Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// download_internal.h
//
// Header file for optional HTTP asset downloading
// Author: Matthew D. Campbell (matt@turtlerockstudios.com), 2004
//
//=======================================================================================//
#ifndef DOWNLOAD_INTERNAL_H
#define DOWNLOAD_INTERNAL_H
/**
* -------------------
* Download overview:
* HTTP downloading is done outside the main thread, to increase responsiveness
* and for code clarity (the download can be a linear sequence of blocking calls).
*
* The process is as follows, from the perspective of the main thread:
* 1. Downloads are queued up when connecting to a server, if the server sends
* a download URL.
* 2. If HTTP downloads are queued up, the client disconnects from the server,
* and puts up a progress bar dialog box for the transfers.
* 3. The CL_HTTPUpdate() function is called every frame, and it does the following:
* a) Starts a download thread if none are active, and at least one is queued up.
* b) Checks on status of the current transfer and updates the progress bar.
* i. If the thread has finished, the file is written out to disk and another
* transfer is started.
* ii. If the thread has aborted/errored out, any partial data is written to
* the cache, the progress bar is removed, and an error message is
* shown, if neccessary.
* c) Checks for old transfers to clean up where the download thread has exited.
* 4. If the user hits Cancel on the progress bar, the current download is told to
* abort, and the progress bar is removed.
*
* The process is as follows, from the perspective of the download thread:
* 1. A complete URL is constructed and verified for correctness.
* 2. The connection is established with the server.
* 3. The file is requested from the server, including the file timestamp and
* byte range for partial transfers (resuming an aborted transfer). A buffer
* for the data is allocated in this thread.
* 4. while the main thread has not requested an abort, read data from the server.
* 5. Upon completion, abort, or an error, the thread does the following:
* a) close any open handles
* b) wait for the main thread to request an exit (so the main thread can read
* any data.)
* c) delete the data buffer (previously allocated in this thread)
* d) sets a flag letting the main thread know this thread is finished.
* e) exit
*
* -------------------
* Thread interaction:
* All thread interaction is handled via a shared RequestContext_t. Interaction is
* structured so that at all times, only one thread can be writing to any given
* variable.
*
* This is an attempt to enumerate all cases of thread interaction:
* 1. Before download thread creation
* a) main thread allocates the RequestContext_t, and zeroes it out.
* b) main thread fills in the baseURL and gamePath strings.
* c) main thread sets cachedTimestamp, nBytesCached, and allocates/fills
* cacheData if there is data from a previous aborted download.
* 2. During thread operation:
* a) download thread can do the following:
* i. for HTTP_CONNECTING, download thread can set nBytesTotal,
* nBytesCached, and nBytesCurrent. It can allocate data, and
* set the status to HTTP_FETCH, HTTP_ABORTED, or HTTP_ERROR.
* ii. for HTTP_FETCH, download thread can write to data, set
* nBytesCurrent, and set status to HTTP_DONE, HTTP_ABORTED,
* or HTTP_ERROR.
* iii. for HTTP_DONE, HTTP_ABORTED, and HTTP_ERROR, the download thread
* can only look at shouldStop until it is set by the main thread.
* b) main thread can look at status.
* i. for HTTP_CONNECTING, nothing is read, and only shouldStop can be set.
* ii. for HTTP_FETCH, nBytesTotal and nBytesCurrent are read, and
* shouldStop can be set.
* iii. for HTTP_DONE, nBytesTotal, nBytesCurrent, and data are read. Also,
* shouldStop can be set.
* iv. for HTTP_ABORTED, nothing is read, and only shouldStop can be set.
* v. for HTTP_ERROR, nBytesTotal, nBytesCurrent, and data are read. Also,
* shouldStop can be set.
* 3. After shouldStop is set by main thread:
* a) if the download thread is in status HTTP_FETCH, it will cease operations
* and set status to HTTP_ABORTED.
* b) download thread will delete data, if it exists.
* c) download thread will set threadDone.
* d) after the main thread set shouldStop, it will only look at threadDone.
* 4. After threadDone is set by download thread:
* a) download thread can safely exit, and will not access the RequestContext_t.
* b) main thread can delete the cacheData, if any exists, and delete the
* RequestContext_t itself. Thus ends the download.
* 5. SPECIAL CASE: if the user hits Cancel during a download, the main thread will
* look at nBytesTotal and nBytesCurrent to determine if there is any data
* present, and read from data if there is. The download thread will most likely
* be in HTTP_CONNECTING or HTTP_FETCH, but could also be in HTTP_DONE or
* HTTP_ERROR at this time. Regardless, this should be safe because of the
* following reasons:
* a) if nBytesCurrent is non-zero, this means data has been allocated, and
* nBytesTotal has been set and won't change.
* b) nBytesCurrent increases monotonically, so the contents of
* data[0..nBytesCurrent] is complete and unchanging.
*
*/
//--------------------------------------------------------------------------------------------------------------
#include "engine/requestcontext.h"
//--------------------------------------------------------------------------------------------------------------
#ifdef POSIX
void DownloadThread( void *voidPtr );
#else
DWORD __stdcall DownloadThread( void *voidPtr );
#endif
#endif // DOWNLOAD_INTERNAL_H
//--------------------------------------------------------------------------------------------------------------