gzip: gzip -l now outputs accurate size

gzip -l now decompresses to see how long the uncompressed file was.
This fixes what is by far the most common bug report for gzip.
It has a significant performance cost, but it’s worth it nowadays.
* gzip.c (main): -l now sets 'test' too.  All uses of
'test' changed.
(treat_stdin, treat_file): Call do_list after decompressing,
so that the length is known.
(do_list): Omit arg IFD, since it is no longer needed.
All callers changed.  Get the CRC and uncompressed size
from input_crc and bytes_out instead of using lseek.
* tests/list-big: New test.
* unzip.c (unzip): Set unzip_crc before returning.
* util.c (write_buf): If 'test', output nothing.
Update bytes_out with output byte count, regardless of 'test'.
All callers changed.

1 files changed, 25 insertions, 41 deletions

diff --git a/gzip.c b/gzip.c
index 735ee0a..ecb19da 100644
--- a/gzip.c
+++ b/gzip.c
@@ -319,7 +319,7 @@ local void discard_input_bytes (size_t nbytes, unsigned int flags);
 local int  make_ofname  (void);
 local void shorten_name  (char *name);
 local int  get_method   (int in);
-local void do_list      (int ifd, int method);
+local void do_list      (int method);
 local int  check_ofname (void);
 local void copy_stat    (struct stat *ifstat);
 local void install_signal_handlers (void);
@@ -535,7 +535,7 @@ int main (int argc, char **argv)
         case 'k':
             keep = 1; break;
         case 'l':
-            list = decompress = to_stdout = 1; break;
+            list = decompress = test = to_stdout = 1; break;
         case 'L':
             license (); finish_out (); break;
         case 'm': /* undocumented, may change later */
@@ -655,7 +655,7 @@ int main (int argc, char **argv)
 
     /* And get to work */
     if (file_count != 0) {
-        if (to_stdout && !test && !list && (!decompress || !ascii)) {
+        if (to_stdout && !test && (!decompress || !ascii)) {
             SET_BINARY_MODE (STDOUT_FILENO);
         }
         while (optind < argc) {
@@ -673,7 +673,7 @@ int main (int argc, char **argv)
       {
         /* Output any totals, and check for output errors.  */
         if (!quiet && 1 < file_count)
-          do_list (-1, -1);
+          do_list (-1);
         if (fflush (stdout) != 0)
           write_error ();
       }
@@ -759,7 +759,7 @@ local void treat_stdin()
     if (decompress || !ascii) {
       SET_BINARY_MODE (STDIN_FILENO);
     }
-    if (!test && !list && (!decompress || !ascii)) {
+    if (!test && (!decompress || !ascii)) {
       SET_BINARY_MODE (STDOUT_FILENO);
     }
     strcpy(ifname, "stdin");
@@ -786,10 +786,6 @@ local void treat_stdin()
             do_exit(exit_code); /* error message already emitted */
         }
     }
-    if (list) {
-        do_list(ifd, method);
-        return;
-    }
 
     /* Actually do the compression/decompression. Loop over zipped members.
      */
@@ -805,6 +801,12 @@ local void treat_stdin()
         bytes_out = 0;            /* required for length check */
     }
 
+    if (list)
+      {
+        do_list (method);
+        return;
+      }
+
     if (verbose) {
         if (test) {
             fprintf(stderr, " OK\n");
@@ -949,7 +951,7 @@ local void treat_file(iname)
     /* Generate output file name. For -r and (-t or -l), skip files
      * without a valid gzip suffix (check done in make_ofname).
      */
-    if (to_stdout && !list && !test) {
+    if (to_stdout && !test) {
         strcpy(ofname, "stdout");
 
     } else if (make_ofname() != OK) {
@@ -967,12 +969,6 @@ local void treat_file(iname)
             return;               /* error message already emitted */
         }
     }
-    if (list) {
-        do_list(ifd, method);
-        if (close (ifd) != 0)
-          read_error ();
-        return;
-    }
 
     /* If compressing to a file, check if ofname is not ambiguous
      * because the operating system truncates names. Otherwise, generate
@@ -992,7 +988,7 @@ local void treat_file(iname)
     /* Keep the name even if not truncated except with --no-name: */
     if (!save_orig_name) save_orig_name = !no_name;
 
-    if (verbose) {
+    if (verbose && !list) {
         fprintf(stderr, "%s:\t", ifname);
     }
 
@@ -1015,6 +1011,12 @@ local void treat_file(iname)
     if (close (ifd) != 0)
       read_error ();
 
+    if (list)
+      {
+        do_list (method);
+        return;
+      }
+
     if (!to_stdout)
       {
         copy_stat (&istat);
@@ -1066,7 +1068,7 @@ local void treat_file(iname)
         } else {
             display_ratio(bytes_in-(bytes_out-header_bytes), bytes_in, stderr);
         }
-        if (!test && !to_stdout)
+        if (!test)
           fprintf(stderr, " -- %s %s", keep ? "created" : "replaced with",
                   ofname);
         fprintf(stderr, "\n");
@@ -1395,7 +1397,8 @@ local int make_ofname()
             /* With -t or -l, try all files (even without .gz suffix)
              * except with -r (behave as with just -dr).
              */
-            if (!recursive && (list || test)) return OK;
+            if (!recursive && test)
+              return OK;
 
             /* Avoid annoying messages with -r */
             if (verbose || (!recursive && !quiet)) {
@@ -1688,7 +1691,6 @@ local int get_method(in)
         last_member = 1;
         if (imagic0 != EOF) {
             write_buf (STDOUT_FILENO, magic, 1);
-            bytes_out++;
         }
     }
     if (method >= 0) return method;
@@ -1724,9 +1726,8 @@ local int get_method(in)
  * If the given method is < 0, display the accumulated totals.
  * IN assertions: time_stamp, header_bytes and ifile_size are initialized.
  */
-local void do_list(ifd, method)
-    int ifd;     /* input file descriptor */
-    int method;  /* compression method */
+static void
+do_list (int method)
 {
     ulg crc;  /* original crc */
     static int first_time = 1;
@@ -1768,26 +1769,9 @@ local void do_list(ifd, method)
         return;
     }
     crc = (ulg)~0; /* unknown */
-    bytes_out = -1L;
-    bytes_in = ifile_size;
 
     if (method == DEFLATED && !last_member) {
-        /* Get the crc and uncompressed size for gzip'ed (not zip'ed) files.
-         * If the lseek fails, we could use read() to get to the end, but
-         * --list is used to get quick results.
-         * Use "gunzip < foo.gz | wc -c" to get the uncompressed size if
-         * you are not concerned about speed.
-         */
-        bytes_in = lseek(ifd, (off_t)(-8), SEEK_END);
-        if (bytes_in != -1L) {
-            uch buf[8];
-            bytes_in += 8L;
-            if (read(ifd, (char*)buf, sizeof(buf)) != sizeof(buf)) {
-                read_error();
-            }
-            crc       = LG(buf);
-            bytes_out = LG(buf+4);
-        }
+      crc = unzip_crc;
     }
 
     if (verbose)