From 839570b6987be5f186ce7846e8dc6ef88c2a4a40 Mon Sep 17 00:00:00 2001
From: cypress <motolegacy@proton.me>
Date: Sun, 7 Jan 2024 10:41:32 -0500
Subject: [PATCH] Add crc16 builtin

---
 source/crc.c     | 21 +++++++++++++++++++++
 source/crc.h     |  3 +++
 source/pr_cmds.c | 16 ++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/source/crc.c b/source/crc.c
index 0d2359a..f76844c 100644
--- a/source/crc.c
+++ b/source/crc.c
@@ -79,3 +79,24 @@ unsigned short CRC_Value(unsigned short crcvalue)
 {
 	return crcvalue ^ CRC_XOR_VALUE;
 }
+
+//
+// taken from darkplaces -- just a shortcut for initialization for
+// use with string-hashing (just progs, likely). -- cypress (07 jan 2024)
+//
+
+unsigned short CRC_Block(const unsigned char *data, size_t size)
+{
+	unsigned short crc = CRC_INIT_VALUE;
+	while (size--)
+		crc = (crc << 8) ^ crctable[(crc >> 8) ^ (*data++)];
+	return crc ^ CRC_XOR_VALUE;
+}
+
+unsigned short CRC_Block_CaseInsensitive(const unsigned char *data, size_t size)
+{
+	unsigned short crc = CRC_INIT_VALUE;
+	while (size--)
+		crc = (crc << 8) ^ crctable[(crc >> 8) ^ (tolower(*data++))];
+	return crc ^ CRC_XOR_VALUE;
+}
\ No newline at end of file
diff --git a/source/crc.h b/source/crc.h
index cad9772..bcaf295 100644
--- a/source/crc.h
+++ b/source/crc.h
@@ -22,3 +22,6 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 void CRC_Init(unsigned short *crcvalue);
 void CRC_ProcessByte(unsigned short *crcvalue, byte data);
 unsigned short CRC_Value(unsigned short crcvalue);
+
+unsigned short CRC_Block(const unsigned char *data, size_t size);
+unsigned short CRC_Block_CaseInsensitive(const unsigned char *data, size_t size);
\ No newline at end of file
diff --git a/source/pr_cmds.c b/source/pr_cmds.c
index 31cfbdf..d1d7af8 100644
--- a/source/pr_cmds.c
+++ b/source/pr_cmds.c
@@ -1425,6 +1425,21 @@ void PF_strtolower(void)
 	G_INT(OFS_RETURN) = pr_string_temp - pr_strings;
 }
 
+/*
+=================
+PF_crc16
+
+float crc16 (float, string)
+=================
+*/
+void PF_crc16(void)
+{
+	int insens = G_FLOAT(OFS_PARM0);
+	char *s = G_STRING(OFS_PARM1);
+
+	G_FLOAT(OFS_RETURN) = (unsigned short) ((insens ? CRC_Block_CaseInsensitive : CRC_Block) ((unsigned char *) s, strlen(s)));
+}
+
 /*
 =================
 PF_stov
@@ -3729,6 +3744,7 @@ ebfs_builtin_t pr_ebfs_builtins[] =
   { 441, "tokenize", PF_tokenize },
   { 442, "argv", PF_ArgV },
   { 480, "strtolower", PF_strtolower },
+  { 494, "crc16", PF_crc16 },
 
   { 500, "songegg", PF_SongEgg },
   {	501, "nzp_maxammo", PF_MaxAmmo },