Mega Code Archive
Bare-bones, unsafe, fast string buffer
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: FastStringBuffer.java 469279 2006-10-30 21:18:02Z minchau $
*/
/**
* Bare-bones, unsafe, fast string buffer. No thread-safety, no
* parameter range checking, exposed fields. Note that in typical
* applications, thread-safety of a StringBuffer is a somewhat
* dubious concept in any case.
* <p>
* Note that Stree and DTM used a single FastStringBuffer as a string pool,
* by recording start and length indices within this single buffer. This
* minimizes heap overhead, but of course requires more work when retrieving
* the data.
* <p>
* FastStringBuffer operates as a "chunked buffer". Doing so
* reduces the need to recopy existing information when an append
* exceeds the space available; we just allocate another chunk and
* flow across to it. (The array of chunks may need to grow,
* admittedly, but that's a much smaller object.) Some excess
* recopying may arise when we extract Strings which cross chunk
* boundaries; larger chunks make that less frequent.
* <p>
* The size values are parameterized, to allow tuning this code. In
* theory, Result Tree Fragments might want to be tuned differently
* from the main document's text.
* <p>
* %REVIEW% An experiment in self-tuning is
* included in the code (using nested FastStringBuffers to achieve
* variation in chunk sizes), but this implementation has proven to
* be problematic when data may be being copied from the FSB into itself.
* We should either re-architect that to make this safe (if possible)
* or remove that code and clean up for performance/maintainability reasons.
* <p>
*/
public class FastStringBuffer
{
// If nonzero, forces the inial chunk size.
/**/static final int DEBUG_FORCE_INIT_BITS=0;
// %BUG% %REVIEW% *****PROBLEM SUSPECTED: If data from an FSB is being copied
// back into the same FSB (variable set from previous variable, for example)
// and blocksize changes in mid-copy... there's risk of severe malfunction in
// the read process, due to how the resizing code re-jiggers storage. Arggh.
// If we want to retain the variable-size-block feature, we need to reconsider
// that issue. For now, I have forced us into fixed-size mode.
static final boolean DEBUG_FORCE_FIXED_CHUNKSIZE=true;
/** Manifest constant: Suppress leading whitespace.
* This should be used when normalize-to-SAX is called for the first chunk of a
* multi-chunk output, or one following unsuppressed whitespace in a previous
* chunk.
* @see #sendNormalizedSAXcharacters(org.xml.sax.ContentHandler,int,int)
*/
public static final int SUPPRESS_LEADING_WS=0x01;
/** Manifest constant: Suppress trailing whitespace.
* This should be used when normalize-to-SAX is called for the last chunk of a
* multi-chunk output; it may have to be or'ed with SUPPRESS_LEADING_WS.
*/
public static final int SUPPRESS_TRAILING_WS=0x02;
/** Manifest constant: Suppress both leading and trailing whitespace.
* This should be used when normalize-to-SAX is called for a complete string.
* (I'm not wild about the name of this one. Ideas welcome.)
* @see #sendNormalizedSAXcharacters(org.xml.sax.ContentHandler,int,int)
*/
public static final int SUPPRESS_BOTH
= SUPPRESS_LEADING_WS | SUPPRESS_TRAILING_WS;
/** Manifest constant: Carry trailing whitespace of one chunk as leading
* whitespace of the next chunk. Used internally; I don't see any reason
* to make it public right now.
*/
private static final int CARRY_WS=0x04;
/**
* Field m_chunkBits sets our chunking strategy, by saying how many
* bits of index can be used within a single chunk before flowing over
* to the next chunk. For example, if m_chunkbits is set to 15, each
* chunk can contain up to 2^15 (32K) characters
*/
int m_chunkBits = 15;
/**
* Field m_maxChunkBits affects our chunk-growth strategy, by saying what
* the largest permissible chunk size is in this particular FastStringBuffer
* hierarchy.
*/
int m_maxChunkBits = 15;
/**
* Field m_rechunkBits affects our chunk-growth strategy, by saying how
* many chunks should be allocated at one size before we encapsulate them
* into the first chunk of the next size up. For example, if m_rechunkBits
* is set to 3, then after 8 chunks at a given size we will rebundle
* them as the first element of a FastStringBuffer using a chunk size
* 8 times larger (chunkBits shifted left three bits).
*/
int m_rebundleBits = 2;
/**
* Field m_chunkSize establishes the maximum size of one chunk of the array
* as 2**chunkbits characters.
* (Which may also be the minimum size if we aren't tuning for storage)
*/
int m_chunkSize; // =1<<(m_chunkBits-1);
/**
* Field m_chunkMask is m_chunkSize-1 -- in other words, m_chunkBits
* worth of low-order '1' bits, useful for shift-and-mask addressing
* within the chunks.
*/
int m_chunkMask; // =m_chunkSize-1;
/**
* Field m_array holds the string buffer's text contents, using an
* array-of-arrays. Note that this array, and the arrays it contains, may be
* reallocated when necessary in order to allow the buffer to grow;
* references to them should be considered to be invalidated after any
* append. However, the only time these arrays are directly exposed
* is in the sendSAXcharacters call.
*/
char[][] m_array;
/**
* Field m_lastChunk is an index into m_array[], pointing to the last
* chunk of the Chunked Array currently in use. Note that additional
* chunks may actually be allocated, eg if the FastStringBuffer had
* previously been truncated or if someone issued an ensureSpace request.
* <p>
* The insertion point for append operations is addressed by the combination
* of m_lastChunk and m_firstFree.
*/
int m_lastChunk = 0;
/**
* Field m_firstFree is an index into m_array[m_lastChunk][], pointing to
* the first character in the Chunked Array which is not part of the
* FastStringBuffer's current content. Since m_array[][] is zero-based,
* the length of that content can be calculated as
* (m_lastChunk<<m_chunkBits) + m_firstFree
*/
int m_firstFree = 0;
/**
* Field m_innerFSB, when non-null, is a FastStringBuffer whose total
* length equals m_chunkSize, and which replaces m_array[0]. This allows
* building a hierarchy of FastStringBuffers, where early appends use
* a smaller chunkSize (for less wasted memory overhead) but later
* ones use a larger chunkSize (for less heap activity overhead).
*/
FastStringBuffer m_innerFSB = null;
/**
* Construct a FastStringBuffer, with allocation policy as per parameters.
* <p>
* For coding convenience, I've expressed both allocation sizes in terms of
* a number of bits. That's needed for the final size of a chunk,
* to permit fast and efficient shift-and-mask addressing. It's less critical
* for the inital size, and may be reconsidered.
* <p>
* An alternative would be to accept integer sizes and round to powers of two;
* that really doesn't seem to buy us much, if anything.
*
* @param initChunkBits Length in characters of the initial allocation
* of a chunk, expressed in log-base-2. (That is, 10 means allocate 1024
* characters.) Later chunks will use larger allocation units, to trade off
* allocation speed of large document against storage efficiency of small
* ones.
* @param maxChunkBits Number of character-offset bits that should be used for
* addressing within a chunk. Maximum length of a chunk is 2^chunkBits
* characters.
* @param rebundleBits Number of character-offset bits that addressing should
* advance before we attempt to take a step from initChunkBits to maxChunkBits
*/
public FastStringBuffer(int initChunkBits, int maxChunkBits,
int rebundleBits)
{
if(DEBUG_FORCE_INIT_BITS!=0) initChunkBits=DEBUG_FORCE_INIT_BITS;
// %REVIEW%
// Should this force to larger value, or smaller? Smaller less efficient, but if
// someone requested variable mode it's because they care about storage space.
// On the other hand, given the other changes I'm making, odds are that we should
// adopt the larger size. Dither, dither, dither... This is just stopgap workaround
// anyway; we need a permanant solution.
//
if(DEBUG_FORCE_FIXED_CHUNKSIZE) maxChunkBits=initChunkBits;
//if(DEBUG_FORCE_FIXED_CHUNKSIZE) initChunkBits=maxChunkBits;
m_array = new char[16][];
// Don't bite off more than we're prepared to swallow!
if (initChunkBits > maxChunkBits)
initChunkBits = maxChunkBits;
m_chunkBits = initChunkBits;
m_maxChunkBits = maxChunkBits;
m_rebundleBits = rebundleBits;
m_chunkSize = 1 << (initChunkBits);
m_chunkMask = m_chunkSize - 1;
m_array[0] = new char[m_chunkSize];
}
/**
* Construct a FastStringBuffer, using a default rebundleBits value.
*
* NEEDSDOC @param initChunkBits
* NEEDSDOC @param maxChunkBits
*/
public FastStringBuffer(int initChunkBits, int maxChunkBits)
{
this(initChunkBits, maxChunkBits, 2);
}
/**
* Construct a FastStringBuffer, using default maxChunkBits and
* rebundleBits values.
* <p>
* ISSUE: Should this call assert initial size, or fixed size?
* Now configured as initial, with a default for fixed.
*
* NEEDSDOC @param initChunkBits
*/
public FastStringBuffer(int initChunkBits)
{
this(initChunkBits, 15, 2);
}
/**
* Construct a FastStringBuffer, using a default allocation policy.
*/
public FastStringBuffer()
{
// 10 bits is 1K. 15 bits is 32K. Remember that these are character
// counts, so actual memory allocation unit is doubled for UTF-16 chars.
//
// For reference: In the original FastStringBuffer, we simply
// overallocated by blocksize (default 1KB) on each buffer-growth.
this(10, 15, 2);
}
/**
* Get the length of the list. Synonym for length().
*
* @return the number of characters in the FastStringBuffer's content.
*/
public final int size()
{
return (m_lastChunk << m_chunkBits) + m_firstFree;
}
/**
* Get the length of the list. Synonym for size().
*
* @return the number of characters in the FastStringBuffer's content.
*/
public final int length()
{
return (m_lastChunk << m_chunkBits) + m_firstFree;
}
/**
* Discard the content of the FastStringBuffer, and most of the memory
* that was allocated by it, restoring the initial state. Note that this
* may eventually be different from setLength(0), which see.
*/
public final void reset()
{
m_lastChunk = 0;
m_firstFree = 0;
// Recover the original chunk size
FastStringBuffer innermost = this;
while (innermost.m_innerFSB != null)
{
innermost = innermost.m_innerFSB;
}
m_chunkBits = innermost.m_chunkBits;
m_chunkSize = innermost.m_chunkSize;
m_chunkMask = innermost.m_chunkMask;
// Discard the hierarchy
m_innerFSB = null;
m_array = new char[16][0];
m_array[0] = new char[m_chunkSize];
}
/**
* Directly set how much of the FastStringBuffer's storage is to be
* considered part of its content. This is a fast but hazardous
* operation. It is not protected against negative values, or values
* greater than the amount of storage currently available... and even
* if additional storage does exist, its contents are unpredictable.
* The only safe use for our setLength() is to truncate the FastStringBuffer
* to a shorter string.
*
* @param l New length. If l<0 or l>=getLength(), this operation will
* not report an error but future operations will almost certainly fail.
*/
public final void setLength(int l)
{
m_lastChunk = l >>> m_chunkBits;
if (m_lastChunk == 0 && m_innerFSB != null)
{
// Replace this FSB with the appropriate inner FSB, truncated
m_innerFSB.setLength(l, this);
}
else
{
m_firstFree = l & m_chunkMask;
// There's an edge case if l is an exact multiple of m_chunkBits, which risks leaving
// us pointing at the start of a chunk which has not yet been allocated. Rather than
// pay the cost of dealing with that in the append loops (more scattered and more
// inner-loop), we correct it here by moving to the safe side of that
// line -- as we would have left the indexes had we appended up to that point.
if(m_firstFree==0 && m_lastChunk>0)
{
--m_lastChunk;
m_firstFree=m_chunkSize;
}
}
}
/**
* Subroutine for the public setLength() method. Deals with the fact
* that truncation may require restoring one of the innerFSBs
*
* NEEDSDOC @param l
* NEEDSDOC @param rootFSB
*/
private final void setLength(int l, FastStringBuffer rootFSB)
{
m_lastChunk = l >>> m_chunkBits;
if (m_lastChunk == 0 && m_innerFSB != null)
{
m_innerFSB.setLength(l, rootFSB);
}
else
{
// Undo encapsulation -- pop the innerFSB data back up to root.
// Inefficient, but attempts to keep the code simple.
rootFSB.m_chunkBits = m_chunkBits;
rootFSB.m_maxChunkBits = m_maxChunkBits;
rootFSB.m_rebundleBits = m_rebundleBits;
rootFSB.m_chunkSize = m_chunkSize;
rootFSB.m_chunkMask = m_chunkMask;
rootFSB.m_array = m_array;
rootFSB.m_innerFSB = m_innerFSB;
rootFSB.m_lastChunk = m_lastChunk;
// Finally, truncate this sucker.
rootFSB.m_firstFree = l & m_chunkMask;
}
}
/**
* Note that this operation has been somewhat deoptimized by the shift to a
* chunked array, as there is no factory method to produce a String object
* directly from an array of arrays and hence a double copy is needed.
* By using ensureCapacity we hope to minimize the heap overhead of building
* the intermediate StringBuffer.
* <p>
* (It really is a pity that Java didn't design String as a final subclass
* of MutableString, rather than having StringBuffer be a separate hierarchy.
* We'd avoid a <strong>lot</strong> of double-buffering.)
*
* @return the contents of the FastStringBuffer as a standard Java string.
*/
public final String toString()
{
int length = (m_lastChunk << m_chunkBits) + m_firstFree;
return getString(new StringBuffer(length), 0, 0, length).toString();
}
/**
* Append a single character onto the FastStringBuffer, growing the
* storage if necessary.
* <p>
* NOTE THAT after calling append(), previously obtained
* references to m_array[][] may no longer be valid....
* though in fact they should be in this instance.
*
* @param value character to be appended.
*/
public final void append(char value)
{
char[] chunk;
// We may have preallocated chunks. If so, all but last should
// be at full size.
if (m_firstFree < m_chunkSize) // Simplified test single-character-fits
chunk = m_array[m_lastChunk];
else
{
// Extend array?
int i = m_array.length;
if (m_lastChunk + 1 == i)
{
char[][] newarray = new char[i + 16][];
System.arraycopy(m_array, 0, newarray, 0, i);
m_array = newarray;
}
// Advance one chunk
chunk = m_array[++m_lastChunk];
if (chunk == null)
{
// Hierarchical encapsulation
if (m_lastChunk == 1 << m_rebundleBits
&& m_chunkBits < m_maxChunkBits)
{
// Should do all the work of both encapsulating
// existing data and establishing new sizes/offsets
m_innerFSB = new FastStringBuffer(this);
}
// Add a chunk.
chunk = m_array[m_lastChunk] = new char[m_chunkSize];
}
m_firstFree = 0;
}
// Space exists in the chunk. Append the character.
chunk[m_firstFree++] = value;
}
/**
* Append the contents of a String onto the FastStringBuffer,
* growing the storage if necessary.
* <p>
* NOTE THAT after calling append(), previously obtained
* references to m_array[] may no longer be valid.
*
* @param value String whose contents are to be appended.
*/
public final void append(String value)
{
if (value == null)
return;
int strlen = value.length();
if (0 == strlen)
return;
int copyfrom = 0;
char[] chunk = m_array[m_lastChunk];
int available = m_chunkSize - m_firstFree;
// Repeat while data remains to be copied
while (strlen > 0)
{
// Copy what fits
if (available > strlen)
available = strlen;
value.getChars(copyfrom, copyfrom + available, m_array[m_lastChunk],
m_firstFree);
strlen -= available;
copyfrom += available;
// If there's more left, allocate another chunk and continue
if (strlen > 0)
{
// Extend array?
int i = m_array.length;
if (m_lastChunk + 1 == i)
{
char[][] newarray = new char[i + 16][];
System.arraycopy(m_array, 0, newarray, 0, i);
m_array = newarray;
}
// Advance one chunk
chunk = m_array[++m_lastChunk];
if (chunk == null)
{
// Hierarchical encapsulation
if (m_lastChunk == 1 << m_rebundleBits
&& m_chunkBits < m_maxChunkBits)
{
// Should do all the work of both encapsulating
// existing data and establishing new sizes/offsets
m_innerFSB = new FastStringBuffer(this);
}
// Add a chunk.
chunk = m_array[m_lastChunk] = new char[m_chunkSize];
}
available = m_chunkSize;
m_firstFree = 0;
}
}
// Adjust the insert point in the last chunk, when we've reached it.
m_firstFree += available;
}
/**
* Append the contents of a StringBuffer onto the FastStringBuffer,
* growing the storage if necessary.
* <p>
* NOTE THAT after calling append(), previously obtained
* references to m_array[] may no longer be valid.
*
* @param value StringBuffer whose contents are to be appended.
*/
public final void append(StringBuffer value)
{
if (value == null)
return;
int strlen = value.length();
if (0 == strlen)
return;
int copyfrom = 0;
char[] chunk = m_array[m_lastChunk];
int available = m_chunkSize - m_firstFree;
// Repeat while data remains to be copied
while (strlen > 0)
{
// Copy what fits
if (available > strlen)
available = strlen;
value.getChars(copyfrom, copyfrom + available, m_array[m_lastChunk],
m_firstFree);
strlen -= available;
copyfrom += available;
// If there's more left, allocate another chunk and continue
if (strlen > 0)
{
// Extend array?
int i = m_array.length;
if (m_lastChunk + 1 == i)
{
char[][] newarray = new char[i + 16][];
System.arraycopy(m_array, 0, newarray, 0, i);
m_array = newarray;
}
// Advance one chunk
chunk = m_array[++m_lastChunk];
if (chunk == null)
{
// Hierarchical encapsulation
if (m_lastChunk == 1 << m_rebundleBits
&& m_chunkBits < m_maxChunkBits)
{
// Should do all the work of both encapsulating
// existing data and establishing new sizes/offsets
m_innerFSB = new FastStringBuffer(this);
}
// Add a chunk.
chunk = m_array[m_lastChunk] = new char[m_chunkSize];
}
available = m_chunkSize;
m_firstFree = 0;
}
}
// Adjust the insert point in the last chunk, when we've reached it.
m_firstFree += available;
}
/**
* Append part of the contents of a Character Array onto the
* FastStringBuffer, growing the storage if necessary.
* <p>
* NOTE THAT after calling append(), previously obtained
* references to m_array[] may no longer be valid.
*
* @param chars character array from which data is to be copied
* @param start offset in chars of first character to be copied,
* zero-based.
* @param length number of characters to be copied
*/
public final void append(char[] chars, int start, int length)
{
int strlen = length;
if (0 == strlen)
return;
int copyfrom = start;
char[] chunk = m_array[m_lastChunk];
int available = m_chunkSize - m_firstFree;
// Repeat while data remains to be copied
while (strlen > 0)
{
// Copy what fits
if (available > strlen)
available = strlen;
System.arraycopy(chars, copyfrom, m_array[m_lastChunk], m_firstFree,
available);
strlen -= available;
copyfrom += available;
// If there's more left, allocate another chunk and continue
if (strlen > 0)
{
// Extend array?
int i = m_array.length;
if (m_lastChunk + 1 == i)
{
char[][] newarray = new char[i + 16][];
System.arraycopy(m_array, 0, newarray, 0, i);
m_array = newarray;
}
// Advance one chunk
chunk = m_array[++m_lastChunk];
if (chunk == null)
{
// Hierarchical encapsulation
if (m_lastChunk == 1 << m_rebundleBits
&& m_chunkBits < m_maxChunkBits)
{
// Should do all the work of both encapsulating
// existing data and establishing new sizes/offsets
m_innerFSB = new FastStringBuffer(this);
}
// Add a chunk.
chunk = m_array[m_lastChunk] = new char[m_chunkSize];
}
available = m_chunkSize;
m_firstFree = 0;
}
}
// Adjust the insert point in the last chunk, when we've reached it.
m_firstFree += available;
}
/**
* Append the contents of another FastStringBuffer onto
* this FastStringBuffer, growing the storage if necessary.
* <p>
* NOTE THAT after calling append(), previously obtained
* references to m_array[] may no longer be valid.
*
* @param value FastStringBuffer whose contents are
* to be appended.
*/
public final void append(FastStringBuffer value)
{
// Complicating factor here is that the two buffers may use
// different chunk sizes, and even if they're the same we're
// probably on a different alignment due to previously appended
// data. We have to work through the source in bite-sized chunks.
if (value == null)
return;
int strlen = value.length();
if (0 == strlen)
return;
int copyfrom = 0;
char[] chunk = m_array[m_lastChunk];
int available = m_chunkSize - m_firstFree;
// Repeat while data remains to be copied
while (strlen > 0)
{
// Copy what fits
if (available > strlen)
available = strlen;
int sourcechunk = (copyfrom + value.m_chunkSize - 1)
>>> value.m_chunkBits;
int sourcecolumn = copyfrom & value.m_chunkMask;
int runlength = value.m_chunkSize - sourcecolumn;
if (runlength > available)
runlength = available;
System.arraycopy(value.m_array[sourcechunk], sourcecolumn,
m_array[m_lastChunk], m_firstFree, runlength);
if (runlength != available)
System.arraycopy(value.m_array[sourcechunk + 1], 0,
m_array[m_lastChunk], m_firstFree + runlength,
available - runlength);
strlen -= available;
copyfrom += available;
// If there's more left, allocate another chunk and continue
if (strlen > 0)
{
// Extend array?
int i = m_array.length;
if (m_lastChunk + 1 == i)
{
char[][] newarray = new char[i + 16][];
System.arraycopy(m_array, 0, newarray, 0, i);
m_array = newarray;
}
// Advance one chunk
chunk = m_array[++m_lastChunk];
if (chunk == null)
{
// Hierarchical encapsulation
if (m_lastChunk == 1 << m_rebundleBits
&& m_chunkBits < m_maxChunkBits)
{
// Should do all the work of both encapsulating
// existing data and establishing new sizes/offsets
m_innerFSB = new FastStringBuffer(this);
}
// Add a chunk.
chunk = m_array[m_lastChunk] = new char[m_chunkSize];
}
available = m_chunkSize;
m_firstFree = 0;
}
}
// Adjust the insert point in the last chunk, when we've reached it.
m_firstFree += available;
}
/**
* @return true if the specified range of characters are all whitespace,
* as defined by XMLCharacterRecognizer.
* <p>
* CURRENTLY DOES NOT CHECK FOR OUT-OF-RANGE.
*
* @param start Offset of first character in the range.
* @param length Number of characters to send.
*/
public boolean isWhitespace(int start, int length)
{
int sourcechunk = start >>> m_chunkBits;
int sourcecolumn = start & m_chunkMask;
int available = m_chunkSize - sourcecolumn;
boolean chunkOK;
while (length > 0)
{
int runlength = (length <= available) ? length : available;
if (sourcechunk == 0 && m_innerFSB != null)
chunkOK = m_innerFSB.isWhitespace(sourcecolumn, runlength);
else
chunkOK = XMLCharacterRecognizer.isWhiteSpace(
m_array[sourcechunk], sourcecolumn, runlength);
if (!chunkOK)
return false;
length -= runlength;
++sourcechunk;
sourcecolumn = 0;
available = m_chunkSize;
}
return true;
}
/**
* @param start Offset of first character in the range.
* @param length Number of characters to send.
* @return a new String object initialized from the specified range of
* characters.
*/
public String getString(int start, int length)
{
int startColumn = start & m_chunkMask;
int startChunk = start >>> m_chunkBits;
if (startColumn + length < m_chunkMask && m_innerFSB == null) {
return getOneChunkString(startChunk, startColumn, length);
}
return getString(new StringBuffer(length), startChunk, startColumn,
length).toString();
}
protected String getOneChunkString(int startChunk, int startColumn,
int length) {
return new String(m_array[startChunk], startColumn, length);
}
/**
* @param sb StringBuffer to be appended to
* @param start Offset of first character in the range.
* @param length Number of characters to send.
* @return sb with the requested text appended to it
*/
StringBuffer getString(StringBuffer sb, int start, int length)
{
return getString(sb, start >>> m_chunkBits, start & m_chunkMask, length);
}
/**
* Internal support for toString() and getString().
* PLEASE NOTE SIGNATURE CHANGE from earlier versions; it now appends into
* and returns a StringBuffer supplied by the caller. This simplifies
* m_innerFSB support.
* <p>
* Note that this operation has been somewhat deoptimized by the shift to a
* chunked array, as there is no factory method to produce a String object
* directly from an array of arrays and hence a double copy is needed.
* By presetting length we hope to minimize the heap overhead of building
* the intermediate StringBuffer.
* <p>
* (It really is a pity that Java didn't design String as a final subclass
* of MutableString, rather than having StringBuffer be a separate hierarchy.
* We'd avoid a <strong>lot</strong> of double-buffering.)
*
*
* @param sb
* @param startChunk
* @param startColumn
* @param length
*
* @return the contents of the FastStringBuffer as a standard Java string.
*/
StringBuffer getString(StringBuffer sb, int startChunk, int startColumn,
int length)
{
int stop = (startChunk << m_chunkBits) + startColumn + length;
int stopChunk = stop >>> m_chunkBits;
int stopColumn = stop & m_chunkMask;
// Factored out
//StringBuffer sb=new StringBuffer(length);
for (int i = startChunk; i < stopChunk; ++i)
{
if (i == 0 && m_innerFSB != null)
m_innerFSB.getString(sb, startColumn, m_chunkSize - startColumn);
else
sb.append(m_array[i], startColumn, m_chunkSize - startColumn);
startColumn = 0; // after first chunk
}
if (stopChunk == 0 && m_innerFSB != null)
m_innerFSB.getString(sb, startColumn, stopColumn - startColumn);
else if (stopColumn > startColumn)
sb.append(m_array[stopChunk], startColumn, stopColumn - startColumn);
return sb;
}
/**
* Get a single character from the string buffer.
*
*
* @param pos character position requested.
* @return A character from the requested position.
*/
public char charAt(int pos)
{
int startChunk = pos >>> m_chunkBits;
if (startChunk == 0 && m_innerFSB != null)
return m_innerFSB.charAt(pos & m_chunkMask);
else
return m_array[startChunk][pos & m_chunkMask];
}
/**
* Sends the specified range of characters as one or more SAX characters()
* events.
* Note that the buffer reference passed to the ContentHandler may be
* invalidated if the FastStringBuffer is edited; it's the user's
* responsibility to manage access to the FastStringBuffer to prevent this
* problem from arising.
* <p>
* Note too that there is no promise that the output will be sent as a
* single call. As is always true in SAX, one logical string may be split
* across multiple blocks of memory and hence delivered as several
* successive events.
*
* @param ch SAX ContentHandler object to receive the event.
* @param start Offset of first character in the range.
* @param length Number of characters to send.
* @exception org.xml.sax.SAXException may be thrown by handler's
* characters() method.
*/
public void sendSAXcharacters(
org.xml.sax.ContentHandler ch, int start, int length)
throws org.xml.sax.SAXException
{
int startChunk = start >>> m_chunkBits;
int startColumn = start & m_chunkMask;
if (startColumn + length < m_chunkMask && m_innerFSB == null) {
ch.characters(m_array[startChunk], startColumn, length);
return;
}
int stop = start + length;
int stopChunk = stop >>> m_chunkBits;
int stopColumn = stop & m_chunkMask;
for (int i = startChunk; i < stopChunk; ++i)
{
if (i == 0 && m_innerFSB != null)
m_innerFSB.sendSAXcharacters(ch, startColumn,
m_chunkSize - startColumn);
else
ch.characters(m_array[i], startColumn, m_chunkSize - startColumn);
startColumn = 0; // after first chunk
}
// Last, or only, chunk
if (stopChunk == 0 && m_innerFSB != null)
m_innerFSB.sendSAXcharacters(ch, startColumn, stopColumn - startColumn);
else if (stopColumn > startColumn)
{
ch.characters(m_array[stopChunk], startColumn,
stopColumn - startColumn);
}
}
/**
* Sends the specified range of characters as one or more SAX characters()
* events, normalizing the characters according to XSLT rules.
*
* @param ch SAX ContentHandler object to receive the event.
* @param start Offset of first character in the range.
* @param length Number of characters to send.
* @return normalization status to apply to next chunk (because we may
* have been called recursively to process an inner FSB):
* <dl>
* <dt>0</dt>
* <dd>if this output did not end in retained whitespace, and thus whitespace
* at the start of the following chunk (if any) should be converted to a
* single space.
* <dt>SUPPRESS_LEADING_WS</dt>
* <dd>if this output ended in retained whitespace, and thus whitespace
* at the start of the following chunk (if any) should be completely
* suppressed.</dd>
* </dd>
* </dl>
* @exception org.xml.sax.SAXException may be thrown by handler's
* characters() method.
*/
public int sendNormalizedSAXcharacters(
org.xml.sax.ContentHandler ch, int start, int length)
throws org.xml.sax.SAXException
{
// This call always starts at the beginning of the
// string being written out, either because it was called directly or
// because it was an m_innerFSB recursion. This is important since
// it gives us a well-known initial state for this flag:
int stateForNextChunk=SUPPRESS_LEADING_WS;
int stop = start + length;
int startChunk = start >>> m_chunkBits;
int startColumn = start & m_chunkMask;
int stopChunk = stop >>> m_chunkBits;
int stopColumn = stop & m_chunkMask;
for (int i = startChunk; i < stopChunk; ++i)
{
if (i == 0 && m_innerFSB != null)
stateForNextChunk=
m_innerFSB.sendNormalizedSAXcharacters(ch, startColumn,
m_chunkSize - startColumn);
else
stateForNextChunk=
sendNormalizedSAXcharacters(m_array[i], startColumn,
m_chunkSize - startColumn,
ch,stateForNextChunk);
startColumn = 0; // after first chunk
}
// Last, or only, chunk
if (stopChunk == 0 && m_innerFSB != null)
stateForNextChunk= // %REVIEW% Is this update really needed?
m_innerFSB.sendNormalizedSAXcharacters(ch, startColumn, stopColumn - startColumn);
else if (stopColumn > startColumn)
{
stateForNextChunk= // %REVIEW% Is this update really needed?
sendNormalizedSAXcharacters(m_array[stopChunk],
startColumn, stopColumn - startColumn,
ch, stateForNextChunk | SUPPRESS_TRAILING_WS);
}
return stateForNextChunk;
}
static final char[] SINGLE_SPACE = {' '};
/**
* Internal method to directly normalize and dispatch the character array.
* This version is aware of the fact that it may be called several times
* in succession if the data is made up of multiple "chunks", and thus
* must actively manage the handling of leading and trailing whitespace.
*
* Note: The recursion is due to the possible recursion of inner FSBs.
*
* @param ch The characters from the XML document.
* @param start The start position in the array.
* @param length The number of characters to read from the array.
* @param handler SAX ContentHandler object to receive the event.
* @param edgeTreatmentFlags How leading/trailing spaces should be handled.
* This is a bitfield contining two flags, bitwise-ORed together:
* <dl>
* <dt>SUPPRESS_LEADING_WS</dt>
* <dd>When false, causes leading whitespace to be converted to a single
* space; when true, causes it to be discarded entirely.
* Should be set TRUE for the first chunk, and (in multi-chunk output)
* whenever the previous chunk ended in retained whitespace.</dd>
* <dt>SUPPRESS_TRAILING_WS</dt>
* <dd>When false, causes trailing whitespace to be converted to a single
* space; when true, causes it to be discarded entirely.
* Should be set TRUE for the last or only chunk.
* </dd>
* </dl>
* @return normalization status, as in the edgeTreatmentFlags parameter:
* <dl>
* <dt>0</dt>
* <dd>if this output did not end in retained whitespace, and thus whitespace
* at the start of the following chunk (if any) should be converted to a
* single space.
* <dt>SUPPRESS_LEADING_WS</dt>
* <dd>if this output ended in retained whitespace, and thus whitespace
* at the start of the following chunk (if any) should be completely
* suppressed.</dd>
* </dd>
* </dl>
*
*
* @exception org.xml.sax.SAXException Any SAX exception, possibly
* wrapping another exception.
*/
static int sendNormalizedSAXcharacters(char ch[],
int start, int length,
org.xml.sax.ContentHandler handler,
int edgeTreatmentFlags)
throws org.xml.sax.SAXException
{
boolean processingLeadingWhitespace =
((edgeTreatmentFlags & SUPPRESS_LEADING_WS) != 0);
boolean seenWhitespace = ((edgeTreatmentFlags & CARRY_WS) != 0);
int currPos = start;
int limit = start+length;
// Strip any leading spaces first, if required
if (processingLeadingWhitespace) {
for (; currPos < limit
&& XMLCharacterRecognizer.isWhiteSpace(ch[currPos]);
currPos++) { }
// If we've only encountered leading spaces, the
// current state remains unchanged
if (currPos == limit) {
return edgeTreatmentFlags;
}
}
// If we get here, there are no more leading spaces to strip
while (currPos < limit) {
int startNonWhitespace = currPos;
// Grab a chunk of non-whitespace characters
for (; currPos < limit
&& !XMLCharacterRecognizer.isWhiteSpace(ch[currPos]);
currPos++) { }
// Non-whitespace seen - emit them, along with a single
// space for any preceding whitespace characters
if (startNonWhitespace != currPos) {
if (seenWhitespace) {
handler.characters(SINGLE_SPACE, 0, 1);
seenWhitespace = false;
}
handler.characters(ch, startNonWhitespace,
currPos - startNonWhitespace);
}
int startWhitespace = currPos;
// Consume any whitespace characters
for (; currPos < limit
&& XMLCharacterRecognizer.isWhiteSpace(ch[currPos]);
currPos++) { }
if (startWhitespace != currPos) {
seenWhitespace = true;
}
}
return (seenWhitespace ? CARRY_WS : 0)
| (edgeTreatmentFlags & SUPPRESS_TRAILING_WS);
}
/**
* Directly normalize and dispatch the character array.
*
* @param ch The characters from the XML document.
* @param start The start position in the array.
* @param length The number of characters to read from the array.
* @param handler SAX ContentHandler object to receive the event.
* @exception org.xml.sax.SAXException Any SAX exception, possibly
* wrapping another exception.
*/
public static void sendNormalizedSAXcharacters(char ch[],
int start, int length,
org.xml.sax.ContentHandler handler)
throws org.xml.sax.SAXException
{
sendNormalizedSAXcharacters(ch, start, length,
handler, SUPPRESS_BOTH);
}
/**
* Sends the specified range of characters as sax Comment.
* <p>
* Note that, unlike sendSAXcharacters, this has to be done as a single
* call to LexicalHandler#comment.
*
* @param ch SAX LexicalHandler object to receive the event.
* @param start Offset of first character in the range.
* @param length Number of characters to send.
* @exception org.xml.sax.SAXException may be thrown by handler's
* characters() method.
*/
public void sendSAXComment(
org.xml.sax.ext.LexicalHandler ch, int start, int length)
throws org.xml.sax.SAXException
{
// %OPT% Do it this way for now...
String comment = getString(start, length);
ch.comment(comment.toCharArray(), 0, length);
}
/**
* Copies characters from this string into the destination character
* array.
*
* @param srcBegin index of the first character in the string
* to copy.
* @param srcEnd index after the last character in the string
* to copy.
* @param dst the destination array.
* @param dstBegin the start offset in the destination array.
* @exception IndexOutOfBoundsException If any of the following
* is true:
* <ul><li><code>srcBegin</code> is negative.
* <li><code>srcBegin</code> is greater than <code>srcEnd</code>
* <li><code>srcEnd</code> is greater than the length of this
* string
* <li><code>dstBegin</code> is negative
* <li><code>dstBegin+(srcEnd-srcBegin)</code> is larger than
* <code>dst.length</code></ul>
* @exception NullPointerException if <code>dst</code> is <code>null</code>
*/
private void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin)
{
// %TBD% Joe needs to write this function. Make public when implemented.
}
/**
* Encapsulation c'tor. After this is called, the source FastStringBuffer
* will be reset to use the new object as its m_innerFSB, and will have
* had its chunk size reset appropriately. IT SHOULD NEVER BE CALLED
* EXCEPT WHEN source.length()==1<<(source.m_chunkBits+source.m_rebundleBits)
*
* NEEDSDOC @param source
*/
private FastStringBuffer(FastStringBuffer source)
{
// Copy existing information into new encapsulation
m_chunkBits = source.m_chunkBits;
m_maxChunkBits = source.m_maxChunkBits;
m_rebundleBits = source.m_rebundleBits;
m_chunkSize = source.m_chunkSize;
m_chunkMask = source.m_chunkMask;
m_array = source.m_array;
m_innerFSB = source.m_innerFSB;
// These have to be adjusted because we're calling just at the time
// when we would be about to allocate another chunk
m_lastChunk = source.m_lastChunk - 1;
m_firstFree = source.m_chunkSize;
// Establish capsule as the Inner FSB, reset chunk sizes/addressing
source.m_array = new char[16][];
source.m_innerFSB = this;
// Since we encapsulated just as we were about to append another
// chunk, return ready to create the chunk after the innerFSB
// -- 1, not 0.
source.m_lastChunk = 1;
source.m_firstFree = 0;
source.m_chunkBits += m_rebundleBits;
source.m_chunkSize = 1 << (source.m_chunkBits);
source.m_chunkMask = source.m_chunkSize - 1;
}
}
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: XMLCharacterRecognizer.java 468655 2006-10-28 07:12:06Z minchau $
*/
/**
* Class used to verify whether the specified <var>ch</var>
* conforms to the XML 1.0 definition of whitespace.
* @xsl.usage internal
*/
class XMLCharacterRecognizer
{
/**
* Returns whether the specified <var>ch</var> conforms to the XML 1.0 definition
* of whitespace. Refer to <A href="http://www.w3.org/TR/1998/REC-xml-19980210#NT-S">
* the definition of <CODE>S</CODE></A> for details.
* @param ch Character to check as XML whitespace.
* @return =true if <var>ch</var> is XML whitespace; otherwise =false.
*/
public static boolean isWhiteSpace(char ch)
{
return (ch == 0x20) || (ch == 0x09) || (ch == 0xD) || (ch == 0xA);
}
/**
* Tell if the string is whitespace.
*
* @param ch Character array to check as XML whitespace.
* @param start Start index of characters in the array
* @param length Number of characters in the array
* @return True if the characters in the array are
* XML whitespace; otherwise, false.
*/
public static boolean isWhiteSpace(char ch[], int start, int length)
{
int end = start + length;
for (int s = start; s < end; s++)
{
if (!isWhiteSpace(ch[s]))
return false;
}
return true;
}
/**
* Tell if the string is whitespace.
*
* @param buf StringBuffer to check as XML whitespace.
* @return True if characters in buffer are XML whitespace, false otherwise
*/
public static boolean isWhiteSpace(StringBuffer buf)
{
int n = buf.length();
for (int i = 0; i < n; i++)
{
if (!isWhiteSpace(buf.charAt(i)))
return false;
}
return true;
}
/**
* Tell if the string is whitespace.
*
* @param s String to check as XML whitespace.
* @return True if characters in buffer are XML whitespace, false otherwise
*/
public static boolean isWhiteSpace(String s)
{
if(null != s)
{
int n = s.length();
for (int i = 0; i < n; i++)
{
if (!isWhiteSpace(s.charAt(i)))
return false;
}
}
return true;
}
}
]]>