diff --git a/kilo b/kilo
index dace6e4..a2e0ad4 100755
--- a/kilo
+++ b/kilo
@@ -3,7 +3,14 @@
 
 namespace Kilo;
 
-require_once __DIR__ . '/src/constants.php';
+// -----------------------------------------------------------------------------
+// ! App Constants
+// -----------------------------------------------------------------------------
+define('KILO_VERSION', '0.0.1');
+define('KILO_TAB_STOP', 4);
+define('KILO_QUIT_TIMES', 3);
+
+require_once __DIR__ . '/src/C.php';
 require_once __DIR__ . '/src/functions.php';
 require_once __DIR__ . '/src/Editor.php';
 
diff --git a/src/C.php b/src/C.php
new file mode 100644
index 0000000..378cd06
--- /dev/null
+++ b/src/C.php
@@ -0,0 +1,146 @@
+<?php declare(strict_types=1);
+
+namespace Kilo;
+
+/**
+ * Just a namespace for C language constants
+ */
+class C {
+	// ------------------------------------------------------------------------
+	// ! Misc I/O constants
+	// ------------------------------------------------------------------------
+
+	public const STDIN_FILENO = 0;
+	public const STDOUT_FILENO = 1;
+	public const STDERR_FILENO = 2;
+	public const TCSAFLUSH = 2;
+
+	// ------------------------------------------------------------------------
+	// ! Termios flags and constants
+	// ------------------------------------------------------------------------
+
+	/* Input modes */
+	public const IGNBRK = (1 << 0);    /* Ignore break condition.  */
+	public const BRKINT = (1 << 1);    /* Signal interrupt on break.  */
+	public const IGNPAR = (1 << 2);    /* Ignore characters with parity errors.  */
+	public const PARMRK = (1 << 3);    /* Mark parity and framing errors.  */
+	public const INPCK = (1 << 4);    /* Enable input parity check.  */
+	public const ISTRIP = (1 << 5);    /* Strip 8th bit off characters.  */
+	public const INLCR = (1 << 6);    /* Map NL to CR on input.  */
+	public const IGNCR = (1 << 7);    /* Ignore CR.  */
+	public const ICRNL = (1 << 8);    /* Map CR to NL on input.  */
+	public const IXON = (1 << 9);    /* Enable start/stop output control.  */
+	public const IXOFF = (1 << 10);    /* Enable start/stop input control.  */
+	public const IXANY = (1 << 11);    /* Any character will restart after stop.  */
+	public const IMAXBEL = (1 << 13);    /* Ring bell when input queue is full.  */
+	public const IUCLC = (1 << 14);    /* Translate upper case input to lower case. */
+
+	/* Output modes */
+	public const OPOST = (1 << 0);    /* Perform output processing.  */
+	public const ONLCR = (1 << 1);    /* Map NL to CR-NL on output.  */
+	public const OXTABS = (1 << 2);        /* Expand tabs to spaces.  */
+	public const ONOEOT = (1 << 3);    /* Discard EOT (^D) on output.  */
+	public const OCRNL = (1 << 4);    /* Map CR to NL.  */
+	public const ONOCR = (1 << 5);    /* Discard CR's when on column 0.  */
+	public const ONLRET = (1 << 6);    /* Move to column 0 on NL.  */
+	public const NLDLY = (3 << 8);    /* NL delay.  */
+	public const NL0 = (0 << 8);    /* NL type 0.  */
+	public const NL1 = (1 << 8);    /* NL type 1.  */
+	public const TABDLY = (3 << 10 | 1 << 2);    /* TAB delay.  */
+	public const TAB0 = (0 << 10);    /* TAB delay type 0.  */
+	public const TAB1 = (1 << 10);    /* TAB delay type 1.  */
+	public const TAB2 = (2 << 10);    /* TAB delay type 2.  */
+	public const TAB3 = (1 << 2);    /* Expand tabs to spaces.  */
+	public const CRDLY = (3 << 12);    /* CR delay.  */
+	public const CR0 = (0 << 12);    /* CR delay type 0.  */
+	public const CR1 = (1 << 12);    /* CR delay type 1.  */
+	public const CR2 = (2 << 12);    /* CR delay type 2.  */
+	public const CR3 = (3 << 12);    /* CR delay type 3.  */
+	public const FFDLY = (1 << 14);    /* FF delay.  */
+	public const FF0 = (0 << 14);    /* FF delay type 0.  */
+	public const FF1 = (1 << 14);    /* FF delay type 1.  */
+	public const BSDLY = (1 << 15);    /* BS delay.  */
+	public const BS0 = (0 << 15);    /* BS delay type 0.  */
+	public const BS1 = (1 << 15);    /* BS delay type 1.  */
+	public const VTDLY = (1 << 16);    /* VT delay.  */
+	public const VT0 = (0 << 16);    /* VT delay type 0.  */
+	public const VT1 = (1 << 16);    /* VT delay type 1.  */
+	public const OLCUC = (1 << 17);    /* Translate lower case output to upper case */
+	public const OFILL = (1 << 18);    /* Send fill characters for delays.  */
+	public const OFDEL = (1 << 19);    /* Fill is DEL.  */
+
+	/* Control modes */
+	public const CIGNORE = (1 << 0);    /* Ignore these control flags.  */
+	public const CS5 = 0;        /* 5 bits per byte.  */
+	public const CS6 = (1 << 8);    /* 6 bits per byte.  */
+	public const CS7 = (1 << 9);    /* 7 bits per byte.  */
+	public const CS8 = (C::CS6|C::CS7);    /* 8 bits per byte.  */
+	public const CSIZE = (C::CS5|C::CS6|C::CS7|C::CS8);    /* Number of bits per byte (mask).  */
+	public const CSTOPB = (1 << 10);    /* Two stop bits instead of one.  */
+	public const CREAD = (1 << 11);    /* Enable receiver.  */
+	public const PARENB = (1 << 12);    /* Parity enable.  */
+	public const PARODD = (1 << 13);    /* Odd parity instead of even.  */
+	public const HUPCL = (1 << 14);    /* Hang up on last close.  */
+	public const CLOCAL = (1 << 15);    /* Ignore modem status lines.  */
+	public const CRTSCTS = (1 << 16);    /* RTS/CTS flow control.  */
+	public const CRTS_IFLOW = C::CRTSCTS;        /* Compatibility.  */
+	public const CCTS_OFLOW = C::CRTSCTS;        /* Compatibility.  */
+	public const CDTRCTS = (1 << 17);    /* DTR/CTS flow control.  */
+	public const MDMBUF = (1 << 20);    /* DTR/DCD flow control.  */
+	public const CHWFLOW = (C::MDMBUF|C::CRTSCTS|C::CDTRCTS); /* All types of flow control.  */
+
+	/* Local modes */
+	public const ECHOKE = (1 << 0);    /* Visual erase for KILL.  */
+	public const _ECHOE = (1 << 1);    /* Visual erase for ERASE.  */
+	public const ECHOE = C::_ECHOE;
+	public const _ECHOK = (1 << 2);    /* Echo NL after KILL.  */
+	public const ECHOK = C::_ECHOK;
+	public const _ECHO = (1 << 3);    /* Enable echo.  */
+	public const ECHO = C::_ECHO;
+	public const _ECHONL = (1 << 4);    /* Echo NL even if ECHO is off.  */
+	public const ECHONL = C::_ECHONL;
+	public const ECHOPRT = (1 << 5);    /* Hardcopy visual erase.  */
+	public const ECHOCTL = (1 << 6);    /* Echo control characters as ^X.  */
+	public const _ISIG = (1 << 7);    /* Enable signals.  */
+	public const ISIG = C::_ISIG;
+	public const _ICANON = (1 << 8);    /* Do erase and kill processing.  */
+	public const ICANON = C::_ICANON;
+	public const ALTWERASE = (1 << 9);    /* Alternate WERASE algorithm.  */
+	public const _IEXTEN = (1 << 10);    /* Enable DISCARD and LNEXT.  */
+	public const IEXTEN = C::_IEXTEN;
+	public const EXTPROC = (1 << 11);    /* External processing.  */
+	public const _TOSTOP = (1 << 22);    /* Send SIGTTOU for background output.  */
+	public const TOSTOP = C::_TOSTOP;
+	public const FLUSHO = (1 << 23);    /* Output being flushed (state).  */
+	public const XCASE = (1 << 24);    /* Canonical upper/lower case.  */
+	public const NOKERNINFO = (1 << 25);    /* Disable VSTATUS.  */
+	public const PENDIN = (1 << 29);    /* Retype pending input (state).  */
+	public const _NOFLSH = (1 << 31);    /* Disable flush after interrupt.  */
+	public const NOFLSH = C::_NOFLSH;
+
+	/* Control characters */
+	public const VEOF = 0;        /* End-of-file character [ICANON].  */
+	public const VEOL = 1;        /* End-of-line character [ICANON].  */
+	public const VEOL2 = 2;        /* Second EOL character [ICANON].  */
+	public const VERASE = 3;        /* Erase character [ICANON].  */
+	public const VWERASE = 4;        /* Word-erase character [ICANON].  */
+	public const VKILL = 5;        /* Kill-line character [ICANON].  */
+	public const VREPRINT = 6;        /* Reprint-line character [ICANON].  */
+	public const VINTR = 8;        /* Interrupt character [ISIG].  */
+	public const VQUIT = 9;        /* Quit character [ISIG].  */
+	public const VSUSP = 10;        /* Suspend character [ISIG].  */
+	public const VDSUSP = 11;        /* Delayed suspend character [ISIG].  */
+	public const VSTART = 12;        /* Start (X-ON) character [IXON, IXOFF].  */
+	public const VSTOP = 13;        /* Stop (X-OFF) character [IXON, IXOFF].  */
+	public const VLNEXT = 14;        /* Literal-next character [IEXTEN].  */
+	public const VDISCARD = 15;        /* Discard character [IEXTEN].  */
+	public const VMIN = 16;        /* Minimum number of bytes read at once [!ICANON].  */
+	public const VTIME = 17;        /* Time-out value (tenths of a second) [!ICANON].  */
+	public const VSTATUS = 18;        /* Status character [ICANON].  */
+	public const NCCS = 20;        /* Value duplicated in <hurd/tioctl.defs>.  */
+
+	// ------------------------------------------------------------------------
+	// ! IOCTL constants
+	// ------------------------------------------------------------------------
+	public const TIOCGWINSZ = 0x5413;
+}
\ No newline at end of file
diff --git a/src/constants.php b/src/constants.php
deleted file mode 100644
index 97d576b..0000000
--- a/src/constants.php
+++ /dev/null
@@ -1,148 +0,0 @@
-<?php declare(strict_types=1);
-
-namespace Kilo;
-
-// -----------------------------------------------------------------------------
-// ! App Constants
-// -----------------------------------------------------------------------------
-define('KILO_VERSION', '0.0.1');
-define('KILO_TAB_STOP', 4);
-define('KILO_QUIT_TIMES', 3);
-
-// -----------------------------------------------------------------------------
-// ! Misc I/O constants
-// -----------------------------------------------------------------------------
-
-define('STDIN_FILENO', 0);
-define('STDOUT_FILENO', 1);
-define('STDERR_FILENO', 2);
-define('TCSAFLUSH', 2);
-
-// -----------------------------------------------------------------------------
-// ! Termios flags and constants
-// -----------------------------------------------------------------------------
-
-/* Input modes */
-define('IGNBRK', (1 << 0));	/* Ignore break condition.  */
-define('BRKINT', (1 << 1));	/* Signal interrupt on break.  */
-define('IGNPAR', (1 << 2));	/* Ignore characters with parity errors.  */
-define('PARMRK', (1 << 3));	/* Mark parity and framing errors.  */
-define('INPCK', (1 << 4));	/* Enable input parity check.  */
-define('ISTRIP', (1 << 5));	/* Strip 8th bit off characters.  */
-define('INLCR', (1 << 6));	/* Map NL to CR on input.  */
-define('IGNCR', (1 << 7));	/* Ignore CR.  */
-define('ICRNL', (1 << 8));	/* Map CR to NL on input.  */
-define('IXON', (1 << 9));	/* Enable start/stop output control.  */
-define('IXOFF', (1 << 10));	/* Enable start/stop input control.  */
-define('IXANY', (1 << 11));	/* Any character will restart after stop.  */
-define('IMAXBEL', (1 << 13));	/* Ring bell when input queue is full.  */
-define('IUCLC', (1 << 14));	/* Translate upper case input to lower case. */
-
-/* Output modes */
-define('OPOST', (1 << 0));	/* Perform output processing.  */
-define('ONLCR', (1 << 1));	/* Map NL to CR-NL on output.  */
-define('OXTABS', (1 << 2));		/* Expand tabs to spaces.  */
-define('ONOEOT', (1 << 3));	/* Discard EOT (^D) on output.  */
-define('OCRNL', (1 << 4));	/* Map CR to NL.  */
-define('ONOCR', (1 << 5));	/* Discard CR's when on column 0.  */
-define('ONLRET', (1 << 6));	/* Move to column 0 on NL.  */
-define('NLDLY', (3 << 8));	/* NL delay.  */
-define('NL0', (0 << 8));	/* NL type 0.  */
-define('NL1', (1 << 8));	/* NL type 1.  */
-define('TABDLY', (3 << 10 | 1 << 2));	/* TAB delay.  */
-define('TAB0', (0 << 10));	/* TAB delay type 0.  */
-define('TAB1', (1 << 10));	/* TAB delay type 1.  */
-define('TAB2', (2 << 10));	/* TAB delay type 2.  */
-define('TAB3', (1 << 2));	/* Expand tabs to spaces.  */
-define('CRDLY', (3 << 12));	/* CR delay.  */
-define('CR0', (0 << 12));	/* CR delay type 0.  */
-define('CR1', (1 << 12));	/* CR delay type 1.  */
-define('CR2', (2 << 12));	/* CR delay type 2.  */
-define('CR3', (3 << 12));	/* CR delay type 3.  */
-define('FFDLY', (1 << 14));	/* FF delay.  */
-define('FF0', (0 << 14));	/* FF delay type 0.  */
-define('FF1', (1 << 14));	/* FF delay type 1.  */
-define('BSDLY', (1 << 15));	/* BS delay.  */
-define('BS0', (0 << 15));	/* BS delay type 0.  */
-define('BS1', (1 << 15));	/* BS delay type 1.  */
-define('VTDLY', (1 << 16));	/* VT delay.  */
-define('VT0', (0 << 16));	/* VT delay type 0.  */
-define('VT1', (1 << 16));	/* VT delay type 1.  */
-define('OLCUC', (1 << 17));	/* Translate lower case output to upper case */
-define('OFILL', (1 << 18));	/* Send fill characters for delays.  */
-define('OFDEL', (1 << 19));	/* Fill is DEL.  */
-
-/* Control modes */
-define('CIGNORE', (1 << 0));	/* Ignore these control flags.  */
-define('CS5', 0);		/* 5 bits per byte.  */
-define('CS6', (1 << 8));	/* 6 bits per byte.  */
-define('CS7', (1 << 9));	/* 7 bits per byte.  */
-define('CS8', (CS6|CS7));	/* 8 bits per byte.  */
-define('CSIZE', (CS5|CS6|CS7|CS8));	/* Number of bits per byte (mask).  */
-define('CSTOPB', (1 << 10));	/* Two stop bits instead of one.  */
-define('CREAD', (1 << 11));	/* Enable receiver.  */
-define('PARENB', (1 << 12));	/* Parity enable.  */
-define('PARODD', (1 << 13));	/* Odd parity instead of even.  */
-define('HUPCL', (1 << 14));	/* Hang up on last close.  */
-define('CLOCAL', (1 << 15));	/* Ignore modem status lines.  */
-define('CRTSCTS', (1 << 16));	/* RTS/CTS flow control.  */
-define('CRTS_IFLOW', CRTSCTS);		/* Compatibility.  */
-define('CCTS_OFLOW', CRTSCTS);		/* Compatibility.  */
-define('CDTRCTS', (1 << 17));	/* DTR/CTS flow control.  */
-define('MDMBUF', (1 << 20));	/* DTR/DCD flow control.  */
-define('CHWFLOW', (MDMBUF|CRTSCTS|CDTRCTS)); /* All types of flow control.  */
-
-/* Local modes */
-define('ECHOKE', (1 << 0));	/* Visual erase for KILL.  */
-define('_ECHOE', (1 << 1));	/* Visual erase for ERASE.  */
-define('ECHOE', _ECHOE);
-define('_ECHOK', (1 << 2));	/* Echo NL after KILL.  */
-define('ECHOK', _ECHOK);
-define('_ECHO', (1 << 3));	/* Enable echo.  */
-define('ECHO', _ECHO);
-define('_ECHONL', (1 << 4));	/* Echo NL even if ECHO is off.  */
-define('ECHONL', _ECHONL);
-define('ECHOPRT', (1 << 5));	/* Hardcopy visual erase.  */
-define('ECHOCTL', (1 << 6));	/* Echo control characters as ^X.  */
-define('_ISIG', (1 << 7));	/* Enable signals.  */
-define('ISIG', _ISIG);
-define('_ICANON', (1 << 8));	/* Do erase and kill processing.  */
-define('ICANON', _ICANON);
-define('ALTWERASE', (1 << 9));	/* Alternate WERASE algorithm.  */
-define('_IEXTEN', (1 << 10));	/* Enable DISCARD and LNEXT.  */
-define('IEXTEN', _IEXTEN);
-define('EXTPROC', (1 << 11));	/* External processing.  */
-define('_TOSTOP', (1 << 22));	/* Send SIGTTOU for background output.  */
-define('TOSTOP', _TOSTOP);
-define('FLUSHO', (1 << 23));	/* Output being flushed (state).  */
-define('XCASE', (1 << 24));	/* Canonical upper/lower case.  */
-define('NOKERNINFO', (1 << 25));	/* Disable VSTATUS.  */
-define('PENDIN', (1 << 29));	/* Retype pending input (state).  */
-define('_NOFLSH', (1 << 31));	/* Disable flush after interrupt.  */
-define('NOFLSH', _NOFLSH);
-
-/* Control characters */
-define('VEOF', 0);		/* End-of-file character [ICANON].  */
-define('VEOL', 1);		/* End-of-line character [ICANON].  */
-define('VEOL2', 2);		/* Second EOL character [ICANON].  */
-define('VERASE', 3);		/* Erase character [ICANON].  */
-define('VWERASE', 4);		/* Word-erase character [ICANON].  */
-define('VKILL', 5);		/* Kill-line character [ICANON].  */
-define('VREPRINT', 6);		/* Reprint-line character [ICANON].  */
-define('VINTR', 8);		/* Interrupt character [ISIG].  */
-define('VQUIT', 9);		/* Quit character [ISIG].  */
-define('VSUSP', 10);		/* Suspend character [ISIG].  */
-define('VDSUSP', 11);		/* Delayed suspend character [ISIG].  */
-define('VSTART', 12);		/* Start (X-ON) character [IXON, IXOFF].  */
-define('VSTOP', 13);		/* Stop (X-OFF) character [IXON, IXOFF].  */
-define('VLNEXT', 14);		/* Literal-next character [IEXTEN].  */
-define('VDISCARD', 15);		/* Discard character [IEXTEN].  */
-define('VMIN', 16);		/* Minimum number of bytes read at once [!ICANON].  */
-define('VTIME', 17);		/* Time-out value (tenths of a second) [!ICANON].  */
-define('VSTATUS', 18);		/* Status character [ICANON].  */
-define('NCCS', 20);		/* Value duplicated in <hurd/tioctl.defs>.  */
-
-// -----------------------------------------------------------------------------
-// ! IOCTL constants
-// -----------------------------------------------------------------------------
-define('TIOCGWINSZ', 0x5413);
\ No newline at end of file
diff --git a/src/functions.php b/src/functions.php
index dcd9faa..8050c1d 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -4,8 +4,8 @@ namespace Kilo;
 
 use FFI;
 
-$ffi = FFI::load(__DIR__ . '/ffi.h');
-$original_termios = $ffi->new('struct termios');
+/** @var FFI\CData $original_termios */
+$original_termios = get_ffi()->new('struct termios');
 
 // ----------------------------------------------------------------------------
 // ! Raw mode / Terminal size
@@ -13,13 +13,15 @@ $original_termios = $ffi->new('struct termios');
 
 function enable_raw_mode(): void
 {
-	global $ffi;
 	global $original_termios;
 
+	// Make sure to restore normal mode on exit/die/crash
 	register_shutdown_function('Kilo\disable_raw_mode');
 
+	$ffi = get_ffi();
+
 	// Populate the original terminal settings
-	$res = $ffi->tcgetattr(STDIN_FILENO, FFI::addr($original_termios));
+	$res = $ffi->tcgetattr(C::STDIN_FILENO, FFI::addr($original_termios));
 	if ($res === -1)
 	{
 		die('tcgetattr');
@@ -27,15 +29,15 @@ function enable_raw_mode(): void
 
 	// So, the only thing that seems to really matter here is that c_oflag is 0...
 	$termios = clone $original_termios;
-	$termios->c_iflag = 0; //$termios->c_iflag & ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
-	$termios->c_oflag = 0; // $termios->c_oflag && ~(OPOST);
-	$termios->c_cflag |= (CS8);
-	$termios->c_lflag = $termios->c_lflag & ~(_ECHO | ICANON | IEXTEN | ISIG);
-	$termios->c_cc[VMIN] = 0;
-	$termios->c_cc[VTIME] = 1;
+	$termios->c_iflag = 0; //$termios->c_iflag & ~(C::BRKINT | C::ICRNL | C::INPCK | C::ISTRIP | C::IXON);
+	$termios->c_oflag = 0; // $termios->c_oflag && ~(C::OPOST);
+	$termios->c_cflag |= (C::CS8);
+	$termios->c_lflag = $termios->c_lflag & ~( C::ECHO | C::ICANON | C::IEXTEN | C::ISIG);
+	$termios->c_cc[C::VMIN] = 0;
+	$termios->c_cc[C::VTIME] = 1;
 
 	// Turn on raw mode
-	$res = $ffi->tcsetattr(STDIN_FILENO, TCSAFLUSH, FFI::addr($termios));
+	$res = $ffi->tcsetattr(C::STDIN_FILENO, C::TCSAFLUSH, FFI::addr($termios));
 	if ($res === -1)
 	{
 		die('tcsetattr');
@@ -44,10 +46,10 @@ function enable_raw_mode(): void
 
 function disable_raw_mode(): void
 {
-	global $ffi;
 	global $original_termios;
 
-	$res = $ffi->tcsetattr(STDIN_FILENO, TCSAFLUSH, FFI::addr($original_termios));
+	$ffi = get_ffi();
+	$res = $ffi->tcsetattr(C::STDIN_FILENO, C::TCSAFLUSH, FFI::addr($original_termios));
 
 	echo "\n";
 
@@ -82,10 +84,10 @@ function get_cursor_position()
 
 function get_window_size()
 {
-	global $ffi;
+	$ffi = get_ffi();
 
 	$ws = $ffi->new('struct winsize');
-	$res = $ffi->ioctl(STDOUT_FILENO, TIOCGWINSZ, FFI::addr($ws));
+	$res = $ffi->ioctl(C::STDOUT_FILENO, C::TIOCGWINSZ, FFI::addr($ws));
 
 	if ($res === -1 || $ws->ws_col === 0)
 	{
@@ -95,8 +97,6 @@ function get_window_size()
 	return [$ws->ws_row, $ws->ws_col];
 }
 
-
-
 // ----------------------------------------------------------------------------
 // ! C function/macro equivalents
 // ----------------------------------------------------------------------------
@@ -115,11 +115,18 @@ function ctrl_key(string $char): int
 		return -1;
 	}
 
-	// b1,100,001 (a) & b0,011,111 = b0,000,001
-	// b1,100,010 (b) & b0,011,111 = b0,000,010
+	// b1,100,001 (a) & b0,011,111 (0x1f) = b0,000,001 (SOH)
+	// b1,100,010 (b) & b0,011,111 (0x1f) = b0,000,010 (STX)
+	// ...and so on
 	return ord($char) & 0x1f;
 }
 
+/**
+ * Does the one-character string contain an ascii ordinal value?
+ *
+ * @param string $single_char
+ * @return bool
+ */
 function is_ascii(string $single_char): bool
 {
 	if (strlen($single_char) > 1)
@@ -130,12 +137,24 @@ function is_ascii(string $single_char): bool
 	return ord($single_char) < 0x80;
 }
 
+/**
+ * Does the one-character string contain an ascii control character?
+ *
+ * @param string $char
+ * @return bool
+ */
 function is_cntrl(string $char): bool
 {
 	$c = ord($char);
 	return is_ascii($char) && ( $c < 0x20 || $c === 0x7f );
 }
 
+/**
+ * Does the one-character string contain an ascii number?
+ *
+ * @param string $char
+ * @return bool
+ */
 function is_digit(string $char): bool
 {
 	$c = ord($char);
@@ -146,6 +165,29 @@ function is_digit(string $char): bool
 // ! Helper functions
 // ----------------------------------------------------------------------------
 
+/**
+ * A 'singleton' function to replace a global variable
+ *
+ * @return FFI
+ */
+function get_ffi(): FFI
+{
+	static $ffi;
+
+	if ($ffi === NULL)
+	{
+		$ffi = FFI::load(__DIR__ . '/ffi.h');
+	}
+
+	return $ffi;
+}
+
+/**
+ * Pull input from the stdin stream.
+ *
+ * @param int $len
+ * @return string
+ */
 function read_stdin(int $len = 128): string
 {
 	$handle = fopen('php://stdin', 'rb');
@@ -155,6 +197,13 @@ function read_stdin(int $len = 128): string
 	return $input;
 }
 
+/**
+ * Write to the stdout stream
+ *
+ * @param string $str
+ * @param int|NULL $len
+ * @return int
+ */
 function write_stdout(string $str, int $len = NULL): int
 {
 	$handle = fopen('php://stdout', 'ab');
@@ -177,3 +226,20 @@ function read_stdout(int $len = 128): string
 
 	return $input;
 }
+
+/**
+ * Replaces a slice of an array with the same value
+ *
+ * @param array $array The array to update
+ * @param int $offset The index of the first location to update
+ * @param int $length The number of indices to update
+ * @param mixed $value The value to replace in the range
+ */
+function array_replace_range(array &$array, int $offset, int $length, $value):void
+{
+	$end = $offset + $length;
+	for ($i = $offset; $i < $end; $i++)
+	{
+		$array[$i] = $value;
+	}
+}