Fix conversion of BIT fields (fixes #2254)

2 files changed, 84 insertions, 14 deletions

diff --git a/Frameworks/SPMySQLFramework/SPMySQL Unit Tests/DataConversion_Tests.m b/Frameworks/SPMySQLFramework/SPMySQL Unit Tests/DataConversion_Tests.m
new file mode 100644
index 00000000..385eb0b2
--- /dev/null
+++ b/Frameworks/SPMySQLFramework/SPMySQL Unit Tests/DataConversion_Tests.m
@@ -0,0 +1,71 @@
+//
+//  DataConversion_Tests.m
+//  SPMySQLFramework
+//
+//  Created by Max Lohrmann on 01.10.15.
+//  Copyright (c) 2015 Max Lohrmann. All rights reserved.
+//
+//  Permission is hereby granted, free of charge, to any person
+//  obtaining a copy of this software and associated documentation
+//  files (the "Software"), to deal in the Software without
+//  restriction, including without limitation the rights to use,
+//  copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the
+//  Software is furnished to do so, subject to the following
+//  conditions:
+//
+//  The above copyright notice and this permission notice shall be
+//  included in all copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+//  OTHER DEALINGS IN THE SOFTWARE.
+//
+//  More info at <https://github.com/sequelpro/sequelpro>
+
+@interface DataConversion_Tests : XCTestCase
+
+- (void)test_bitStringWithBytes;
+
+@end
+
+@implementation DataConversion_Tests
+
+- (void)test_bitStringWithBytes
+{
+	// BIT(1)
+	{
+		unsigned char y = 1;
+		unsigned char n = 0;
+		XCTAssertEqualObjects(_bitStringWithBytes(&y,sizeof(y),1), @"1");
+		XCTAssertEqualObjects(_bitStringWithBytes(&n,sizeof(n),0), @"0");
+	}
+	// BIT(3)
+	{
+		const char input[] = {5};
+		NSUInteger bitSize = 3;
+		NSString *res = _bitStringWithBytes(input,sizeof(input),bitSize);
+		XCTAssertEqualObjects(res, @"101");
+	}
+	// BIT(16)
+	{
+		const char input[] = {0xcc,0xf0};
+		NSUInteger bitSize = 16;
+		NSString *res = _bitStringWithBytes(input,sizeof(input),bitSize);
+		XCTAssertEqualObjects(res, @"1100110011110000");
+	}
+	// BIT(20)
+	{
+		const char input[] = {0x0f,0xcc,0xf0};
+		NSUInteger bitSize = 20;
+		NSString *res = _bitStringWithBytes(input,sizeof(input),bitSize);
+		XCTAssertEqualObjects(res, @"11111100110011110000");
+	}
+}
+
+@end
diff --git a/Frameworks/SPMySQLFramework/Source/SPMySQLResult Categories/Data Conversion.m b/Frameworks/SPMySQLFramework/Source/SPMySQLResult Categories/Data Conversion.m
index 639ff0b9..8c5b9181 100644
--- a/Frameworks/SPMySQLFramework/Source/SPMySQLResult Categories/Data Conversion.m
+++ b/Frameworks/SPMySQLFramework/Source/SPMySQLResult Categories/Data Conversion.m
@@ -209,27 +209,26 @@ static inline NSString * _bitStringWithBytes(const char *bytes, NSUInteger lengt
 		return nil;
 	}
 
-	// Ensure padLength is never lower than the length
-	if (padLength < bitLength) {
-		padLength = bitLength;
-	}
-
+	// use whatever is smaller. padLength comes from BIT(x), bitLength from the actual bytes transmitted.
+	// if bitLength < padLength it means the value is smaller than what the field can accomodate.
+	// if bitLength > padLength it means BIT(x) is not a full n bytes long and was extended by mysqls storage.
+	//   In that case the additional bits should still be 0 as mysql does not allow to set bits over the size of x.
+	bitLength = MIN(bitLength,padLength);
 	// Generate a nul-terminated C string representation of the binary data
 	char *cStringBuffer = malloc(padLength + 1);
-	cStringBuffer[padLength] = '\0';
+	memset(cStringBuffer, '0', padLength);
 
 	while (i < bitLength)
 	{
+		// start with the least significant bit (the rightmost bit in the last byte) and move left
+		unsigned char bitInByteMask =  i % 8; // 0-7, the cycle is 0,1,...,7,0,...
+		unsigned long bytesOffset = (length - 1) - (i >> 3); // i>>3 == floor(i/8)
 		++i;
-
-		cStringBuffer[padLength - i] = ((bytes[length - 1 - (i >> 3)] >> (i & 0x7)) & 1 ) ? '1' : '0';
+		cStringBuffer[padLength - i] = ((bytes[bytesOffset] & (1 << bitInByteMask)) != 0) ? '1' : '0';
 	}
-
-	while (i++ < padLength)
-	{
-		cStringBuffer[padLength - i] = '0';
-	}
-
+	
+	cStringBuffer[padLength] = '\0';
+	
 	// Convert to a string
 	NSString *returnString = [NSString stringWithUTF8String:cStringBuffer];