Quake DeveLS - Accessing files
Author: Nathan
Craig
Difficulty: Easy/Medium
The basics: If you've ever
picked up a book on ANSI C you've probably seen a little bit of C's file
handling capabilities. Since you can use the STL from within Quake II, let's
see what we can do in the way of opening, closing, and displaying the contents of
a file.
Note:
Text in red = Quake II's code
Text in
blue = Our code
Text in
gray = Comments
To start, switch to your
Quake II directory and use edit.com to create a new text file with the
contents:
Hello, World!
Save it as
hello.txt. Next we need to give Quake II the ability to load, close, and
display the contents of files. I chose to make a new module: g_fileio.c.
The first order of
business is to make g_fileio.c talk to Quake II's files. So, we simply add:
#include "g_local.h"
Not only
are we talking to Quake II now, but g_local.h (through q_shared.h) also loads
the STL headers assert.h, math.h, stdio.h, stdarg.h, string.h, stdlib.h, and
time.h.
I chose to implement three
global variables: one that pointed to the file's data, one that is an array for
the file's name and one that tells whether there is a file loaded or not (Note:
with this architecture, you can only load one file at a time. For an example of
loading multiple files see "Accessing files from Quake II: The Advanced
Version").
These variables are
declared as:
FILE *in; // the file
char *filename; // the file's name
qboolean FileLoaded = false; // whether or not the file is loaded (defaults to no file loaded)
Now, to
load a file. This function takes an edict_t *ent. This is so we can know who to
print the information on loading status to.
void LoadFile(edict_t *ent){if (!FileLoaded) { // if there is not already a file open
filename = gi.args(); // copy the desired filename into 'filename'
if ((in = fopen(filename, "r")) == NULL) { // test to see if file opened
// file did not load
gi.cprintf (ent, PRINT_HIGH, "Could not load file %s.\n", filename); FileLoaded = false; } else {// file did load
gi.cprintf(ent, PRINT_HIGH, "File %s loaded.\n", filename); FileLoaded = true; } }else // there's already a file open
gi.cprintf(ent, PRINT_HIGH, "File %s is already loaded.\n, filename");}
This
function uses the STL call fopen(). The "r" parameter denotes load a
file only if it exists (don't create a new file) and for read-only purposes.
Closing a file is just as simple:
void CloseFile(edict_t *ent){if (FileLoaded) { // if there is a file open
fclose(in); // use STL to close it
FileLoaded = false; gi.cprintf(ent, PRINT_HIGH, "File %s closed.\n", filename); // notify user }else // no file is opened
gi.cprintf(ent, PRINT_HIGH, "No file is currently loaded.\n");}
This uses
the C STL call fopen() with the parameter "r." Fopen() will load the
file for read-only purposes and will return zero if the file does not already
exist.
To display the contents of
a file:
void ShowFile(edict_t *ent){int c; // variable to hold temporary file data
if (FileLoaded) { // if there is a file loaded
// this while loop completes two tasks: checks to see if we // are at the end of the file, and assigns 'c' to the data// at the position of the file pointer
while ((c = fgetc(in)) != EOF)gi.cprintf(ent, PRINT_HIGH, "%c", c); // output 'c'
gi.cprintf(ent, PRINT_HIGH, "\nend of %s", filename); }else // no file is loaded
gi.cprintf(ent, PRINT_HIGH, "No file is currently loaded.\n");}
This uses
fgetc() to get data from the file byte by byte.
Now we must integrate
these functions with the rest of the Quake II code. In g_local.h, around line
704, add this:
//// g_main.c//void SaveClientData (void);void FetchClientEntData (edict_t *ent); //// g_fileio.c//
void LoadFile(edict_t *ent);void CloseFile(edict_t *ent);void ShowFile(edict_t *ent);
Now we can
access these functions from anywhere within Quake II's code. The last step,
then, is to allow the user to access these commands from the console. Around
line 647 of g_cmds.c, add this:
else if (Q_stricmp (cmd, "fov") == 0) { ent->client->ps.fov = atoi(gi.argv(1)); if (ent->client->ps.fov < 1) ent->client->ps.fov = 90; else if (ent->client->ps.fov > 160) ent->client->ps.fov = 160;}
// FILEIO else if (Q_stricmp(cmd, "loadfile") == 0) LoadFile(ent); else if (Q_stricmp(cmd, "closefile") == 0) CloseFile(ent); else if (Q_stricmp(cmd, "showfile") == 0) ShowFile(ent);
Finally,
compile the .dll (with g_fileio.c included), copy it to a subdirectory of your
Quake II directory and name it "gamex86.dll." Run Quake II:
quake2.exe +set game "whatever_dir_you_chose" +map base1
When you
enter the game, bring down the console and type:
cmd loadfile hello.txtcmd showfile
This will
display the contents of hello.txt. Finally, close the file:
cmd closefile
Remember:
This source could be modified and used maliciously. Don't be a loser.
But, most importantly, have fun – and learn!
Here's a complete listing
of g_fileio.c for you cut and paste purposes:
/* * G_fileio.c */ // STL files are included by g_local.h#include "g_local.h" FILE *in; // the filechar *filename; // the file's nameqboolean FileLoaded = false; // whether or not the file is loaded (defaults to no file loaded) void LoadFile(edict_t *ent){ if (!FileLoaded) { // if there is not already a file open filename = gi.args(); // copy the desired filename into 'filename' if ((in = fopen(filename, "r")) == NULL) { // test to see if file opened // file did not load gi.cprintf (ent, PRINT_HIGH, "Could not load file %s.\n", filename); FileLoaded = false; } else { // file did load gi.cprintf(ent, PRINT_HIGH, "File %s loaded.\n", filename); FileLoaded = true; } } else // there's already a file open gi.cprintf(ent, PRINT_HIGH, "File %s is already loaded.\n, filename");} void CloseFile(edict_t *ent){ if (FileLoaded) { // if there is a file open fclose(in); // use STL to close it FileLoaded = false; gi.cprintf(ent, PRINT_HIGH, "File %s closed.\n", filename); // notify user } else // no file is opened gi.cprintf(ent, PRINT_HIGH, "No file is currently loaded.\n");} void ShowFile(edict_t *ent){ int c; // variable to hold temporary file data if (FileLoaded) { // if there is a file loaded // this while loop completes two tasks: checks to see if we // are at the end of the file, and assigns 'c' to the data // at the position of the file pointer while ((c = fgetc(in)) != EOF) gi.cprintf(ent, PRINT_HIGH, "%c", c); // output 'c' gi.cprintf(ent, PRINT_HIGH, "\nend of %s", filename); } else // no file is loaded gi.cprintf(ent, PRINT_HIGH, "No file is currently loaded.\n");}
Tutorial
by Nathan Craig
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