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third-party/scintilla/Partitioning.h

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+// Scintilla source code edit control
+/** @file Partitioning.h
+ ** Data structure used to partition an interval. Used for holding line start/end positions.
+ **/
+// Copyright 1998-2007 by Neil Hodgson <neilh@scintilla.org>
+// The License.txt file describes the conditions under which this software may be distributed.
+
+#ifndef PARTITIONING_H
+#define PARTITIONING_H
+
+#ifdef SCI_NAMESPACE
+namespace Scintilla {
+#endif
+
+/// A split vector of integers with a method for adding a value to all elements
+/// in a range.
+/// Used by the Partitioning class.
+
+class SplitVectorWithRangeAdd : public SplitVector<int> {
+public:
+	explicit SplitVectorWithRangeAdd(int growSize_) {
+		SetGrowSize(growSize_);
+		ReAllocate(growSize_);
+	}
+	~SplitVectorWithRangeAdd() {
+	}
+	void RangeAddDelta(int start, int end, int delta) {
+		// end is 1 past end, so end-start is number of elements to change
+		int i = 0;
+		int rangeLength = end - start;
+		int range1Length = rangeLength;
+		int part1Left = part1Length - start;
+		if (range1Length > part1Left)
+			range1Length = part1Left;
+		while (i < range1Length) {
+			body[start++] += delta;
+			i++;
+		}
+		start += gapLength;
+		while (i < rangeLength) {
+			body[start++] += delta;
+			i++;
+		}
+	}
+};
+
+/// Divide an interval into multiple partitions.
+/// Useful for breaking a document down into sections such as lines.
+/// A 0 length interval has a single 0 length partition, numbered 0
+/// If interval not 0 length then each partition non-zero length
+/// When needed, positions after the interval are considered part of the last partition
+/// but the end of the last partition can be found with PositionFromPartition(last+1).
+
+class Partitioning {
+private:
+	// To avoid calculating all the partition positions whenever any text is inserted
+	// there may be a step somewhere in the list.
+	int stepPartition;
+	int stepLength;
+	SplitVectorWithRangeAdd *body;
+
+	// Move step forward
+	void ApplyStep(int partitionUpTo) {
+		if (stepLength != 0) {
+			body->RangeAddDelta(stepPartition+1, partitionUpTo + 1, stepLength);
+		}
+		stepPartition = partitionUpTo;
+		if (stepPartition >= body->Length()-1) {
+			stepPartition = body->Length()-1;
+			stepLength = 0;
+		}
+	}
+
+	// Move step backward
+	void BackStep(int partitionDownTo) {
+		if (stepLength != 0) {
+			body->RangeAddDelta(partitionDownTo+1, stepPartition+1, -stepLength);
+		}
+		stepPartition = partitionDownTo;
+	}
+
+	void Allocate(int growSize) {
+		body = new SplitVectorWithRangeAdd(growSize);
+		stepPartition = 0;
+		stepLength = 0;
+		body->Insert(0, 0);	// This value stays 0 for ever
+		body->Insert(1, 0);	// This is the end of the first partition and will be the start of the second
+	}
+	
+	// no copy ctr or assignment op
+	Partitioning(const Partitioning &);
+	Partitioning &operator =(const Partitioning &);
+
+public:
+	explicit Partitioning(int growSize) {
+		Allocate(growSize);
+	}
+
+	~Partitioning() {
+		delete body;
+		body = 0;
+	}
+
+	int Partitions() const {
+		return body->Length()-1;
+	}
+
+	void InsertPartition(int partition, int pos) {
+		if (stepPartition < partition) {
+			ApplyStep(partition);
+		}
+		body->Insert(partition, pos);
+		stepPartition++;
+	}
+
+	void SetPartitionStartPosition(int partition, int pos) {
+		ApplyStep(partition+1);
+		if ((partition < 0) || (partition > body->Length())) {
+			return;
+		}
+		body->SetValueAt(partition, pos);
+	}
+
+	void InsertText(int partitionInsert, int delta) {
+		// Point all the partitions after the insertion point further along in the buffer
+		if (stepLength != 0) {
+			if (partitionInsert >= stepPartition) {
+				// Fill in up to the new insertion point
+				ApplyStep(partitionInsert);
+				stepLength += delta;
+			} else if (partitionInsert >= (stepPartition - body->Length() / 10)) {
+				// Close to step but before so move step back
+				BackStep(partitionInsert);
+				stepLength += delta;
+			} else {
+				ApplyStep(body->Length()-1);
+				stepPartition = partitionInsert;
+				stepLength = delta;
+			}
+		} else {
+			stepPartition = partitionInsert;
+			stepLength = delta;
+		}
+	}
+
+	void RemovePartition(int partition) {
+		if (partition > stepPartition) {
+			ApplyStep(partition);
+			stepPartition--;
+		} else {
+			stepPartition--;
+		}
+		body->Delete(partition);
+	}
+
+	int PositionFromPartition(int partition) const {
+		PLATFORM_ASSERT(partition >= 0);
+		PLATFORM_ASSERT(partition < body->Length());
+		if ((partition < 0) || (partition >= body->Length())) {
+			return 0;
+		}
+		int pos = body->ValueAt(partition);
+		if (partition > stepPartition)
+			pos += stepLength;
+		return pos;
+	}
+
+	/// Return value in range [0 .. Partitions() - 1] even for arguments outside interval
+	int PartitionFromPosition(int pos) const {
+		if (body->Length() <= 1)
+			return 0;
+		if (pos >= (PositionFromPartition(body->Length()-1)))
+			return body->Length() - 1 - 1;
+		int lower = 0;
+		int upper = body->Length()-1;
+		do {
+			int middle = (upper + lower + 1) / 2; 	// Round high
+			int posMiddle = body->ValueAt(middle);
+			if (middle > stepPartition)
+				posMiddle += stepLength;
+			if (pos < posMiddle) {
+				upper = middle - 1;
+			} else {
+				lower = middle;
+			}
+		} while (lower < upper);
+		return lower;
+	}
+
+	void DeleteAll() {
+		int growSize = body->GetGrowSize();
+		delete body;
+		Allocate(growSize);
+	}
+};
+
+
+#ifdef SCI_NAMESPACE
+}
+#endif
+
+#endif