Public bug reported:
Binary package hint: bsdmainutils
referring to hexdump from package bsdmainutils-6.1.10ubuntu3
option skip does lseek() for regular files only, 1-byte read()-calls are
executed for anything else.
if one wants to look at a disk device at gigabyte offsets, this takes ages.
Here is my patch, I have also added typedefs quad_t for compilation under
cygwin.
-----------------------------------------------------------------------------------
--- bsdmainutils-6.1.10ubuntu3.orig/usr.bin/hexdump/display.c 2006-08-15
08:03:30.000000000 +0200
+++ bsdmainutils-6.1.10ubuntu3/usr.bin/hexdump/display.c 2009-07-29
20:51:51.593750000 +0200
@@ -341,28 +341,43 @@
doskip(const char *fname, int statok)
{
int cnt;
struct stat sb;
char ch;
+ off_t rc;
if (statok) {
if (fstat(0, &sb))
err(1, "%s", fname);
+
if (S_ISREG(sb.st_mode) && skip >= sb.st_size) {
address += sb.st_size;
skip -= sb.st_size;
return;
}
}
- if (S_ISREG(sb.st_mode)) {
- if ((lseek(0, skip, SEEK_SET)) == -1)
- err(1, "%s", fname);
- address += skip;
+
+
+ /* try lseek() first */
+ rc = lseek(0, skip, SEEK_SET);
+ if (rc >= 0)
+ {
+ /* should work for files and hard disk devices */
+ address += rc;
skip = 0;
- } else {
+ }
+ else
+ {
+ /* calling read() for single bytes results in poor performance */
+ /* probably a pipe or socket file descriptor
*/
for (cnt = 0; cnt < skip; ++cnt)
- if (read(0, &ch, 1) != 1)
+ {
+ rc = read(0, &ch, 1);
+ if (rc != 1)
break;
+ }
address += cnt;
skip -= cnt;
}
+ if (rc == -1)
+ err(1, "%s", fname);
}
--- bsdmainutils-6.1.10ubuntu3.orig/usr.bin/hexdump/hexdump.h 2006-08-15
08:03:30.000000000 +0200
+++ bsdmainutils-6.1.10ubuntu3/usr.bin/hexdump/hexdump.h 2009-07-26
21:26:44.169811000 +0200
@@ -99,5 +99,10 @@
void nomem(void);
void oldsyntax(int, char ***);
void rewrite(FS *);
int size(FS *);
void usage(void);
+
+#if defined(__CYGWIN__)
+typedef long long quad_t;
+typedef unsigned long long u_quad_t;
+#endif
** Affects: bsdmainutils (Ubuntu)
Importance: Undecided
Status: New
--
hexdump -s (8GB) /dev/sda - unacceptable performance
https://bugs.launchpad.net/bugs/406583
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