Add string_builder

asl/BUILD.bazel

@@ -26,6 +26,7 @@ cc_library(
         "status.hpp",
         "status_or.hpp",
         "string.hpp",
+        "string_builder.hpp",
         "string_view.hpp",
         "utility.hpp",
     ],
@@ -71,6 +72,7 @@ cc_library(
     "status",
     "status_or",
     "string",
+    "string_builder",
     "string_view",
     "utility",
 ]]

asl/buffer.hpp

@@ -88,11 +88,11 @@ private:
     constexpr T* push_uninit()
     {
         isize_t sz = size();
-        resize_uninit(sz + 1);
+        resize_uninit_inner(sz + 1);
         return data() + sz;
     }
 
-    constexpr void resize_uninit(isize_t new_size)
+    constexpr void resize_uninit_inner(isize_t new_size)
     {
         isize_t old_size = size();
         if (!trivially_destructible<T> && new_size < old_size)
@@ -142,7 +142,7 @@ private:
         {
             isize_t other_n = other.size();
             isize_t this_n = size();
-            resize_uninit(other_n);
+            resize_uninit_inner(other_n);
             if (other_n <= this_n)
             {
                 relocate_assign_n(data(), other.data(), other_n);
@@ -175,7 +175,7 @@ private:
         isize_t this_size = size();
         isize_t new_size = to_copy.size();
         
-        resize_uninit(to_copy.size());
+        resize_uninit_inner(to_copy.size());
         ASL_ASSERT(capacity() >= new_size);
         ASL_ASSERT(size() == to_copy.size());
 
@@ -197,8 +197,8 @@ private:
         ASL_ASSERT(new_size >= 0);
 
         isize_t old_size = size();
-        resize_uninit(new_size);
-
+        resize_uninit_inner(new_size);
+    
         T* data_ptr = data();
         T* end = data_ptr + new_size;
 
@@ -343,6 +343,25 @@ public:
         store_size_encoded(encode_size_heap(current_size));
     }
 
+    constexpr void resize_uninit(isize_t new_size)
+        requires trivially_default_constructible<T> && trivially_destructible<T>
+    {
+        reserve_capacity(new_size);
+        set_size(new_size);
+    }
+
+    constexpr void resize_zero(isize_t new_size)
+        requires trivially_default_constructible<T> && trivially_destructible<T>
+    {
+        isize_t old_size = size();
+        resize_uninit(new_size);
+
+        if (new_size > old_size)
+        {
+            memzero(data() + old_size, (new_size - old_size) * size_of<T>);
+        }
+    }
+
     void resize(isize_t new_size)
         requires default_constructible<T>
     {

asl/string.hpp

@@ -11,6 +11,13 @@ class string
 {
     buffer<char, Allocator> m_buffer;
 
+    explicit constexpr string(buffer<char, Allocator>&& buffer) :
+        m_buffer{ASL_MOVE(buffer)}
+    {}
+
+    template<allocator A>
+    friend class string_builder;
+
 public:
     constexpr string() requires default_constructible<Allocator> = default;
     explicit constexpr string(Allocator allocator) : m_buffer{ASL_MOVE(allocator)} {}

asl/string_builder.hpp

@@ -0,0 +1,89 @@
+#pragma once
+
+#include "asl/buffer.hpp"
+#include "asl/string.hpp"
+#include "asl/string_view.hpp"
+
+namespace asl
+{
+
+template<allocator Allocator = DefaultAllocator>
+class string_builder
+{
+    buffer<char, Allocator> m_buffer;
+
+public:
+    constexpr string_builder() requires default_constructible<Allocator> = default;
+    explicit constexpr string_builder(Allocator allocator) : m_buffer{ASL_MOVE(allocator)} {}
+
+    constexpr ~string_builder() = default;
+
+    constexpr string_builder(const string_builder&) requires copy_constructible<Allocator> = default;
+    constexpr string_builder(string_builder&&) = default;
+
+    constexpr string_builder& operator=(const string_builder&) requires copy_assignable<Allocator> = default;
+    constexpr string_builder& operator=(string_builder&&) = default;
+
+    constexpr string_view as_string_view() const
+    {
+        auto span = m_buffer.as_span();
+        return string_view{span.data(), span.size()};
+    }
+
+    void reset()
+    {
+        m_buffer.clear();
+    }
+
+    // @Todo(C++23) Deducing this
+
+    string_builder& push(string_view sv) &
+    {
+        isize_t old_size = m_buffer.size();
+        m_buffer.resize_zero(old_size + sv.size());
+        asl::memcpy(m_buffer.data() + old_size, sv.data(), sv.size());
+        return *this;
+    }
+
+    string_builder&& push(string_view sv) &&
+    {
+        isize_t old_size = m_buffer.size();
+        m_buffer.resize_zero(old_size + sv.size());
+        asl::memcpy(m_buffer.data() + old_size, sv.data(), sv.size());
+        return ASL_MOVE(*this);
+    }
+
+    string_builder& push(char c) &
+    {
+        m_buffer.push(c);
+        return *this;
+    }
+
+    string_builder&& push(char c) &&
+    {
+        m_buffer.push(c);
+        return ASL_MOVE(*this);
+    }
+
+    string<Allocator> finish() &&
+    {
+        return string<Allocator>{ASL_MOVE(m_buffer)};
+    }
+
+    template<allocator StringAllocator = Allocator>
+    string<StringAllocator> as_string()
+        requires default_constructible<StringAllocator>
+    {
+        return string<StringAllocator>{as_string_view()};
+    }
+
+    template<allocator StringAllocator = Allocator>
+    string<StringAllocator> as_string(Allocator allocator)
+    {
+        return string<StringAllocator>{as_string_view(), ASL_MOVE(allocator)};
+    }
+};
+
+string_builder() -> string_builder<>;
+
+} // namespace asl

asl/tests/buffer_tests.cpp

@@ -583,3 +583,21 @@ ASL_TEST(resize)
     ASL_TEST_EXPECT(buf[1] == 6);
 }
 
+ASL_TEST(resize_zero)
+{
+    asl::buffer<int> buf;
+    for (int i = 0; i < 100; ++i)
+    {
+        buf.push(i);
+    }
+    
+    buf.resize_zero(200);
+    ASL_TEST_ASSERT(buf.size() == 200);
+    
+    for (int i = 0; i < 100; ++i)
+    {
+        ASL_TEST_EXPECT(buf[i] == i);
+        ASL_TEST_EXPECT(buf[100 + i] == 0);
+    }
+}
+

asl/tests/string_builder_tests.cpp

@@ -0,0 +1,23 @@
+#include "asl/string_builder.hpp"
+#include "asl/testing/testing.hpp"
+
+ASL_TEST(string_builder)
+{
+    asl::string_builder b;
+    b.push('a');
+    b.push("bcdef");
+    b.push('g');
+
+    ASL_TEST_EXPECT(b.as_string_view() == "abcdefg");
+
+    asl::string s = b.as_string();
+    ASL_TEST_EXPECT(s == "abcdefg");
+}
+
+ASL_TEST(string_builder_rvalue)
+{
+    asl::string s = asl::string_builder{}.push('a').push("bcdef").push('g').finish();
+
+    ASL_TEST_EXPECT(s == "abcdefg");
+}
+