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Enhance the showdb tool to show a btree page layout. Add limit checks so that

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overflow content does not overflow the buffer.

FossilOrigin-Name: 57ffa07e26a26d2f4527c8e6d7a9c1f48f380bf7
This commit is contained in:
drh
2011-01-06 01:26:38 +00:00
parent b2c062df71
commit 5240aebdd8
3 changed files with 91 additions and 23 deletions
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94
tool/showdb.c
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@ -57,7 +57,7 @@ static void out_of_memory(void){
*/
static unsigned char *getContent(int ofst, int nByte){
unsigned char *aData;
aData = malloc(nByte);
aData = malloc(nByte+32);
if( aData==0 ) out_of_memory();
lseek(db, ofst, SEEK_SET);
read(db, aData, nByte);
@ -184,29 +184,33 @@ static void print_db_header(void){
** Describe cell content.
*/
static int describeContent(
unsigned char *a,
char *zDesc
unsigned char *a, /* Cell content */
int nLocal, /* Bytes in a[] */
char *zDesc /* Write description here */
){
int nDesc = 0;
int n, i, j;
i64 x, v;
const unsigned char *pData;
const unsigned char *pLimit;
char sep = ' ';
pLimit = &a[nLocal];
n = decodeVarint(a, &x);
pData = &a[x];
a += n;
i = x - n;
while( i>0 ){
while( i>0 && pData<=pLimit ){
n = decodeVarint(a, &x);
a += n;
i -= n;
nLocal -= n;
zDesc[0] = sep;
sep = ',';
nDesc++;
zDesc++;
if( x==0 ){
sprintf(zDesc, "null");
sprintf(zDesc, "*"); /* NULL is a "*" */
}else if( x>=1 && x<=6 ){
v = (signed char)pData[0];
pData++;
@ -230,7 +234,7 @@ static int describeContent(
if( (x&1)==0 ){
sprintf(zDesc, "blob(%d)", size);
}else{
sprintf(zDesc, "text(%d)", size);
sprintf(zDesc, "txt(%d)", size);
}
pData += size;
}
@ -240,10 +244,42 @@ static int describeContent(
}
return nDesc;
}
/*
** Compute the local payload size given the total payload size and
** the page size.
*/
static int localPayload(i64 nPayload, char cType){
int maxLocal;
int minLocal;
int surplus;
int nLocal;
if( cType==13 ){
/* Table leaf */
maxLocal = pagesize-35;
minLocal = (pagesize-12)*32/255-23;
}else{
maxLocal = (pagesize-12)*64/255-23;
minLocal = (pagesize-12)*32/255-23;
}
if( nPayload>maxLocal ){
surplus = minLocal + (nPayload-minLocal)%(pagesize-4);
if( surplus<=maxLocal ){
nLocal = surplus;
}else{
nLocal = minLocal;
}
}else{
nLocal = nPayload;
}
return nLocal;
}
/*
** Create a description for a single cell.
**
** The return value is the local cell size.
*/
static int describeCell(
unsigned char cType, /* Page type */
@ -273,6 +309,9 @@ static int describeCell(
n += i;
sprintf(&zDesc[nDesc], "n: %lld ", nPayload);
nDesc += strlen(&zDesc[nDesc]);
nLocal = localPayload(nPayload, cType);
}else{
nPayload = nLocal = 0;
}
if( cType==5 || cType==13 ){
i = decodeVarint(a, &rowid);
@ -282,10 +321,10 @@ static int describeCell(
nDesc += strlen(&zDesc[nDesc]);
}
if( showCellContent && cType!=5 ){
nDesc += describeContent(a, &zDesc[nDesc]);
nDesc += describeContent(a, nLocal, &zDesc[nDesc-1]);
}
*pzDesc = zDesc;
return n;
return nLocal+n;
}
/*
@ -299,9 +338,11 @@ static void decode_btree_page(
){
const char *zType = "unknown";
int nCell;
int i;
int i, j;
int iCellPtr;
int showCellContent = 0;
int showMap = 0;
char *zMap = 0;
switch( a[0] ){
case 2: zType = "index interior node"; break;
case 5: zType = "table interior node"; break;
@ -311,6 +352,7 @@ static void decode_btree_page(
while( zArgs[0] ){
switch( zArgs[0] ){
case 'c': showCellContent = 1; break;
case 'm': showMap = 1; break;
}
zArgs++;
}
@ -321,22 +363,46 @@ static void decode_btree_page(
nCell = a[3]*256 + a[4];
print_decode_line(a, 5, 2, "Offset to cell content area");
print_decode_line(a, 7, 1, "Fragmented byte count");
if( nCell>0 ){
printf(" key: lx=left-child n=payload-size r=rowid\n");
}
if( a[0]==2 || a[0]==5 ){
print_decode_line(a, 8, 4, "Right child");
iCellPtr = 12;
}else{
iCellPtr = 8;
}
if( nCell>0 ){
printf(" key: lx=left-child n=payload-size r=rowid\n");
}
if( showMap ){
zMap = malloc(pagesize);
memset(zMap, '.', pagesize);
memset(zMap, '1', hdrSize);
memset(&zMap[hdrSize], 'H', iCellPtr);
memset(&zMap[hdrSize+iCellPtr], 'P', 2*nCell);
}
for(i=0; i<nCell; i++){
int cofst = iCellPtr + i*2;
char *zDesc;
int n;
cofst = a[cofst]*256 + a[cofst+1];
describeCell(a[0], &a[cofst-hdrSize], showCellContent, &zDesc);
n = describeCell(a[0], &a[cofst-hdrSize], showCellContent, &zDesc);
if( showMap ){
char zBuf[30];
memset(&zMap[cofst], '*', n);
zMap[cofst] = '[';
zMap[cofst+n-1] = ']';
sprintf(zBuf, "%d", i);
j = strlen(zBuf);
if( j<=n-2 ) memcpy(&zMap[cofst+1], zBuf, j);
}
printf(" %03x: cell[%d] %s\n", cofst, i, zDesc);
}
if( showMap ){
for(i=0; i<pagesize; i+=64){
printf(" %03x: %.64s\n", i, &zMap[i]);
}
free(zMap);
}
}
/*
@ -386,6 +452,8 @@ static void usage(const char *argv0){
" NNN..MMM Show hex of pages NNN through MMM\n"
" NNN..end Show hex of pages NNN through end of file\n"
" NNNb Decode btree page NNN\n"
" NNNbc Decode btree page NNN and show content\n"
" NNNbm Decode btree page NNN and show a layout map\n"
" NNNt Decode freelist trunk page NNN\n"
" NNNtd Show leave freelist pages on the decode\n"
" NNNtr Recurisvely decode freelist starting at NNN\n"