FCL/sf/os/persistentdata: comparison persistentstorage/sql/SQLite/vdbemem.c

equal deleted inserted replaced

--1:000000000000
+:08ec8eefde2f
+/*
+** 2004 May 26
+**
+** 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 contains code use to manipulate "Mem" structure.  A "Mem"
+** stores a single value in the VDBE.  Mem is an opaque structure visible
+** only within the VDBE.  Interface routines refer to a Mem using the
+** name sqlite_value
+**
+** $Id: vdbemem.c,v 1.121 2008/08/01 20:10:09 drh Exp $
+*/
+#include "sqliteInt.h"
+#include <ctype.h>
+#include "vdbeInt.h"
+/*
+** Call sqlite3VdbeMemExpandBlob() on the supplied value (type Mem*)
+** P if required.
+*/
+#define expandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)
+/*
+** If pMem is an object with a valid string representation, this routine
+** ensures the internal encoding for the string representation is
+** 'desiredEnc', one of SQLITE_UTF8, SQLITE_UTF16LE or SQLITE_UTF16BE.
+**
+** If pMem is not a string object, or the encoding of the string
+** representation is already stored using the requested encoding, then this
+** routine is a no-op.
+**
+** SQLITE_OK is returned if the conversion is successful (or not required).
+** SQLITE_NOMEM may be returned if a malloc() fails during conversion
+** between formats.
+*/
+int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
+int rc;
+if( !(pMem->flags&MEM_Str) || pMem->enc==desiredEnc ){
+return SQLITE_OK;
+}
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+#ifdef SQLITE_OMIT_UTF16
+return SQLITE_ERROR;
+#else
+/* MemTranslate() may return SQLITE_OK or SQLITE_NOMEM. If NOMEM is returned,
+** then the encoding of the value may not have changed.
+*/
+rc = sqlite3VdbeMemTranslate(pMem, desiredEnc);
+assert(rc==SQLITE_OK    || rc==SQLITE_NOMEM);
+assert(rc==SQLITE_OK    || pMem->enc!=desiredEnc);
+assert(rc==SQLITE_NOMEM || pMem->enc==desiredEnc);
+return rc;
+#endif
+}
+/*
+** Make sure pMem->z points to a writable allocation of at least
+** n bytes.
+**
+** If the memory cell currently contains string or blob data
+** and the third argument passed to this function is true, the
+** current content of the cell is preserved. Otherwise, it may
+** be discarded.
+**
+** This function sets the MEM_Dyn flag and clears any xDel callback.
+** It also clears MEM_Ephem and MEM_Static. If the preserve flag is
+** not set, Mem.n is zeroed.
+*/
+int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve){
+assert( 1 >=
+((pMem->zMalloc && pMem->zMalloc==pMem->z) ? 1 : 0) +
+(((pMem->flags&MEM_Dyn)&&pMem->xDel) ? 1 : 0) +
+((pMem->flags&MEM_Ephem) ? 1 : 0) +
+((pMem->flags&MEM_Static) ? 1 : 0)
+);
+if( n<32 ) n = 32;
+if( sqlite3DbMallocSize(pMem->db, pMem->zMalloc)<n ){
+if( preserve && pMem->z==pMem->zMalloc ){
+pMem->z = pMem->zMalloc = sqlite3DbReallocOrFree(pMem->db, pMem->z, n);
+if( !pMem->z ){
+pMem->flags = MEM_Null;
+}
+preserve = 0;
+}else{
+sqlite3DbFree(pMem->db, pMem->zMalloc);
+pMem->zMalloc = sqlite3DbMallocRaw(pMem->db, n);
+}
+}
+if( preserve && pMem->z && pMem->zMalloc && pMem->z!=pMem->zMalloc ){
+memcpy(pMem->zMalloc, pMem->z, pMem->n);
+}
+if( pMem->flags&MEM_Dyn && pMem->xDel ){
+pMem->xDel((void *)(pMem->z));
+}
+pMem->z = pMem->zMalloc;
+pMem->flags &= ~(MEM_Ephem|MEM_Static);
+pMem->xDel = 0;
+return (pMem->z ? SQLITE_OK : SQLITE_NOMEM);
+}
+/*
+** Make the given Mem object MEM_Dyn.  In other words, make it so
+** that any TEXT or BLOB content is stored in memory obtained from
+** malloc().  In this way, we know that the memory is safe to be
+** overwritten or altered.
+**
+** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
+*/
+int sqlite3VdbeMemMakeWriteable(Mem *pMem){
+int f;
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+expandBlob(pMem);
+f = pMem->flags;
+if( (f&(MEM_Str|MEM_Blob)) && pMem->z!=pMem->zMalloc ){
+if( sqlite3VdbeMemGrow(pMem, pMem->n + 2, 1) ){
+return SQLITE_NOMEM;
+}
+pMem->z[pMem->n] = 0;
+pMem->z[pMem->n+1] = 0;
+pMem->flags |= MEM_Term;
+}
+return SQLITE_OK;
+}
+/*
+** If the given Mem* has a zero-filled tail, turn it into an ordinary
+** blob stored in dynamically allocated space.
+*/
+#ifndef SQLITE_OMIT_INCRBLOB
+int sqlite3VdbeMemExpandBlob(Mem *pMem){
+if( pMem->flags & MEM_Zero ){
+int nByte;
+assert( pMem->flags&MEM_Blob );
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+/* Set nByte to the number of bytes required to store the expanded blob. */
+nByte = pMem->n + pMem->u.i;
+if( nByte<=0 ){
+nByte = 1;
+}
+if( sqlite3VdbeMemGrow(pMem, nByte, 1) ){
+return SQLITE_NOMEM;
+}
+memset(&pMem->z[pMem->n], 0, pMem->u.i);
+pMem->n += pMem->u.i;
+pMem->flags &= ~(MEM_Zero|MEM_Term);
+}
+return SQLITE_OK;
+}
+#endif
+/*
+** Make sure the given Mem is \u0000 terminated.
+*/
+int sqlite3VdbeMemNulTerminate(Mem *pMem){
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+if( (pMem->flags & MEM_Term)!=0 || (pMem->flags & MEM_Str)==0 ){
+return SQLITE_OK;   /* Nothing to do */
+}
+if( sqlite3VdbeMemGrow(pMem, pMem->n+2, 1) ){
+return SQLITE_NOMEM;
+}
+pMem->z[pMem->n] = 0;
+pMem->z[pMem->n+1] = 0;
+pMem->flags |= MEM_Term;
+return SQLITE_OK;
+}
+/*
+** Add MEM_Str to the set of representations for the given Mem.  Numbers
+** are converted using sqlite3_snprintf().  Converting a BLOB to a string
+** is a no-op.
+**
+** Existing representations MEM_Int and MEM_Real are *not* invalidated.
+**
+** A MEM_Null value will never be passed to this function. This function is
+** used for converting values to text for returning to the user (i.e. via
+** sqlite3_value_text()), or for ensuring that values to be used as btree
+** keys are strings. In the former case a NULL pointer is returned the
+** user and the later is an internal programming error.
+*/
+int sqlite3VdbeMemStringify(Mem *pMem, int enc){
+int rc = SQLITE_OK;
+int fg = pMem->flags;
+const int nByte = 32;
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+assert( !(fg&MEM_Zero) );
+assert( !(fg&(MEM_Str|MEM_Blob)) );
+assert( fg&(MEM_Int|MEM_Real) );
+if( sqlite3VdbeMemGrow(pMem, nByte, 0) ){
+return SQLITE_NOMEM;
+}
+/* For a Real or Integer, use sqlite3_mprintf() to produce the UTF-8
+** string representation of the value. Then, if the required encoding
+** is UTF-16le or UTF-16be do a translation.
+**
+** FIX ME: It would be better if sqlite3_snprintf() could do UTF-16.
+*/
+if( fg & MEM_Int ){
+sqlite3_snprintf(nByte, pMem->z, "%lld", pMem->u.i);
+}else{
+assert( fg & MEM_Real );
+sqlite3_snprintf(nByte, pMem->z, "%!.15g", pMem->r);
+}
+pMem->n = strlen(pMem->z);
+pMem->enc = SQLITE_UTF8;
+pMem->flags |= MEM_Str|MEM_Term;
+sqlite3VdbeChangeEncoding(pMem, enc);
+return rc;
+}
+/*
+** Memory cell pMem contains the context of an aggregate function.
+** This routine calls the finalize method for that function.  The
+** result of the aggregate is stored back into pMem.
+**
+** Return SQLITE_ERROR if the finalizer reports an error.  SQLITE_OK
+** otherwise.
+*/
+int sqlite3VdbeMemFinalize(Mem *pMem, FuncDef *pFunc){
+int rc = SQLITE_OK;
+if( pFunc && pFunc->xFinalize ){
+sqlite3_context ctx;
+assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+ctx.s.flags = MEM_Null;
+ctx.s.db = pMem->db;
+ctx.s.zMalloc = 0;
+ctx.pMem = pMem;
+ctx.pFunc = pFunc;
+ctx.isError = 0;
+pFunc->xFinalize(&ctx);
+assert( 0==(pMem->flags&MEM_Dyn) && !pMem->xDel );
+sqlite3DbFree(pMem->db, pMem->zMalloc);
+*pMem = ctx.s;
+rc = (ctx.isError?SQLITE_ERROR:SQLITE_OK);
+}
+return rc;
+}
+/*
+** If the memory cell contains a string value that must be freed by
+** invoking an external callback, free it now. Calling this function
+** does not free any Mem.zMalloc buffer.
+*/
+void sqlite3VdbeMemReleaseExternal(Mem *p){
+assert( p->db==0 || sqlite3_mutex_held(p->db->mutex) );
+if( p->flags&MEM_Agg ){
+sqlite3VdbeMemFinalize(p, p->u.pDef);
+assert( (p->flags & MEM_Agg)==0 );
+sqlite3VdbeMemRelease(p);
+}else if( p->flags&MEM_Dyn && p->xDel ){
+p->xDel((void *)p->z);
+p->xDel = 0;
+}
+}
+/*
+** Release any memory held by the Mem. This may leave the Mem in an
+** inconsistent state, for example with (Mem.z==0) and
+** (Mem.type==SQLITE_TEXT).
+*/
+void sqlite3VdbeMemRelease(Mem *p){
+sqlite3VdbeMemReleaseExternal(p);
+sqlite3DbFree(p->db, p->zMalloc);
+p->z = 0;
+p->zMalloc = 0;
+p->xDel = 0;
+}
+/*
+** Convert a 64-bit IEEE double into a 64-bit signed integer.
+** If the double is too large, return 0x8000000000000000.
+**
+** Most systems appear to do this simply by assigning
+** variables and without the extra range tests.  But
+** there are reports that windows throws an expection
+** if the floating point value is out of range. (See ticket #2880.)
+** Because we do not completely understand the problem, we will
+** take the conservative approach and always do range tests
+** before attempting the conversion.
+*/
+static i64 doubleToInt64(double r){
+/*
+** Many compilers we encounter do not define constants for the
+** minimum and maximum 64-bit integers, or they define them
+** inconsistently.  And many do not understand the "LL" notation.
+** So we define our own static constants here using nothing
+** larger than a 32-bit integer constant.
+*/
+static const i64 maxInt = LARGEST_INT64;
+static const i64 minInt = SMALLEST_INT64;
+if( r<(double)minInt ){
+return minInt;
+}else if( r>(double)maxInt ){
+return minInt;
+}else{
+return (i64)r;
+}
+}
+/*
+** Return some kind of integer value which is the best we can do
+** at representing the value that *pMem describes as an integer.
+** If pMem is an integer, then the value is exact.  If pMem is
+** a floating-point then the value returned is the integer part.
+** If pMem is a string or blob, then we make an attempt to convert
+** it into a integer and return that.  If pMem is NULL, return 0.
+**
+** If pMem is a string, its encoding might be changed.
+*/
+i64 sqlite3VdbeIntValue(Mem *pMem){
+int flags;
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+flags = pMem->flags;
+if( flags & MEM_Int ){
+return pMem->u.i;
+}else if( flags & MEM_Real ){
+return doubleToInt64(pMem->r);
+}else if( flags & (MEM_Str|MEM_Blob) ){
+i64 value;
+pMem->flags |= MEM_Str;
+if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
+|| sqlite3VdbeMemNulTerminate(pMem) ){
+return 0;
+}
+assert( pMem->z );
+sqlite3Atoi64(pMem->z, &value);
+return value;
+}else{
+return 0;
+}
+}
+/*
+** Return the best representation of pMem that we can get into a
+** double.  If pMem is already a double or an integer, return its
+** value.  If it is a string or blob, try to convert it to a double.
+** If it is a NULL, return 0.0.
+*/
+double sqlite3VdbeRealValue(Mem *pMem){
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+if( pMem->flags & MEM_Real ){
+return pMem->r;
+}else if( pMem->flags & MEM_Int ){
+return (double)pMem->u.i;
+}else if( pMem->flags & (MEM_Str|MEM_Blob) ){
+double val = 0.0;
+pMem->flags |= MEM_Str;
+if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
+|| sqlite3VdbeMemNulTerminate(pMem) ){
+return 0.0;
+}
+assert( pMem->z );
+sqlite3AtoF(pMem->z, &val);
+return val;
+}else{
+return 0.0;
+}
+}
+/*
+** The MEM structure is already a MEM_Real.  Try to also make it a
+** MEM_Int if we can.
+*/
+void sqlite3VdbeIntegerAffinity(Mem *pMem){
+assert( pMem->flags & MEM_Real );
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+pMem->u.i = doubleToInt64(pMem->r);
+if( pMem->r==(double)pMem->u.i ){
+pMem->flags |= MEM_Int;
+}
+}
+static void setTypeFlag(Mem *pMem, int f){
+MemSetTypeFlag(pMem, f);
+}
+/*
+** Convert pMem to type integer.  Invalidate any prior representations.
+*/
+int sqlite3VdbeMemIntegerify(Mem *pMem){
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+pMem->u.i = sqlite3VdbeIntValue(pMem);
+setTypeFlag(pMem, MEM_Int);
+return SQLITE_OK;
+}
+/*
+** Convert pMem so that it is of type MEM_Real.
+** Invalidate any prior representations.
+*/
+int sqlite3VdbeMemRealify(Mem *pMem){
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+pMem->r = sqlite3VdbeRealValue(pMem);
+setTypeFlag(pMem, MEM_Real);
+return SQLITE_OK;
+}
+/*
+** Convert pMem so that it has types MEM_Real or MEM_Int or both.
+** Invalidate any prior representations.
+*/
+int sqlite3VdbeMemNumerify(Mem *pMem){
+double r1, r2;
+i64 i;
+assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_Null))==0 );
+assert( (pMem->flags & (MEM_Blob|MEM_Str))!=0 );
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+r1 = sqlite3VdbeRealValue(pMem);
+i = doubleToInt64(r1);
+r2 = (double)i;
+if( r1==r2 ){
+sqlite3VdbeMemIntegerify(pMem);
+}else{
+pMem->r = r1;
+setTypeFlag(pMem, MEM_Real);
+}
+return SQLITE_OK;
+}
+/*
+** Delete any previous value and set the value stored in *pMem to NULL.
+*/
+void sqlite3VdbeMemSetNull(Mem *pMem){
+setTypeFlag(pMem, MEM_Null);
+pMem->type = SQLITE_NULL;
+}
+/*
+** Delete any previous value and set the value to be a BLOB of length
+** n containing all zeros.
+*/
+void sqlite3VdbeMemSetZeroBlob(Mem *pMem, int n){
+sqlite3VdbeMemRelease(pMem);
+setTypeFlag(pMem, MEM_Blob);
+pMem->flags = MEM_Blob|MEM_Zero;
+pMem->type = SQLITE_BLOB;
+pMem->n = 0;
+if( n<0 ) n = 0;
+pMem->u.i = n;
+pMem->enc = SQLITE_UTF8;
+}
+/*
+** Delete any previous value and set the value stored in *pMem to val,
+** manifest type INTEGER.
+*/
+void sqlite3VdbeMemSetInt64(Mem *pMem, i64 val){
+sqlite3VdbeMemRelease(pMem);
+pMem->u.i = val;
+pMem->flags = MEM_Int;
+pMem->type = SQLITE_INTEGER;
+}
+/*
+** Delete any previous value and set the value stored in *pMem to val,
+** manifest type REAL.
+*/
+void sqlite3VdbeMemSetDouble(Mem *pMem, double val){
+if( sqlite3IsNaN(val) ){
+sqlite3VdbeMemSetNull(pMem);
+}else{
+sqlite3VdbeMemRelease(pMem);
+pMem->r = val;
+pMem->flags = MEM_Real;
+pMem->type = SQLITE_FLOAT;
+}
+}
+/*
+** Return true if the Mem object contains a TEXT or BLOB that is
+** too large - whose size exceeds SQLITE_MAX_LENGTH.
+*/
+int sqlite3VdbeMemTooBig(Mem *p){
+assert( p->db!=0 );
+if( p->flags & (MEM_Str|MEM_Blob) ){
+int n = p->n;
+if( p->flags & MEM_Zero ){
+n += p->u.i;
+}
+return n>p->db->aLimit[SQLITE_LIMIT_LENGTH];
+}
+return 0;
+}
+/*
+** Size of struct Mem not including the Mem.zMalloc member.
+*/
+#define MEMCELLSIZE (size_t)(&(((Mem *)0)->zMalloc))
+/*
+** Make an shallow copy of pFrom into pTo.  Prior contents of
+** pTo are freed.  The pFrom->z field is not duplicated.  If
+** pFrom->z is used, then pTo->z points to the same thing as pFrom->z
+** and flags gets srcType (either MEM_Ephem or MEM_Static).
+*/
+void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType){
+sqlite3VdbeMemReleaseExternal(pTo);
+memcpy(pTo, pFrom, MEMCELLSIZE);
+pTo->xDel = 0;
+if( (pFrom->flags&MEM_Dyn)!=0 || pFrom->z==pFrom->zMalloc ){
+pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
+assert( srcType==MEM_Ephem || srcType==MEM_Static );
+pTo->flags |= srcType;
+}
+}
+/*
+** Make a full copy of pFrom into pTo.  Prior contents of pTo are
+** freed before the copy is made.
+*/
+int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
+int rc = SQLITE_OK;
+sqlite3VdbeMemReleaseExternal(pTo);
+memcpy(pTo, pFrom, MEMCELLSIZE);
+pTo->flags &= ~MEM_Dyn;
+if( pTo->flags&(MEM_Str|MEM_Blob) ){
+if( 0==(pFrom->flags&MEM_Static) ){
+pTo->flags |= MEM_Ephem;
+rc = sqlite3VdbeMemMakeWriteable(pTo);
+}
+}
+return rc;
+}
+/*
+** Transfer the contents of pFrom to pTo. Any existing value in pTo is
+** freed. If pFrom contains ephemeral data, a copy is made.
+**
+** pFrom contains an SQL NULL when this routine returns.
+*/
+void sqlite3VdbeMemMove(Mem *pTo, Mem *pFrom){
+assert( pFrom->db==0 || sqlite3_mutex_held(pFrom->db->mutex) );
+assert( pTo->db==0 || sqlite3_mutex_held(pTo->db->mutex) );
+assert( pFrom->db==0 || pTo->db==0 || pFrom->db==pTo->db );
+sqlite3VdbeMemRelease(pTo);
+memcpy(pTo, pFrom, sizeof(Mem));
+pFrom->flags = MEM_Null;
+pFrom->xDel = 0;
+pFrom->zMalloc = 0;
+}
+/*
+** Change the value of a Mem to be a string or a BLOB.
+**
+** The memory management strategy depends on the value of the xDel
+** parameter. If the value passed is SQLITE_TRANSIENT, then the
+** string is copied into a (possibly existing) buffer managed by the
+** Mem structure. Otherwise, any existing buffer is freed and the
+** pointer copied.
+*/
+int sqlite3VdbeMemSetStr(
+Mem *pMem,          /* Memory cell to set to string value */
+const char *z,      /* String pointer */
+int n,              /* Bytes in string, or negative */
+u8 enc,             /* Encoding of z.  0 for BLOBs */
+void (*xDel)(void*) /* Destructor function */
+){
+int nByte = n;      /* New value for pMem->n */
+int iLimit;         /* Maximum allowed string or blob size */
+int flags = 0;      /* New value for pMem->flags */
+assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+/* If z is a NULL pointer, set pMem to contain an SQL NULL. */
+if( !z ){
+sqlite3VdbeMemSetNull(pMem);
+return SQLITE_OK;
+}
+if( pMem->db ){
+iLimit = pMem->db->aLimit[SQLITE_LIMIT_LENGTH];
+}else{
+iLimit = SQLITE_MAX_LENGTH;
+}
+flags = (enc==0?MEM_Blob:MEM_Str);
+if( nByte<0 ){
+assert( enc!=0 );
+if( enc==SQLITE_UTF8 ){
+for(nByte=0; nByte<=iLimit && z[nByte]; nByte++){}
+}else{
+for(nByte=0; nByte<=iLimit && (z[nByte] | z[nByte+1]); nByte+=2){}
+}
+flags |= MEM_Term;
+}
+if( nByte>iLimit ){
+return SQLITE_TOOBIG;
+}
+/* The following block sets the new values of Mem.z and Mem.xDel. It
+** also sets a flag in local variable "flags" to indicate the memory
+** management (one of MEM_Dyn or MEM_Static).
+*/
+if( xDel==SQLITE_TRANSIENT ){
+int nAlloc = nByte;
+if( flags&MEM_Term ){
+nAlloc += (enc==SQLITE_UTF8?1:2);
+}
+if( sqlite3VdbeMemGrow(pMem, nAlloc, 0) ){
+return SQLITE_NOMEM;
+}
+memcpy(pMem->z, z, nAlloc);
+}else if( xDel==SQLITE_DYNAMIC ){
+sqlite3VdbeMemRelease(pMem);
+pMem->zMalloc = pMem->z = (char *)z;
+pMem->xDel = 0;
+}else{
+sqlite3VdbeMemRelease(pMem);
+pMem->z = (char *)z;
+pMem->xDel = xDel;
+flags |= ((xDel==SQLITE_STATIC)?MEM_Static:MEM_Dyn);
+}
+pMem->n = nByte;
+pMem->flags = flags;
+pMem->enc = (enc==0 ? SQLITE_UTF8 : enc);
+pMem->type = (enc==0 ? SQLITE_BLOB : SQLITE_TEXT);
+#ifndef SQLITE_OMIT_UTF16
+if( pMem->enc!=SQLITE_UTF8 && sqlite3VdbeMemHandleBom(pMem) ){
+return SQLITE_NOMEM;
+}
+#endif
+return SQLITE_OK;
+}
+/*
+** Compare the values contained by the two memory cells, returning
+** negative, zero or positive if pMem1 is less than, equal to, or greater
+** than pMem2. Sorting order is NULL's first, followed by numbers (integers
+** and reals) sorted numerically, followed by text ordered by the collating
+** sequence pColl and finally blob's ordered by memcmp().
+**
+** Two NULL values are considered equal by this function.
+*/
+int sqlite3MemCompare(const Mem *pMem1, const Mem *pMem2, const CollSeq *pColl){
+int rc;
+int f1, f2;
+int combined_flags;
+/* Interchange pMem1 and pMem2 if the collating sequence specifies
+** DESC order.
+*/
+f1 = pMem1->flags;
+f2 = pMem2->flags;
+combined_flags = f1|f2;
+/* If one value is NULL, it is less than the other. If both values
+** are NULL, return 0.
+*/
+if( combined_flags&MEM_Null ){
+return (f2&MEM_Null) - (f1&MEM_Null);
+}
+/* If one value is a number and the other is not, the number is less.
+** If both are numbers, compare as reals if one is a real, or as integers
+** if both values are integers.
+*/
+if( combined_flags&(MEM_Int|MEM_Real) ){
+if( !(f1&(MEM_Int|MEM_Real)) ){
+return 1;
+}
+if( !(f2&(MEM_Int|MEM_Real)) ){
+return -1;
+}
+if( (f1 & f2 & MEM_Int)==0 ){
+double r1, r2;
+if( (f1&MEM_Real)==0 ){
+r1 = pMem1->u.i;
+}else{
+r1 = pMem1->r;
+}
+if( (f2&MEM_Real)==0 ){
+r2 = pMem2->u.i;
+}else{
+r2 = pMem2->r;
+}
+if( r1<r2 ) return -1;
+if( r1>r2 ) return 1;
+return 0;
+}else{
+assert( f1&MEM_Int );
+assert( f2&MEM_Int );
+if( pMem1->u.i < pMem2->u.i ) return -1;
+if( pMem1->u.i > pMem2->u.i ) return 1;
+return 0;
+}
+}
+/* If one value is a string and the other is a blob, the string is less.
+** If both are strings, compare using the collating functions.
+*/
+if( combined_flags&MEM_Str ){
+if( (f1 & MEM_Str)==0 ){
+return 1;
+}
+if( (f2 & MEM_Str)==0 ){
+return -1;
+}
+assert( pMem1->enc==pMem2->enc );
+assert( pMem1->enc==SQLITE_UTF8 ||
+pMem1->enc==SQLITE_UTF16LE || pMem1->enc==SQLITE_UTF16BE );
+/* The collation sequence must be defined at this point, even if
+** the user deletes the collation sequence after the vdbe program is
+** compiled (this was not always the case).
+*/
+assert( !pColl || pColl->xCmp );
+if( pColl ){
+if( pMem1->enc==pColl->enc ){
+/* The strings are already in the correct encoding.  Call the
+** comparison function directly */
+return pColl->xCmp(pColl->pUser,pMem1->n,pMem1->z,pMem2->n,pMem2->z);
+}else{
+u8 origEnc = pMem1->enc;
+const void *v1, *v2;
+int n1, n2;
+/* Convert the strings into the encoding that the comparison
+** function expects */
+v1 = sqlite3ValueText((sqlite3_value*)pMem1, pColl->enc);
+n1 = v1==0 ? 0 : pMem1->n;
+assert( n1==sqlite3ValueBytes((sqlite3_value*)pMem1, pColl->enc) );
+v2 = sqlite3ValueText((sqlite3_value*)pMem2, pColl->enc);
+n2 = v2==0 ? 0 : pMem2->n;
+assert( n2==sqlite3ValueBytes((sqlite3_value*)pMem2, pColl->enc) );
+/* Do the comparison */
+rc = pColl->xCmp(pColl->pUser, n1, v1, n2, v2);
+/* Convert the strings back into the database encoding */
+sqlite3ValueText((sqlite3_value*)pMem1, origEnc);
+sqlite3ValueText((sqlite3_value*)pMem2, origEnc);
+return rc;
+}
+}
+/* If a NULL pointer was passed as the collate function, fall through
+** to the blob case and use memcmp().  */
+}
+/* Both values must be blobs.  Compare using memcmp().  */
+rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
+if( rc==0 ){
+rc = pMem1->n - pMem2->n;
+}
+return rc;
+}
+/*
+** Move data out of a btree key or data field and into a Mem structure.
+** The data or key is taken from the entry that pCur is currently pointing
+** to.  offset and amt determine what portion of the data or key to retrieve.
+** key is true to get the key or false to get data.  The result is written
+** into the pMem element.
+**
+** The pMem structure is assumed to be uninitialized.  Any prior content
+** is overwritten without being freed.
+**
+** If this routine fails for any reason (malloc returns NULL or unable
+** to read from the disk) then the pMem is left in an inconsistent state.
+*/
+int sqlite3VdbeMemFromBtree(
+BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
+int offset,       /* Offset from the start of data to return bytes from. */
+int amt,          /* Number of bytes to return. */
+int key,          /* If true, retrieve from the btree key, not data. */
+Mem *pMem         /* OUT: Return data in this Mem structure. */
+){
+char *zData;       /* Data from the btree layer */
+int available = 0; /* Number of bytes available on the local btree page */
+sqlite3 *db;       /* Database connection */
+int rc = SQLITE_OK;
+db = sqlite3BtreeCursorDb(pCur);
+assert( sqlite3_mutex_held(db->mutex) );
+if( key ){
+zData = (char *)sqlite3BtreeKeyFetch(pCur, &available);
+}else{
+zData = (char *)sqlite3BtreeDataFetch(pCur, &available);
+}
+assert( zData!=0 );
+if( offset+amt<=available && ((pMem->flags&MEM_Dyn)==0 || pMem->xDel) ){
+sqlite3VdbeMemRelease(pMem);
+pMem->z = &zData[offset];
+pMem->flags = MEM_Blob|MEM_Ephem;
+}else if( SQLITE_OK==(rc = sqlite3VdbeMemGrow(pMem, amt+2, 0)) ){
+pMem->flags = MEM_Blob|MEM_Dyn|MEM_Term;
+pMem->enc = 0;
+pMem->type = SQLITE_BLOB;
+if( key ){
+rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
+}else{
+rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
+}
+pMem->z[amt] = 0;
+pMem->z[amt+1] = 0;
+if( rc!=SQLITE_OK ){
+sqlite3VdbeMemRelease(pMem);
+}
+}
+pMem->n = amt;
+return rc;
+}
+#if 0
+/*
+** Perform various checks on the memory cell pMem. An assert() will
+** fail if pMem is internally inconsistent.
+*/
+void sqlite3VdbeMemSanity(Mem *pMem){
+int flags = pMem->flags;
+assert( flags!=0 );  /* Must define some type */
+if( flags & (MEM_Str|MEM_Blob) ){
+int x = flags & (MEM_Static|MEM_Dyn|MEM_Ephem|MEM_Short);
+assert( x!=0 );            /* Strings must define a string subtype */
+assert( (x & (x-1))==0 );  /* Only one string subtype can be defined */
+assert( pMem->z!=0 );      /* Strings must have a value */
+/* Mem.z points to Mem.zShort iff the subtype is MEM_Short */
+assert( (x & MEM_Short)==0 || pMem->z==pMem->zShort );
+assert( (x & MEM_Short)!=0 || pMem->z!=pMem->zShort );
+/* No destructor unless there is MEM_Dyn */
+assert( pMem->xDel==0 || (pMem->flags & MEM_Dyn)!=0 );
+if( (flags & MEM_Str) ){
+assert( pMem->enc==SQLITE_UTF8 ||
+pMem->enc==SQLITE_UTF16BE ||
+pMem->enc==SQLITE_UTF16LE
+);
+/* If the string is UTF-8 encoded and nul terminated, then pMem->n
+** must be the length of the string.  (Later:)  If the database file
+** has been corrupted, '\000' characters might have been inserted
+** into the middle of the string.  In that case, the strlen() might
+** be less.
+*/
+if( pMem->enc==SQLITE_UTF8 && (flags & MEM_Term) ){
+assert( strlen(pMem->z)<=pMem->n );
+assert( pMem->z[pMem->n]==0 );
+}
+}
+}else{
+/* Cannot define a string subtype for non-string objects */
+assert( (pMem->flags & (MEM_Static|MEM_Dyn|MEM_Ephem|MEM_Short))==0 );
+assert( pMem->xDel==0 );
+}
+/* MEM_Null excludes all other types */
+assert( (pMem->flags&(MEM_Str|MEM_Int|MEM_Real|MEM_Blob))==0
+|| (pMem->flags&MEM_Null)==0 );
+/* If the MEM is both real and integer, the values are equal */
+assert( (pMem->flags & (MEM_Int|MEM_Real))!=(MEM_Int|MEM_Real)
+|| pMem->r==pMem->u.i );
+}
+#endif
+/* This function is only available internally, it is not part of the
+** external API. It works in a similar way to sqlite3_value_text(),
+** except the data returned is in the encoding specified by the second
+** parameter, which must be one of SQLITE_UTF16BE, SQLITE_UTF16LE or
+** SQLITE_UTF8.
+**
+** (2006-02-16:)  The enc value can be or-ed with SQLITE_UTF16_ALIGNED.
+** If that is the case, then the result must be aligned on an even byte
+** boundary.
+*/
+const void *sqlite3ValueText(sqlite3_value* pVal, u8 enc){
+if( !pVal ) return 0;
+assert( pVal->db==0 || sqlite3_mutex_held(pVal->db->mutex) );
+assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
+if( pVal->flags&MEM_Null ){
+return 0;
+}
+assert( (MEM_Blob>>3) == MEM_Str );
+pVal->flags |= (pVal->flags & MEM_Blob)>>3;
+expandBlob(pVal);
+if( pVal->flags&MEM_Str ){
+sqlite3VdbeChangeEncoding(pVal, enc & ~SQLITE_UTF16_ALIGNED);
+if( (enc & SQLITE_UTF16_ALIGNED)!=0 && 1==(1&SQLITE_PTR_TO_INT(pVal->z)) ){
+assert( (pVal->flags & (MEM_Ephem|MEM_Static))!=0 );
+if( sqlite3VdbeMemMakeWriteable(pVal)!=SQLITE_OK ){
+return 0;
+}
+}
+sqlite3VdbeMemNulTerminate(pVal);
+}else{
+assert( (pVal->flags&MEM_Blob)==0 );
+sqlite3VdbeMemStringify(pVal, enc);
+assert( 0==(1&(int)pVal->z) );
+}
+assert(pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) || pVal->db==0
+|| pVal->db->mallocFailed );
+if( pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) ){
+return pVal->z;
+}else{
+return 0;
+}
+}
+/*
+** Create a new sqlite3_value object.
+*/
+sqlite3_value *sqlite3ValueNew(sqlite3 *db){
+Mem *p = sqlite3DbMallocZero(db, sizeof(*p));
+if( p ){
+p->flags = MEM_Null;
+p->type = SQLITE_NULL;
+p->db = db;
+}
+return p;
+}
+/*
+** Create a new sqlite3_value object, containing the value of pExpr.
+**
+** This only works for very simple expressions that consist of one constant
+** token (i.e. "5", "5.1", "'a string'"). If the expression can
+** be converted directly into a value, then the value is allocated and
+** a pointer written to *ppVal. The caller is responsible for deallocating
+** the value by passing it to sqlite3ValueFree() later on. If the expression
+** cannot be converted to a value, then *ppVal is set to NULL.
+*/
+int sqlite3ValueFromExpr(
+sqlite3 *db,              /* The database connection */
+Expr *pExpr,              /* The expression to evaluate */
+u8 enc,                   /* Encoding to use */
+u8 affinity,              /* Affinity to use */
+sqlite3_value **ppVal     /* Write the new value here */
+){
+int op;
+char *zVal = 0;
+sqlite3_value *pVal = 0;
+if( !pExpr ){
+*ppVal = 0;
+return SQLITE_OK;
+}
+op = pExpr->op;
+if( op==TK_STRING || op==TK_FLOAT || op==TK_INTEGER ){
+zVal = sqlite3DbStrNDup(db, (char*)pExpr->token.z, pExpr->token.n);
+pVal = sqlite3ValueNew(db);
+if( !zVal || !pVal ) goto no_mem;
+sqlite3Dequote(zVal);
+sqlite3ValueSetStr(pVal, -1, zVal, SQLITE_UTF8, SQLITE_DYNAMIC);
+if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_NONE ){
+sqlite3ValueApplyAffinity(pVal, SQLITE_AFF_NUMERIC, enc);
+}else{
+sqlite3ValueApplyAffinity(pVal, affinity, enc);
+}
+}else if( op==TK_UMINUS ) {
+if( SQLITE_OK==sqlite3ValueFromExpr(db,pExpr->pLeft,enc,affinity,&pVal) ){
+pVal->u.i = -1 * pVal->u.i;
+pVal->r = -1.0 * pVal->r;
+}
+}
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+else if( op==TK_BLOB ){
+int nVal;
+assert( pExpr->token.n>=3 );
+assert( pExpr->token.z[0]=='x' || pExpr->token.z[0]=='X' );
+assert( pExpr->token.z[1]=='\'' );
+assert( pExpr->token.z[pExpr->token.n-1]=='\'' );
+pVal = sqlite3ValueNew(db);
+nVal = pExpr->token.n - 3;
+zVal = (char*)pExpr->token.z + 2;
+sqlite3VdbeMemSetStr(pVal, sqlite3HexToBlob(db, zVal, nVal), nVal/2,
+0, SQLITE_DYNAMIC);
+}
+#endif
+*ppVal = pVal;
+return SQLITE_OK;
+no_mem:
+db->mallocFailed = 1;
+sqlite3DbFree(db, zVal);
+sqlite3ValueFree(pVal);
+*ppVal = 0;
+return SQLITE_NOMEM;
+}
+/*
+** Change the string value of an sqlite3_value object
+*/
+void sqlite3ValueSetStr(
+sqlite3_value *v,     /* Value to be set */
+int n,                /* Length of string z */
+const void *z,        /* Text of the new string */
+u8 enc,               /* Encoding to use */
+void (*xDel)(void*)   /* Destructor for the string */
+){
+if( v ) sqlite3VdbeMemSetStr((Mem *)v, z, n, enc, xDel);
+}
+/*
+** Free an sqlite3_value object
+*/
+void sqlite3ValueFree(sqlite3_value *v){
+if( !v ) return;
+sqlite3VdbeMemRelease((Mem *)v);
+sqlite3DbFree(((Mem*)v)->db, v);
+}
+/*
+** Return the number of bytes in the sqlite3_value object assuming
+** that it uses the encoding "enc"
+*/
+int sqlite3ValueBytes(sqlite3_value *pVal, u8 enc){
+Mem *p = (Mem*)pVal;
+if( (p->flags & MEM_Blob)!=0 || sqlite3ValueText(pVal, enc) ){
+if( p->flags & MEM_Zero ){
+return p->n+p->u.i;
+}else{
+return p->n;
+}
+}
+return 0;
+}