BAN: String now uses union for its sso storage
This allows String to shrink by 8 bytes since Variant's 8 index is no longer stored in here. This required me to make Strings max size one bit less, but that should still be fine. There should never be strings with size of over half of the computer's address space.
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@ -1,6 +1,5 @@
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#include <BAN/String.h>
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#include <BAN/New.h>
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#include <BAN/Variant.h>
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namespace BAN
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{
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@ -32,8 +31,7 @@ namespace BAN
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String& String::operator=(const String& other)
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{
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clear();
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if (!other.fits_in_sso())
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MUST(ensure_capacity(other.size()));
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MUST(ensure_capacity(other.size()));
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memcpy(data(), other.data(), other.size() + 1);
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m_size = other.size();
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return *this;
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@ -43,14 +41,18 @@ namespace BAN
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{
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clear();
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if (other.fits_in_sso())
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if (other.has_sso())
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memcpy(data(), other.data(), other.size() + 1);
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else
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m_storage = other.m_storage.get<GeneralStorage>();
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{
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m_storage.general_storage = other.m_storage.general_storage;
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m_has_sso = false;
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}
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m_size = other.m_size;
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other.m_size = 0;
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other.m_storage = SSOStorage();
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other.m_storage.sso_storage = SSOStorage();
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other.m_has_sso = true;
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return *this;
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}
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@ -58,8 +60,7 @@ namespace BAN
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String& String::operator=(StringView other)
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{
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clear();
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if (!fits_in_sso(other.size()))
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MUST(ensure_capacity(other.size()));
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MUST(ensure_capacity(other.size()));
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memcpy(data(), other.data(), other.size());
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m_size = other.size();
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data()[m_size] = '\0';
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@ -125,8 +126,9 @@ namespace BAN
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{
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if (!has_sso())
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{
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deallocator(m_storage.get<GeneralStorage>().data);
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m_storage = SSOStorage();
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deallocator(m_storage.general_storage.data);
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m_storage.sso_storage = SSOStorage();
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m_has_sso = true;
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}
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m_size = 0;
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data()[m_size] = '\0';
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@ -167,15 +169,6 @@ namespace BAN
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return {};
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}
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// shrink general -> sso
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if (!has_sso() && fits_in_sso(new_size))
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{
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char* data = m_storage.get<GeneralStorage>().data;
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m_storage = SSOStorage();
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memcpy(m_storage.get<SSOStorage>().storage, data, new_size);
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deallocator(data);
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}
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m_size = new_size;
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data()[m_size] = '\0';
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return {};
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@ -194,20 +187,21 @@ namespace BAN
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if (fits_in_sso())
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{
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char* data = m_storage.get<GeneralStorage>().data;
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m_storage = SSOStorage();
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memcpy(m_storage.get<SSOStorage>().storage, data, m_size + 1);
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char* data = m_storage.general_storage.data;
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m_storage.sso_storage = SSOStorage();
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m_has_sso = true;
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memcpy(this->data(), data, m_size + 1);
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deallocator(data);
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return {};
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}
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GeneralStorage& storage = m_storage.get<GeneralStorage>();
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GeneralStorage& storage = m_storage.general_storage;
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if (storage.capacity == m_size)
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return {};
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char* new_data = (char*)allocator(m_size + 1);
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if (new_data == nullptr)
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return BAN::Error::from_errno(ENOMEM);
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return Error::from_errno(ENOMEM);
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memcpy(new_data, storage.data, m_size);
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deallocator(storage.data);
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@ -222,40 +216,45 @@ namespace BAN
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{
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if (has_sso())
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return sso_capacity;
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return m_storage.get<GeneralStorage>().capacity;
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return m_storage.general_storage.capacity;
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}
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char* String::data()
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{
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if (has_sso())
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return m_storage.get<SSOStorage>().storage;
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return m_storage.get<GeneralStorage>().data;
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return m_storage.sso_storage.data;
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return m_storage.general_storage.data;
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}
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const char* String::data() const
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{
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if (has_sso())
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return m_storage.get<SSOStorage>().storage;
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return m_storage.get<GeneralStorage>().data;
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return m_storage.sso_storage.data;
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return m_storage.general_storage.data;
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}
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ErrorOr<void> String::ensure_capacity(size_type new_size)
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{
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if (m_size >= new_size || fits_in_sso(new_size))
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if (m_size >= new_size)
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return {};
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if (has_sso() && fits_in_sso(new_size))
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return {};
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char* new_data = (char*)allocator(new_size + 1);
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if (new_data == nullptr)
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return BAN::Error::from_errno(ENOMEM);
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return Error::from_errno(ENOMEM);
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memcpy(new_data, data(), m_size + 1);
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if (has_sso())
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m_storage = GeneralStorage();
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{
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m_storage.general_storage = GeneralStorage();
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m_has_sso = false;
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}
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else
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deallocator(m_storage.get<GeneralStorage>().data);
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deallocator(m_storage.general_storage.data);
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auto& storage = m_storage.get<GeneralStorage>();
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auto& storage = m_storage.general_storage;
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storage.capacity = new_size;
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storage.data = new_data;
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@ -264,7 +263,7 @@ namespace BAN
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bool String::has_sso() const
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{
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return m_storage.has<SSOStorage>();
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return m_has_sso;
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}
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}
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@ -82,17 +82,21 @@ namespace BAN
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private:
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struct SSOStorage
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{
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char storage[sso_capacity + 1] {};
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char data[sso_capacity + 1] {};
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};
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struct GeneralStorage
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{
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size_type capacity { 0 };
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char* data;
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size_type capacity { 0 };
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char* data { nullptr };
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};
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private:
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Variant<SSOStorage, GeneralStorage> m_storage { SSOStorage() };
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size_type m_size { 0 };
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union {
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SSOStorage sso_storage;
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GeneralStorage general_storage;
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} m_storage { .sso_storage = SSOStorage() };
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size_type m_size : sizeof(size_type) * 8 - 1 { 0 };
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size_type m_has_sso : 1 { true };
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};
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template<typename... Args>
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