From 3fee67533e265be377125faf3c73d26c90914f13 Mon Sep 17 00:00:00 2001 From: drh <> Date: Tue, 16 Mar 2021 14:12:26 +0000 Subject: [PATCH] Comment and stylistic changes to the appendvfs.c implementation. FossilOrigin-Name: 25c3186aa143328157fb506a29802e87099cd14be4fa218230484a3212f20621 --- ext/misc/appendvfs.c | 164 +++++++++++++++++++++---------------------- manifest | 14 ++-- manifest.uuid | 2 +- 3 files changed, 89 insertions(+), 91 deletions(-) diff --git a/ext/misc/appendvfs.c b/ext/misc/appendvfs.c index 477e1eafc6..6975a6abff 100644 --- a/ext/misc/appendvfs.c +++ b/ext/misc/appendvfs.c @@ -38,8 +38,8 @@ ** (5) Otherwise, SQLITE_CANTOPEN is returned. ** ** To avoid unnecessary complications with the PENDING_BYTE, the size of -** the file containing the database is limited to 1GB. (1000013824 bytes) -** This VFS will not read or write past the 1GB mark. This restriction +** the file containing the database is limited to 1GiB. (1073741824 bytes) +** This VFS will not read or write past the 1GiB mark. This restriction ** might be lifted in future versions. For now, if you need a larger ** database, then keep it in a separate file. ** @@ -68,14 +68,16 @@ SQLITE_EXTENSION_INIT1 ** Maximum size of the combined prefix + database + append-mark. This ** must be less than 0x40000000 to avoid locking issues on Windows. */ -#define APND_MAX_SIZE (65536*15259) +#define APND_MAX_SIZE (0x40000000) /* -** Size of storage page upon which to align appendvfs portion. +** Try to align the database to an even multiple of APND_ROUNDUP bytes. */ -#ifndef APND_ROUNDUP_BITS -#define APND_ROUNDUP_BITS 12 +#ifndef APND_ROUNDUP +#define APND_ROUNDUP 4096 #endif +#define APND_ALIGN_MASK ((sqlite3_int64)(APND_ROUNDUP-1)) +#define APND_START_ROUNDUP(fsz) (((fsz)+APND_ALIGN_MASK) & ~APND_ALIGN_MASK) /* ** Forward declaration of objects used by this utility @@ -89,43 +91,45 @@ typedef struct ApndFile ApndFile; #define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData)) #define ORIGFILE(p) ((sqlite3_file*)(((ApndFile*)(p))+1)) -/* Invariants for an open appendvfs file: - * Once an appendvfs file is opened, it will be in one of three states: - * State 0: Never written. Underlying file (if any) is unaltered. - * State 1: Append mark is persisted, content write is in progress. - * State 2: Append mark is persisted, content writes are complete. - * - * State 0 is persistent in the sense that nothing will have been done - * to the underlying file, including any attempt to convert it to an - * appendvfs file. - * - * State 1 is normally transitory. However, if a write operation ends - * abnormally (disk full, power loss, process kill, etc.), then State 1 - * may be persistent on disk with an incomplete content write-out. This - * is logically equivalent to an interrupted write to an ordinary file, - * where some unknown portion of to-be-written data is persisted while - * the remainder is not. Database integrity in such cases is maintained - * (or not) by the same measures available for ordinary file access. - * - * State 2 is persistent under normal circumstances (when there is no - * abnormal termination of a write operation such that data provided - * to the underlying VFS write method has not yet reached storage.) - * - * In order to maintain the state invariant, the append mark is written - * in advance of content writes where any part of such content would - * overwrite an existing (or yet to be written) append mark. - */ +/* An open appendvfs file +** +** An instance of this structure describes the appended database file. +** A separate sqlite3_file object is always appended. The appended +** sqlite3_file object (which can be accessed using ORIGFILE()) describes +** the entire file, including the prefix, the database, and the +** append-mark. +** +** The structure of an AppendVFS database is like this: +** +** +-------------+---------+----------+-------------+ +** | prefix-file | padding | database | append-mark | +** +-------------+---------+----------+-------------+ +** ^ ^ +** | | +** iPgOne iMark +** +** +** "prefix file" - file onto which the database has been appended. +** "padding" - zero or more bytes inserted so that "database" +** starts on an APND_ROUNDUP boundary +** "database" - The SQLite database file +** "append-mark" - The 25-byte "Start-Of-SQLite3-NNNNNNNN" that indicates +** the offset from the start of prefix-file to the start +** of "database". +** +** The size of the database is iMark - iPgOne. +** +** The NNNNNNNN in the "Start-Of-SQLite3-NNNNNNNN" suffix is the value +** of iPgOne stored as a big-ending 64-bit integer. +** +** iMark will be the size of the underlying file minus 25 (APND_MARKSIZE). +** Or, iMark is -1 to indicate that it has not yet been written. +*/ struct ApndFile { - /* Access to IO methods of the underlying file */ - sqlite3_file base; - /* File offset to beginning of appended content (unchanging) */ - sqlite3_int64 iPgOne; - /* File offset of written append-mark, or -1 if unwritten */ - sqlite3_int64 iMark; - /* Whenever file is open and .iMark >= 0, and file size changes are - * not in progress, .iMark + sizeof(append mark) == base file size, - * and append file size == .iMark - .iPgOne . - */ + sqlite3_file base; /* Subclass. MUST BE FIRST! */ + sqlite3_int64 iPgOne; /* Offset to the start of the database */ + sqlite3_int64 iMark; /* Offset of the append mark. -1 if unwritten */ + /* Always followed by another sqlite3_file that describes the whole file */ }; /* @@ -221,7 +225,6 @@ static const sqlite3_io_methods apnd_io_methods = { ** Close an apnd-file. */ static int apndClose(sqlite3_file *pFile){ - assert((ApndFile*)pFile == ORIGFILE(pFile)); pFile = ORIGFILE(pFile); return pFile->pMethods->xClose(pFile); } @@ -255,9 +258,8 @@ static int apndWriteMark( int i = APND_MARK_FOS_SZ; int rc; assert(pFile == ORIGFILE(paf)); - /* assert(pFile == paf->base); */ memcpy(a, APND_MARK_PREFIX, APND_MARK_PREFIX_SZ); - while (--i >= 0) { + while( --i >= 0 ){ a[APND_MARK_PREFIX_SZ+i] = (unsigned char)(iPgOne & 0xff); iPgOne >>= 8; } @@ -282,12 +284,10 @@ static int apndWrite( sqlite_int64 iWriteEnd = iOfst + iAmt; if( iWriteEnd>=APND_MAX_SIZE ) return SQLITE_FULL; pFile = ORIGFILE(pFile); - /* assert(pFile == paf->base); */ /* If append-mark is absent or will be overwritten, write it. */ if( paf->iMark < 0 || paf->iPgOne + iWriteEnd > paf->iMark ){ int rc = apndWriteMark(paf, pFile, iWriteEnd); - if( SQLITE_OK!=rc ) - return rc; + if( SQLITE_OK!=rc ) return rc; } return pFile->pMethods->xWrite(pFile, zBuf, iAmt, paf->iPgOne+iOfst); } @@ -299,8 +299,7 @@ static int apndTruncate(sqlite3_file *pFile, sqlite_int64 size){ ApndFile *paf = (ApndFile *)pFile; pFile = ORIGFILE(pFile); /* The append mark goes out first so truncate failure does not lose it. */ - if( SQLITE_OK!=apndWriteMark(paf, pFile, size) ) - return SQLITE_IOERR; + if( SQLITE_OK!=apndWriteMark(paf, pFile, size) ) return SQLITE_IOERR; /* Truncate underlying file just past append mark */ return pFile->pMethods->xTruncate(pFile, paf->iMark+APND_MARK_SIZE); } @@ -416,8 +415,9 @@ static int apndFetch( void **pp ){ ApndFile *p = (ApndFile *)pFile; - if( p->iMark < 0 || iOfst+iAmt > p->iMark) + if( p->iMark < 0 || iOfst+iAmt > p->iMark ){ return SQLITE_IOERR; /* Cannot read what is not yet there. */ + } pFile = ORIGFILE(pFile); return pFile->pMethods->xFetch(pFile, iOfst+p->iPgOne, iAmt, pp); } @@ -468,14 +468,18 @@ static int apndIsAppendvfsDatabase(sqlite3_int64 sz, sqlite3_file *pFile){ char zHdr[16]; sqlite3_int64 iMark = apndReadMark(sz, pFile); if( iMark>=0 ){ - /* If file has right end-marker, the expected odd size, and the - * SQLite DB type marker where the end-marker puts it, then it - * is an appendvfs database (to be treated as such.) - */ + /* If file has the correct end-marker, the expected odd size, and the + ** SQLite DB type marker where the end-marker puts it, then it + ** is an appendvfs database. + */ rc = pFile->pMethods->xRead(pFile, zHdr, sizeof(zHdr), iMark); - if( SQLITE_OK==rc && memcmp(zHdr, apvfsSqliteHdr, sizeof(zHdr))==0 - && (sz & 0x1ff)== APND_MARK_SIZE && sz>=512+APND_MARK_SIZE ) + if( SQLITE_OK==rc + && memcmp(zHdr, apvfsSqliteHdr, sizeof(zHdr))==0 + && (sz & 0x1ff) == APND_MARK_SIZE + && sz>=512+APND_MARK_SIZE + ){ return 1; /* It's an appendvfs database */ + } } return 0; } @@ -497,11 +501,6 @@ static int apndIsOrdinaryDatabaseFile(sqlite3_int64 sz, sqlite3_file *pFile){ } } -/* Round-up used to get appendvfs portion to begin at a page boundary. */ -#define APND_ALIGN_MASK(nbits) ((1<xOpen(pBaseVfs, zName, pFile, flags, pOutFlags); } memset(pApndFile, 0, sizeof(ApndFile)); pFile->pMethods = &apnd_io_methods; - /* Record that append mark has not been written until seen otherwise. */ - pApndFile->iMark = -1; + pApndFile->iMark = -1; /* Append mark not yet written */ rc = pBaseVfs->xOpen(pBaseVfs, zName, pBaseFile, flags, pOutFlags); - if( rc ) goto apnd_open_done; - rc = pBaseFile->pMethods->xFileSize(pBaseFile, &sz); + if( rc==SQLITE_OK ){ + rc = pBaseFile->pMethods->xFileSize(pBaseFile, &sz); + } if( rc ){ pBaseFile->pMethods->xClose(pBaseFile); - goto apnd_open_done; + pFile->pMethods = 0; + return rc; } if( apndIsOrdinaryDatabaseFile(sz, pBaseFile) ){ /* The file being opened appears to be just an ordinary DB. Copy - * the base dispatch-table so this instance mimics the base VFS. - */ + ** the base dispatch-table so this instance mimics the base VFS. + */ memmove(pApndFile, pBaseFile, pBaseVfs->szOsFile); return SQLITE_OK; } pApndFile->iPgOne = apndReadMark(sz, pFile); if( pApndFile->iPgOne>=0 ){ - /* Append mark was found, infer its offset */ - pApndFile->iMark = sz - APND_MARK_SIZE; - /* pApndFile->base = pBaseFile; */ + pApndFile->iMark = sz - APND_MARK_SIZE; /* Append mark found */ return SQLITE_OK; } if( (flags & SQLITE_OPEN_CREATE)==0 ){ pBaseFile->pMethods->xClose(pBaseFile); rc = SQLITE_CANTOPEN; + pFile->pMethods = 0; + }else{ + /* Round newly added appendvfs location to #define'd page boundary. + ** Note that nothing has yet been written to the underlying file. + ** The append mark will be written along with first content write. + ** Until then, paf->iMark value indicates it is not yet written. + */ + pApndFile->iPgOne = APND_START_ROUNDUP(sz); } - /* Round newly added appendvfs location to #define'd page boundary. - * Note that nothing has yet been written to the underlying file. - * The append mark will be written along with first content write. - * Until then, paf->iMark value indicates it is not yet written. - */ - pApndFile->iPgOne = APND_START_ROUNDUP(sz, APND_ROUNDUP_BITS); -apnd_open_done: - if( rc ) pFile->pMethods = 0; return rc; } diff --git a/manifest b/manifest index 8697813227..57975f75a1 100644 --- a/manifest +++ b/manifest @@ -1,5 +1,5 @@ -C Fix\sassert\stypo. -D 2021-03-16T07:06:29.878 +C Comment\sand\sstylistic\schanges\sto\sthe\sappendvfs.c\simplementation. +D 2021-03-16T14:12:26.803 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724 @@ -286,7 +286,7 @@ F ext/lsm1/tool/mklsm1c.tcl f31561bbee5349f0a554d1ad7236ac1991fc09176626f529f607 F ext/misc/README.md d6dd0fe1d8af77040216798a6a2b0c46c73054d2f0ea544fbbcdccf6f238c240 F ext/misc/amatch.c e3ad5532799cee9a97647f483f67f43b38796b84b5a8c60594fe782a4338f358 F ext/misc/anycollseq.c 5ffdfde9829eeac52219136ad6aa7cd9a4edb3b15f4f2532de52f4a22525eddb -F ext/misc/appendvfs.c 1dad6e7dc162ad36367513c1f985a1b474c3f3517f53ba22a6a89ce980843098 +F ext/misc/appendvfs.c 390c411f14e66abb2f30b9023ebc57334288780c9388cdc6e0a25deb5d40e3b2 F ext/misc/blobio.c a867c4c4617f6ec223a307ebfe0eabb45e0992f74dd47722b96f3e631c0edb2a F ext/misc/btreeinfo.c d28ce349b40054eaa9473e835837bad7a71deec33ba13e39f963d50933bfa0f9 F ext/misc/carray.c b75a0f207391038bf1540d3372f482a95c3613511c7c474db51ede1196321c7c @@ -1910,7 +1910,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0 -P eae8236f3b9bc326648d1c8fca61cb3c38f821d06fe915fd0978cffeb1f6152b -R 32b396e0e85126b3386d72e2bc6e8e4c -U larrybr -Z f8d4366505c35a746a63af41266ec4f5 +P 3aedf818c1cfc88ee1103abd8b20e787f6be1bcc4c9350963f0cd52f5ac04154 +R d4d0d407c45719772ccdc3772a06a769 +U drh +Z 2e9ac8f611b5ac99207230cf538d46c9 diff --git a/manifest.uuid b/manifest.uuid index b9d2df6bbf..283bb8a435 100644 --- a/manifest.uuid +++ b/manifest.uuid @@ -1 +1 @@ -3aedf818c1cfc88ee1103abd8b20e787f6be1bcc4c9350963f0cd52f5ac04154 \ No newline at end of file +25c3186aa143328157fb506a29802e87099cd14be4fa218230484a3212f20621 \ No newline at end of file