Name
easy:SetOpt_WriteFunction -- set callback for writing received data
Synopsis
easy:SetOpt_WriteFunction(write_callback[, userdata])
Function
Pass a callback function. This callback function gets called by libcurl as soon as there is data received that needs to be saved. For most transfers, this callback gets called many times and each invoke delivers another chunk of data.

The first parameter that is passed to your callback function is a string that contains the raw binary data just received. If you pass the optional userdata argument, the value you pass in userdata will be passed to your callback function as a second parameter. The userdata parameter can be of any type.

The callback function will be passed as much data as possible in all invokes, but you must not make any assumptions. It may be one byte, it may be thousands. The maximum amount of body data that will be passed to the write callback is defined as follows: #CURL_MAX_WRITE_SIZE (the usual default is 16K). If #CURLOPT_HEADER is enabled, which makes header data get passed to the write callback, you can get up to #CURL_MAX_HTTP_HEADER bytes of header data passed into it. This usually means 100K.

This function may be called with zero bytes data if the transferred file is empty.

Your callback should return the number of bytes actually taken care of. If that amount differs from the amount passed to your callback function, it'll signal an error condition to the library. This will cause the transfer to get aborted and the libcurl function used will return #CURLE_WRITE_ERROR.

If your write function returns nothing, this will signal success and the transfer will be continued.

If your callback function returns #CURL_WRITEFUNC_PAUSE it will cause this transfer to become paused. See easy:Pause() for further details.

Inputs
write_callback
input value
userdata
optional: user data to pass to callback function
Example
Function p_WriteData(data$)
   WriteBytes(1, data$)
EndFunction
e:SetOpt_WriteFunction(p_WriteData)
The code above will install a write function that will write all data it receives to the file using the identifier 1.

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