source: tests/collections/string-ctx-manage.cfa

#include <string.hfa>
#include <string_sharectx.hfa>
#include <string_res.hfa>

// In these tests, shared heaps are never remotely full and string sizes are tiny.
// So here, the SUT should put a yes-sharing string in a heap with lots of spare room.
// The SUT should always keep a no-sharing string's buffer 1x--2x the string's size.
// This check uses 3x as a heuristic split between those cases.
void assertSpareRoomInHeap( string & s, bool expectOversized ) {
    double bytesInHeap = DEBUG_string_bytes_in_heap(s.inner->Handle.ulink);
    double bytesUsed =  s.inner->Handle.lnth;
    double overhead = bytesInHeap / bytesUsed;
    assert (overhead >= 1);
    if ( expectOversized )
        assert( overhead >= 3.0 );
    else 
        assert( overhead < 3.0 );
}

void baseline() {
    string x = "hi";
    assertSpareRoomInHeap( x, true );

    string y = x; // construct y in same context, no write yet => no copy yet
    assertSpareRoomInHeap( y, true );
    assert( y.inner->Handle.s == x.inner->Handle.s);
    sout | y; // hi

    x = "bye";
    assertSpareRoomInHeap( x, true );
    y = x; // y in same context, no write yet => no copy yet
    assertSpareRoomInHeap( y, true );
    assert( y.inner->Handle.s == x.inner->Handle.s);
    sout | y; // bye
}

void eagerCopy() {
    string x = "hi";
    assertSpareRoomInHeap( x, true );
    string_sharectx c = { NEW_SHARING };

    string y = x; // construct y in different context => eager copy
    assertSpareRoomInHeap( y, true );
    assert( y.inner->Handle.s != x.inner->Handle.s);
    sout | y; // hi

    x = "bye";
    assertSpareRoomInHeap( x, true );
    y = x; // y was already in different context => eager copy
    assertSpareRoomInHeap( y, true );
    assert( y.inner->Handle.s != x.inner->Handle.s);
    sout | y; // bye
}

void soloAlloc() {
    string x = "hi";
    assertSpareRoomInHeap( x, true );
    string_sharectx c = { NO_SHARING };
    
    string y = x; // y allocates into private pad, implying eager copy
    assertSpareRoomInHeap( y, false );
    assert( y.inner->Handle.s != x.inner->Handle.s);
    sout | y; // hi

    x = "bye";
    assertSpareRoomInHeap( x, true );
    y = x; // into private y => eager copy
    assertSpareRoomInHeap( y, false );
    assert( y.inner->Handle.s != x.inner->Handle.s);
    sout | y; // bye
}


int main() {
    baseline();
    eagerCopy();
    soloAlloc();
    printf("done\n");
}