1 files changed, 92 insertions, 0 deletions
diff --git a/src/func.c b/src/func.c
index 9a62470a0..6a279a9d7 100644
--- a/src/func.c
+++ b/src/func.c
@@ -1224,6 +1224,96 @@ static void hexFunc(
 }
 
 /*
+** Buffer zStr contains nStr bytes of utf-8 encoded text. Return 1 if zStr
+** contains character ch, or 0 if it does not.
+*/
+static int strContainsChar(const u8 *zStr, int nStr, u32 ch){
+  const u8 *zEnd = &zStr[nStr];
+  const u8 *z = zStr;
+  while( z<zEnd ){
+    u32 tst = Utf8Read(z);
+    if( tst==ch ) return 1;
+  }
+  return 0;
+}
+
+/*
+** The unhex() function. This function may be invoked with either one or
+** two arguments. In both cases the first argument is interpreted as text
+** a text value containing a set of pairs of hexadecimal digits which are
+** decoded and returned as a blob.
+**
+** If there is only a single argument, then it must consist only of an
+** even number of hexadeximal digits. Otherwise, return NULL.
+**
+** Or, if there is a second argument, then any character that appears in
+** the second argument is also allowed to appear between pairs of hexadecimal
+** digits in the first argument. If any other character appears in the
+** first argument, or if one of the allowed characters appears between 
+** two hexadecimal digits that make up a single byte, NULL is returned.
+**
+** The following expressions are all true:
+**
+**     unhex('ABCD')       IS x'ABCD'
+**     unhex('AB CD')      IS NULL
+**     unhex('AB CD', ' ') IS x'ABCD'
+**     unhex('A BCD', ' ') IS NULL
+*/
+static void unhexFunc(
+  sqlite3_context *pCtx,
+  int argc,
+  sqlite3_value **argv
+){
+  const u8 *zPass = (const u8*)"";
+  int nPass = 0;
+  const u8 *zHex = sqlite3_value_text(argv[0]);
+  int nHex = sqlite3_value_bytes(argv[0]);
+#ifdef SQLITE_DEBUG
+  const u8 *zEnd = &zHex[nHex];
+#endif
+  u8 *pBlob = 0;
+  u8 *p = 0;
+
+  assert( argc==1 || argc==2 );
+  if( argc==2 ){
+    zPass = sqlite3_value_text(argv[1]);
+    nPass = sqlite3_value_bytes(argv[1]);
+  }
+  if( !zHex || !zPass ) return;
+
+  p = pBlob = contextMalloc(pCtx, (nHex/2)+1);
+  if( pBlob ){
+    u8 c;                         /* Most significant digit of next byte */
+    u8 d;                         /* Least significant digit of next byte */
+
+    while( (c = *zHex)!=0x00 ){
+      while( !sqlite3Isxdigit(c) ){
+        u32 ch = Utf8Read(zHex);
+        assert( zHex<=zEnd );
+        if( !strContainsChar(zPass, nPass, ch) ) goto unhex_null;
+        c = *zHex;
+        if( c==0x00 ) goto unhex_done;
+      }
+      zHex++;
+      assert( *zEnd==0x00 );
+      assert( zHex<=zEnd );
+      d = *(zHex++);
+      if( !sqlite3Isxdigit(d) ) goto unhex_null;
+      *(p++) = (sqlite3HexToInt(c)<<4) | sqlite3HexToInt(d);
+    }
+  }
+
+ unhex_done:
+  sqlite3_result_blob(pCtx, pBlob, (p - pBlob), sqlite3_free);
+  return;
+
+ unhex_null:
+  sqlite3_free(pBlob);
+  return;
+}
+
+
+/*
 ** The zeroblob(N) function returns a zero-filled blob of size N bytes.
 */
 static void zeroblobFunc(
@@ -2287,6 +2377,8 @@ void sqlite3RegisterBuiltinFunctions(void){
     FUNCTION(upper,              1, 0, 0, upperFunc        ),
     FUNCTION(lower,              1, 0, 0, lowerFunc        ),
     FUNCTION(hex,                1, 0, 0, hexFunc          ),
+    FUNCTION(unhex,              1, 0, 0, unhexFunc        ),
+    FUNCTION(unhex,              2, 0, 0, unhexFunc        ),
     INLINE_FUNC(ifnull,          2, INLINEFUNC_coalesce, 0 ),
     VFUNCTION(random,            0, 0, 0, randomFunc       ),
     VFUNCTION(randomblob,        1, 0, 0, randomBlob       ),