Check remaining space to avoid buffer overruns; some cleanups

src/Common/UnicodeBar.cpp

@@ -9,6 +9,13 @@
 
 #include <iostream>
 
+namespace DB
+{
+    namespace ErrorCodes
+    {
+        extern const int LOGICAL_ERROR;
+    }
+}
 
 namespace UnicodeBar
 {
@@ -26,36 +33,61 @@ namespace UnicodeBar
         return (x - min) / (max - min) * max_width;
     }
 
+    /// We use the following Unicode characters to draw the bar:
+    /// U+2588 "█" Full block
+    /// U+2589 "▉" Left seven eighths block
+    /// U+258A "▊" Left three quarters block
+    /// U+258B "▋" Left five eighths block
+    /// U+258C "▌" Left half block
+    /// U+258D "▍" Left three eighths block
+    /// U+258E "▎" Left one quarter block
+    /// U+258F "▏" Left one eighth block
+    constexpr size_t GRADES_IN_FULL_BAR = 8;
+    constexpr char FULL_BAR[] = "█";
+    constexpr char FRACTIONAL_BARS[] = "▏▎▍▌▋▊▉";   /// 7 elements: 1/8, 2/8, 3/8, 4/8, 5/8, 6/8, 7/8
+
     size_t getWidthInBytes(double width)
     {
-        return static_cast<size_t>(ceil(width - 1.0 / 8) * UNICODE_BAR_CHAR_SIZE);
+        Int64 int_width = Int64(width * GRADES_IN_FULL_BAR);
+        return (int_width / GRADES_IN_FULL_BAR) * UNICODE_BAR_CHAR_SIZE + (int_width % GRADES_IN_FULL_BAR ? UNICODE_BAR_CHAR_SIZE : 0);
     }
 
-    void render(double width, char * dst)
+    static char* checkedCopy(const char * src, size_t src_size, char * dst, const char * dst_end)
     {
-        size_t floor_width = static_cast<size_t>(floor(width));
+        if (dst + src_size > dst_end)
+            throw DB::Exception(
+                DB::ErrorCodes::LOGICAL_ERROR,
+                "Not enough space in buffer for UnicodeBar::render, required: {}, got: {}",
+                src_size, dst_end - dst);
+
+        memcpy(dst, src, src_size);
+        return dst + src_size;
+    }
+
+    void render(double width, char * dst, const char * dst_end)
+    {
+        Int64 int_width = Int64(width * GRADES_IN_FULL_BAR);
+        size_t floor_width = (int_width / GRADES_IN_FULL_BAR);
 
         for (size_t i = 0; i < floor_width; ++i)
         {
-            memcpy(dst, "█", UNICODE_BAR_CHAR_SIZE);
-            dst += UNICODE_BAR_CHAR_SIZE;
+            dst = checkedCopy(FULL_BAR, UNICODE_BAR_CHAR_SIZE, dst, dst_end);
         }
 
-        size_t remainder = static_cast<size_t>(floor((width - floor_width) * 8));
+        size_t remainder = int_width % GRADES_IN_FULL_BAR;
 
         if (remainder)
         {
-            memcpy(dst, &"▏▎▍▌▋▋▊▉"[(remainder - 1) * UNICODE_BAR_CHAR_SIZE], UNICODE_BAR_CHAR_SIZE);
-            dst += UNICODE_BAR_CHAR_SIZE;
+            dst = checkedCopy(&FRACTIONAL_BARS[(remainder - 1) * UNICODE_BAR_CHAR_SIZE], UNICODE_BAR_CHAR_SIZE, dst, dst_end);
         }
 
-        *dst = 0;
+        dst = checkedCopy("\0", 1, dst, dst_end);
     }
 
     std::string render(double width)
     {
-        std::string res(getWidthInBytes(width), '\0');
-        render(width, res.data());
+        std::string res(getWidthInBytes(width) + 1, '\0');
+        render(width, res.data(), res.data() + res.size());
         return res;
     }
 }

src/Common/UnicodeBar.h

@@ -14,6 +14,6 @@ namespace UnicodeBar
     size_t getWidthInBytes(double width);
 
     /// In `dst` there must be a space for barWidthInBytes(width) characters and a trailing zero.
-    void render(double width, char * dst);
+    void render(double width, char * dst, const char * dst_end);
     std::string render(double width);
 }

src/Functions/bar.cpp

@@ -118,7 +118,7 @@ public:
 
             size_t next_size = current_offset + UnicodeBar::getWidthInBytes(width) + 1;
             dst_chars.resize(next_size);
-            UnicodeBar::render(width, reinterpret_cast<char *>(&dst_chars[current_offset]));
+            UnicodeBar::render(width, reinterpret_cast<char *>(&dst_chars[current_offset]), reinterpret_cast<char *>(&dst_chars[next_size]));
             current_offset = next_size;
             dst_offsets[i] = current_offset;
         }