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Add the ext/misc/tmeplatevtab.c template for virtual tables. This is a

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work-in-progress as it still needs improvements to the comments in order to
be useful as a template.

FossilOrigin-Name: 22358fb5495c727a4dde129128fe409a7b929a5ffa143b1e2879f84d7680ec3c
This commit is contained in:
drh
2018-04-19 16:14:59 +00:00
parent bb6b1ca73d
commit 55a3490cf2
3 changed files with 258 additions and 6 deletions
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251
ext/misc/templatevtab.c Normal file
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@@ -0,0 +1,251 @@
/*
** 2018-04-19
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file implements a template virtual-table implementation.
** Developers can make a copy of this file as a baseline for writing
** new virtual tables and/or table-valued functions.
**
** Steps for writing a new virtual table implementation:
**
** (1) Make a copy of this file. Prehaps "mynewvtab.c"
**
** (2) Replace this header comment with something appropriate for
** the new virtual table
**
** (3) Change every occurrence of "templatevtab" to some other string
** appropriate for the new virtual table. Ideally, the new string
** should be the basename of the source file: "mynewvtab".
**
** (4) Run a test compilation to make sure the unmodified virtual
** table works.
**
** (5) Begin making changes to make the new virtual table do what you
** want it to do.
**
** (6) Ensure that all the "FIXME" comments in the file have been dealt
** with.
**
** This template is minimal, in the sense that it uses only the required
** methods on the sqlite3_module object. As a result, templatevtab is
** a read-only and eponymous-only table. Those limitation can be removed
** by adding new methods.
*/
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
#endif
SQLITE_EXTENSION_INIT1
#include <string.h>
/* templatevtab_vtab is a subclass of sqlite3_vtab which is
** underlying representation of the virtual table
*/
typedef struct templatevtab_vtab templatevtab_vtab;
struct templatevtab_vtab {
sqlite3_vtab base; /* Base class - must be first */
/* Add new fields here, as necessary */
};
/* templatevtab_cursor is a subclass of sqlite3_vtab_cursor which will
** serve as the underlying representation of a cursor that scans
** over rows of the result
*/
typedef struct templatevtab_cursor templatevtab_cursor;
struct templatevtab_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
/* Insert new fields here. For this templatevtab we only keep track
** of the rowid */
sqlite3_int64 iRowid; /* The rowid */
};
/*
** The templatevtabConnect() method is invoked to create a new
** template virtual table.
**
** Think of this routine as the constructor for templatevtab_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the templatevtab_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against the virtual table will look like.
*/
static int templatevtabConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
templatevtab_vtab *pNew;
int rc;
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x(a,b)"
);
if( rc==SQLITE_OK ){
pNew = sqlite3_malloc( sizeof(*pNew) );
*ppVtab = (sqlite3_vtab*)pNew;
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
}
return rc;
}
/*
** This method is the destructor for templatevtab_vtab objects.
*/
static int templatevtabDisconnect(sqlite3_vtab *pVtab){
templatevtab_vtab *p = (templatevtab_vtab*)pVtab;
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Constructor for a new templatevtab_cursor object.
*/
static int templatevtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
templatevtab_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Destructor for a templatevtab_cursor.
*/
static int templatevtabClose(sqlite3_vtab_cursor *cur){
templatevtab_cursor *pCur = (templatevtab_cursor*)cur;
sqlite3_free(pCur);
return SQLITE_OK;
}
/*
** Advance a templatevtab_cursor to its next row of output.
*/
static int templatevtabNext(sqlite3_vtab_cursor *cur){
templatevtab_cursor *pCur = (templatevtab_cursor*)cur;
pCur->iRowid++;
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the templatevtab_cursor
** is currently pointing.
*/
static int templatevtabColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
templatevtab_cursor *pCur = (templatevtab_cursor*)cur;
sqlite3_result_int(ctx, (i+1)*1000 + pCur->iRowid);
return SQLITE_OK;
}
/*
** Return the rowid for the current row. In this implementation, the
** rowid is the same as the output value.
*/
static int templatevtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
templatevtab_cursor *pCur = (templatevtab_cursor*)cur;
*pRowid = pCur->iRowid;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int templatevtabEof(sqlite3_vtab_cursor *cur){
templatevtab_cursor *pCur = (templatevtab_cursor*)cur;
return pCur->iRowid>=10;
}
/*
** This method is called to "rewind" the templatevtab_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to templatevtabColumn() or templatevtabRowid() or
** templatevtabEof().
*/
static int templatevtabFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
templatevtab_cursor *pCur = (templatevtab_cursor *)pVtabCursor;
pCur->iRowid = 1;
return SQLITE_OK;
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
*/
static int templatevtabBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
pIdxInfo->estimatedCost = (double)10;
pIdxInfo->estimatedRows = 10;
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** virtual table.
*/
static sqlite3_module templatevtabModule = {
/* iVersion */ 0,
/* xCreate */ 0,
/* xConnect */ templatevtabConnect,
/* xBestIndex */ templatevtabBestIndex,
/* xDisconnect */ templatevtabDisconnect,
/* xDestroy */ 0,
/* xOpen */ templatevtabOpen,
/* xClose */ templatevtabClose,
/* xFilter */ templatevtabFilter,
/* xNext */ templatevtabNext,
/* xEof */ templatevtabEof,
/* xColumn */ templatevtabColumn,
/* xRowid */ templatevtabRowid,
/* xUpdate */ 0,
/* xBegin */ 0,
/* xSync */ 0,
/* xCommit */ 0,
/* xRollback */ 0,
/* xFindMethod */ 0,
/* xRename */ 0,
/* xSavepoint */ 0,
/* xRelease */ 0,
/* xRollbackTo */ 0
};
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_templatevtab_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
rc = sqlite3_create_module(db, "templatevtab", &templatevtabModule, 0);
return rc;
}

11
manifest
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@@ -1,5 +1,5 @@
C Fix\sa\sproblem\sin\sthe\snew\supsert\simplemention,\sdiscovered\sby\sOSSFuzz.
D 2018-04-19T13:52:39.607
C Add\sthe\sext/misc/tmeplatevtab.c\stemplate\sfor\svirtual\stables.\s\sThis\sis\sa\nwork-in-progress\sas\sit\sstill\sneeds\simprovements\sto\sthe\scomments\sin\sorder\sto\nbe\suseful\sas\sa\stemplate.
D 2018-04-19T16:14:59.612
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F Makefile.in 5ce9343cba9c189046f1afe6d2bcc1f68079439febc05267b98aec6ecc752439
@@ -297,6 +297,7 @@ F ext/misc/showauth.c 732578f0fe4ce42d577e1c86dc89dd14a006ab52
F ext/misc/spellfix.c 54d650f44f3a69a851814791bd4d304575cdbbf78d96d4f0801b44a8f31a58c5
F ext/misc/sqlar.c 57d5bc45cd5492208e451f697404be88f8612527d64c9d42f96b325b64983d74
F ext/misc/stmt.c 6f16443abb3551e3f5813bb13ba19a30e7032830015b0f92fe0c0453045c0a11
F ext/misc/templatevtab.c 52b9363de0ae4a695728a52769a2e2dab8a0a2db77ca753ad9e1a0d0f32d1f89
F ext/misc/totype.c 4a167594e791abeed95e0a8db028822b5e8fe512
F ext/misc/unionvtab.c 0b3173f69b8899da640a13a345dc5ef1400199405f738abe6145b2454195b8ff
F ext/misc/vfslog.c fe40fab5c077a40477f7e5eba994309ecac6cc95
@@ -1723,7 +1724,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
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U drh
Z 90e6c0b9939b6f41ccf20e0efc9fa0c1
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@@ -1 +1 @@
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