1 files changed, 556 insertions, 0 deletions
diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c
new file mode 100644
index 00000000000..cd7da900b4f
--- /dev/null
+++ b/src/backend/storage/file/buffile.c
@@ -0,0 +1,556 @@
+/*-------------------------------------------------------------------------
+ *
+ * buffile.c
+ *	  Management of large buffered files, primarily temporary files.
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/file/buffile.c,v 1.1 1999/10/13 15:02:29 tgl Exp $
+ *
+ * NOTES:
+ *
+ * BufFiles provide a very incomplete emulation of stdio atop virtual Files
+ * (as managed by fd.c).  Currently, we only support the buffered-I/O
+ * aspect of stdio: a read or write of the low-level File occurs only
+ * when the buffer is filled or emptied.  This is an even bigger win
+ * for virtual Files than for ordinary kernel files, since reducing the
+ * frequency with which a virtual File is touched reduces "thrashing"
+ * of opening/closing file descriptors.
+ *
+ * Note that BufFile structs are allocated with palloc(), and therefore
+ * will go away automatically at transaction end.  If the underlying
+ * virtual File is made with OpenTemporaryFile, then all resources for
+ * the file are certain to be cleaned up even if processing is aborted
+ * by elog(ERROR).  To avoid confusion, the caller should take care that
+ * all calls for a single BufFile are made in the same palloc context.
+ *
+ * BufFile also supports temporary files that exceed the OS file size limit
+ * (by opening multiple fd.c temporary files).  This is an essential feature
+ * for sorts and hashjoins on large amounts of data.  It is possible to have
+ * more than one BufFile reading/writing the same temp file, although the
+ * caller is responsible for avoiding ill effects from buffer overlap when
+ * this is done.
+ *-------------------------------------------------------------------------
+ */
+
+#include <errno.h>
+
+#include "postgres.h"
+
+#include "storage/buffile.h"
+
+/*
+ * The maximum safe file size is presumed to be RELSEG_SIZE * BLCKSZ.
+ * Note we adhere to this limit whether or not LET_OS_MANAGE_FILESIZE
+ * is defined, although md.c ignores it when that symbol is defined.
+ */
+#define MAX_PHYSICAL_FILESIZE  (RELSEG_SIZE * BLCKSZ)
+
+/*
+ * To handle multiple BufFiles on a single logical temp file, we use this
+ * data structure representing a logical file (which can be made up of
+ * multiple physical files to get around the OS file size limit).
+ */
+typedef struct LogicalFile
+{
+	int			refCount;		/* number of BufFiles using me */
+	bool		isTemp;			/* can only add files if this is TRUE */
+	int			numFiles;		/* number of physical files in set */
+	/* all files except the last have length exactly MAX_PHYSICAL_FILESIZE */
+
+	File	   *files;			/* palloc'd array with numFiles entries */
+	long	   *offsets;		/* palloc'd array with numFiles entries */
+	/* offsets[i] is the current seek position of files[i].  We use this
+	 * to avoid making redundant FileSeek calls.
+	 */
+} LogicalFile;
+
+/*
+ * A single file buffer looks like this.
+ */
+struct BufFile
+{
+	LogicalFile *logFile;		/* the underlying LogicalFile */
+	bool		dirty;			/* does buffer need to be written? */
+	/*
+	 * "current pos" is position of start of buffer within LogicalFile.
+	 * Position as seen by user of BufFile is (curFile, curOffset + pos).
+	 */
+	int			curFile;		/* file index (0..n) part of current pos */
+	int			curOffset;		/* offset part of current pos */
+	int			pos;			/* next read/write position in buffer */
+	int			nbytes;			/* total # of valid bytes in buffer */
+	char		buffer[BLCKSZ];
+};
+
+static LogicalFile *makeLogicalFile(File firstfile);
+static void extendLogicalFile(LogicalFile *file);
+static void deleteLogicalFile(LogicalFile *file);
+static void BufFileLoadBuffer(BufFile *file);
+static void BufFileDumpBuffer(BufFile *file);
+static int	BufFileFlush(BufFile *file);
+
+
+/*
+ * Create a LogicalFile with one component file and refcount 1.
+ * NOTE: caller must set isTemp true if appropriate.
+ */
+static LogicalFile *
+makeLogicalFile(File firstfile)
+{
+	LogicalFile *file = (LogicalFile *) palloc(sizeof(LogicalFile));
+
+	file->refCount = 1;
+	file->isTemp = false;
+	file->numFiles = 1;
+	file->files = (File *) palloc(sizeof(File));
+	file->files[0] = firstfile;
+	file->offsets = (long *) palloc(sizeof(long));
+	file->offsets[0] = 0L;
+
+	return file;
+}
+
+/*
+ * Add another component temp file.
+ */
+static void
+extendLogicalFile(LogicalFile *file)
+{
+	File		pfile;
+
+	Assert(file->isTemp);
+	pfile = OpenTemporaryFile();
+	Assert(pfile >= 0);
+
+	file->files = (File *) repalloc(file->files,
+									(file->numFiles+1) * sizeof(File));
+	file->offsets = (long *) repalloc(file->offsets,
+									  (file->numFiles+1) * sizeof(long));
+	file->files[file->numFiles] = pfile;
+	file->offsets[file->numFiles] = 0L;
+	file->numFiles++;
+}
+
+/*
+ * Close and delete a LogicalFile when its refCount has gone to zero.
+ */
+static void
+deleteLogicalFile(LogicalFile *file)
+{
+	int i;
+
+	for (i = 0; i < file->numFiles; i++)
+		FileClose(file->files[i]);
+	pfree(file->files);
+	pfree(file->offsets);
+	pfree(file);
+}
+
+/*
+ * Create a BufFile for a new temporary file (which will expand to become
+ * multiple temporary files if more than MAX_PHYSICAL_FILESIZE bytes are
+ * written to it).
+ */
+BufFile *
+BufFileCreateTemp(void)
+{
+	BufFile    *bfile = (BufFile *) palloc(sizeof(BufFile));
+	File		pfile;
+	LogicalFile *lfile;
+
+	pfile = OpenTemporaryFile();
+	Assert(pfile >= 0);
+
+	lfile = makeLogicalFile(pfile);
+	lfile->isTemp = true;
+
+	bfile->logFile = lfile;
+	bfile->dirty = false;
+	bfile->curFile = 0;
+	bfile->curOffset = 0L;
+	bfile->pos = 0;
+	bfile->nbytes = 0;
+
+	return bfile;
+}
+
+/*
+ * Create a BufFile and attach it to an already-opened virtual File.
+ *
+ * This is comparable to fdopen() in stdio.  This is the only way at present
+ * to attach a BufFile to a non-temporary file.  Note that BufFiles created
+ * in this way CANNOT be expanded into multiple files.
+ */
+BufFile *
+BufFileCreate(File file)
+{
+	BufFile    *bfile = (BufFile *) palloc(sizeof(BufFile));
+	LogicalFile *lfile;
+
+	lfile = makeLogicalFile(file);
+
+	bfile->logFile = lfile;
+	bfile->dirty = false;
+	bfile->curFile = 0;
+	bfile->curOffset = 0L;
+	bfile->pos = 0;
+	bfile->nbytes = 0;
+
+	return bfile;
+}
+
+/*
+ * Create an additional BufFile accessing the same underlying file as an
+ * existing BufFile.  This is useful for having multiple read/write access
+ * positions in a single temporary file.  Note the caller is responsible
+ * for avoiding trouble due to overlapping buffer positions!  (Caller may
+ * assume that buffer size is BLCKSZ...)
+ */
+BufFile *
+BufFileReaccess(BufFile *file)
+{
+	BufFile    *bfile = (BufFile *) palloc(sizeof(BufFile));
+
+	bfile->logFile = file->logFile;
+	bfile->logFile->refCount++;
+	bfile->dirty = false;
+	bfile->curFile = 0;
+	bfile->curOffset = 0L;
+	bfile->pos = 0;
+	bfile->nbytes = 0;
+
+	return bfile;
+}
+
+/*
+ * Close a BufFile
+ *
+ * Like fclose(), this also implicitly FileCloses the underlying File.
+ */
+void
+BufFileClose(BufFile *file)
+{
+	/* flush any unwritten data */
+	BufFileFlush(file);
+	/* close the underlying (with delete if it's a temp file) */
+	if (--(file->logFile->refCount) <= 0)
+		deleteLogicalFile(file->logFile);
+	/* release the buffer space */
+	pfree(file);
+}
+
+/* BufFileLoadBuffer
+ *
+ * Load some data into buffer, if possible, starting from curOffset.
+ * At call, must have dirty = false, pos and nbytes = 0.
+ * On exit, nbytes is number of bytes loaded.
+ */
+static void
+BufFileLoadBuffer(BufFile *file)
+{
+	LogicalFile *lfile = file->logFile;
+	File	thisfile;
+
+	/*
+	 * Advance to next component file if necessary and possible.
+	 *
+	 * This path can only be taken if there is more than one component,
+	 * so it won't interfere with reading a non-temp file that is over
+	 * MAX_PHYSICAL_FILESIZE.
+	 */
+	if (file->curOffset >= MAX_PHYSICAL_FILESIZE &&
+		file->curFile+1 < lfile->numFiles)
+	{
+		file->curFile++;
+		file->curOffset = 0L;
+	}
+	thisfile = lfile->files[file->curFile];
+	/*
+	 * May need to reposition physical file, if more than one BufFile
+	 * is using it.
+	 */
+	if (file->curOffset != lfile->offsets[file->curFile])
+	{
+		if (FileSeek(thisfile, file->curOffset, SEEK_SET) != file->curOffset)
+			return;				/* seek failed, read nothing */
+		lfile->offsets[file->curFile] = file->curOffset;
+	}
+	file->nbytes = FileRead(thisfile, file->buffer, sizeof(file->buffer));
+	if (file->nbytes < 0)
+		file->nbytes = 0;
+	lfile->offsets[file->curFile] += file->nbytes;
+	/* we choose not to advance curOffset here */
+}
+
+/* BufFileDumpBuffer
+ *
+ * Dump buffer contents starting at curOffset.
+ * At call, should have dirty = true, nbytes > 0.
+ * On exit, dirty is cleared if successful write, and curOffset is advanced.
+ */
+static void
+BufFileDumpBuffer(BufFile *file)
+{
+	LogicalFile *lfile = file->logFile;
+	int			wpos = 0;
+	int			bytestowrite;
+	File		thisfile;
+
+	/*
+	 * Unlike BufFileLoadBuffer, we must dump the whole buffer even if
+	 * it crosses a component-file boundary; so we need a loop.
+	 */
+	while (wpos < file->nbytes)
+	{
+		/*
+		 * Advance to next component file if necessary and possible.
+		 */
+		if (file->curOffset >= MAX_PHYSICAL_FILESIZE && lfile->isTemp)
+		{
+			while (file->curFile+1 >= lfile->numFiles)
+				extendLogicalFile(lfile);
+			file->curFile++;
+			file->curOffset = 0L;
+		}
+		/*
+		 * Enforce per-file size limit only for temp files, else just try
+		 * to write as much as asked...
+		 */
+		bytestowrite = file->nbytes - wpos;
+		if (lfile->isTemp)
+		{
+			long	availbytes = MAX_PHYSICAL_FILESIZE - file->curOffset;
+
+			if ((long) bytestowrite > availbytes)
+				bytestowrite = (int) availbytes;
+		}
+		thisfile = lfile->files[file->curFile];
+		/*
+		 * May need to reposition physical file, if more than one BufFile
+		 * is using it.
+		 */
+		if (file->curOffset != lfile->offsets[file->curFile])
+		{
+			if (FileSeek(thisfile, file->curOffset, SEEK_SET) != file->curOffset)
+				return;			/* seek failed, give up */
+			lfile->offsets[file->curFile] = file->curOffset;
+		}
+		bytestowrite = FileWrite(thisfile, file->buffer, bytestowrite);
+		if (bytestowrite <= 0)
+			return;				/* failed to write */
+		lfile->offsets[file->curFile] += bytestowrite;
+		file->curOffset += bytestowrite;
+		wpos += bytestowrite;
+	}
+	file->dirty = false;
+	/*
+	 * At this point, curOffset has been advanced to the end of the buffer,
+	 * ie, its original value + nbytes.  We need to make it point to the
+	 * logical file position, ie, original value + pos, in case that is less
+	 * (as could happen due to a small backwards seek in a dirty buffer!)
+	 */
+	file->curOffset -= (file->nbytes - file->pos);
+	if (file->curOffset < 0)	/* handle possible segment crossing */
+	{
+		file->curFile--;
+		Assert(file->curFile >= 0);
+		file->curOffset += MAX_PHYSICAL_FILESIZE;
+	}
+	/* Now we can set the buffer empty without changing the logical position */
+	file->pos = 0;
+	file->nbytes = 0;
+}
+
+/* BufFileRead
+ *
+ * Like fread() except we assume 1-byte element size.
+ */
+size_t
+BufFileRead(BufFile *file, void *ptr, size_t size)
+{
+	size_t		nread = 0;
+	size_t		nthistime;
+
+	if (file->dirty)
+	{
+		if (BufFileFlush(file) != 0)
+			return 0;			/* could not flush... */
+		Assert(! file->dirty);
+	}
+
+	while (size > 0)
+	{
+		if (file->pos >= file->nbytes)
+		{
+			/* Try to load more data into buffer. */
+			file->curOffset += file->pos;
+			file->pos = 0;
+			file->nbytes = 0;
+			BufFileLoadBuffer(file);
+			if (file->nbytes <= 0)
+				break;			/* no more data available */
+		}
+
+		nthistime = file->nbytes - file->pos;
+		if (nthistime > size)
+			nthistime = size;
+		Assert(nthistime > 0);
+
+		memcpy(ptr, file->buffer + file->pos, nthistime);
+
+		file->pos += nthistime;
+		ptr = (void *) ((char *) ptr + nthistime);
+		size -= nthistime;
+		nread += nthistime;
+	}
+
+	return nread;
+}
+
+/* BufFileWrite
+ *
+ * Like fwrite() except we assume 1-byte element size.
+ */
+size_t
+BufFileWrite(BufFile *file, void *ptr, size_t size)
+{
+	size_t		nwritten = 0;
+	size_t		nthistime;
+
+	while (size > 0)
+	{
+		if (file->pos >= BLCKSZ)
+		{
+			/* Buffer full, dump it out */
+			if (file->dirty)
+			{
+				BufFileDumpBuffer(file);
+				if (file->dirty)
+					break;		/* I/O error */
+			}
+			else
+			{
+				/* Hmm, went directly from reading to writing? */
+				file->curOffset += file->pos;
+				file->pos = 0;
+				file->nbytes = 0;
+			}
+		}
+
+		nthistime = BLCKSZ - file->pos;
+		if (nthistime > size)
+			nthistime = size;
+		Assert(nthistime > 0);
+
+		memcpy(file->buffer + file->pos, ptr, nthistime);
+
+		file->dirty = true;
+		file->pos += nthistime;
+		if (file->nbytes < file->pos)
+			file->nbytes = file->pos;
+		ptr = (void *) ((char *) ptr + nthistime);
+		size -= nthistime;
+		nwritten += nthistime;
+	}
+
+	return nwritten;
+}
+
+/* BufFileFlush
+ *
+ * Like fflush()
+ */
+static int
+BufFileFlush(BufFile *file)
+{
+	if (file->dirty)
+	{
+		BufFileDumpBuffer(file);
+		if (file->dirty)
+			return EOF;
+	}
+
+	return 0;
+}
+
+/* BufFileSeek
+ *
+ * Like fseek().  Result is 0 if OK, EOF if not.
+ */
+int
+BufFileSeek(BufFile *file, int fileno, long offset, int whence)
+{
+	int newFile;
+	long newOffset;
+	switch (whence)
+	{
+		case SEEK_SET:
+			if (fileno < 0 || fileno >= file->logFile->numFiles ||
+				offset < 0)
+				return EOF;
+			newFile = fileno;
+			newOffset = offset;
+			break;
+		case SEEK_CUR:
+			/*
+			 * Relative seek considers only the signed offset, ignoring fileno.
+			 * Note that large offsets (> 1 gig) risk overflow.
+			 */
+			newFile = file->curFile;
+			newOffset = (file->curOffset + file->pos) + offset;
+			break;
+#ifdef NOT_USED
+		case SEEK_END:
+			/* could be implemented, not needed currently */
+			break;
+#endif
+		default:
+			elog(ERROR, "BufFileSeek: invalid whence: %d", whence);
+			return EOF;
+	}
+	while (newOffset < 0)
+	{
+		if (--newFile < 0)
+			return EOF;
+		newOffset += MAX_PHYSICAL_FILESIZE;
+	}
+	if (file->logFile->isTemp)
+	{
+		while (newOffset > MAX_PHYSICAL_FILESIZE)
+		{
+			if (++newFile >= file->logFile->numFiles)
+				return EOF;
+			newOffset -= MAX_PHYSICAL_FILESIZE;
+		}
+	}
+	if (newFile == file->curFile &&
+		newOffset >= file->curOffset &&
+		newOffset <= file->curOffset + file->nbytes)
+	{
+		/*
+		 * Seek is to a point within existing buffer; we can just adjust
+		 * pos-within-buffer, without flushing buffer.  Note this is OK
+		 * whether reading or writing, but buffer remains dirty if we
+		 * were writing.
+		 */
+		file->pos = (int) (newOffset - file->curOffset);
+		return 0;
+	}
+	/* Otherwise, must reposition buffer, so flush any dirty data */
+	if (BufFileFlush(file) != 0)
+		return EOF;
+	file->curFile = newFile;
+	file->curOffset = newOffset;
+	file->pos = 0;
+	file->nbytes = 0;
+	return 0;
+}
+
+extern void
+BufFileTell(BufFile *file, int *fileno, long *offset)
+{
+	*fileno = file->curFile;
+	*offset = file->curOffset + file->pos;
+}