basic_string.cpp.hpp

Go to the documentation of this file.

#include "fl/stl/basic_string.h"
#include "fl/stl/cstring.h"
#include "fl/stl/noexcept.h"
#include "fl/stl/span.h"
#include "fl/stl/string_view.h"
#include "fl/system/sketch_macros.h"  // FL_PLATFORM_HAS_LARGE_MEMORY -- gates int64 itoa path
 
namespace fl {
 
// ODR-use definition
const fl::size basic_string::npos;
 
// ======= PUBLIC CONSTRUCTORS (span delegate) =======
 
basic_string::basic_string(fl::span<char, static_cast<fl::size>(-1)> storage) FL_NO_EXCEPT
    : basic_string(storage.data(), storage.size()) {}
 
// ======= DESTRUCTOR =======
 
basic_string::~basic_string() FL_DTOR_NOEXCEPT {}
 
// ======= string_view CONSTRUCTOR FROM basic_string =======
// Defined here (in the same TU as basic_string itself) so
// string_view.h can stay light: it forward-declares basic_string
// and declares this ctor without needing basic_string's complete
// type.
 
string_view::string_view(const basic_string& str) FL_NO_EXCEPT
    : mData(str.c_str()), mSize(str.size()) {}
 
// ======= ACCESSORS =======
 
const char* basic_string::c_str() const FL_NO_EXCEPT {
    if (mStorage.is<ConstView>()) {
        const ConstView& view = mStorage.get<ConstView>();
        if (view.data && view.length > 0 && view.data[view.length] != '\0') {
            const_cast<basic_string*>(this)->materialize();
        }
    }
    return constData();
}
 
char* basic_string::c_str_mutable() FL_NO_EXCEPT {
    // Inline mode — already mutable
    if (mStorage.empty()) {
        return inlineBufferPtr();
    }
    struct Visitor {
        basic_string* self;
        char* result;
        void accept(NotNullStringHolderPtr& heap) FL_NO_EXCEPT {
            if (heap.get().use_count() > 1) {
                // COW: detach from shared data before returning mutable pointer
                self->mStorage = NotNullStringHolderPtr(
                    fl::make_shared<StringHolder>(heap->data(), self->mLength));
                result = self->heapData()->data();
            } else {
                result = heap->data();
            }
        }
        void accept(ConstLiteral&) FL_NO_EXCEPT {
            self->materialize();
            result = self->hasHeapData() ? self->heapData()->data()
                                         : self->inlineBufferPtr();
        }
        void accept(ConstView&) FL_NO_EXCEPT {
            self->materialize();
            result = self->hasHeapData() ? self->heapData()->data()
                                         : self->inlineBufferPtr();
        }
    };
    Visitor v{this, nullptr};
    mStorage.visit(v);
    return v.result;
}
 
fl::size basic_string::capacity() const FL_NO_EXCEPT {
    if (hasHeapData()) {
        return heapData()->capacity();
    } else if (isNonOwning()) {
        return 0;
    }
    return mInlineCapacity;
}
 
// ======= ELEMENT ACCESS =======
 
char basic_string::operator[](fl::size index) const FL_NO_EXCEPT {
    if (index >= mLength) {
        return '\0';
    }
    return c_str()[index];
}
 
char& basic_string::operator[](fl::size index) FL_NO_EXCEPT {
    static char dummy = '\0';
    if (index >= mLength) {
        dummy = '\0';
        return dummy;
    }
    return c_str_mutable()[index];
}
 
char& basic_string::at(fl::size pos) FL_NO_EXCEPT {
    static char dummy = '\0';
    if (pos >= mLength) {
        dummy = '\0';
        return dummy;
    }
    return c_str_mutable()[pos];
}
 
const char& basic_string::at(fl::size pos) const FL_NO_EXCEPT {
    static char dummy = '\0';
    if (pos >= mLength) {
        dummy = '\0';
        return dummy;
    }
    return c_str()[pos];
}
 
char basic_string::front() const FL_NO_EXCEPT {
    if (empty()) return '\0';
    return c_str()[0];
}
 
char basic_string::back() const FL_NO_EXCEPT {
    if (empty()) return '\0';
    return c_str()[mLength - 1];
}
 
char basic_string::charAt(fl::size index) const FL_NO_EXCEPT {
    if (index >= mLength) return '\0';
    return c_str()[index];
}
 
// ======= COMPARISON OPERATORS =======
 
bool basic_string::operator==(const basic_string& other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other.c_str()) == 0; }
bool basic_string::operator!=(const basic_string& other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other.c_str()) != 0; }
bool basic_string::operator<(const basic_string& other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other.c_str()) < 0; }
bool basic_string::operator>(const basic_string& other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other.c_str()) > 0; }
bool basic_string::operator<=(const basic_string& other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other.c_str()) <= 0; }
bool basic_string::operator>=(const basic_string& other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other.c_str()) >= 0; }
 
bool basic_string::operator==(const char* other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other ? other : "") == 0; }
bool basic_string::operator!=(const char* other) const FL_NO_EXCEPT { return fl::strcmp(c_str(), other ? other : "") != 0; }
 
// ======= HELPER METHODS =======
 
const char* basic_string::constData() const FL_NO_EXCEPT {
    if (isInline()) {
        return inlineBufferPtr();
    } else if (mStorage.is<NotNullStringHolderPtr>()) {
        return mStorage.get<NotNullStringHolderPtr>()->data();
    } else if (mStorage.is<ConstLiteral>()) {
        return mStorage.get<ConstLiteral>().data;
    } else if (mStorage.is<ConstView>()) {
        return mStorage.get<ConstView>().data;
    }
    return "";
}
 
void basic_string::materialize() FL_NO_EXCEPT {
    if (mStorage.is<ConstLiteral>()) {
        const char* data = mStorage.get<ConstLiteral>().data;
        if (!data) {
            mLength = 0;
            mStorage.reset();
            inlineBufferPtr()[0] = '\0';
            return;
        }
        fl::size len = mLength;
        if (len + 1 <= mInlineCapacity) {
            fl::memcpy(inlineBufferPtr(), data, len);
            inlineBufferPtr()[len] = '\0';
            mStorage.reset();
        } else {
            mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(data, len));
        }
    } else if (mStorage.is<ConstView>()) {
        const ConstView& view = mStorage.get<ConstView>();
        if (!view.data) {
            mLength = 0;
            mStorage.reset();
            inlineBufferPtr()[0] = '\0';
            return;
        }
        fl::size len = view.length;
        mLength = len;
        if (len + 1 <= mInlineCapacity) {
            fl::memcpy(inlineBufferPtr(), view.data, len);
            inlineBufferPtr()[len] = '\0';
            mStorage.reset();
        } else {
            mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(view.data, len));
        }
    }
}
 
NotNullStringHolderPtr& basic_string::heapData() FL_NO_EXCEPT {
    if (!mStorage.is<NotNullStringHolderPtr>()) {
        mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(0));
    }
    return mStorage.get<NotNullStringHolderPtr>();
}
 
const NotNullStringHolderPtr& basic_string::heapData() const FL_NO_EXCEPT {
    return mStorage.get<NotNullStringHolderPtr>();
}
 
// ======= WRITE =======
 
// Trivial delegates to the workhorse write(const char*, fl::size) below.
// Folding away the address-of-byte indirection that write(u8) previously
// did, and dropping the verbose static_cast<void*> intermediate from
// write(u8*) — shrinks each call site by a few bytes (#3122 B5 /
// #2886 Stage 5).
fl::size basic_string::write(const fl::u8* data, fl::size n) FL_NO_EXCEPT {
    return write(fl::bit_cast_ptr<const char>(data), n);
}
 
fl::size basic_string::write(char c) FL_NO_EXCEPT { return write(&c, 1); }
 
fl::size basic_string::write(fl::u8 c) FL_NO_EXCEPT {
    return write(static_cast<char>(c));
}
 
fl::size basic_string::write(const char* str, fl::size n) FL_NO_EXCEPT {
    fl::size newLen = mLength + n;
 
    // Handle non-owning storage
    if (isNonOwning()) {
        const char* existingData = constData();
        fl::size existingLen = mLength;
        if (newLen + 1 <= mInlineCapacity) {
            if (existingLen > 0 && existingData) {
                fl::memcpy(inlineBufferPtr(), existingData, existingLen);
            }
            fl::memcpy(inlineBufferPtr() + existingLen, str, n);
            inlineBufferPtr()[newLen] = '\0';
            mStorage.reset();
            mLength = newLen;
        } else {
            NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
            if (existingLen > 0 && existingData) {
                fl::memcpy(newData->data(), existingData, existingLen);
            }
            fl::memcpy(newData->data() + existingLen, str, n);
            newData->data()[newLen] = '\0';
            mStorage = newData;
            mLength = newLen;
        }
        return mLength;
    }
 
    if (hasHeapData() && heapData().get().use_count() <= 1) {
        NotNullStringHolderPtr& heap = heapData();
        if (!heap->hasCapacity(newLen)) {
            // Check if str points into our buffer (self-referential write).
            // grow() uses realloc which can relocate the buffer.
            const char* bufStart = heap->data();
            fl::size grow_length = fl::max(3, newLen * 3 / 2);
            if (str >= bufStart && str < bufStart + mLength + 1) {
                fl::size offset = static_cast<fl::size>(str - bufStart);
                heap->grow(grow_length);
                str = heap->data() + offset; // update to new location
            } else {
                heap->grow(grow_length);
            }
        }
        fl::memcpy(heap->data() + mLength, str, n);
        mLength = newLen;
        heap->data()[mLength] = '\0';
        return mLength;
    } else if (hasHeapData()) {
        // Copy-on-write
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        {
            const NotNullStringHolderPtr& heap = heapData();
            fl::memcpy(newData->data(), heap->data(), mLength);
            fl::memcpy(newData->data() + mLength, str, n);
            newData->data()[newLen] = '\0';
            mStorage = newData;
            mLength = newLen;
        }
        return mLength;
    }
    if (newLen + 1 <= mInlineCapacity) {
        FL_DISABLE_WARNING_PUSH
        FL_DISABLE_WARNING(array-bounds)
        fl::memcpy(inlineBufferPtr() + mLength, str, n);
        FL_DISABLE_WARNING_POP
        mLength = newLen;
        inlineBufferPtr()[mLength] = '\0';
        return mLength;
    }
    // Transition from inline to heap
    NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
    {
        fl::memcpy(newData->data(), inlineBufferPtr(), mLength);
        fl::memcpy(newData->data() + mLength, str, n);
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
    }
    return mLength;
}
 
fl::size basic_string::write(const fl::u16& n) FL_NO_EXCEPT {
    char buf[64] = {0};
    int len = fl::utoa32(static_cast<fl::u32>(n), buf, 10);
    return write(buf, len);
}
 
fl::size basic_string::write(const fl::u32& val) FL_NO_EXCEPT {
    char buf[64] = {0};
    int len = fl::utoa32(val, buf, 10);
    return write(buf, len);
}
 
fl::size basic_string::write(const u64& val) FL_NO_EXCEPT {
    char buf[64] = {0};
#if FL_PLATFORM_HAS_LARGE_MEMORY
    int len = fl::utoa64(val, buf, 10);
#else
    // Low-memory gate per #3224 Tier 3G: route through the 32-bit utoa to
    // avoid `__udivmoddi4` + `__clzdi2` (libgcc-nofp's 64-bit divmod cascade,
    // ~1.5 KB on Cortex-M0+). Values larger than UINT32_MAX saturate.
    int len = fl::utoa32(val > 0xFFFFFFFFull ? 0xFFFFFFFFu
                                              : static_cast<fl::u32>(val),
                         buf, 10);
#endif
    return write(buf, len);
}
 
fl::size basic_string::write(const i64& val) FL_NO_EXCEPT {
    char buf[64] = {0};
#if FL_PLATFORM_HAS_LARGE_MEMORY
    int len = fl::itoa64(val, buf, 10);
#else
    // Low-memory gate per #3224 Tier 3G: route through the 32-bit itoa to
    // avoid `__udivmoddi4` + `__clzdi2`. Values outside INT32 range saturate
    // to INT32_MIN / INT32_MAX. Sketches that need full int64 formatting on
    // Low-memory can opt in by defining FL_PLATFORM_HAS_LARGE_MEMORY=1.
    fl::i32 narrow = val >  2147483647LL ?  2147483647
                   : val < -2147483648LL ? -2147483648
                                          : static_cast<fl::i32>(val);
    int len = fl::itoa(narrow, buf, 10);
#endif
    return write(buf, len);
}
 
fl::size basic_string::write(const fl::i32& val) FL_NO_EXCEPT {
    char buf[64] = {0};
    int len = fl::itoa(val, buf, 10);
    return write(buf, len);
}
 
fl::size basic_string::write(const fl::i8 val) FL_NO_EXCEPT {
    char buf[64] = {0};
    int len = fl::itoa(static_cast<fl::i32>(val), buf, 10);
    return write(buf, len);
}
 
// ======= COPY =======
 
void basic_string::copy(const char* str) FL_NO_EXCEPT {
    fl::size len = fl::strlen(str);
    mLength = len;
    if (len + 1 <= mInlineCapacity) {
        if (!isInline()) {
            mStorage.reset();
        }
        fl::memcpy(inlineBufferPtr(), str, len + 1);
    } else {
        if (hasHeapData() && heapData().get().use_count() <= 1) {
            heapData()->copy(str, len);
            return;
        }
        mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(str));
    }
}
 
void basic_string::copy(const char* str, fl::size len) FL_NO_EXCEPT {
    mLength = len;
    if (len + 1 <= mInlineCapacity) {
        if (!isInline()) {
            mStorage.reset();
        }
        fl::memcpy(inlineBufferPtr(), str, len);
        inlineBufferPtr()[len] = '\0';
    } else {
        if (hasHeapData() && heapData().get().use_count() <= 1) {
            heapData()->copy(str, len);
            return;
        }
        mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(str, len));
    }
}
 
void basic_string::copy(const basic_string& other) FL_NO_EXCEPT {
    fl::size len = other.size();
    if (other.hasHeapData()) {
        // Share the heap pointer
        const auto& otherHeap = other.mStorage.get<NotNullStringHolderPtr>();
        mStorage = otherHeap;
    } else if (len + 1 <= mInlineCapacity) {
        if (!isInline()) {
            mStorage.reset();
        }
        const char* src = other.c_str();
        char* dst = inlineBufferPtr();
        fl::memcpy(dst, src, len + 1);
    } else {
        mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(other.c_str()));
    }
    mLength = len;
}
 
fl::size basic_string::copy(char* dest, fl::size count, fl::size pos) const FL_NO_EXCEPT {
    if (!dest) return 0;
    if (pos >= mLength) return 0;
    fl::size actualCount = count;
    if (actualCount > mLength - pos) {
        actualCount = mLength - pos;
    }
    if (actualCount > 0) {
        fl::memcpy(dest, c_str() + pos, actualCount);
    }
    return actualCount;
}
 
// ======= ASSIGN =======
 
void basic_string::assign(const char* str, fl::size len) FL_NO_EXCEPT {
    mLength = len;
    if (len + 1 <= mInlineCapacity) {
        if (!isInline()) {
            mStorage.reset();
        }
        fl::memcpy(inlineBufferPtr(), str, len);
        inlineBufferPtr()[len] = '\0';
    } else {
        mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(str, len));
    }
}
 
basic_string& basic_string::assign(const basic_string& str) FL_NO_EXCEPT {
    copy(str);
    return *this;
}
 
basic_string& basic_string::assign(const basic_string& str, fl::size pos, fl::size count) FL_NO_EXCEPT {
    if (pos >= str.size()) {
        clear();
        return *this;
    }
    fl::size actualCount = count;
    if (actualCount == npos || pos + actualCount > str.size()) {
        actualCount = str.size() - pos;
    }
    copy(str.c_str() + pos, actualCount);
    return *this;
}
 
basic_string& basic_string::assign(fl::size count, char c) FL_NO_EXCEPT {
    if (count == 0) {
        clear();
        return *this;
    }
    mLength = count;
    if (count + 1 <= mInlineCapacity) {
        if (!isInline()) {
            mStorage.reset();
        }
        for (fl::size i = 0; i < count; ++i) {
            inlineBufferPtr()[i] = c;
        }
        inlineBufferPtr()[count] = '\0';
    } else {
        mStorage = NotNullStringHolderPtr(fl::make_shared<StringHolder>(count));
        NotNullStringHolderPtr& ptr = heapData();
        for (fl::size i = 0; i < count; ++i) {
            ptr->data()[i] = c;
        }
        ptr->data()[count] = '\0';
    }
    return *this;
}
 
basic_string& basic_string::assign(basic_string&& str) FL_NO_EXCEPT {
    moveAssign(fl::move(str));
    return *this;
}
 
// ======= MEMORY MANAGEMENT =======
 
void basic_string::reserve(fl::size newCapacity) FL_NO_EXCEPT {
    if (newCapacity <= mLength) return;
    if (newCapacity + 1 <= mInlineCapacity) return;
    if (hasHeapData()) {
        const NotNullStringHolderPtr& heap = heapData();
        if (heap.get().use_count() <= 1 && heap->hasCapacity(newCapacity)) {
            return;
        }
    }
    NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newCapacity));
    fl::memcpy(newData->data(), c_str(), mLength);
    newData->data()[mLength] = '\0';
    mStorage = newData;
}
 
void basic_string::clear(bool freeMemory) FL_NO_EXCEPT {
    mLength = 0;
    if (isNonOwning() || (freeMemory && hasHeapData())) {
        mStorage.reset();
        inlineBufferPtr()[0] = '\0';
    } else {
        c_str_mutable()[0] = '\0';
    }
}
 
void basic_string::shrink_to_fit() FL_NO_EXCEPT {
    if (hasHeapData()) {
        NotNullStringHolderPtr& heap = heapData();
        if (heap.get().use_count() > 1) return;
        if (heap->capacity() <= mLength + 1) return;
        if (mLength + 1 <= mInlineCapacity) {
            fl::memcpy(inlineBufferPtr(), heap->data(), mLength + 1);
            mStorage.reset();
            return;
        }
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(mLength));
        fl::memcpy(newData->data(), heap->data(), mLength + 1);
        mStorage = newData;
    }
}
 
// ======= FIND =======
 
fl::size basic_string::find(const char& value) const FL_NO_EXCEPT {
    for (fl::size i = 0; i < mLength; ++i) {
        if (c_str()[i] == value) return i;
    }
    return npos;
}
 
fl::size basic_string::find(const char* substr) const FL_NO_EXCEPT {
    if (!substr) return npos;
    auto begin_ptr = c_str();
    const char* found = fl::strstr(begin_ptr, substr);
    if (found) return found - begin_ptr;
    return npos;
}
 
fl::size basic_string::find(const char& value, fl::size start_pos) const FL_NO_EXCEPT {
    if (start_pos >= mLength) return npos;
    for (fl::size i = start_pos; i < mLength; ++i) {
        if (c_str()[i] == value) return i;
    }
    return npos;
}
 
fl::size basic_string::find(const char* substr, fl::size start_pos) const FL_NO_EXCEPT {
    if (!substr || start_pos >= mLength) return npos;
    auto begin_ptr = c_str() + start_pos;
    const char* found = fl::strstr(begin_ptr, substr);
    if (found) return found - c_str();
    return npos;
}
 
fl::size basic_string::find(const basic_string& other) const FL_NO_EXCEPT { return find(other.c_str()); }
fl::size basic_string::find(const basic_string& other, fl::size start_pos) const FL_NO_EXCEPT { return find(other.c_str(), start_pos); }
 
// ======= RFIND =======
 
fl::size basic_string::rfind(char c, fl::size pos) const FL_NO_EXCEPT {
    if (mLength == 0) return npos;
    fl::size searchPos = (pos >= mLength || pos == npos) ? (mLength - 1) : pos;
    const char* str = c_str();
    for (fl::size i = searchPos + 1; i > 0; --i) {
        if (str[i - 1] == c) return i - 1;
    }
    return npos;
}
 
fl::size basic_string::rfind(const char* s, fl::size pos, fl::size count) const FL_NO_EXCEPT {
    if (!s || count == 0) {
        if (count == 0) return (pos > mLength) ? mLength : pos;
        return npos;
    }
    if (count > mLength) return npos;
    fl::size maxStart = mLength - count;
    fl::size searchStart = (pos >= mLength || pos == npos) ? maxStart : pos;
    if (searchStart + count > mLength) searchStart = maxStart;
    const char* str = c_str();
    for (fl::size i = searchStart + 1; i > 0; --i) {
        fl::size idx = i - 1;
        if (idx + count > mLength) continue;
        bool match = true;
        for (fl::size j = 0; j < count; ++j) {
            if (str[idx + j] != s[j]) { match = false; break; }
        }
        if (match) return idx;
    }
    return npos;
}
 
fl::size basic_string::rfind(const char* s, fl::size pos) const FL_NO_EXCEPT {
    if (!s) return npos;
    return rfind(s, pos, fl::strlen(s));
}
 
fl::size basic_string::rfind(const basic_string& str, fl::size pos) const FL_NO_EXCEPT { return rfind(str.c_str(), pos, str.size()); }
 
// ======= FIND_FIRST_OF =======
 
fl::size basic_string::find_first_of(const char* s, fl::size pos, fl::size count) const FL_NO_EXCEPT {
    if (!s || count == 0) return npos;
    if (pos >= mLength) return npos;
    const char* str = c_str();
    for (fl::size i = pos; i < mLength; ++i) {
        for (fl::size j = 0; j < count; ++j) {
            if (str[i] == s[j]) return i;
        }
    }
    return npos;
}
 
fl::size basic_string::find_first_of(const char* s, fl::size pos) const FL_NO_EXCEPT {
    if (!s) return npos;
    return find_first_of(s, pos, fl::strlen(s));
}
 
fl::size basic_string::find_first_of(char c, fl::size pos) const FL_NO_EXCEPT { return find(c, pos); }
fl::size basic_string::find_first_of(const basic_string& str, fl::size pos) const FL_NO_EXCEPT { return find_first_of(str.c_str(), pos, str.size()); }
 
// ======= FIND_LAST_OF =======
 
fl::size basic_string::find_last_of(const char* s, fl::size pos, fl::size count) const FL_NO_EXCEPT {
    if (!s || count == 0) return npos;
    if (mLength == 0) return npos;
    fl::size searchPos = (pos >= mLength || pos == npos) ? (mLength - 1) : pos;
    const char* str = c_str();
    for (fl::size i = searchPos + 1; i > 0; --i) {
        for (fl::size j = 0; j < count; ++j) {
            if (str[i - 1] == s[j]) return i - 1;
        }
    }
    return npos;
}
 
fl::size basic_string::find_last_of(const char* s, fl::size pos) const FL_NO_EXCEPT {
    if (!s) return npos;
    return find_last_of(s, pos, fl::strlen(s));
}
 
fl::size basic_string::find_last_of(char c, fl::size pos) const FL_NO_EXCEPT { return rfind(c, pos); }
fl::size basic_string::find_last_of(const basic_string& str, fl::size pos) const FL_NO_EXCEPT { return find_last_of(str.c_str(), pos, str.size()); }
 
// ======= FIND_FIRST_NOT_OF =======
 
fl::size basic_string::find_first_not_of(char c, fl::size pos) const FL_NO_EXCEPT {
    if (pos >= mLength) return npos;
    const char* str = c_str();
    for (fl::size i = pos; i < mLength; ++i) {
        if (str[i] != c) return i;
    }
    return npos;
}
 
fl::size basic_string::find_first_not_of(const char* s, fl::size pos, fl::size count) const FL_NO_EXCEPT {
    if (!s || count == 0) return (pos < mLength) ? pos : npos;
    if (pos >= mLength) return npos;
    const char* str = c_str();
    for (fl::size i = pos; i < mLength; ++i) {
        bool found_in_set = false;
        for (fl::size j = 0; j < count; ++j) {
            if (str[i] == s[j]) { found_in_set = true; break; }
        }
        if (!found_in_set) return i;
    }
    return npos;
}
 
fl::size basic_string::find_first_not_of(const char* s, fl::size pos) const FL_NO_EXCEPT {
    if (!s) return (pos < mLength) ? pos : npos;
    return find_first_not_of(s, pos, fl::strlen(s));
}
 
fl::size basic_string::find_first_not_of(const basic_string& str, fl::size pos) const FL_NO_EXCEPT { return find_first_not_of(str.c_str(), pos, str.size()); }
 
// ======= FIND_LAST_NOT_OF =======
 
fl::size basic_string::find_last_not_of(char c, fl::size pos) const FL_NO_EXCEPT {
    if (mLength == 0) return npos;
    fl::size searchPos = (pos >= mLength || pos == npos) ? (mLength - 1) : pos;
    const char* str = c_str();
    for (fl::size i = searchPos + 1; i > 0; --i) {
        if (str[i - 1] != c) return i - 1;
    }
    return npos;
}
 
fl::size basic_string::find_last_not_of(const char* s, fl::size pos, fl::size count) const FL_NO_EXCEPT {
    if (!s || count == 0) {
        if (mLength == 0) return npos;
        fl::size searchPos = (pos >= mLength || pos == npos) ? (mLength - 1) : pos;
        return searchPos;
    }
    if (mLength == 0) return npos;
    fl::size searchPos = (pos >= mLength || pos == npos) ? (mLength - 1) : pos;
    const char* str = c_str();
    for (fl::size i = searchPos + 1; i > 0; --i) {
        bool found_in_set = false;
        for (fl::size j = 0; j < count; ++j) {
            if (str[i - 1] == s[j]) { found_in_set = true; break; }
        }
        if (!found_in_set) return i - 1;
    }
    return npos;
}
 
fl::size basic_string::find_last_not_of(const char* s, fl::size pos) const FL_NO_EXCEPT {
    if (!s) {
        if (mLength == 0) return npos;
        fl::size searchPos = (pos >= mLength || pos == npos) ? (mLength - 1) : pos;
        return searchPos;
    }
    return find_last_not_of(s, pos, fl::strlen(s));
}
 
fl::size basic_string::find_last_not_of(const basic_string& str, fl::size pos) const FL_NO_EXCEPT { return find_last_not_of(str.c_str(), pos, str.size()); }
 
// ======= CONTAINS =======
 
bool basic_string::contains(const char* substr) const FL_NO_EXCEPT { return find(substr) != npos; }
bool basic_string::contains(char c) const FL_NO_EXCEPT { return find(c) != npos; }
bool basic_string::contains(const basic_string& other) const FL_NO_EXCEPT { return find(other.c_str()) != npos; }
 
// ======= STARTS_WITH / ENDS_WITH =======
 
bool basic_string::starts_with(const char* prefix) const FL_NO_EXCEPT {
    if (!prefix) return true;
    fl::size prefix_len = fl::strlen(prefix);
    if (prefix_len > mLength) return false;
    return fl::strncmp(c_str(), prefix, prefix_len) == 0;
}
 
bool basic_string::ends_with(const char* suffix) const FL_NO_EXCEPT {
    if (!suffix) return true;
    fl::size suffix_len = fl::strlen(suffix);
    if (suffix_len > mLength) return false;
    return fl::strncmp(c_str() + mLength - suffix_len, suffix, suffix_len) == 0;
}
 
bool basic_string::starts_with(char c) const FL_NO_EXCEPT { return mLength > 0 && c_str()[0] == c; }
bool basic_string::starts_with(const basic_string& prefix) const FL_NO_EXCEPT { return starts_with(prefix.c_str()); }
bool basic_string::ends_with(char c) const FL_NO_EXCEPT { return mLength > 0 && c_str()[mLength - 1] == c; }
bool basic_string::ends_with(const basic_string& suffix) const FL_NO_EXCEPT { return ends_with(suffix.c_str()); }
 
// ======= STACK OPERATIONS =======
 
void basic_string::push_back(char c) FL_NO_EXCEPT { write(c); }
void basic_string::push_ascii(char c) FL_NO_EXCEPT { write(c); }
 
// ======= POP_BACK =======
 
void basic_string::pop_back() FL_NO_EXCEPT {
    if (mLength > 0) {
        mLength--;
        c_str_mutable()[mLength] = '\0';
    }
}
 
// ======= INSERT =======
 
basic_string& basic_string::insert(fl::size pos, fl::size count, char ch) FL_NO_EXCEPT {
    if (pos > mLength) pos = mLength;
    if (count == 0) return *this;
 
    // Materialize non-owning storage before modifying
    if (isNonOwning()) {
        materialize();
    }
 
    fl::size newLen = mLength + count;
 
    // Handle COW
    if (hasHeapData() && heapData().get().use_count() > 1) {
        const NotNullStringHolderPtr& heap = heapData();
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        if (pos > 0) fl::memcpy(newData->data(), heap->data(), pos);
        for (fl::size i = 0; i < count; ++i) newData->data()[pos + i] = ch;
        if (pos < mLength) fl::memcpy(newData->data() + pos + count, heap->data() + pos, mLength - pos);
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
        return *this;
    }
 
    // Inline buffer
    if (newLen + 1 <= mInlineCapacity && !hasHeapData()) {
        if (pos < mLength) {
            fl::memmove(inlineBufferPtr() + pos + count, inlineBufferPtr() + pos, mLength - pos);
        }
        for (fl::size i = 0; i < count; ++i) inlineBufferPtr()[pos + i] = ch;
        mLength = newLen;
        inlineBufferPtr()[mLength] = '\0';
        return *this;
    }
 
    // Heap in-place or new allocation
    bool canInsertInPlace = hasHeapData();
    if (canInsertInPlace) {
        NotNullStringHolderPtr& heap = heapData();
        canInsertInPlace = heap.get().use_count() <= 1 && heap->hasCapacity(newLen);
        if (canInsertInPlace) {
            char* data = heap->data();
            if (pos < mLength) fl::memmove(data + pos + count, data + pos, mLength - pos);
            for (fl::size i = 0; i < count; ++i) data[pos + i] = ch;
            mLength = newLen;
            data[mLength] = '\0';
        }
    }
    if (!canInsertInPlace) {
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        const char* src = c_str();
        if (pos > 0) fl::memcpy(newData->data(), src, pos);
        for (fl::size i = 0; i < count; ++i) newData->data()[pos + i] = ch;
        if (pos < mLength) fl::memcpy(newData->data() + pos + count, src + pos, mLength - pos);
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
    }
    return *this;
}
 
basic_string& basic_string::insert(fl::size pos, const char* s) FL_NO_EXCEPT {
    if (!s) return *this;
    return insert(pos, s, fl::strlen(s));
}
 
basic_string& basic_string::insert(fl::size pos, const basic_string& str) FL_NO_EXCEPT {
    return insert(pos, str.c_str(), str.size());
}
 
basic_string& basic_string::insert(fl::size pos, const basic_string& str, fl::size pos2, fl::size count) FL_NO_EXCEPT {
    if (pos2 >= str.size()) return *this;
    fl::size actualCount = count;
    if (actualCount == npos || pos2 + actualCount > str.size()) {
        actualCount = str.size() - pos2;
    }
    return insert(pos, str.c_str() + pos2, actualCount);
}
 
basic_string& basic_string::insert(fl::size pos, const char* s, fl::size count) FL_NO_EXCEPT {
    if (pos > mLength) pos = mLength;
    if (!s || count == 0) return *this;
 
    // Materialize non-owning storage before modifying
    if (isNonOwning()) {
        materialize();
    }
 
    fl::size newLen = mLength + count;
 
    // Handle COW
    if (hasHeapData() && heapData().get().use_count() > 1) {
        const NotNullStringHolderPtr& heap = heapData();
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        if (pos > 0) fl::memcpy(newData->data(), heap->data(), pos);
        fl::memcpy(newData->data() + pos, s, count);
        if (pos < mLength) fl::memcpy(newData->data() + pos + count, heap->data() + pos, mLength - pos);
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
        return *this;
    }
 
    // Inline buffer
    if (newLen + 1 <= mInlineCapacity && !hasHeapData()) {
        if (pos < mLength) {
            fl::memmove(inlineBufferPtr() + pos + count, inlineBufferPtr() + pos, mLength - pos);
        }
        fl::memcpy(inlineBufferPtr() + pos, s, count);
        mLength = newLen;
        inlineBufferPtr()[mLength] = '\0';
        return *this;
    }
 
    // Heap in-place or new allocation
    bool canInsertInPlace = hasHeapData();
    if (canInsertInPlace) {
        NotNullStringHolderPtr& heap = heapData();
        canInsertInPlace = heap.get().use_count() <= 1 && heap->hasCapacity(newLen);
        if (canInsertInPlace) {
            char* data = heap->data();
            if (pos < mLength) fl::memmove(data + pos + count, data + pos, mLength - pos);
            fl::memcpy(data + pos, s, count);
            mLength = newLen;
            data[mLength] = '\0';
        }
    }
    if (!canInsertInPlace) {
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        const char* src = c_str();
        if (pos > 0) fl::memcpy(newData->data(), src, pos);
        fl::memcpy(newData->data() + pos, s, count);
        if (pos < mLength) fl::memcpy(newData->data() + pos + count, src + pos, mLength - pos);
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
    }
    return *this;
}
 
// ======= ERASE =======
 
basic_string& basic_string::erase(fl::size pos, fl::size count) FL_NO_EXCEPT {
    if (pos >= mLength) return *this;
 
    fl::size actualCount = count;
    if (actualCount == npos || pos + actualCount > mLength) {
        actualCount = mLength - pos;
    }
    if (actualCount == 0) return *this;
 
    // Handle COW
    if (hasHeapData() && heapData().get().use_count() > 1) {
        const NotNullStringHolderPtr& heap = heapData();
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(mLength - actualCount));
        if (pos > 0) fl::memcpy(newData->data(), heap->data(), pos);
        fl::size remainingLen = mLength - pos - actualCount;
        if (remainingLen > 0) {
            fl::memcpy(newData->data() + pos, heap->data() + pos + actualCount, remainingLen);
        }
        mLength = mLength - actualCount;
        newData->data()[mLength] = '\0';
        mStorage = newData;
        return *this;
    }
 
    fl::size remainingLen = mLength - pos - actualCount;
    if (remainingLen > 0) {
        char* data = c_str_mutable();
        fl::memmove(data + pos, data + pos + actualCount, remainingLen);
    }
    mLength -= actualCount;
    c_str_mutable()[mLength] = '\0';
    return *this;
}
 
// ======= REPLACE =======
 
basic_string& basic_string::replace(fl::size pos, fl::size count, const basic_string& str) FL_NO_EXCEPT {
    return replace(pos, count, str.c_str(), str.size());
}
 
basic_string& basic_string::replace(fl::size pos, fl::size count, const basic_string& str,
                     fl::size pos2, fl::size count2) FL_NO_EXCEPT {
    if (pos2 >= str.size()) return erase(pos, count);
    fl::size actualCount2 = count2;
    if (actualCount2 == npos || pos2 + actualCount2 > str.size()) {
        actualCount2 = str.size() - pos2;
    }
    return replace(pos, count, str.c_str() + pos2, actualCount2);
}
 
basic_string& basic_string::replace(fl::size pos, fl::size count, const char* s, fl::size count2) FL_NO_EXCEPT {
    if (pos > mLength) return *this;
    if (!s) return erase(pos, count);
 
    // Materialize non-owning storage before modifying
    if (isNonOwning()) {
        materialize();
    }
 
    fl::size actualCount = count;
    if (actualCount == npos || pos + actualCount > mLength) {
        actualCount = mLength - pos;
    }
    fl::size newLen = mLength - actualCount + count2;
 
    // Handle COW
    if (hasHeapData() && heapData().get().use_count() > 1) {
        const NotNullStringHolderPtr& heap = heapData();
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        if (pos > 0) fl::memcpy(newData->data(), heap->data(), pos);
        fl::memcpy(newData->data() + pos, s, count2);
        fl::size remainingLen = mLength - pos - actualCount;
        if (remainingLen > 0) {
            fl::memcpy(newData->data() + pos + count2, heap->data() + pos + actualCount, remainingLen);
        }
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
        return *this;
    }
 
    // Inline buffer
    if (newLen + 1 <= mInlineCapacity && !hasHeapData()) {
        if (count2 != actualCount) {
            fl::size remainingLen = mLength - pos - actualCount;
            if (remainingLen > 0) {
                fl::memmove(inlineBufferPtr() + pos + count2, inlineBufferPtr() + pos + actualCount, remainingLen);
            }
        }
        fl::memcpy(inlineBufferPtr() + pos, s, count2);
        mLength = newLen;
        inlineBufferPtr()[mLength] = '\0';
        return *this;
    }
 
    // Heap in-place or new allocation
    bool canReplaceInPlace = hasHeapData();
    if (canReplaceInPlace) {
        NotNullStringHolderPtr& heap = heapData();
        canReplaceInPlace = heap.get().use_count() <= 1 && heap->hasCapacity(newLen);
        if (canReplaceInPlace) {
            char* data = heap->data();
            if (count2 != actualCount) {
                fl::size remainingLen = mLength - pos - actualCount;
                if (remainingLen > 0) {
                    fl::memmove(data + pos + count2, data + pos + actualCount, remainingLen);
                }
            }
            fl::memcpy(data + pos, s, count2);
            mLength = newLen;
            data[mLength] = '\0';
        }
    }
    if (!canReplaceInPlace) {
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        const char* src = c_str();
        if (pos > 0) fl::memcpy(newData->data(), src, pos);
        fl::memcpy(newData->data() + pos, s, count2);
        fl::size remainingLen = mLength - pos - actualCount;
        if (remainingLen > 0) {
            fl::memcpy(newData->data() + pos + count2, src + pos + actualCount, remainingLen);
        }
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
    }
    return *this;
}
 
basic_string& basic_string::replace(fl::size pos, fl::size count, const char* s) FL_NO_EXCEPT {
    if (!s) return erase(pos, count);
    return replace(pos, count, s, fl::strlen(s));
}
 
basic_string& basic_string::replace(fl::size pos, fl::size count, fl::size count2, char ch) FL_NO_EXCEPT {
    if (pos > mLength) return *this;
 
    // Materialize non-owning storage before modifying
    if (isNonOwning()) {
        materialize();
    }
 
    fl::size actualCount = count;
    if (actualCount == npos || pos + actualCount > mLength) {
        actualCount = mLength - pos;
    }
    fl::size newLen = mLength - actualCount + count2;
 
    // Handle COW
    if (hasHeapData() && heapData().get().use_count() > 1) {
        const NotNullStringHolderPtr& heap = heapData();
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        if (pos > 0) fl::memcpy(newData->data(), heap->data(), pos);
        for (fl::size i = 0; i < count2; ++i) newData->data()[pos + i] = ch;
        fl::size remainingLen = mLength - pos - actualCount;
        if (remainingLen > 0) {
            fl::memcpy(newData->data() + pos + count2, heap->data() + pos + actualCount, remainingLen);
        }
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
        return *this;
    }
 
    // Inline buffer
    if (newLen + 1 <= mInlineCapacity && !hasHeapData()) {
        if (count2 != actualCount) {
            fl::size remainingLen = mLength - pos - actualCount;
            if (remainingLen > 0) {
                fl::memmove(inlineBufferPtr() + pos + count2, inlineBufferPtr() + pos + actualCount, remainingLen);
            }
        }
        for (fl::size i = 0; i < count2; ++i) inlineBufferPtr()[pos + i] = ch;
        mLength = newLen;
        inlineBufferPtr()[mLength] = '\0';
        return *this;
    }
 
    // Heap in-place or new allocation
    bool canReplaceInPlace = hasHeapData();
    if (canReplaceInPlace) {
        NotNullStringHolderPtr& heap = heapData();
        canReplaceInPlace = heap.get().use_count() <= 1 && heap->hasCapacity(newLen);
        if (canReplaceInPlace) {
            char* data = heap->data();
            if (count2 != actualCount) {
                fl::size remainingLen = mLength - pos - actualCount;
                if (remainingLen > 0) {
                    fl::memmove(data + pos + count2, data + pos + actualCount, remainingLen);
                }
            }
            for (fl::size i = 0; i < count2; ++i) data[pos + i] = ch;
            mLength = newLen;
            data[mLength] = '\0';
        }
    }
    if (!canReplaceInPlace) {
        NotNullStringHolderPtr newData = NotNullStringHolderPtr(fl::make_shared<StringHolder>(newLen));
        const char* src = c_str();
        if (pos > 0) fl::memcpy(newData->data(), src, pos);
        for (fl::size i = 0; i < count2; ++i) newData->data()[pos + i] = ch;
        fl::size remainingLen = mLength - pos - actualCount;
        if (remainingLen > 0) {
            fl::memcpy(newData->data() + pos + count2, src + pos + actualCount, remainingLen);
        }
        newData->data()[newLen] = '\0';
        mStorage = newData;
        mLength = newLen;
    }
    return *this;
}
 
// ======= COMPARE =======
 
int basic_string::compare(const basic_string& str) const FL_NO_EXCEPT { return fl::strcmp(c_str(), str.c_str()); }
 
int basic_string::compare(fl::size pos1, fl::size count1, const basic_string& str) const FL_NO_EXCEPT {
    if (pos1 > mLength) {
        return str.empty() ? 0 : -1;
    }
    fl::size actualCount1 = count1;
    if (actualCount1 == npos || pos1 + actualCount1 > mLength) {
        actualCount1 = mLength - pos1;
    }
    fl::size minLen = (actualCount1 < str.size()) ? actualCount1 : str.size();
    int result = fl::strncmp(c_str() + pos1, str.c_str(), minLen);
    if (result != 0) return result;
    if (actualCount1 < str.size()) return -1;
    if (actualCount1 > str.size()) return 1;
    return 0;
}
 
int basic_string::compare(fl::size pos1, fl::size count1, const basic_string& str,
                     fl::size pos2, fl::size count2) const FL_NO_EXCEPT {
    if (pos1 > mLength || pos2 >= str.size()) {
        if (pos1 > mLength && pos2 >= str.size()) return 0;
        if (pos1 > mLength) return -1;
        return 1;
    }
    fl::size actualCount1 = count1;
    if (actualCount1 == npos || pos1 + actualCount1 > mLength) {
        actualCount1 = mLength - pos1;
    }
    fl::size actualCount2 = count2;
    if (actualCount2 == npos || pos2 + actualCount2 > str.size()) {
        actualCount2 = str.size() - pos2;
    }
    fl::size minLen = (actualCount1 < actualCount2) ? actualCount1 : actualCount2;
    int result = fl::strncmp(c_str() + pos1, str.c_str() + pos2, minLen);
    if (result != 0) return result;
    if (actualCount1 < actualCount2) return -1;
    if (actualCount1 > actualCount2) return 1;
    return 0;
}
 
int basic_string::compare(const char* s) const FL_NO_EXCEPT {
    if (!s) return mLength > 0 ? 1 : 0;
    return fl::strcmp(c_str(), s);
}
 
int basic_string::compare(fl::size pos1, fl::size count1, const char* s) const FL_NO_EXCEPT {
    if (!s) {
        if (pos1 >= mLength) return 0;
        fl::size actualCount1 = count1;
        if (actualCount1 == npos || pos1 + actualCount1 > mLength) {
            actualCount1 = mLength - pos1;
        }
        return (actualCount1 > 0) ? 1 : 0;
    }
    if (pos1 > mLength) return (s[0] == '\0') ? 0 : -1;
    fl::size actualCount1 = count1;
    if (actualCount1 == npos || pos1 + actualCount1 > mLength) {
        actualCount1 = mLength - pos1;
    }
    fl::size sLen = fl::strlen(s);
    fl::size minLen = (actualCount1 < sLen) ? actualCount1 : sLen;
    int result = fl::strncmp(c_str() + pos1, s, minLen);
    if (result != 0) return result;
    if (actualCount1 < sLen) return -1;
    if (actualCount1 > sLen) return 1;
    return 0;
}
 
int basic_string::compare(fl::size pos1, fl::size count1, const char* s, fl::size count2) const FL_NO_EXCEPT {
    if (!s) {
        if (pos1 >= mLength) return (count2 == 0) ? 0 : -1;
        fl::size actualCount1 = count1;
        if (actualCount1 == npos || pos1 + actualCount1 > mLength) {
            actualCount1 = mLength - pos1;
        }
        return (actualCount1 > 0) ? 1 : ((count2 == 0) ? 0 : -1);
    }
    if (pos1 > mLength) return (count2 == 0) ? 0 : -1;
    fl::size actualCount1 = count1;
    if (actualCount1 == npos || pos1 + actualCount1 > mLength) {
        actualCount1 = mLength - pos1;
    }
    fl::size minLen = (actualCount1 < count2) ? actualCount1 : count2;
    int result = fl::strncmp(c_str() + pos1, s, minLen);
    if (result != 0) return result;
    if (actualCount1 < count2) return -1;
    if (actualCount1 > count2) return 1;
    return 0;
}
 
// ======= PROTECTED: MOVE / SWAP / FACTORY HELPERS =======
 
void basic_string::moveFrom(basic_string&& other) FL_NO_EXCEPT {
    if (other.isInline()) {
        mLength = other.mLength;
        fl::memcpy(inlineBufferPtr(), other.inlineBufferPtr(), other.mLength + 1);
        // mStorage is already empty (inline mode) from constructor
    } else {
        mLength = other.mLength;
        mStorage = fl::move(other.mStorage);
    }
    other.mLength = 0;
    other.mStorage.reset();
    other.inlineBufferPtr()[0] = '\0';
}
 
void basic_string::moveAssign(basic_string&& other) FL_NO_EXCEPT {
    if (this == &other) return;
    if (other.isInline()) {
        mLength = other.mLength;
        mStorage.reset();
        fl::memcpy(inlineBufferPtr(), other.inlineBufferPtr(), other.mLength + 1);
    } else {
        mLength = other.mLength;
        mStorage = fl::move(other.mStorage);
    }
    other.mLength = 0;
    other.mStorage.reset();
    other.inlineBufferPtr()[0] = '\0';
}
 
void basic_string::swapWith(basic_string& other) FL_NO_EXCEPT {
    if (this == &other) return;
 
    bool thisInline = isInline();
    bool otherInline = other.isInline();
 
    if (!thisInline && !otherInline) {
        // Both non-inline: swap variant + length
        fl::swap(mStorage, other.mStorage);
        fl::swap(mLength, other.mLength);
    } else if (thisInline && otherInline) {
        // Both inline: check capacity before swapping
        bool thisFits = other.mLength + 1 <= mInlineCapacity;
        bool otherFits = mLength + 1 <= other.mInlineCapacity;
        if (thisFits && otherFits) {
            // Both fit: swap buffer contents directly
            fl::size maxLen = fl::max(mLength, other.mLength);
            for (fl::size i = 0; i <= maxLen; ++i) {
                char tmp = inlineBufferPtr()[i];
                inlineBufferPtr()[i] = other.inlineBufferPtr()[i];
                other.inlineBufferPtr()[i] = tmp;
            }
            fl::swap(mLength, other.mLength);
        } else {
            // Capacity mismatch: promote to heap where needed
            NotNullStringHolderPtr thisData(
                fl::make_shared<StringHolder>(inlineBufferPtr(), mLength));
            NotNullStringHolderPtr otherData(
                fl::make_shared<StringHolder>(other.inlineBufferPtr(), other.mLength));
            fl::size thisLen = mLength;
            fl::size otherLen = other.mLength;
            if (thisFits) {
                mStorage.reset();
                fl::memcpy(inlineBufferPtr(), otherData->data(), otherLen + 1);
            } else {
                mStorage = otherData;
            }
            mLength = otherLen;
            if (otherFits) {
                other.mStorage.reset();
                fl::memcpy(other.inlineBufferPtr(), thisData->data(), thisLen + 1);
            } else {
                other.mStorage = thisData;
            }
            other.mLength = thisLen;
        }
    } else if (thisInline) {
        // this inline, other non-inline
        fl::size thisLen = mLength;
        // Take other's non-inline storage
        mStorage = fl::move(other.mStorage);
        mLength = other.mLength;
        // Put this's old inline data into other
        other.mStorage.reset();
        if (thisLen + 1 <= other.mInlineCapacity) {
            fl::memcpy(other.inlineBufferPtr(), inlineBufferPtr(), thisLen + 1);
        } else {
            other.mStorage = NotNullStringHolderPtr(
                fl::make_shared<StringHolder>(inlineBufferPtr(), thisLen));
        }
        other.mLength = thisLen;
    } else {
        // this non-inline, other inline — reverse
        other.swapWith(*this);
    }
}
 
void basic_string::setLiteral(const char* literal) FL_NO_EXCEPT {
    if (literal) {
        mLength = fl::strlen(literal);
        mStorage = ConstLiteral(literal);
    }
}
 
void basic_string::setView(const char* data, fl::size len) FL_NO_EXCEPT {
    if (data && len > 0) {
        mLength = len;
        mStorage = ConstView(data, len);
    }
}
 
void basic_string::setSharedHolder(const fl::shared_ptr<StringHolder>& holder) FL_NO_EXCEPT {
    if (!holder || holder->length() == 0) return;
    mLength = holder->length();
    mStorage = NotNullStringHolderPtr(holder);
}
 
// ======= APPEND =======
 
basic_string& basic_string::append(const char* str) FL_NO_EXCEPT {
    write(str, fl::strlen(str));
    return *this;
}
 
basic_string& basic_string::append(const char* str, fl::size len) FL_NO_EXCEPT {
    write(str, len);
    return *this;
}
 
basic_string& basic_string::append(char c) FL_NO_EXCEPT {
    write(&c, 1);
    return *this;
}
 
basic_string& basic_string::append(const i8& val) FL_NO_EXCEPT {
    write(val);
    return *this;
}
 
basic_string& basic_string::append(const u8& val) FL_NO_EXCEPT {
    write(static_cast<fl::u16>(val));
    return *this;
}
 
basic_string& basic_string::append(const bool& val) FL_NO_EXCEPT {
    if (val) {
        write("true", 4);
    } else {
        write("false", 5);
    }
    return *this;
}
 
basic_string& basic_string::append(const i16& val) FL_NO_EXCEPT {
    write(static_cast<fl::i32>(val));
    return *this;
}
 
basic_string& basic_string::append(const u16& val) FL_NO_EXCEPT {
    write(val);
    return *this;
}
 
basic_string& basic_string::append(const i32& val) FL_NO_EXCEPT {
    write(val);
    return *this;
}
 
basic_string& basic_string::append(const u32& val) FL_NO_EXCEPT {
    write(val);
    return *this;
}
 
basic_string& basic_string::append(const i64& val) FL_NO_EXCEPT {
    write(val);
    return *this;
}
 
basic_string& basic_string::append(const u64& val) FL_NO_EXCEPT {
    write(val);
    return *this;
}
 
basic_string& basic_string::append(const float& val) FL_NO_EXCEPT {
    char buf[64] = {0};
    fl::ftoa(val, buf, 2);
    write(buf, fl::strlen(buf));
    return *this;
}
 
basic_string& basic_string::append(const float& val, int precision) FL_NO_EXCEPT {
    char buf[64] = {0};
    fl::ftoa(val, buf, precision);
    write(buf, fl::strlen(buf));
    return *this;
}
 
basic_string& basic_string::append(const double& val) FL_NO_EXCEPT {
    return append(static_cast<float>(val));
}
 
basic_string& basic_string::append(const basic_string& str) FL_NO_EXCEPT {
    write(str.c_str(), str.size());
    return *this;
}
 
// ======= HEX/OCT APPEND =======
 
basic_string& basic_string::appendHex(i32 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::itoa(val,b,16); write(b,l); return *this; }
basic_string& basic_string::appendHex(u32 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::utoa32(val,b,16); write(b,l); return *this; }
basic_string& basic_string::appendHex(i64 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::itoa64(val,b,16); write(b,l); return *this; }
basic_string& basic_string::appendHex(u64 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::utoa64(val,b,16); write(b,l); return *this; }
basic_string& basic_string::appendHex(i16 val) FL_NO_EXCEPT { return appendHex(static_cast<i32>(val)); }
basic_string& basic_string::appendHex(u16 val) FL_NO_EXCEPT { return appendHex(static_cast<u32>(val)); }
basic_string& basic_string::appendHex(i8 val) FL_NO_EXCEPT { return appendHex(static_cast<i32>(val)); }
basic_string& basic_string::appendHex(u8 val) FL_NO_EXCEPT { return appendHex(static_cast<u32>(val)); }
 
basic_string& basic_string::appendOct(i32 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::itoa(val,b,8); write(b,l); return *this; }
basic_string& basic_string::appendOct(u32 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::utoa32(val,b,8); write(b,l); return *this; }
basic_string& basic_string::appendOct(i64 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::itoa64(val,b,8); write(b,l); return *this; }
basic_string& basic_string::appendOct(u64 val) FL_NO_EXCEPT { char b[64]={0}; int l=fl::utoa64(val,b,8); write(b,l); return *this; }
basic_string& basic_string::appendOct(i16 val) FL_NO_EXCEPT { return appendOct(static_cast<i32>(val)); }
basic_string& basic_string::appendOct(u16 val) FL_NO_EXCEPT { return appendOct(static_cast<u32>(val)); }
basic_string& basic_string::appendOct(i8 val) FL_NO_EXCEPT { return appendOct(static_cast<i32>(val)); }
basic_string& basic_string::appendOct(u8 val) FL_NO_EXCEPT { return appendOct(static_cast<u32>(val)); }
 
// ======= OTHER =======
 
float basic_string::toFloat() const FL_NO_EXCEPT { return fl::parseFloat(c_str(), mLength); }
 
// ======= RESIZE =======
 
void basic_string::resize(fl::size count) FL_NO_EXCEPT { resize(count, char()); }
 
void basic_string::resize(fl::size count, char ch) FL_NO_EXCEPT {
    if (count < mLength) {
        mLength = count;
        c_str_mutable()[mLength] = '\0';
    } else if (count > mLength) {
        fl::size additional_chars = count - mLength;
        reserve(count);
        char* data_ptr = c_str_mutable();
        for (fl::size i = 0; i < additional_chars; ++i) {
            data_ptr[mLength + i] = ch;
        }
        mLength = count;
        data_ptr[mLength] = '\0';
    }
}
 
} // namespace fl