monotone

monotone Mtn Source Tree

Root/sqlite/vdbefifo.c

1/*
2** 2005 June 16
3**
4** The author disclaims copyright to this source code. In place of
5** a legal notice, here is a blessing:
6**
7** May you do good and not evil.
8** May you find forgiveness for yourself and forgive others.
9** May you share freely, never taking more than you give.
10**
11*************************************************************************
12** This file implements a FIFO queue of rowids used for processing
13** UPDATE and DELETE statements.
14*/
15#include "sqliteInt.h"
16#include "vdbeInt.h"
17
18/*
19** Allocate a new FifoPage and return a pointer to it. Return NULL if
20** we run out of memory. Leave space on the page for nEntry entries.
21*/
22static FifoPage *allocateFifoPage(int nEntry){
23 FifoPage *pPage;
24 if( nEntry>32767 ){
25 nEntry = 32767;
26 }
27 pPage = sqliteMallocRaw( sizeof(FifoPage) + sizeof(i64)*(nEntry-1) );
28 if( pPage ){
29 pPage->nSlot = nEntry;
30 pPage->iWrite = 0;
31 pPage->iRead = 0;
32 pPage->pNext = 0;
33 }
34 return pPage;
35}
36
37/*
38** Initialize a Fifo structure.
39*/
40void sqlite3VdbeFifoInit(Fifo *pFifo){
41 memset(pFifo, 0, sizeof(*pFifo));
42}
43
44/*
45** Push a single 64-bit integer value into the Fifo. Return SQLITE_OK
46** normally. SQLITE_NOMEM is returned if we are unable to allocate
47** memory.
48*/
49int sqlite3VdbeFifoPush(Fifo *pFifo, i64 val){
50 FifoPage *pPage;
51 pPage = pFifo->pLast;
52 if( pPage==0 ){
53 pPage = pFifo->pLast = pFifo->pFirst = allocateFifoPage(20);
54 if( pPage==0 ){
55 return SQLITE_NOMEM;
56 }
57 }else if( pPage->iWrite>=pPage->nSlot ){
58 pPage->pNext = allocateFifoPage(pFifo->nEntry);
59 if( pPage->pNext==0 ){
60 return SQLITE_NOMEM;
61 }
62 pPage = pFifo->pLast = pPage->pNext;
63 }
64 pPage->aSlot[pPage->iWrite++] = val;
65 pFifo->nEntry++;
66 return SQLITE_OK;
67}
68
69/*
70** Extract a single 64-bit integer value from the Fifo. The integer
71** extracted is the one least recently inserted. If the Fifo is empty
72** return SQLITE_DONE.
73*/
74int sqlite3VdbeFifoPop(Fifo *pFifo, i64 *pVal){
75 FifoPage *pPage;
76 if( pFifo->nEntry==0 ){
77 return SQLITE_DONE;
78 }
79 assert( pFifo->nEntry>0 );
80 pPage = pFifo->pFirst;
81 assert( pPage!=0 );
82 assert( pPage->iWrite>pPage->iRead );
83 assert( pPage->iWrite<=pPage->nSlot );
84 assert( pPage->iRead<pPage->nSlot );
85 assert( pPage->iRead>=0 );
86 *pVal = pPage->aSlot[pPage->iRead++];
87 pFifo->nEntry--;
88 if( pPage->iRead>=pPage->iWrite ){
89 pFifo->pFirst = pPage->pNext;
90 sqliteFree(pPage);
91 if( pFifo->nEntry==0 ){
92 assert( pFifo->pLast==pPage );
93 pFifo->pLast = 0;
94 }else{
95 assert( pFifo->pFirst!=0 );
96 }
97 }else{
98 assert( pFifo->nEntry>0 );
99 }
100 return SQLITE_OK;
101}
102
103/*
104** Delete all information from a Fifo object. Free all memory held
105** by the Fifo.
106*/
107void sqlite3VdbeFifoClear(Fifo *pFifo){
108 FifoPage *pPage, *pNextPage;
109 for(pPage=pFifo->pFirst; pPage; pPage=pNextPage){
110 pNextPage = pPage->pNext;
111 sqliteFree(pPage);
112 }
113 sqlite3VdbeFifoInit(pFifo);
114}

Archive Download this file

Branches

Tags

Quick Links:     www.monotone.ca    -     Downloads    -     Documentation    -     Wiki    -     Code Forge    -     Build Status