From 8049252f651bb31f6965303c7f141980b0aa5c6b Mon Sep 17 00:00:00 2001
From: Dale Weiler <killfieldengine@gmail.com>
Date: Tue, 24 Apr 2012 08:19:48 -0400
Subject: [PATCH] new progs format proposal for engine developers (45% of
 globals are 0, why write them, let the engine populate them. We can
 essentially save 9884 bytes in xonotic's progs.dat with this new format.)

---
 code.c      | 20 +++++++++++++++++---
 gmqcc.h     |  1 +
 main.c      | 12 +++++++++---
 propsal.txt | 35 +++++++++++++++++++++++++++++++++++
 4 files changed, 62 insertions(+), 6 deletions(-)
 create mode 100644 propsal.txt

diff --git a/code.c b/code.c
index 66dc951..3925088 100644
--- a/code.c
+++ b/code.c
@@ -28,8 +28,11 @@ typedef struct {
 } prog_section;
 
 typedef struct {
-    uint32_t     version;      /* Program version (6)     */
-    uint32_t     crc16;        /* What is this?           */
+    uint16_t     version;      /* Program version (6)     */
+    uint16_t     flags;        /* see propsal.txt         */
+    uint16_t     crc16;        /* What is this?           */
+    uint16_t     skip;         /* see propsal.txt         */
+    
     prog_section statements;   /* prog_section_statement  */
     prog_section defs;         /* prog_section_def        */
     prog_section fields;       /* prog_section_field      */
@@ -90,6 +93,10 @@ int code_strings_add(const char *src) {
 }
 
 void code_init() {
+    /* omit creation of null code */
+    if (opts_omit_nullcode)
+        return;
+        
     /*
      * The way progs.dat is suppose to work is odd, there needs to be
      * some null (empty) statements, functions, and 28 globals
@@ -137,6 +144,13 @@ void code_test() {
 
 void code_write() {
     prog_header code_header={0};
+
+    /* see proposal.txt */
+    if (opts_omit_nullcode) {
+        code_header.skip   = 28;
+        code_header.flags  = 1;
+    }
+    
     code_header.version    = 6;
     code_header.crc16      = 0; /* TODO: */
     code_header.statements = (prog_section){sizeof(prog_header), code_statements_elements };
@@ -150,7 +164,7 @@ void code_write() {
     if (opts_darkplaces_stringtablebug) {
         util_debug("GEN", "Patching stringtable for -fdarkplaces-stringtablebug\n");
 
-        /* >= + padd */
+        /* >= + P */
         code_chars_add('\0'); /* > */
         code_chars_add('\0'); /* = */
         code_chars_add('\0'); /* P */
diff --git a/gmqcc.h b/gmqcc.h
index f27f41e..5edaeae 100644
--- a/gmqcc.h
+++ b/gmqcc.h
@@ -485,4 +485,5 @@ enum {
 extern int opts_debug;
 extern int opts_memchk;
 extern int opts_darkplaces_stringtablebug;
+extern int opts_omit_nullcode;
 #endif
diff --git a/main.c b/main.c
index 2c0be85..e24a7fe 100644
--- a/main.c
+++ b/main.c
@@ -30,6 +30,7 @@ int opts_debug                     = 0;
 int opts_memchk                    = 0;
 int opts_compiler                  = COMPILER_GMQCC;
 int opts_darkplaces_stringtablebug = 0;
+int opts_omit_nullcode             = 0;
 
 static const int usage(const char *const app) {
     printf("usage:\n");
@@ -48,8 +49,9 @@ static const int usage(const char *const app) {
     printf("            -std=ftqecc  -- fteqcc QuakeC\n");
     printf("            -std=qccx    -- qccx QuakeC\n");
     printf("            -std=gmqcc   -- this compiler QuakeC (default selection)\n");
-    printf("    code flags -f*\n");
-    printf("        -fdarkplaces-stringtablebug -- patches the string table to work with bugged versions of darkplaces\n");
+    printf("    codegen flags:\n");
+    printf("        -fdarkplaces-string-table-bug -- patches the string table to work with bugged versions of darkplaces\n");
+    printf("        -fomit-nullcode               -- omits the generation of null code (will break everywhere see propsal.txt)\n");
     return -1;
 }
 
@@ -92,10 +94,14 @@ int main(int argc, char **argv) {
                 }
 
                 /* code specific switches */
-                if (!strncmp(&argv[1][1], "fdarkplaces-stringtablebug", 26)) {
+                if (!strcmp(&argv[1][1], "fdarkplaces-string-table-bug")) {
                     opts_darkplaces_stringtablebug = 1;
                     break;
                 }
+                if (!strcmp(&argv[1][1], "fomit-nullcode")) {
+                    opts_omit_nullcode = 1;
+                    break;
+                }
                 return usage(app);
                 
         }
diff --git a/propsal.txt b/propsal.txt
new file mode 100644
index 0000000..88658e1
--- /dev/null
+++ b/propsal.txt
@@ -0,0 +1,35 @@
+This is a propsal to extend the progs.dat file format without breaking
+backwards compatability.  Currently the progs file format header has a
+description simaler to this:
+
+struct {
+    uint32_t     version;
+    uint32_t     crc16;
+    ....
+    uint32_t     entfield;
+}
+
+The obvious notable issue here is version and crc16 are larger than they
+essentially need to be, if we made version and crc16 both uint16_t we can
+give ourselfs 32 bytes (2x16) to store additional data that can be used
+to make smaller progs.dat files.
+
+I propose a new structual layout like this:
+struct {
+    uint16_t     version;
+    uint16_t     flags;   /* contains a skip field */
+    uint16_t     crc16;
+    uint16_t     skip;    /* skiped globals        */
+    ....
+    uint32_t     entfield;
+}
+
+about 45% of globals are zero, if we could order them at the top of the
+globals array we can essentially use the skip field to specify how much
+zero globals the engine would have to populate (instead of being stored
+in the actual file itself) flags can specify if the progs.dat file skiped
+globals on the write of the progs.dat file.
+
+Of course only one bit in the flags would have to be set to specify if the
+file contains a skip field.  Which lends itself to the fact that flags could
+later be extended for other things.
-- 
2.39.2