diff options
Diffstat (limited to 'src/backend/storage/file/buffile.c')
| -rw-r--r-- | src/backend/storage/file/buffile.c | 94 |
1 files changed, 57 insertions, 37 deletions
diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c index 2af57b56380..d62ed2670c8 100644 --- a/src/backend/storage/file/buffile.c +++ b/src/backend/storage/file/buffile.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/storage/file/buffile.c,v 1.4 2000/01/26 05:56:55 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/storage/file/buffile.c,v 1.5 2000/04/12 17:15:35 momjian Exp $ * * NOTES: * @@ -23,11 +23,11 @@ * 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 + * 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 + * (by opening multiple fd.c temporary files). This is an essential feature * for sorts and hashjoins on large amounts of data. *------------------------------------------------------------------------- */ @@ -56,15 +56,19 @@ struct BufFile /* 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 + + /* + * offsets[i] is the current seek position of files[i]. We use this * to avoid making redundant FileSeek calls. */ bool isTemp; /* can only add files if this is TRUE */ bool dirty; /* does buffer need to be written? */ + /* - * "current pos" is position of start of buffer within the logical file. - * Position as seen by user of BufFile is (curFile, curOffset + pos). + * "current pos" is position of start of buffer within the logical + * file. 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 */ @@ -87,7 +91,7 @@ static int BufFileFlush(BufFile *file); static BufFile * makeBufFile(File firstfile) { - BufFile *file = (BufFile *) palloc(sizeof(BufFile)); + BufFile *file = (BufFile *) palloc(sizeof(BufFile)); file->numFiles = 1; file->files = (File *) palloc(sizeof(File)); @@ -117,9 +121,9 @@ extendBufFile(BufFile *file) Assert(pfile >= 0); file->files = (File *) repalloc(file->files, - (file->numFiles+1) * sizeof(File)); + (file->numFiles + 1) * sizeof(File)); file->offsets = (long *) repalloc(file->offsets, - (file->numFiles+1) * sizeof(long)); + (file->numFiles + 1) * sizeof(long)); file->files[file->numFiles] = pfile; file->offsets[file->numFiles] = 0L; file->numFiles++; @@ -130,7 +134,7 @@ extendBufFile(BufFile *file) * multiple temporary files if more than MAX_PHYSICAL_FILESIZE bytes are * written to it). */ -BufFile * +BufFile * BufFileCreateTemp(void) { BufFile *file; @@ -152,7 +156,7 @@ BufFileCreateTemp(void) * to attach a BufFile to a non-temporary file. Note that BufFiles created * in this way CANNOT be expanded into multiple files. */ -BufFile * +BufFile * BufFileCreate(File file) { return makeBufFile(file); @@ -166,7 +170,7 @@ BufFileCreate(File file) void BufFileClose(BufFile *file) { - int i; + int i; /* flush any unwritten data */ BufFileFlush(file); @@ -189,21 +193,22 @@ BufFileClose(BufFile *file) static void BufFileLoadBuffer(BufFile *file) { - File thisfile; + 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 + * 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 < file->numFiles) + file->curFile + 1 < file->numFiles) { file->curFile++; file->curOffset = 0L; } + /* * May need to reposition physical file. */ @@ -214,6 +219,7 @@ BufFileLoadBuffer(BufFile *file) return; /* seek failed, read nothing */ file->offsets[file->curFile] = file->curOffset; } + /* * Read whatever we can get, up to a full bufferload. */ @@ -239,21 +245,23 @@ BufFileDumpBuffer(BufFile *file) File thisfile; /* - * Unlike BufFileLoadBuffer, we must dump the whole buffer even if - * it crosses a component-file boundary; so we need a loop. + * 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 && file->isTemp) { - while (file->curFile+1 >= file->numFiles) + while (file->curFile + 1 >= file->numFiles) extendBufFile(file); file->curFile++; file->curOffset = 0L; } + /* * Enforce per-file size limit only for temp files, else just try * to write as much as asked... @@ -261,11 +269,12 @@ BufFileDumpBuffer(BufFile *file) bytestowrite = file->nbytes - wpos; if (file->isTemp) { - long availbytes = MAX_PHYSICAL_FILESIZE - file->curOffset; + long availbytes = MAX_PHYSICAL_FILESIZE - file->curOffset; if ((long) bytestowrite > availbytes) bytestowrite = (int) availbytes; } + /* * May need to reposition physical file. */ @@ -284,11 +293,13 @@ BufFileDumpBuffer(BufFile *file) 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!) + * 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 */ @@ -297,7 +308,11 @@ BufFileDumpBuffer(BufFile *file) Assert(file->curFile >= 0); file->curOffset += MAX_PHYSICAL_FILESIZE; } - /* Now we can set the buffer empty without changing the logical position */ + + /* + * Now we can set the buffer empty without changing the logical + * position + */ file->pos = 0; file->nbytes = 0; } @@ -317,7 +332,7 @@ BufFileRead(BufFile *file, void *ptr, size_t size) { if (BufFileFlush(file) != 0) return 0; /* could not flush... */ - Assert(! file->dirty); + Assert(!file->dirty); } while (size > 0) @@ -430,8 +445,9 @@ BufFileFlush(BufFile *file) int BufFileSeek(BufFile *file, int fileno, long offset, int whence) { - int newFile; - long newOffset; + int newFile; + long newOffset; + switch (whence) { case SEEK_SET: @@ -441,9 +457,11 @@ BufFileSeek(BufFile *file, int fileno, long offset, int whence) newOffset = offset; break; case SEEK_CUR: + /* - * Relative seek considers only the signed offset, ignoring fileno. - * Note that large offsets (> 1 gig) risk overflow in this add... + * Relative seek considers only the signed offset, ignoring + * fileno. Note that large offsets (> 1 gig) risk overflow in + * this add... */ newFile = file->curFile; newOffset = (file->curOffset + file->pos) + offset; @@ -467,11 +485,12 @@ BufFileSeek(BufFile *file, int fileno, long offset, int whence) 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. + * 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; @@ -479,10 +498,11 @@ BufFileSeek(BufFile *file, int fileno, long offset, int whence) /* Otherwise, must reposition buffer, so flush any dirty data */ if (BufFileFlush(file) != 0) return EOF; + /* - * At this point and no sooner, check for seek past last segment. - * The above flush could have created a new segment, so - * checking sooner would not work (at least not with this code). + * At this point and no sooner, check for seek past last segment. The + * above flush could have created a new segment, so checking sooner + * would not work (at least not with this code). */ if (file->isTemp) { @@ -544,7 +564,7 @@ BufFileSeekBlock(BufFile *file, long blknum) long BufFileTellBlock(BufFile *file) { - long blknum; + long blknum; blknum = (file->curOffset + file->pos) / BLCKSZ; blknum += file->curFile * RELSEG_SIZE; |