see attached. On my old laptop:
context: 3.482 seconds
context --jit: 2.742 seconds
context --jiton: 2.693 seconds
Cheers, Henri
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\startluacode
local ffi = assert(require("ffi"))
-- Definition copied straight from curl.h
ffi.cdef[[
typedef struct Curl_easy CURL;
typedef int CURLcode;
typedef int CURLoption;
typedef int CURLINFO;
typedef size_t(*callback)(void *buffer, size_t size, size_t nmemb, void *userp);
CURLcode curl_global_init(long flags);
CURL *curl_easy_init(void);
CURLcode curl_easy_setopt(CURL *curl, CURLoption option, ...);
CURLcode curl_easy_perform(CURL *curl);
CURLcode curl_easy_getinfo(CURL *curl, CURLINFO info, ...);
void curl_easy_cleanup(CURL *curl);
void curl_global_cleanup(void);
]]
-- Magic numbers
-- for more complex applications one should copy the full enums
-- CURLcode, CURLoption, and CURLINFO into ffi.cdef
local CURLE_OK = 0
local CURL_GLOBAL_DEFAULT = 3
local CURLOPT_URL = 10002
local CURLOPT_NOBODY = 44
local CURLOPT_HEADER = 42
local CURLOPT_WRITEFUNCTION = 20011
local CURLINFO_RESPONSE_CODE = 0x200000 + 2
local lcurl = assert(ffi.load("curl"))
-- Callback function for data received by the request
local function discard(buffer, size, nmemb, userp)
return size * nmemb
end
-- Initialize the curl session
lcurl.curl_global_init(CURL_GLOBAL_DEFAULT)
-- Make the cleanup function available globally so we can call it when
-- ConTeXt is done
curl_global_cleanup = lcurl.curl_global_cleanup
function curl_check_status(url)
-- Start a libcurl easy session
local curl = assert(lcurl.curl_easy_init())
-- URL to work on
assert(CURLE_OK == lcurl.curl_easy_setopt(curl, CURLOPT_URL, url))
-- Do not get the body contents
assert(CURLE_OK == lcurl.curl_easy_setopt(curl, CURLOPT_NOBODY, ffi.cast("long",1)))
-- Include the header in the body output
assert(CURLE_OK == lcurl.curl_easy_setopt(curl, CURLOPT_HEADER, ffi.cast("long",1)))
-- Callback for writing data
assert(CURLE_OK == lcurl.curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, ffi.cast("callback",discard)))
-- perform a blocking file transfer
assert(CURLE_OK == lcurl.curl_easy_perform(curl))
-- extract last received response code from a curl handle
local c_http_code = ffi.new("long[1]")
assert(CURLE_OK == lcurl.curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, c_http_code))
-- End a libcurl easy handle
lcurl.curl_easy_cleanup(curl)
-- Convert C long* to Lua number
return tonumber(c_http_code[0])
end
\stopluacode
\appendtoks
\ctxlua{curl_global_cleanup()}
\to \everystoptext
\starttext
HTTP: \ctxlua{context(curl_check_status("http://example.com/"))}
HTTPS: \ctxlua{context(curl_check_status("https://example.com/"))}
404: \ctxlua{context(curl_check_status("https://example.com/xyz"))}
\stoptext
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