1 files changed, 99 insertions, 0 deletions
diff --git a/tool/showlocks.c b/tool/showlocks.c
new file mode 100644
index 000000000000..4159a71f8ac8
--- /dev/null
+++ b/tool/showlocks.c
@@ -0,0 +1,99 @@
+/*
+** This file implements a simple command-line utility that shows all of the
+** Posix Advisory Locks on a file.
+**
+** Usage:
+**
+**     showlocks FILENAME
+**
+** To compile:  gcc -o showlocks showlocks.c
+*/
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* This utility only looks for locks in the first 2 billion bytes */
+#define MX_LCK 2147483647
+
+/*
+** Print all locks on the inode of "fd" that occur in between
+** lwr and upr, inclusive.
+*/
+static int showLocksInRange(int fd, off_t lwr, off_t upr){
+  int cnt = 0;
+  struct flock x;
+  struct lockRange {
+    off_t lwr;
+    off_t upr;
+  } *aPending = 0;
+  int nAlloc = 1;
+  int nPending = 0;
+  int nDone = 0;
+
+  nPending = 1;
+  aPending = malloc( sizeof(aPending[0]) );
+  if( aPending==0 ){
+    fprintf(stderr, "out of memory\n");
+    exit(1);
+  }
+  aPending[0].lwr = lwr;
+  aPending[0].upr = upr;
+
+  for(nDone=0; nDone<nPending; nDone++){
+    lwr = aPending[nDone].lwr;
+    upr = aPending[nDone].upr;
+    if( lwr>=upr ) continue;
+    x.l_type = F_WRLCK;
+    x.l_whence = SEEK_SET;
+    x.l_start = lwr;
+    x.l_len = upr - lwr;
+    fcntl(fd, F_GETLK, &x);
+    if( x.l_type==F_UNLCK ) continue;
+    printf("start: %-12d len: %-5d pid: %-5d type: %s\n",
+         (int)x.l_start, (int)x.l_len,
+         x.l_pid, x.l_type==F_WRLCK ? "WRLCK" : "RDLCK");
+    cnt++;
+    if( nPending+2 > nAlloc ){
+      nAlloc = nAlloc*2 + 2;
+      aPending = realloc(aPending, sizeof(aPending[0])*nAlloc );
+    }
+    if( aPending==0 ){
+      fprintf(stderr, "unable to realloc for %d bytes\n",
+                      (int)sizeof(aPending[0])*(nPending+2));
+      exit(1);
+    }
+    if( lwr<x.l_start ){
+      aPending[nPending].lwr = lwr;
+      aPending[nPending].upr = x.l_start;
+      nPending++;
+    }
+    if( x.l_start+x.l_len<=upr ){
+      aPending[nPending].lwr = x.l_start + x.l_len;
+      aPending[nPending].upr = upr;
+      nPending++;
+    }
+  }
+  free(aPending);
+  return cnt;
+}
+
+int main(int argc, char **argv){
+  int fd;
+  int cnt;
+
+  if( argc!=2 ){
+    fprintf(stderr, "Usage: %s FILENAME\n", argv[0]);
+    return 1;
+  }
+  fd = open(argv[1], O_RDWR, 0);
+  if( fd<0 ){
+    fprintf(stderr, "%s: cannot open %s\n", argv[0], argv[1]);
+    return 1;
+  }
+  cnt = showLocksInRange(fd, 0, MX_LCK);
+  if( cnt==0 ) printf("no locks\n");  
+  close(fd);
+  return 0;
+}