An API to build slices into read parts of Reader buffer.
This commit is contained in:
parent
e493e7299d
commit
892aed303f
|
@ -242,8 +242,158 @@ final class Reader
|
||||||
final Encoding encoding() @safe pure nothrow const @nogc { return encoding_; }
|
final Encoding encoding() @safe pure nothrow const @nogc { return encoding_; }
|
||||||
}
|
}
|
||||||
|
|
||||||
private:
|
|
||||||
|
|
||||||
|
/// Used to build slices of already read data in Reader buffer, avoiding allocations.
|
||||||
|
///
|
||||||
|
/// Usually these slices point to unchanged Reader data, but sometimes the data is
|
||||||
|
/// changed due to how YAML interprets certain characters/strings.
|
||||||
|
///
|
||||||
|
/// See begin() documentation.
|
||||||
|
struct SliceBuilder
|
||||||
|
{
|
||||||
|
private:
|
||||||
|
// No copying by the user.
|
||||||
|
@disable this(this);
|
||||||
|
@disable void opAssign(ref SliceBuilder);
|
||||||
|
|
||||||
|
// Reader this builder works in.
|
||||||
|
Reader reader_;
|
||||||
|
|
||||||
|
// Start of the slice om reader_.buffer_ (size_t.max while no slice being build)
|
||||||
|
size_t start_ = size_t.max;
|
||||||
|
// End of the slice om reader_.buffer_ (size_t.max while no slice being build)
|
||||||
|
size_t end_ = size_t.max;
|
||||||
|
|
||||||
|
// Stack of slice ends to revert to (see Transaction)
|
||||||
|
//
|
||||||
|
// Very few levels as we don't want arbitrarily nested transactions.
|
||||||
|
size_t[4] endStack_;
|
||||||
|
// The number of elements currently in endStack_.
|
||||||
|
size_t endStackUsed_ = 0;
|
||||||
|
|
||||||
|
@safe pure nothrow const @nogc invariant()
|
||||||
|
{
|
||||||
|
if(!inProgress) { return; }
|
||||||
|
assert(end_ <= reader_.bufferOffset_, "Slice ends after buffer position");
|
||||||
|
assert(start_ <= end_, "Slice start after slice end");
|
||||||
|
}
|
||||||
|
|
||||||
|
// Is a slice currently being built?
|
||||||
|
bool inProgress() @safe pure nothrow const @nogc
|
||||||
|
{
|
||||||
|
assert(start_ == size_t.max ? end_ == size_t.max :
|
||||||
|
end_ != size_t.max, "start_/end_ are not consistent");
|
||||||
|
return start_ != size_t.max;
|
||||||
|
}
|
||||||
|
|
||||||
|
public:
|
||||||
|
/// Begin building a slice.
|
||||||
|
///
|
||||||
|
/// Only one slice can be built at any given time; before beginning a new slice,
|
||||||
|
/// finish the previous one (if any).
|
||||||
|
///
|
||||||
|
/// The slice starts at the current position in the Reader buffer. It can only be
|
||||||
|
/// extended up to the current position in the buffer; Reader methods get() and
|
||||||
|
/// forward() move the position. E.g. it is valid to extend a slice by write()-ing
|
||||||
|
/// a string just returned by get() - but not one returned by prefix() unless the
|
||||||
|
/// position has changed since the prefix() call.
|
||||||
|
void begin() @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(!inProgress, "Beginning a slice while another slice is being built");
|
||||||
|
assert(endStackUsed_ == 0, "Slice stack not empty at slice begin");
|
||||||
|
|
||||||
|
start_ = reader_.bufferOffset_;
|
||||||
|
end_ = reader_.bufferOffset_;
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Finish building a slice and return it.
|
||||||
|
///
|
||||||
|
/// Any Transactions on the slice must be committed or destroyed before the slice
|
||||||
|
/// is finished.
|
||||||
|
dstring finish() @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(inProgress, "sliceFinish called without sliceBegin");
|
||||||
|
assert(endStackUsed_ == 0, "Finishing a slice with running transactions.");
|
||||||
|
|
||||||
|
const result = cast(dstring)reader_.buffer_[start_ .. end_];
|
||||||
|
start_ = end_ = size_t.max;
|
||||||
|
return result;
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Write a string to the slice being built.
|
||||||
|
///
|
||||||
|
/// Data can only be written up to the current position in the Reader buffer.
|
||||||
|
///
|
||||||
|
/// If str is a string returned by a Reader method, and str starts right after the
|
||||||
|
/// end of the slice being built, the slice is extended (trivial operation).
|
||||||
|
///
|
||||||
|
/// See_Also: begin
|
||||||
|
void write(dstring str) @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(inProgress, "sliceWrite called without sliceBegin");
|
||||||
|
|
||||||
|
// If str starts at the end of the slice (is a string returned by a Reader
|
||||||
|
// method), just extend the slice to contain str.
|
||||||
|
if(str.ptr == reader_.buffer_.ptr + end_)
|
||||||
|
{
|
||||||
|
end_ += str.length;
|
||||||
|
}
|
||||||
|
// Even if str does not start at the end of the slice, it still may be returned
|
||||||
|
// by a Reader method and point to buffer. So we need to memmove.
|
||||||
|
else
|
||||||
|
{
|
||||||
|
core.stdc.string.memmove(reader_.buffer_.ptr + end_, cast(dchar*)str.ptr,
|
||||||
|
str.length * dchar.sizeof);
|
||||||
|
end_ += str.length;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Write a character to the slice being built.
|
||||||
|
///
|
||||||
|
/// Data can only be written up to the current position in the Reader buffer.
|
||||||
|
///
|
||||||
|
/// See_Also: begin
|
||||||
|
void write(dchar c) @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(inProgress, "sliceWrite called without sliceBegin");
|
||||||
|
|
||||||
|
reader_.buffer_[end_++] = c;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
private:
|
||||||
|
// Push the current end of the slice so we can revert to it if needed.
|
||||||
|
//
|
||||||
|
// Used by Transaction.
|
||||||
|
void push() @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(inProgress, "slicePush called without sliceBegin");
|
||||||
|
assert(endStackUsed_ < endStack_.length, "Slice stack overflow");
|
||||||
|
endStack_[endStackUsed_++] = end_;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Pop the current end of endStack_ and set the end of the slice to the popped
|
||||||
|
// value, reverting changes since the old end was pushed.
|
||||||
|
//
|
||||||
|
// Used by Transaction.
|
||||||
|
void pop() @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(inProgress, "slicePop called without sliceBegin");
|
||||||
|
assert(endStackUsed_ > 0, "Trying to pop an empty slice stack");
|
||||||
|
end_ = endStack_[--endStackUsed_];
|
||||||
|
}
|
||||||
|
|
||||||
|
// Pop the current end of endStack_, but keep the current end of the slice, applying
|
||||||
|
// changes made since pushing the old end.
|
||||||
|
//
|
||||||
|
// Used by Transaction.
|
||||||
|
void apply() @system pure nothrow @nogc
|
||||||
|
{
|
||||||
|
assert(inProgress, "sliceApply called without sliceBegin");
|
||||||
|
assert(endStackUsed_ > 0, "Trying to apply an empty slice stack");
|
||||||
|
--endStackUsed_;
|
||||||
|
}
|
||||||
|
}
|
||||||
// Decode an UTF-8/16/32 buffer to UTF-32 (for UTF-32 this does nothing).
|
// Decode an UTF-8/16/32 buffer to UTF-32 (for UTF-32 this does nothing).
|
||||||
//
|
//
|
||||||
// Params:
|
// Params:
|
||||||
|
|
Loading…
Reference in a new issue