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cleanup emplace code in Appender #1684

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67a3199
cleanup emplace code in Appender
monarchdodra Nov 8, 2013
50f49a5
Chnage capacity/length in Appender
monarchdodra Nov 10, 2013
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118 changes: 44 additions & 74 deletions std/array.d
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Original file line number Diff line number Diff line change
Expand Up @@ -2113,8 +2113,9 @@ struct Appender(A : T[], T)
{
private struct Data
{
size_t capacity;
// arr is as long as its capacity.
Unqual!T[] arr;
size_t length;
}

private Data* _data;
Expand All @@ -2127,9 +2128,12 @@ struct Appender(A : T[], T)
*/
this(Unqual!T[] arr) @safe pure nothrow
{
// initialize to a given array.
// intialize Data
_data = new Data;

// initialize to a given array.
_data.arr = arr;
_data.length = arr.length;

if (__ctfe)
return;
Expand All @@ -2142,7 +2146,6 @@ struct Appender(A : T[], T)
arr = ()@trusted{ return arr.ptr[0 .. cap]; }();
// we assume no reallocation occurred
assert(arr.ptr is _data.arr.ptr);
_data.capacity = arr.length;
}

/**
Expand All @@ -2154,7 +2157,7 @@ struct Appender(A : T[], T)
{
if (_data)
{
if (newCapacity > _data.capacity)
if (newCapacity > _data.arr.length)
ensureAddable(newCapacity - _data.arr.length);
}
else
Expand All @@ -2170,7 +2173,7 @@ struct Appender(A : T[], T)
*/
@property size_t capacity() const @safe pure nothrow
{
return _data ? _data.capacity : 0;
return _data ? _data.arr.length : 0;
}

/**
Expand All @@ -2181,62 +2184,62 @@ struct Appender(A : T[], T)
/* @trusted operation:
* casting Unqual!T[] to inout(T)[]
*/
return cast(typeof(return))(_data ? _data.arr : null);
return cast(typeof(return))(_data ? _data.arr[0 .. _data.length] : null);
}

// ensure we can add nelems elements, resizing as necessary
private void ensureAddable(size_t nelems) @safe pure nothrow
{
if (!_data)
_data = new Data;
immutable len = _data.arr.length;
immutable reqlen = len + nelems;

if (()@trusted{ return _data.capacity; }() >= reqlen)
immutable len = _data.length;
immutable cap = _data.arr.length;
immutable reqcap = len + nelems;

if (cap >= reqcap)
return;

// need to increase capacity
if (__ctfe)
{
static if (__traits(compiles, new Unqual!T[1]))
{
_data.arr.length = reqlen;
_data.arr.length = reqcap;
}
else
{
// avoid restriction of @disable this()
()@trusted{ _data.arr = _data.arr[0 .. _data.capacity]; }();
foreach (i; _data.capacity .. reqlen)
foreach (i; cap .. reqcap)
_data.arr ~= Unqual!T.init;
}
_data.arr = _data.arr[0 .. len];
_data.capacity = reqlen;
}
else
{
// Time to reallocate.
// We need to almost duplicate what's in druntime, except we
// have better access to the capacity field.
auto newlen = appenderNewCapacity!(T.sizeof)(_data.capacity, reqlen);
auto newcap = appenderNewCapacity!(T.sizeof)(cap, reqcap);
// first, try extending the current block
auto u = ()@trusted{ return
GC.extend(_data.arr.ptr, nelems * T.sizeof, (newlen - len) * T.sizeof);
GC.extend(_data.arr.ptr, (reqcap - cap) * T.sizeof, (newcap - cap) * T.sizeof);
}();
if (u)
{
// extend worked, update the capacity
_data.capacity = u / T.sizeof;
// extend worked, update the array
()@trusted{ _data.arr = _data.arr.ptr[0 .. u / T.sizeof]; }();
}
else
{
// didn't work, must reallocate
auto bi = ()@trusted{ return
GC.qalloc(newlen * T.sizeof, (typeid(T[]).next.flags & 1) ? 0 : GC.BlkAttr.NO_SCAN);
GC.qalloc(newcap * T.sizeof, (typeid(T[]).next.flags & 1) ? 0 : GC.BlkAttr.NO_SCAN);
}();
_data.capacity = bi.size / T.sizeof;
if (len)
()@trusted{ memcpy(bi.base, _data.arr.ptr, len * T.sizeof); }();
_data.arr = ()@trusted{ return (cast(Unqual!T*)bi.base)[0 .. len]; }();
()@trusted{
_data.arr = (cast(Unqual!T*)bi.base)[0 .. bi.size / T.sizeof];
}();
// leave the old data, for safety reasons
}
}
Expand Down Expand Up @@ -2279,31 +2282,15 @@ struct Appender(A : T[], T)
else
{
ensureAddable(1);
immutable len = _data.arr.length;
immutable len = _data.length;

auto bigDataFun() @trusted nothrow { return _data.arr.ptr[0 .. len + 1];}
auto bigData = bigDataFun();

static if (is(Unqual!T == T))
alias uitem = item;
static if (is(U : Unqual!T))
emplace(&_data.arr[len], item);
else
auto ref uitem() @trusted nothrow @property { return cast(Unqual!T)item;}

//The idea is to only call emplace if we must.
static if ( is(typeof(bigData[0].opAssign(uitem))) ||
!is(typeof(bigData[0] = uitem)))
{
//pragma(msg, T.stringof); pragma(msg, U.stringof);
emplace(&bigData[len], uitem);
}
else
{
//pragma(msg, T.stringof); pragma(msg, U.stringof);
bigData[len] = uitem;
}
emplace(&_data.arr[len], cast(Unqual!T)item);

//We do this at the end, in case of exceptions
_data.arr = bigData;
++_data.length;
}
}

Expand All @@ -2323,7 +2310,7 @@ struct Appender(A : T[], T)
// another because we can't trust the length portion.
static if (!(isSomeChar!T && isSomeChar!(ElementType!Range) &&
!is(immutable Range == immutable T[])) &&
is(typeof(items.length) == size_t))
(hasLength!Range || isSomeString!Range))
{
// optimization -- if this type is something other than a string,
// and we are adding exactly one element, call the version for one
Expand All @@ -2338,47 +2325,30 @@ struct Appender(A : T[], T)
}

// make sure we have enough space, then add the items
ensureAddable(items.length);
immutable len = _data.arr.length;
immutable newlen = len + items.length;

auto bigDataFun() @trusted nothrow { return _data.arr.ptr[0 .. newlen];}
auto bigData = bigDataFun();
immutable itemslen = items.length;
ensureAddable(itemslen);

enum mustEmplace = is(typeof(bigData[0].opAssign(cast(Unqual!T)items.front))) ||
!is(typeof(bigData[0] = cast(Unqual!T)items.front));
immutable len = _data.length;
immutable newlen = len + itemslen;

static if (is(typeof(_data.arr[] = items[])) && !mustEmplace)
{
//pragma(msg, T.stringof); pragma(msg, Range.stringof);
bigData[len .. newlen] = items[];
}
else static if (is(Unqual!T == ElementType!Range))
static if (is(typeof(_data.arr[] = items[])) && !hasElaborateAssign!(Unqual!T) )
{
foreach (ref it ; bigData[len .. newlen])
{
static if (mustEmplace)
emplace(&it, items.front);
else
it = items.front;
items.popFront();
}
_data.arr[len .. newlen] = items[];
}
else
{
static auto ref getUItem(U)(U item) @trusted {return cast(Unqual!T)item;}
foreach (ref it ; bigData[len .. newlen])
foreach (size_t i ; len .. newlen)
{
static if (mustEmplace)
emplace(&it, getUItem(items.front));
static if (is(U : Unqual!T))
emplace(&_data.arr[i], items.front);
else
it = getUItem(items.front);
emplace(&_data.arr[i], cast(Unqual!T)items.front);
items.popFront();
}
}

//We do this at the end, in case of exceptions
_data.arr = bigData;
_data.length = newlen;
}
else
{
Expand Down Expand Up @@ -2427,7 +2397,7 @@ struct Appender(A : T[], T)
{
if (_data)
{
_data.arr = ()@trusted{ return _data.arr.ptr[0 .. 0]; }();
_data.length = 0;
}
}

Expand All @@ -2440,8 +2410,8 @@ struct Appender(A : T[], T)
{
if (_data)
{
enforce(newlength <= _data.arr.length);
_data.arr = ()@trusted{ return _data.arr.ptr[0 .. newlength]; }();
enforce(newlength <= _data.length);
_data.length = newlength;
}
else
enforce(newlength == 0);
Expand Down