118 lines
6.2 KiB
C
118 lines
6.2 KiB
C
|
//========= 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
|
||
|
|
|
||
|
|
//--------------------------------------------------------------------------------------------------------------
|