PackedString

String packed into one word.

Length is stored in upper lengthBits of pointer/word _raw.

All length bits set means memory bits of _raw points to string. This makes PackedString nothrow.

TODO: If D's GC doesn't ignore the upper lengthBits bits of pointer, make core.memory.GC be told that every PackedString should be bit-anded with addressMask before scanned for an address. Related functions: - isLarge.

Proposed API for specifying this is: `__traits(adressBitMask, declaration, mask) where declaration.sizeof == size_t.sizeof`.

@safe

struct PackedString {

enum size_t lengthMask;

enum size_t addressMask;

alias Large = immutable(char)[];

this(string x);

bool isLarge [@property getter];

immutable(char)* ptr();

size_t length();

string opSlice();

void toString(Sink sink);

}

Constructors

this this(string x): Undocumented in source.

Alias This

opSlice

Members

Aliases

Large alias Large = immutable(char)[]: Undocumented in source.

Functions

length size_t length(): Get length.
opSlice string opSlice(): Get slice.
ptr immutable(char)* ptr(): Get pointer to characters.
toString void toString(Sink sink): Undocumented in source. Be warned that the author may not have intended to support it.

Manifest constants

addressBits enum addressBits;: Number of bits used to memory address.
lengthBits enum lengthBits;: Number of bits used to store length. 2024-01-01: Address space of a single Linux user process is 47 bits.
smallCapacity enum smallCapacity;: Capacity of small variant where length fits in lengthBits.
totalBits enum totalBits;: Undocumented in source.

Properties

isLarge bool isLarge [@property getter]

Variables

addressMask enum size_t addressMask;: Bit mask of address part.
lengthMask enum size_t lengthMask;: Bit mask of length part.

Examples

const s = "alpha";
PackedString p = s;
assert(p.ptr == s.ptr);
assert(p.length == s.length);
assert(p[] == s);
assert(p == s);

string s;
s.length = PackedString.smallCapacity;
PackedString p = s;
assert(p.ptr == s.ptr);
assert(p.length == s.length);
assert(p[] == s);
assert(p == s);
assert(p is s);