Function bin for uint uses writeBinByte, correct for single zero

src/Common/hex.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <string>
+#include <bit>
 
 
 /// Maps 0..15 to 0..9A..F or 0..9a..f correspondingly.
@@ -46,6 +47,20 @@ inline void writeBinByte(UInt8 byte, void * out)
     memcpy(out, &bin_byte_to_char_table[static_cast<size_t>(byte) * 8], 8);
 }
 
+inline size_t writeBinByteNoLeadZeros(UInt8 byte, char * out)
+{
+    if (byte == 0)
+        return 0;
+
+    int clz = std::countl_zero(byte);
+    for (Int8 offset = sizeof(UInt8) * 8 - clz - 1; offset >= 0; --offset)
+    {
+        *out = ((byte >> offset) & 1) ? '1' : '0';
+        ++out;
+    }
+    return sizeof(UInt8) * 8 - clz;
+}
+
 /// Produces hex representation of an unsigned int with leading zeros (for checksums)
 template <typename TUInt>
 inline void writeHexUIntImpl(TUInt uint_, char * out, const char * const table)

src/Functions/FunctionsCoding.h

@@ -1344,30 +1344,32 @@ struct BinImpl
     static void executeOneUInt(T x, char *& out)
     {
         bool was_nonzero = false;
-        T t = 1;
-
-        for (Int8 offset = sizeof(x) * 8 - 1; offset >= 0; --offset)
+        for (int offset = (sizeof(T) - 1) * 8; offset >= 0; offset -= 8)
         {
-            t = t << offset;
-            if ((x & t) == t)
+            UInt8 byte = x >> offset;
+
+            /// Skip leading zeros
+            if (byte == 0 && !was_nonzero)
+                continue;
+
+            /// First non-zero byte without leading zeros
+            if (was_nonzero)
             {
-                x = x - t;
-                was_nonzero = true;
-                *out = '1';
-                t = 1;
+                writeBinByte(byte, out);
+                out += word_size;
             }
             else
             {
-                t = 1;
-                if (!was_nonzero)
-                {
-                    continue;
-                }
-                *out = '0';
+                size_t written = writeBinByteNoLeadZeros(byte, out);
+                out += written;
             }
+            was_nonzero = true;
+        }
+        if (!was_nonzero)
+        {
+            *out = '0';
             ++out;
         }
-
         *out = '\0';
         ++out;
     }

tests/queries/0_stateless/01926_bin_unbin.reference

@@ -1,4 +1,5 @@
 
+0
 1
 1010
 1111111
@@ -13,6 +14,14 @@
 0000000000000000000011000011110101011101010100111010101000000001
 0011000100110010001100110011001100110010001101000011001000110100
 0011000100110010001100110011001100110010001101000011001000110100
+0011000100110010001100110011001100110010001101000011001000110100
+0011000100110010001100110011001100110010001101000011001000110100
+
 0
 10
 测试
+0
+0
+0
+1
+1

tests/queries/0_stateless/01926_bin_unbin.sql

@@ -1,3 +1,4 @@
+select bin('');
 select bin(0);
 select bin(1);
 select bin(10);
@@ -12,8 +13,17 @@ select bin(toFloat64(1.2));
 select bin(toDecimal32(1.2, 8));
 select bin(toDecimal64(1.2, 17));
 select bin('12332424');
+select bin(materialize('12332424'));
+select bin(toNullable(materialize('12332424')));
 select bin(toLowCardinality(materialize('12332424')));
 
+select unbin('');
 select unbin('00110000'); -- 0
 select unbin('0011000100110000'); -- 10
 select unbin('111001101011010110001011111010001010111110010101'); -- 测试
+select unbin(materialize('00110000'));
+select unbin(toNullable(materialize('00110000')));
+select unbin(toLowCardinality(materialize('00110000')));
+
+select unbin(bin('')) == '';
+select bin(unbin('')) == '';