Add the showshm utility program for printing out the shm header in a

human-readable format.

FossilOrigin-Name: f6304fd142c998aba44f02c6018223af2630671b4791d750b70a59ab1adb8d6d

tool/showshm.c

@@ -0,0 +1,158 @@
+/*
+** A utility for printing content from the wal-index or "shm" file.
+*/
+#include <stdio.h>
+#include <ctype.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <assert.h>
+
+#define ISDIGIT(X)  isdigit((unsigned char)(X))
+#define ISPRINT(X)  isprint((unsigned char)(X))
+
+#if !defined(_MSC_VER)
+#include <unistd.h>
+#include <sys/types.h>
+#else
+#include <io.h>
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+
+static int fd = -1;             /* The open SHM file */
+
+/* Report an out-of-memory error and die.
+*/
+static void out_of_memory(void){
+  fprintf(stderr,"Out of memory...\n");
+  exit(1);
+}
+
+/*
+** Read content from the file.
+**
+** Space to hold the content is obtained from malloc() and needs to be
+** freed by the caller.
+*/
+static unsigned char *getContent(int ofst, int nByte){
+  unsigned char *aData;
+  aData = malloc(nByte);
+  if( aData==0 ) out_of_memory();
+  lseek(fd, ofst, SEEK_SET);
+  read(fd, aData, nByte);
+  return aData;
+}
+
+/*
+** Flags values
+*/
+#define FG_HEX     1    /* Show as hex */
+#define FG_NBO     2    /* Native byte order */
+#define FG_PGSZ    4    /* Show as page-size */
+
+/* Print a line of decode output showing a 4-byte integer.
+*/
+static void print_decode_line(
+  unsigned char *aData,      /* Content being decoded */
+  int ofst, int nByte,       /* Start and size of decode */
+  unsigned flg,              /* Display flags */
+  const char *zMsg           /* Message to append */
+){
+  int i, j;
+  int val = aData[ofst];
+  char zBuf[100];
+  sprintf(zBuf, " %03x: %02x", ofst, aData[ofst]);
+  i = (int)strlen(zBuf);
+  for(j=1; j<4; j++){
+    if( j>=nByte ){
+      sprintf(&zBuf[i], "   ");
+    }else{
+      sprintf(&zBuf[i], " %02x", aData[ofst+j]);
+      val = val*256 + aData[ofst+j];
+    }
+    i += (int)strlen(&zBuf[i]);
+  }
+  if( nByte==8 ){
+    for(j=4; j<8; j++){
+      sprintf(&zBuf[i], " %02x", aData[ofst+j]);
+      i += (int)strlen(&zBuf[i]);
+    }
+  }
+  if( flg & FG_NBO ){
+    assert( nByte==4 );
+    memcpy(&val, aData+ofst, 4);
+  }
+  sprintf(&zBuf[i], "            ");
+  i += 12;
+  if( flg & FG_PGSZ ){
+    unsigned short sz;
+    memcpy(&sz, aData+ofst, 2);
+    sprintf(&zBuf[i], "   %9d", sz==1 ? 65536 : sz);
+  }else if( flg & FG_HEX ){
+    sprintf(&zBuf[i], "  0x%08x", val);
+  }else if( nByte<8 ){
+    sprintf(&zBuf[i], "   %9d", val);
+  }
+  printf("%s  %s\n", zBuf, zMsg);
+}
+
+/*
+** Print an instance of the WalIndexHdr object.  ix is either 0 or 1
+** to select which header to print.
+*/
+static void print_index_hdr(unsigned char *aData, int ix){
+  int i;
+  assert( ix==0 || ix==1 );
+  i = ix ? 48 : 0;
+  print_decode_line(aData, 0+i, 4, FG_NBO,  "Wal-index version");
+  print_decode_line(aData, 4+i, 4, 0,       "unused padding");
+  print_decode_line(aData, 8+i, 4, FG_NBO,  "transaction counter");
+  print_decode_line(aData,12+i, 1, 0,       "1 when initialized");
+  print_decode_line(aData,13+i, 1, 0,       "true if WAL cksums are bigendian");
+  print_decode_line(aData,14+i, 2, FG_PGSZ, "database page size");
+  print_decode_line(aData,16+i, 4, FG_NBO,  "mxFrame");
+  print_decode_line(aData,20+i, 4, FG_NBO,  "Size of database in pages");
+  print_decode_line(aData,24+i, 8, 0, "Cksum of last frame in -wal");
+  print_decode_line(aData,32+i, 8, 0,  "Salt values from the -wal");
+  print_decode_line(aData,40+i, 8, 0,  "Cksum over all prior fields");
+}
+
+/*
+** Print the WalCkptInfo object
+*/
+static void print_ckpt_info(unsigned char *aData){
+  const int i = 96;
+  int j;
+  print_decode_line(aData, 0+i, 4, FG_NBO,  "nBackfill");
+  for(j=0; j<5; j++){
+    char zLabel[100];
+    sprintf(zLabel, "aReadMark[%d]", j);
+    print_decode_line(aData, 4*j+4+i, 4, FG_NBO, zLabel);
+  }
+  print_decode_line(aData,24+i, 8, 0,       "aLock");
+  print_decode_line(aData,32+i, 4, FG_NBO,  "nBackfillAttempted");
+  print_decode_line(aData,36+i, 4, FG_NBO,  "notUsed0");
+}
+
+
+int main(int argc, char **argv){
+  unsigned char *aData;
+  if( argc<2 ){
+    fprintf(stderr,"Usage: %s FILENAME\n", argv[0]);
+    exit(1);
+  }
+  fd = open(argv[1], O_RDONLY);
+  if( fd<0 ){
+    fprintf(stderr,"%s: can't open %s\n", argv[0], argv[1]);
+    exit(1);
+  }
+  aData = getContent(0, 136);
+  print_index_hdr(aData, 0);
+  print_index_hdr(aData, 1);
+  print_ckpt_info(aData);
+  free(aData);
+  close(fd);
+  return 0;
+}