update slice builder

gojo/strings/builder.mojo

@@ -134,7 +134,7 @@ struct StringBuilder(Stringable, Sized, io.Writer, io.ByteWriter, io.StringWrite
 
 
 @value
-struct NewStringBuilder(Stringable, Sized):
+struct NewStringBuilder[growth_factor: Float32 = 2](Stringable, Sized):
     """
     A string builder class that allows for efficient string management and concatenation.
     This class is useful when you need to build a string by appending multiple strings
@@ -164,6 +164,7 @@ struct NewStringBuilder(Stringable, Sized):
 
     @always_inline
     fn __init__(inout self, *, capacity: Int = 4096):
+        constrained[growth_factor >= 1.25]()
         self.data = DTypePointer[DType.uint8]().alloc(capacity)
         self.size = 0
         self.capacity = capacity
@@ -177,10 +178,19 @@ struct NewStringBuilder(Stringable, Sized):
           The string representation of the string builder. Returns an empty
           string if the string builder is empty.
         """
-        var copy = DTypePointer[DType.uint8]().alloc(self.size + 1)
+        var copy = DTypePointer[DType.uint8]().alloc(self.size)
         memcpy(copy, self.data, self.size)
-        copy[self.size] = 0
-        return StringRef(copy, self.size + 1)
+        return StringRef(copy, self.size)
+
+    @always_inline
+    fn render(self: Reference[Self]) -> StringSlice[self.is_mutable, self.lifetime]:
+        """
+        Return a StringSlice view of the data owned by the builder.
+
+        Returns:
+          The string representation of the string builder. Returns an empty string if the string builder is empty.
+        """
+        return StringSlice[self.is_mutable, self.lifetime](unsafe_from_utf8_strref=StringRef(self[].data, self[].size))
 
     @always_inline
     fn __del__(owned self):
@@ -212,7 +222,7 @@ struct NewStringBuilder(Stringable, Sized):
           src: The byte array to append.
         """
         if len(src) > self.capacity - self.size:
-            self._resize(self.capacity * 2)
+            self._resize(int(self.capacity * growth_factor))
 
         memcpy(self.data.offset(self.size), src._data, len(src))
         self.size += len(src)

goodies/std.mojo

@@ -39,7 +39,7 @@ struct STDWriter(Copyable, io.Writer, io.StringWriter):
         )
 
         if write_count == -1:
-            return 0, Error("Failed to write to file descriptor " + String(self.fd))
+            return 0, Error("Failed to write to file descriptor " + str(self.fd))
 
         return write_count, Error()
 

tests/test_performance.mojo

@@ -9,7 +9,7 @@ fn test_string_builder() raises:
     # Create a string from the buffer
     var builder_write_start_time = now()
     var builder = StringBuilder()
-    for _ in range(100):
+    for _ in range(10000):
         _ = builder.write_string(
             "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod"
             " tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim"
@@ -30,7 +30,7 @@ fn test_string_builder() raises:
     # Create a string from the buffer
     var new_builder_write_start_time = now()
     var new_builder = NewStringBuilder()
-    for _ in range(100):
+    for _ in range(10000):
         _ = new_builder.write_string(
             "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod"
             " tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim"
@@ -47,10 +47,16 @@ fn test_string_builder() raises:
     var new_builder_execution_time = now() - new_builder_start_time
     print("NewStringBuilder buffer len", len(new_output), "\n")
 
+    var new_builder_render_start_time = now()
+    var new_output_render = str(new_builder.render())
+    var new_builder_render_execution_time = now() - new_builder_render_start_time
+    print("NewStringBuilder buffer len", len(new_output_render), "\n")
+    # print(new_output_render)
+
     # Create a string using the + operator
     print("Testing string concatenation performance")
     var vec = List[String]()
-    for i in range(100):
+    for i in range(10000):
         vec.append(
             "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod"
             " tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim"
@@ -72,7 +78,7 @@ fn test_string_builder() raises:
     var buffer_write_start_time = now()
     print("Testing bytes buffer performance")
     var buf = buffer.new_buffer()
-    for i in range(100):
+    for i in range(10000):
         _ = buf.write_string(
             "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod"
             " tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim"
@@ -92,11 +98,12 @@ fn test_string_builder() raises:
     print("\nWrite times:")
     print("StringBuilder:", "(", builder_write_execution_time, "ns)")
     print("NewStringBuilder:", "(", new_builder_write_execution_time, "ns)")
-    print("Bytes buffer write time:", "(", buffer_write_execution_time, "ns)", "\n")
+    print("Bytes buffer write time:", "(", buffer_write_execution_time, "ns)")
 
     print("\nExecution times:")
     print("StringBuilder:", "(", builder_execution_time, "ns)")
     print("NewStringBuilder:", "(", new_builder_execution_time, "ns)")
+    print("NewStringBuilder Render:", "(", new_builder_render_execution_time, "ns)")
     print("String concat:", "(", concat_execution_time, "ns)")
     print("Bytes Buffer:", "(", buffer_execution_time, "ns)")
 

tests/test_strings_stringbuilder.mojo

@@ -13,7 +13,7 @@ fn test_write_string() raises:
         _ = builder.write_string("Lorem ipsum dolor sit amet ")
 
     test.assert_equal(
-        String(builder),
+        str(builder),
         "Lorem ipsum dolor sit amet Lorem ipsum dolor sit amet Lorem ipsum dolor sit amet ",
     )
 
@@ -24,7 +24,7 @@ fn test_write() raises:
     # Create a string from the builder by writing bytes to it.
     var builder = StringBuilder()
     _ = builder.write(String("Hello").as_bytes())
-    test.assert_equal(String(builder), "Hello")
+    test.assert_equal(str(builder), "Hello")
 
 
 fn test_write_byte() raises:
@@ -33,7 +33,7 @@ fn test_write_byte() raises:
     # Create a string from the builder by writing bytes to it.
     var builder = StringBuilder()
     _ = builder.write_byte(32)
-    test.assert_equal(String(builder), " ")
+    test.assert_equal(str(builder), " ")
 
 
 fn main() raises: