tool/offsets.c

   1 /*
   2 ** This program searches an SQLite database file for the lengths and
   3 ** offsets for all TEXT or BLOB entries for a particular column of a
   4 ** particular table.  The rowid, size and offset for the column are
   5 ** written to standard output.  There are three arguments, which are the
   6 ** name of the database file, the table, and the column.
   7 */
   8 #include "sqlite3.h"
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <stdarg.h>
  12 #include <string.h>
  13
  14 typedef unsigned char u8;
  15 typedef struct GState GState;
  16
  17 #define ArraySize(X)   (sizeof(X)/sizeof(X[0]))
  18
  19 /*
  20 ** Global state information for this program.
  21 */
  22 struct GState {
  23   char *zErr;           /* Error message text */
  24   FILE *f;              /* Open database file */
  25   int szPg;             /* Page size for the database file */
  26   int iRoot;            /* Root page of the table */
  27   int iCol;             /* Column number for the column */
  28   int pgno;             /* Current page number */
  29   u8 *aPage;            /* Current page content */
  30   u8 *aStack[20];       /* Page stack */
  31   int aPgno[20];        /* Page number stack */
  32   int nStack;           /* Depth of stack */
  33   int bTrace;           /* True for tracing output */
  34 };
  35
  36 /*
  37 ** Write an error.
  38 */
  39 static void ofstError(GState *p, const char *zFormat, ...){
  40   va_list ap;
  41   sqlite3_free(p->zErr);
  42   va_start(ap, zFormat);
  43   p->zErr = sqlite3_vmprintf(zFormat, ap);
  44   va_end(ap);
  45 }
  46
  47 /*
  48 ** Write a trace message
  49 */
  50 static void ofstTrace(GState *p, const char *zFormat, ...){
  51   va_list ap;
  52   if( p->bTrace ){
  53     va_start(ap, zFormat);
  54     vprintf(zFormat, ap);
  55     va_end(ap);
  56   }
  57 }
  58
  59 /*
  60 ** Find the root page of the table and the column number of the column.
  61 */
  62 static void ofstRootAndColumn(
  63   GState *p,              /* Global state */
  64   const char *zFile,      /* Name of the database file */
  65   const char *zTable,     /* Name of the table */
  66   const char *zColumn     /* Name of the column */
  67 ){
  68   sqlite3 *db = 0;
  69   sqlite3_stmt *pStmt = 0;
  70   char *zSql = 0;
  71   int rc;
  72   if( p->zErr ) return;
  73   rc = sqlite3_open(zFile, &db);
  74   if( rc ){
  75     ofstError(p, "cannot open database file \"%s\"", zFile);
  76     goto rootAndColumn_exit;
  77   }
  78   zSql = sqlite3_mprintf("SELECT rootpage FROM sqlite_master WHERE name=%Q",
  79                          zTable);
  80   rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
  81   if( rc ) ofstError(p, "%s: [%s]", sqlite3_errmsg(db), zSql);
  82   sqlite3_free(zSql);
  83   if( p->zErr ) goto rootAndColumn_exit;
  84   if( sqlite3_step(pStmt)!=SQLITE_ROW ){
  85     ofstError(p, "cannot find table [%s]\n", zTable);
  86     sqlite3_finalize(pStmt);
  87     goto rootAndColumn_exit;
  88   }
  89   p->iRoot = sqlite3_column_int(pStmt , 0);
  90   sqlite3_finalize(pStmt);
  91
  92   p->iCol = -1;
  93   zSql = sqlite3_mprintf("PRAGMA table_info(%Q)", zTable);
  94   rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
  95   if( rc ) ofstError(p, "%s: [%s}", sqlite3_errmsg(db), zSql);
  96   sqlite3_free(zSql);
  97   if( p->zErr ) goto rootAndColumn_exit;
  98   while( sqlite3_step(pStmt)==SQLITE_ROW ){
  99     const char *zCol = sqlite3_column_text(pStmt, 1);
 100     if( strlen(zCol)==strlen(zColumn)
 101      && sqlite3_strnicmp(zCol, zColumn, strlen(zCol))==0
 102     ){
 103       p->iCol = sqlite3_column_int(pStmt, 0);
 104       break;
 105     }
 106   }
 107   sqlite3_finalize(pStmt);
 108   if( p->iCol<0 ){
 109     ofstError(p, "no such column: %s.%s", zTable, zColumn);
 110     goto rootAndColumn_exit;
 111   }
 112
 113   zSql = sqlite3_mprintf("PRAGMA page_size");
 114   rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
 115   if( rc )  ofstError(p, "%s: [%s]", sqlite3_errmsg(db), zSql);
 116   sqlite3_free(zSql);
 117   if( p->zErr ) goto rootAndColumn_exit;
 118   if( sqlite3_step(pStmt)!=SQLITE_ROW ){
 119     ofstError(p, "cannot find page size");
 120   }else{
 121     p->szPg = sqlite3_column_int(pStmt, 0);
 122   }
 123   sqlite3_finalize(pStmt);
 124
 125 rootAndColumn_exit:
 126   sqlite3_close(db);
 127   return;
 128 }
 129
 130 /*
 131 ** Pop a page from the stack
 132 */
 133 static void ofstPopPage(GState *p){
 134   if( p->nStack<=0 ) return;
 135   p->nStack--;
 136   sqlite3_free(p->aStack[p->nStack]);
 137   p->pgno = p->aPgno[p->nStack-1];
 138   p->aPage = p->aStack[p->nStack-1];
 139 }
 140
 141
 142 /*
 143 ** Push a new page onto the stack.
 144 */
 145 static void ofstPushPage(GState *p, int pgno){
 146   u8 *pPage;
 147   size_t got;
 148   if( p->zErr ) return;
 149   if( p->nStack >= ArraySize(p->aStack) ){
 150     ofstError(p, "page stack overflow");
 151     return;
 152   }
 153   p->aPgno[p->nStack] = pgno;
 154   p->aStack[p->nStack] = pPage = sqlite3_malloc( p->szPg );
 155   if( pPage==0 ){
 156     fprintf(stderr, "out of memory\n");
 157     exit(1);
 158   }
 159   p->nStack++;
 160   p->aPage = pPage;
 161   p->pgno = pgno;
 162   fseek(p->f, (pgno-1)*p->szPg, SEEK_SET);
 163   got = fread(pPage, 1, p->szPg, p->f);
 164   if( got!=p->szPg ){
 165     ofstError(p, "unable to read page %d", pgno);
 166     ofstPopPage(p);
 167   }
 168 }
 169
 170 /* Read a two-byte integer at the given offset into the current page */
 171 static int ofst2byte(GState *p, int ofst){
 172   int x = p->aPage[ofst];
 173   return (x<<8) + p->aPage[ofst+1];
 174 }
 175
 176 /* Read a four-byte integer at the given offset into the current page */
 177 static int ofst4byte(GState *p, int ofst){
 178   int x = p->aPage[ofst];
 179   x = (x<<8) + p->aPage[ofst+1];
 180   x = (x<<8) + p->aPage[ofst+2];
 181   x = (x<<8) + p->aPage[ofst+3];
 182   return x;
 183 }
 184
 185 /* Read a variable-length integer.  Update the offset */
 186 static sqlite3_int64 ofstVarint(GState *p, int *pOfst){
 187   sqlite3_int64 x = 0;
 188   u8 *a = &p->aPage[*pOfst];
 189   int n = 0;
 190   while( n<8 && (a[0] & 0x80)!=0 ){
 191     x = (x<<7) + (a[0] & 0x7f);
 192     n++;
 193     a++;
 194   }
 195   if( n==8 ){
 196     x = (x<<8) + a[0];
 197   }else{
 198     x = (x<<7) + a[0];
 199   }
 200   *pOfst += (n+1);
 201   return x;
 202 }
 203
 204 /* Return the absolute offset into a file for the given offset
 205 ** into the current page */
 206 static int ofstInFile(GState *p, int ofst){
 207   return p->szPg*(p->pgno-1) + ofst;
 208 }
 209
 210 /* Return the size (in bytes) of the data corresponding to the
 211 ** given serial code */
 212 static int ofstSerialSize(int scode){
 213   if( scode<5 ) return scode;
 214   if( scode==5 ) return 6;
 215   if( scode<8 ) return 8;
 216   if( scode<12 ) return 0;
 217   return (scode-12)/2;
 218 }
 219
 220 /* Forward reference */
 221 static void ofstWalkPage(GState*, int);
 222
 223 /* Walk an interior btree page */
 224 static void ofstWalkInteriorPage(GState *p){
 225   int nCell;
 226   int i;
 227   int ofst;
 228   int iChild;
 229
 230   nCell = ofst2byte(p, 3);
 231   for(i=0; i<nCell; i++){
 232     ofst = ofst2byte(p, 12+i*2);
 233     iChild = ofst4byte(p, ofst);
 234     ofstWalkPage(p, iChild);
 235     if( p->zErr ) return;
 236   }
 237   ofstWalkPage(p, ofst4byte(p, 8));
 238 }
 239
 240 /* Walk a leaf btree page */
 241 static void ofstWalkLeafPage(GState *p){
 242   int nCell;
 243   int i;
 244   int ofst;
 245   int nPayload;
 246   sqlite3_int64 rowid;
 247   int nHdr;
 248   int j;
 249   int scode;
 250   int sz;
 251   int dataOfst;
 252   char zMsg[200];
 253
 254   nCell = ofst2byte(p, 3);
 255   for(i=0; i<nCell; i++){
 256     ofst = ofst2byte(p, 8+i*2);
 257     nPayload = ofstVarint(p, &ofst);
 258     rowid = ofstVarint(p, &ofst);
 259     if( nPayload > p->szPg-35 ){
 260       sqlite3_snprintf(sizeof(zMsg), zMsg,
 261          "# overflow rowid %lld", rowid);
 262       printf("%s\n", zMsg);
 263       continue;
 264     }
 265     dataOfst = ofst;
 266     nHdr = ofstVarint(p, &ofst);
 267     dataOfst += nHdr;
 268     for(j=0; j<p->iCol; j++){
 269       scode = ofstVarint(p, &ofst);
 270       dataOfst += ofstSerialSize(scode);
 271     }
 272     scode = ofstVarint(p, &ofst);
 273     sz = ofstSerialSize(scode);
 274     sqlite3_snprintf(sizeof(zMsg), zMsg,
 275          "rowid %12lld size %5d offset %8d",
 276           rowid, sz, ofstInFile(p, dataOfst));
 277     printf("%s\n", zMsg);
 278   }
 279 }
 280
 281 /*
 282 ** Output results from a single page.
 283 */
 284 static void ofstWalkPage(GState *p, int pgno){
 285   if( p->zErr ) return;
 286   ofstPushPage(p, pgno);
 287   if( p->zErr ) return;
 288   if( p->aPage[0]==5 ){
 289     ofstWalkInteriorPage(p);
 290   }else if( p->aPage[0]==13 ){
 291     ofstWalkLeafPage(p);
 292   }else{
 293     ofstError(p, "page %d has a faulty type byte: %d", pgno, p->aPage[0]);
 294   }
 295   ofstPopPage(p);
 296 }
 297
 298 int main(int argc, char **argv){
 299   GState g;
 300   memset(&g, 0, sizeof(g));
 301   if( argc>2 && strcmp(argv[1],"--trace")==0 ){
 302     g.bTrace = 1;
 303     argc--;
 304     argv++;
 305   }
 306   if( argc!=4 ){
 307     fprintf(stderr, "Usage: %s DATABASE TABLE COLUMN\n", *argv);
 308     exit(1);
 309   }
 310   ofstRootAndColumn(&g, argv[1], argv[2], argv[3]);
 311   if( g.zErr ){
 312     fprintf(stderr, "%s\n", g.zErr);
 313     exit(1);
 314   }
 315   ofstTrace(&g, "# szPg = %d\n", g.szPg);
 316   ofstTrace(&g, "# iRoot = %d\n", g.iRoot);
 317   ofstTrace(&g, "# iCol = %d\n", g.iCol);
 318   g.f = fopen(argv[1], "rb");
 319   if( g.f==0 ){
 320     fprintf(stderr, "cannot open \"%s\"\n", argv[1]);
 321     exit(1);
 322   }
 323   ofstWalkPage(&g, g.iRoot);
 324   if( g.zErr ){
 325     fprintf(stderr, "%s\n", g.zErr);
 326     exit(1);
 327   }
 328   return 0;
 329 }