[cfe-commits] r49689 - in /cfe/trunk: include/clang/Rewrite/RewriteRope.h lib/Rewrite/RewriteRope.cpp
Chris Lattner
sabre at nondot.org
Mon Apr 14 14:41:02 PDT 2008
Author: lattner
Date: Mon Apr 14 16:41:00 2008
New Revision: 49689
URL: http://llvm.org/viewvc/llvm-project?rev=49689&view=rev
Log:
Add a bunch of comments, move RewriteRope::MakeRopeString out of line.
Modified:
cfe/trunk/include/clang/Rewrite/RewriteRope.h
cfe/trunk/lib/Rewrite/RewriteRope.cpp
Modified: cfe/trunk/include/clang/Rewrite/RewriteRope.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Rewrite/RewriteRope.h?rev=49689&r1=49688&r2=49689&view=diff
==============================================================================
--- cfe/trunk/include/clang/Rewrite/RewriteRope.h (original)
+++ cfe/trunk/include/clang/Rewrite/RewriteRope.h Mon Apr 14 16:41:00 2008
@@ -22,7 +22,10 @@
// RopeRefCountString Class
//===--------------------------------------------------------------------===//
- /// RopeRefCountString
+ /// RopeRefCountString - This struct is allocated with 'new char[]' from the
+ /// heap, and represents a reference counted chunk of string data. When its
+ /// ref count drops to zero, it is delete[]'d. This is primarily managed
+ /// through the RopePiece class below.
struct RopeRefCountString {
unsigned RefCount;
char Data[1]; // Variable sized.
@@ -41,6 +44,14 @@
// RopePiece Class
//===--------------------------------------------------------------------===//
+ /// RopePiece - This class represents a view into a RopeRefCountString object.
+ /// This allows references to string data to be efficiently chopped up and
+ /// moved around without having to push around the string data itself.
+ ///
+ /// For example, we could have a 1M RopePiece and want to insert something
+ /// into the middle of it. To do this, we split it into two RopePiece objects
+ /// that both refer to the same underlying RopeRefCountString (just with
+ /// different offsets) which is a nice constant time operation.
struct RopePiece {
RopeRefCountString *StrData;
unsigned StartOffs;
@@ -49,11 +60,11 @@
RopePiece() : StrData(0), StartOffs(0), EndOffs(0) {}
RopePiece(RopeRefCountString *Str, unsigned Start, unsigned End)
- : StrData(Str), StartOffs(Start), EndOffs(End) {
+ : StrData(Str), StartOffs(Start), EndOffs(End) {
StrData->addRef();
}
RopePiece(const RopePiece &RP)
- : StrData(RP.StrData), StartOffs(RP.StartOffs), EndOffs(RP.EndOffs) {
+ : StrData(RP.StrData), StartOffs(RP.StartOffs), EndOffs(RP.EndOffs) {
StrData->addRef();
}
@@ -85,7 +96,10 @@
// RopePieceBTreeIterator Class
//===--------------------------------------------------------------------===//
- /// RopePieceBTreeIterator - Provide read-only forward iteration.
+ /// RopePieceBTreeIterator - This class provides read-only forward iteration
+ /// over bytes that are in a RopePieceBTree. This first iterates over bytes
+ /// in a RopePiece, then iterates over RopePiece's in a RopePieceBTreeLeaf,
+ /// then iterates over RopePieceBTreeLeaf's in a RopePieceBTree.
class RopePieceBTreeIterator :
public forward_iterator<const char, ptrdiff_t> {
/// CurNode - The current B+Tree node that we are inspecting.
@@ -95,7 +109,6 @@
const RopePiece *CurPiece;
/// CurChar - The current byte in the RopePiece we are pointing to.
unsigned CurChar;
- friend class RewriteRope;
public:
// begin iterator.
RopePieceBTreeIterator(const void /*RopePieceBTreeNode*/ *N);
@@ -120,11 +133,9 @@
MoveToNextPiece();
return *this;
}
-
inline RopePieceBTreeIterator operator++(int) { // Postincrement
RopePieceBTreeIterator tmp = *this; ++*this; return tmp;
}
-
private:
void MoveToNextPiece();
};
@@ -158,7 +169,9 @@
// RewriteRope Class
//===--------------------------------------------------------------------===//
-/// RewriteRope - A powerful string class, todo generalize this.
+/// RewriteRope - A powerful string class. This class supports extremely
+/// efficient insertions and deletions into the middle of it, even for
+/// ridiculously long strings.
class RewriteRope {
RopePieceBTree Chunks;
@@ -205,45 +218,7 @@
}
private:
- RopePiece MakeRopeString(const char *Start, const char *End) {
- unsigned Len = End-Start;
-
- // If we have space for this string in the current alloc buffer, use it.
- if (AllocOffs+Len <= AllocChunkSize) {
- memcpy(AllocBuffer->Data+AllocOffs, Start, Len);
- AllocOffs += Len;
- return RopePiece(AllocBuffer, AllocOffs-Len, AllocOffs);
- }
-
- // If we don't have enough room because this specific allocation is huge,
- // just allocate a new rope piece for it alone.
- if (Len > AllocChunkSize) {
- unsigned Size = End-Start+sizeof(RopeRefCountString)-1;
- RopeRefCountString *Res =
- reinterpret_cast<RopeRefCountString *>(new char[Size]);
- Res->RefCount = 0;
- memcpy(Res->Data, Start, End-Start);
- return RopePiece(Res, 0, End-Start);
- }
-
- // Otherwise, this was a small request but we just don't have space for it
- // Make a new chunk and share it with later allocations.
-
- // If we had an old allocation, drop our reference to it.
- if (AllocBuffer && --AllocBuffer->RefCount == 0)
- delete [] (char*)AllocBuffer;
-
- unsigned AllocSize = sizeof(RopeRefCountString)-1+AllocChunkSize;
- AllocBuffer = reinterpret_cast<RopeRefCountString *>(new char[AllocSize]);
- AllocBuffer->RefCount = 0;
- memcpy(AllocBuffer->Data, Start, Len);
- AllocOffs = Len;
-
- // Start out the new allocation with a refcount of 1, since we have an
- // internal reference to it.
- AllocBuffer->addRef();
- return RopePiece(AllocBuffer, 0, Len);
- }
+ RopePiece MakeRopeString(const char *Start, const char *End);
};
} // end namespace clang
Modified: cfe/trunk/lib/Rewrite/RewriteRope.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Rewrite/RewriteRope.cpp?rev=49689&r1=49688&r2=49689&view=diff
==============================================================================
--- cfe/trunk/lib/Rewrite/RewriteRope.cpp (original)
+++ cfe/trunk/lib/Rewrite/RewriteRope.cpp Mon Apr 14 16:41:00 2008
@@ -13,6 +13,7 @@
#include "clang/Rewrite/RewriteRope.h"
#include "llvm/Support/Casting.h"
+#include <algorithm>
using namespace clang;
using llvm::dyn_cast;
using llvm::cast;
@@ -670,3 +671,49 @@
// #2. Do the erasing.
getRoot(Root)->erase(Offset, NumBytes);
}
+
+//===----------------------------------------------------------------------===//
+// RewriteRope Implementation
+//===----------------------------------------------------------------------===//
+
+RopePiece RewriteRope::MakeRopeString(const char *Start, const char *End) {
+ unsigned Len = End-Start;
+
+ // If we have space for this string in the current alloc buffer, use it.
+ if (AllocOffs+Len <= AllocChunkSize) {
+ memcpy(AllocBuffer->Data+AllocOffs, Start, Len);
+ AllocOffs += Len;
+ return RopePiece(AllocBuffer, AllocOffs-Len, AllocOffs);
+ }
+
+ // If we don't have enough room because this specific allocation is huge,
+ // just allocate a new rope piece for it alone.
+ if (Len > AllocChunkSize) {
+ unsigned Size = End-Start+sizeof(RopeRefCountString)-1;
+ RopeRefCountString *Res =
+ reinterpret_cast<RopeRefCountString *>(new char[Size]);
+ Res->RefCount = 0;
+ memcpy(Res->Data, Start, End-Start);
+ return RopePiece(Res, 0, End-Start);
+ }
+
+ // Otherwise, this was a small request but we just don't have space for it
+ // Make a new chunk and share it with later allocations.
+
+ // If we had an old allocation, drop our reference to it.
+ if (AllocBuffer && --AllocBuffer->RefCount == 0)
+ delete [] (char*)AllocBuffer;
+
+ unsigned AllocSize = sizeof(RopeRefCountString)-1+AllocChunkSize;
+ AllocBuffer = reinterpret_cast<RopeRefCountString *>(new char[AllocSize]);
+ AllocBuffer->RefCount = 0;
+ memcpy(AllocBuffer->Data, Start, Len);
+ AllocOffs = Len;
+
+ // Start out the new allocation with a refcount of 1, since we have an
+ // internal reference to it.
+ AllocBuffer->addRef();
+ return RopePiece(AllocBuffer, 0, Len);
+}
+
+
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