Add an optional function to the chsumvfs extension. When activated by

the SQLITE_CKSUMVFS_INIT_FUNCNAME macro, this function will invoke the
file-control that sets the number of reserved bytes to 8.  This can be
used to initialize a cksumvfs database file by programming languages
that do not have access to the sqlite3_file_control() interface.

FossilOrigin-Name: 01841fb4bf3d6c5fd5bcbc7d1338998c50f69f84ca475fba7cf764d636714678

ext/misc/cksumvfs.c

@@ -356,6 +356,41 @@ static void cksmVerifyFunc(
   sqlite3_result_int(context, memcmp(data+nByte-8,cksum,8)==0);
 }
 
+#ifdef SQLITE_CKSUMVFS_INIT_FUNCNAME
+/*
+** SQL function:    initialize_cksumvfs(SCHEMANAME)
+**
+** This SQL functions (whose name is actually determined at compile-time
+** by the value of the SQLITE_CKSUMVFS_INIT_FUNCNAME macro) invokes:
+**
+**   sqlite3_file_control(db, SCHEMANAME, SQLITE_FCNTL_RESERVE_BYTE, &n);
+**
+** In order to set the reserve bytes value to 8, so that cksumvfs will
+** operation.  This feature is provided (if and only if the
+** SQLITE_CKSUMVFS_INIT_FUNCNAME compile-time option is set to a string
+** which is the name of the SQL function) so as to provide the ability
+** to invoke the file-control in programming languages that lack
+** direct access to the sqlite3_file_control() interface (ex: Java).
+**
+** This interface is undocumented, apart from this comment.  Usage
+** example:
+**
+**    1.  Compile with -DSQLITE_CKSUMVFS_INIT_FUNCNAME="ckvfs_init"
+**    2.  Run:  "SELECT cksum_init('main'); VACUUM;"
+*/
+static void cksmInitFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int nByte = 8;
+  const char *zSchemaName = (const char*)sqlite3_value_text(argv[0]);
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  sqlite3_file_control(db, zSchemaName, SQLITE_FCNTL_RESERVE_BYTES, &nByte);
+  /* Return NULL */
+}
+#endif /* SQLITE_CKSUMBFS_INIT_FUNCNAME */
+
 /*
 ** Close a cksm-file.
 */
@@ -746,6 +781,11 @@ static int cksmRegisterFunc(
   rc = sqlite3_create_function(db, "verify_checksum", 1,
                    SQLITE_UTF8|SQLITE_INNOCUOUS|SQLITE_DETERMINISTIC,
                    0, cksmVerifyFunc, 0, 0);
+#ifdef SQLITE_CKSUMVFS_INIT_FUNCNAME
+  (void)sqlite3_create_function(db, SQLITE_CKSUMVFS_INIT_FUNCNAME, 1,
+                   SQLITE_UTF8|SQLITE_DIRECTONLY,
+                   0, cksmInitFunc, 0, 0);
+#endif
   return rc;
 }
 

manifest

@@ -1,5 +1,5 @@
-C Fix\scompilation\sissues\swith\sMSVC\srelated\sto\sC99.
-D 2020-12-09T23:35:51.896
+C Add\san\soptional\sfunction\sto\sthe\schsumvfs\sextension.\s\sWhen\sactivated\sby\nthe\sSQLITE_CKSUMVFS_INIT_FUNCNAME\smacro,\sthis\sfunction\swill\sinvoke\sthe\nfile-control\sthat\ssets\sthe\snumber\sof\sreserved\sbytes\sto\s8.\s\sThis\scan\sbe\nused\sto\sinitialize\sa\scksumvfs\sdatabase\sfile\sby\sprogramming\slanguages\nthat\sdo\snot\shave\saccess\sto\sthe\ssqlite3_file_control()\sinterface.
+D 2020-12-10T13:49:00.833
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -291,7 +291,7 @@ F ext/misc/blobio.c a867c4c4617f6ec223a307ebfe0eabb45e0992f74dd47722b96f3e631c0e
 F ext/misc/btreeinfo.c d28ce349b40054eaa9473e835837bad7a71deec33ba13e39f963d50933bfa0f9
 F ext/misc/carray.c b75a0f207391038bf1540d3372f482a95c3613511c7c474db51ede1196321c7c
 F ext/misc/carray.h de74ac70b2338f416723f7d538026e8ec0b7f1d388319f8f140c9a4d7677f02e
-F ext/misc/cksumvfs.c c4e7ebeae5aa578df98f23bddb63ecbcbe913ee3c32b8b769525af100d752061
+F ext/misc/cksumvfs.c 688a59d6c5dc7e7e0aba09654d8cbeeb7d04bad8cf57902df86aa06c2f723ff4
 F ext/misc/closure.c dbfd8543b2a017ae6b1a5843986b22ddf99ff126ec9634a2f4047cd14c85c243
 F ext/misc/completion.c 6dafd7f4348eecc7be9e920d4b419d1fb2af75d938cd9c59a20cfe8beb2f22b9
 F ext/misc/compress.c 3354c77a7c8e86e07d849916000cdac451ed96500bfb5bd83b20eb61eee012c9
@@ -1888,7 +1888,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 818c647cec7063b33b6c5de3e23599a1d61439fa6e9bf6c974b2522a5a9e1b44
-R f5a4c0e24239e1b152c6955913834244
-U mistachkin
-Z ac2c81554df4b37487abc146a7fda901
+P c0de6c1fb2c486be1da01e5e4ca8c5634ba37822e418d57f272e018c3e3fc0a2
+R 6c67d7c383f4b37d548756594c8d9b75
+U drh
+Z ffe92d1035962188772639969e0a3892

manifest.uuid

@@ -1 +1 @@
-c0de6c1fb2c486be1da01e5e4ca8c5634ba37822e418d57f272e018c3e3fc0a2
+01841fb4bf3d6c5fd5bcbc7d1338998c50f69f84ca475fba7cf764d636714678