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initial loader implementation - provides a queue that is worked off from the main loop; a timeout ensures responsiveness.

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this is the framework that will allow progress bar updates.

This was SVN commit r2027.
This commit is contained in:
janwas 2005-03-20 14:32:43 +00:00
parent 06d6cd17f5
commit 77d3c5d0b5
2 changed files with 287 additions and 0 deletions
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222
source/ps/Loader.cpp Normal file
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#include "precompiled.h"
#include <deque>
#include "lib.h" // error codes
#include "timer.h"
#include "loader.h"
#include "CStr.h"
// note: not thread-safe!
// need to maintain this counter ourselves so we can reset after each load.
static int progress_percent = 0;
// main purpose is to indicate whether a load is in progress, so that
// LDR_ProgressiveLoad can return 0 iff loading just completed.
// the REGISTERING state allows us to detect 2 simultaneous loads (bogus).
static enum
{
IDLE,
REGISTERING,
LOADING,
}
state = IDLE;
// holds all state for one load request; stored in queue.
struct LoadRequest
{
// member documentation is in LDR_Register (avoid duplication).
LoadFunc func;
void* param;
const CStrW description;
// rationale:
// - don't just store a pointer - the caller's string may be volatile.
// - the module interface must work in C, so we get/set as wchar_t*.
int progress_percent_after_completion;
int estimated_duration_ms;
// LDR_Register gets these as parameters; pack everything together.
LoadRequest(LoadFunc func_, void* param_, const wchar_t* desc_, int pc_, int ms_)
: func(func_), param(param_), description(desc_),
progress_percent_after_completion(pc_), estimated_duration_ms(ms_)
{
}
};
typedef std::deque<const LoadRequest> LoadRequests;
static LoadRequests load_requests;
// call before starting to register load requests.
// this routine is provided so we can prevent 2 simultaneous load operations,
// which is bogus. that can happen by clicking the load button quickly,
// or issuing via console while already loading.
int LDR_BeginRegistering()
{
if(state != IDLE)
return -1;
state = REGISTERING;
load_requests.clear();
return 0;
}
// register a load request (later processed in FIFO order).
// <func>: function that will perform the actual work; see LoadFunc.
// <param>: (optional) parameter/persistent state; must be freed by func.
// <description>: user-visible description of the current task, e.g.
// "Loading map".
// <progress_percent_after_completion>: optional; if non-zero, progress is
// set to this value after the current task completes.
// must increase monotonically.
// <estimated_duration_ms>: optional; if non-zero, this task will be
// postponed until the next LDR_ProgressiveLoad timeslice if there's not
// much time left. this reduces overruns of the timeslice => main loop is
// more responsive.
int LDR_Register(LoadFunc func, void* param, const wchar_t* description,
int progress_percent_after_completion, int estimated_duration_ms)
{
if(state != REGISTERING)
return -1;
const LoadRequest lr(func, param, description,
progress_percent_after_completion, estimated_duration_ms);
load_requests.push_back(lr);
return 0;
}
// call when finished registering load requests; subsequent calls to
// LDR_ProgressiveLoad will then work off the queued entries.
int LDR_EndRegistering()
{
if(state != REGISTERING)
return -1;
state = LOADING;
progress_percent = 0;
return 0;
}
// immediately cancel the load. note: no special notification will be
// returned by LDR_ProgressiveLoad.
int LDR_Cancel()
{
// note: calling during registering doesn't make sense - that
// should be an atomic sequence of begin, register [..], end.
if(state != LOADING)
return -1;
state = IDLE;
// the queue doesn't need to be emptied now; that'll happen during the
// next LDR_StartRegistering. for now, it is sufficient to set the
// state, so that LDR_ProgressiveLoad is a no-op.
return 0;
}
// helper routine for LDR_ProgressiveLoad.
// tries to prevent starting a long task when at the end of a timeslice.
static bool HaveTimeForNextTask(double time_left, double time_budget, int estimated_duration_ms)
{
// have already exceeded our time budget => stop for now.
if(time_left <= 0.0)
return false;
// we've already used up more than 60%
// (if it's less than that, we won't check the next task length)
if(time_left < 0.40*time_budget)
{
const double estimated_duration = estimated_duration_ms * 1e-3;
// .. next task is expected to be long - do it next call
if(estimated_duration > time_left + time_budget*0.20)
return false;
}
return true;
}
// process as many of the queued load requests as possible within
// <time_budget> [s]. if a request is lengthy, the budget may be exceeded.
// call from the main loop.
//
// passes back a description of the last task undertaken and the progress
// value established by the last request to complete.
//
// return semantics:
// - if loading just completed, return 0.
// - if loading is in progress but didn't finish, return ERR_TIMED_OUT.
// - if not currently loading (no-op), return 1.
// - any other value indicates a failure; the request has been de-queued.
//
// string interface rationale: for better interoperability, we avoid C++
// std::wstring and PS CStr. since the registered description may not be
// persistent, we can't just store a pointer. returning a pointer to
// our copy of the description doesn't work either, since it's freed when
// the request is de-queued. that leaves writing into caller's buffer.
int LDR_ProgressiveLoad(double time_budget, wchar_t* current_description,
size_t max_chars, int* progress_percent_)
{
// we're called unconditionally from the main loop, so this isn't
// an error; there is just nothing to do.
if(state != LOADING)
return 1;
const double end_time = get_time() + time_budget;
// in case it's never set below (because all LoadRequests have
// progress_percent_after_completion = 0)
*progress_percent_ = progress_percent;
// (function will return immediately on failure or timeout)
while(!load_requests.empty())
{
const double time_left = end_time - get_time();
const LoadRequest& lr = load_requests.front();
// latch description of the current task now (it may be removed below)
wcscpy_s(current_description, max_chars, lr.description);
// do actual work of loading
int ret = lr.func(lr.param, time_left);
// .. either finished entirely, or failed => remove from queue
if(ret != ERR_TIMED_OUT)
load_requests.pop_front();
// .. failed or timed out => abort immediately; loading will
// continue when we're called in the next iteration of the main loop.
// rationale: bail immediately instead of remembering the first error
// that came up, so that we report can all errors that happen.
if(ret != 0)
return ret;
// .. completed normally:
// update progress
const int new_pc = lr.progress_percent_after_completion;
if(new_pc)
{
assert(new_pc > progress_percent);
*progress_percent_ = progress_percent = new_pc;
}
// check if we're out of time; take into account next task length.
// note: do this at the end of the loop to make sure there's
// progress even if the timer is low-resolution (=> time_left = 0).
if(!HaveTimeForNextTask(time_left, time_budget, lr.estimated_duration_ms))
return ERR_TIMED_OUT;
}
// queue is empty, we just finished.
state = IDLE;
assert(progress_percent == 100);
return 0;
}

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source/ps/Loader.h Normal file
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#include <wchar.h>
// call before starting to register load requests.
// this routine is provided so we can prevent 2 simultaneous load operations,
// which is bogus. that can happen by clicking the load button quickly,
// or issuing via console while already loading.
extern int LDR_BeginRegistering();
// callback function of a load request; performs the actual work.
// it receives a param (see below) and the exact time remaining [s].
//
// return semantics:
// - if the work can be split into smaller subtasks, process those until
// <time_left> is reached or exceeded and then return ERR_TIMED_OUT.
// - if the entire task was successfully completed, return 0:
// the load request will then be de-queued.
// - any other return value indicates failure and causes
// LDR_ProgressiveLoad to immediately abort and return that.
typedef int (*LoadFunc)(void* param, double time_left);
// register a load request (later processed in FIFO order).
// <func>: function that will perform the actual work; see LoadFunc above.
// <param>: (optional) parameter/persistent state; must be freed by func.
// <description>: user-visible description of the current task, e.g.
// "Loading map".
// <progress_percent_after_completion>: optional; if non-zero, progress is
// set to this value after the current task completes.
// must increase monotonically.
// <estimated_duration_ms>: optional; if non-zero, this task will be
// postponed until the next LDR_ProgressiveLoad timeslice if there's not
// much time left. this reduces overruns of the timeslice => main loop is
// more responsive.
extern int LDR_Register(LoadFunc func, void* param, const wchar_t* description,
int progress_percent_after_completion = 0, int estimated_duration_ms = 0);
// call when finished registering load requests; subsequent calls to
// LDR_ProgressiveLoad will then work off the queued entries.
extern int LDR_EndRegistering();
// immediately cancel the load. note: no special notification will be
// returned by LDR_ProgressiveLoad.
extern int LDR_Cancel();
// process as many of the queued load requests as possible within
// <time_budget> [s]. if a request is lengthy, the budget may be exceeded.
// call from the main loop.
//
// passes back a description of the last task undertaken and the progress
// value established by the last request to complete.
//
// return semantics:
// - if loading just completed, return 0.
// - if loading is in progress but didn't finish, return ERR_TIMED_OUT.
// - if not currently loading (no-op), return 1.
// - any other value indicates a failure; the request has been de-queued.
//
// string interface rationale: for better interoperability, we avoid C++
// std::wstring and PS CStr. since the registered description may not be
// persistent, we can't just store a pointer. returning a pointer to
// our copy of the description doesn't work either, since it's freed when
// the request is de-queued. that leaves writing into caller's buffer.
extern int LDR_ProgressiveLoad(double time_budget, wchar_t* current_description,
size_t max_chars, int* progress_percent);