Bug 1249174 (part 4) - Don't store unused XPTHeader fields in memory. r=khuey.

This requires merging XPT_DoHeaderPrologue() and XPT_DoHeader(), which is
straightforward.

This reduces "xpti-working-set" by 16 KiB on 64-bit platforms.

--HG--
extra : rebase_source : 74510d6aefe8adc20064bee2c729d7a55fe4b58a

xpcom/typelib/xpt/xpt_struct.cpp

@@ -45,25 +45,29 @@ DoParamDescriptor(XPTArena *arena, XPTCursor *cursor, XPTParamDescriptor *pd,
 /***************************************************************************/
 
 XPT_PUBLIC_API(PRBool)
-XPT_DoHeaderPrologue(XPTArena *arena, XPTCursor *cursor, XPTHeader **headerp, uint32_t * ide_offset)
+XPT_DoHeader(XPTArena *arena, XPTCursor *cursor, XPTHeader **headerp)
 {
     unsigned int i;
+    uint32_t file_length = 0;
+    uint32_t ide_offset;
+
     XPTHeader* header = XPT_NEWZAP(arena, XPTHeader);
     if (!header)
         return PR_FALSE;
     *headerp = header;
 
-    for (i = 0; i < sizeof(header->magic); i++) {
-        if (!XPT_Do8(cursor, &header->magic[i]))
+    uint8_t magic[16];
+    for (i = 0; i < sizeof(magic); i++) {
+        if (!XPT_Do8(cursor, &magic[i]))
             return PR_FALSE;
     }
 
-    if (strncmp((const char*)header->magic, XPT_MAGIC, 16) != 0) {
+    if (strncmp((const char*)magic, XPT_MAGIC, 16) != 0) {
         /* Require that the header contain the proper magic */
         fprintf(stderr,
                 "libxpt: bad magic header in input file; "
                 "found '%s', expected '%s'\n",
-                header->magic, XPT_MAGIC_STRING);
+                magic, XPT_MAGIC_STRING);
         return PR_FALSE;
     }
 
@@ -77,43 +81,31 @@ XPT_DoHeaderPrologue(XPTArena *arena, XPTCursor *cursor, XPTHeader **headerp, ui
          * number. We must set the header state thusly and return.
          */
         header->num_interfaces = 0;
-        header->file_length = 0;
         return PR_TRUE;
     }
 
     if (!XPT_Do16(cursor, &header->num_interfaces) ||
-        !XPT_Do32(cursor, &header->file_length) ||
-        (ide_offset != NULL && !XPT_Do32(cursor, ide_offset))) {
+        !XPT_Do32(cursor, &file_length) ||
+        !XPT_Do32(cursor, &ide_offset)) {
         return PR_FALSE;
     }
-    return PR_TRUE;
-}
 
-XPT_PUBLIC_API(PRBool)
-XPT_DoHeader(XPTArena *arena, XPTCursor *cursor, XPTHeader **headerp)
-{
-    XPTHeader * header;
-    uint32_t ide_offset;
-    int i;
-
-    if (!XPT_DoHeaderPrologue(arena, cursor, headerp, &ide_offset))
-        return PR_FALSE;
-    header = *headerp;
     /* 
      * Make sure the file length reported in the header is the same size as
      * as our buffer unless it is zero (not set) 
      */
-    if (header->file_length != 0 && 
-        cursor->state->pool_allocated < header->file_length) {
+    if (file_length != 0 && 
+        cursor->state->pool_allocated < file_length) {
         fputs("libxpt: File length in header does not match actual length. File may be corrupt\n",
             stderr);
         return PR_FALSE;
     }
 
-    if (!XPT_Do32(cursor, &header->data_pool))
+    uint32_t data_pool;
+    if (!XPT_Do32(cursor, &data_pool))
         return PR_FALSE;
 
-    XPT_SetDataOffset(cursor->state, header->data_pool);
+    XPT_SetDataOffset(cursor->state, data_pool);
 
     if (header->num_interfaces) {
         header->interface_directory = 

xpcom/typelib/xpt/xpt_struct.h

@@ -56,13 +56,17 @@ typedef struct nsID nsID;
  * Every XPCOM typelib file begins with a header.
  */
 struct XPTHeader {
-    uint8_t                     magic[16];
+    // Some of these fields exists in the on-disk format but don't need to be
+    // stored in memory (other than very briefly, which can be done with local
+    // variables).
+
+    //uint8_t                   magic[16];
     uint8_t                     major_version;
     uint8_t                     minor_version;
     uint16_t                    num_interfaces;
-    uint32_t                    file_length;
+    //uint32_t                  file_length;
     XPTInterfaceDirectoryEntry  *interface_directory;
-    uint32_t                    data_pool;
+    //uint32_t                  data_pool;
 };
 
 #define XPT_MAGIC "XPCOM\nTypeLib\r\n\032"
@@ -71,15 +75,14 @@ struct XPTHeader {
 #define XPT_MAJOR_VERSION 0x01
 #define XPT_MINOR_VERSION 0x02
 
-/* Any file with a major version number of XPT_MAJOR_INCOMPATIBLE_VERSION 
+/* Any file with a major version number of XPT_MAJOR_INCOMPATIBLE_VERSION
  * or higher is to be considered incompatible by this version of xpt and
  * we will refuse to read it. We will return a header with magic, major and
- * minor versions set from the file. num_interfaces and file_length will be
- * set to zero to confirm our inability to read the file; i.e. even if some
- * client of this library gets out of sync with us regarding the agreed upon
- * value for XPT_MAJOR_INCOMPATIBLE_VERSION, anytime num_interfaces and
- * file_length are both zero we *know* that this library refused to read the 
- * file due to version imcompatibility.  
+ * minor versions set from the file. num_interfaces will be set to zero to
+ * confirm our inability to read the file; i.e. even if some client of this
+ * library gets out of sync with us regarding the agreed upon value for
+ * XPT_MAJOR_INCOMPATIBLE_VERSION, anytime num_interfaces is zero we *know*
+ * that this library refused to read the file due to version incompatibility.
  */
 #define XPT_MAJOR_INCOMPATIBLE_VERSION 0x02
 

xpcom/typelib/xpt/xpt_xdr.h

@@ -41,8 +41,6 @@ XPT_Do16(XPTCursor *cursor, uint16_t *u16p);
 extern XPT_PUBLIC_API(PRBool)
 XPT_Do8(XPTCursor *cursor, uint8_t *u8p);
 
-extern XPT_PUBLIC_API(PRBool)
-XPT_DoHeaderPrologue(XPTArena *arena, XPTCursor *cursor, XPTHeader **headerp, uint32_t * ide_offset);
 extern XPT_PUBLIC_API(PRBool)
 XPT_DoHeader(XPTArena *arena, XPTCursor *cursor, XPTHeader **headerp);