From 30407e1f4fc290468f3d8ec31cb933402767568d Mon Sep 17 00:00:00 2001
From: Pieter Noordhuis <pcnoordhuis@gmail.com>
Date: Wed, 15 Dec 2010 00:42:32 +0100
Subject: [PATCH] Make SETBIT return original bit value

---
 src/t_string.c       | 41 +++++++++++++++++++++++++----------------
 tests/unit/basic.tcl | 24 ++++++++++++------------
 2 files changed, 37 insertions(+), 28 deletions(-)

diff --git a/src/t_string.c b/src/t_string.c
index 736b1673d..f1bab4dad 100644
--- a/src/t_string.c
+++ b/src/t_string.c
@@ -111,17 +111,18 @@ void setbitCommand(redisClient *c) {
     robj *o;
     char *err = "bit is not an integer or out of range";
     size_t bitoffset;
-    long long bitvalue;
-    int byte, bit, on;
+    int byte, bit;
+    int byteval, bitval;
+    long on;
 
     if (getBitOffsetFromArgument(c,c->argv[2],&bitoffset) != REDIS_OK)
         return;
 
-    if (getLongLongFromObjectOrReply(c,c->argv[3],&bitvalue,err) != REDIS_OK)
+    if (getLongFromObjectOrReply(c,c->argv[3],&on,err) != REDIS_OK)
         return;
 
-    /* A bit can only be set to be on or off... */
-    if (bitvalue & ~1) {
+    /* Bits can only be set or cleared... */
+    if (on & ~1) {
         addReplyError(c,err);
         return;
     }
@@ -142,23 +143,30 @@ void setbitCommand(redisClient *c) {
         }
     }
 
+    /* Grow sds value to the right length if necessary */
     byte = bitoffset >> 3;
-    bit = 7 - (bitoffset & 0x7);
-    on = bitvalue & 0x1;
     o->ptr = sdsgrowzero(o->ptr,byte+1);
-    ((char*)o->ptr)[byte] |= on << bit;
-    ((char*)o->ptr)[byte] &= ~((!on) << bit);
 
+    /* Get current values */
+    byteval = ((char*)o->ptr)[byte];
+    bit = 7 - (bitoffset & 0x7);
+    bitval = byteval & (1 << bit);
+
+    /* Update byte with new bit value and return original value */
+    byteval &= ~(1 << bit);
+    byteval |= ((on & 0x1) << bit);
+    ((char*)o->ptr)[byte] = byteval;
     touchWatchedKey(c->db,c->argv[1]);
     server.dirty++;
-    addReply(c,shared.cone);
+    addReply(c, bitval ? shared.cone : shared.czero);
 }
 
 void getbitCommand(redisClient *c) {
     robj *o;
-    size_t bitoffset, byte, bitmask;
-    int on = 0;
     char llbuf[32];
+    size_t bitoffset;
+    size_t byte, bit;
+    size_t bitval = 0;
 
     if (getBitOffsetFromArgument(c,c->argv[2],&bitoffset) != REDIS_OK)
         return;
@@ -167,15 +175,16 @@ void getbitCommand(redisClient *c) {
         checkType(c,o,REDIS_STRING)) return;
 
     byte = bitoffset >> 3;
-    bitmask = 1 << (7 - (bitoffset & 0x7));
+    bit = 7 - (bitoffset & 0x7);
     if (o->encoding != REDIS_ENCODING_RAW) {
         if (byte < (size_t)ll2string(llbuf,sizeof(llbuf),(long)o->ptr))
-            on = llbuf[byte] & bitmask;
+            bitval = llbuf[byte] & (1 << bit);
     } else {
         if (byte < sdslen(o->ptr))
-            on = ((sds)o->ptr)[byte] & bitmask;
+            bitval = ((char*)o->ptr)[byte] & (1 << bit);
     }
-    addReply(c, on ? shared.cone : shared.czero);
+
+    addReply(c, bitval ? shared.cone : shared.czero);
 }
 
 void setrangeCommand(redisClient *c) {
diff --git a/tests/unit/basic.tcl b/tests/unit/basic.tcl
index 7d5667726..901507964 100644
--- a/tests/unit/basic.tcl
+++ b/tests/unit/basic.tcl
@@ -377,29 +377,29 @@ start_server {tags {"basic"}} {
 
     test "SETBIT against non-existing key" {
         r del mykey
-
-        # Setting 2nd bit to on is integer 64, ascii "@"
-        assert_equal 1 [r setbit mykey 1 1]
-        assert_equal "@" [r get mykey]
+        assert_equal 0 [r setbit mykey 1 1]
+        assert_equal [binary format B* 01000000] [r get mykey]
     }
 
     test "SETBIT against string-encoded key" {
-        # Single byte with 2nd bit set
+        # Ascii "@" is integer 64 = 01 00 00 00
         r set mykey "@"
 
-        # 64 + 32 = 96 => ascii "`" (backtick)
-        assert_equal 1 [r setbit mykey 2 1]
-        assert_equal "`" [r get mykey]
+        assert_equal 0 [r setbit mykey 2 1]
+        assert_equal [binary format B* 01100000] [r get mykey]
+        assert_equal 1 [r setbit mykey 1 0]
+        assert_equal [binary format B* 00100000] [r get mykey]
     }
 
     test "SETBIT against integer-encoded key" {
+        # Ascii "1" is integer 49 = 00 11 00 01
         r set mykey 1
         assert_encoding int mykey
 
-        # Ascii "1" is integer 49 = 00 11 00 01
-        # Setting 7th bit = 51 => ascii "3"
-        assert_equal 1 [r setbit mykey 6 1]
-        assert_equal "3" [r get mykey]
+        assert_equal 0 [r setbit mykey 6 1]
+        assert_equal [binary format B* 00110011] [r get mykey]
+        assert_equal 1 [r setbit mykey 2 0]
+        assert_equal [binary format B* 00010011] [r get mykey]
     }
 
     test "SETBIT against key with wrong type" {