libbb: introduce and use xrealloc_vector

function                                             old     new   delta
xrealloc_vector_helper                                 -      51     +51
create_list                                           84      99     +15
getopt_main                                          690     695      +5
passwd_main                                         1049    1053      +4
get_cached                                            85      89      +4
msh_main                                            1377    1380      +3
add_match                                             42      41      -1
read_lines                                           720     718      -2
grave                                               1068    1066      -2
fill_match_lines                                     143     141      -2
add_to_dirlist                                        67      65      -2
add_input_file                                        49      47      -2
act                                                  252     250      -2
fsck_main                                           2252    2246      -6
man_main                                             765     757      -8
bb_internal_initgroups                               228     220      -8
cut_main                                            1052    1041     -11
add_edge_to_node                                      55      43     -12
dpkg_main                                           3851    3835     -16
ifupdown_main                                       2202    2178     -24
sort_main                                            838     812     -26
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 5/15 up/down: 82/-124)          Total: -42 bytes

1 files changed, 49 insertions, 0 deletions

diff --git a/libbb/read.c b/libbb/read.c
index 7b804125a..405e216dc 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -291,3 +291,52 @@ void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *sizep)
                 bb_perror_msg_and_die("can't read '%s'", filename);
         return buf;
 }
+
+/* libbb candidate */
+#if 0
+static void *xmalloc_read(int fd, size_t *sizep)
+{
+        char *buf;
+        size_t size, rd_size, total;
+        off_t to_read;
+        struct stat st;
+
+        to_read = sizep ? *sizep : INT_MAX; /* max to read */
+
+        /* Estimate file size */
+        st.st_size = 0; /* in case fstat fails, assume 0 */
+        fstat(fd, &st);
+        /* /proc/N/stat files report st_size 0 */
+        /* In order to make such files readable, we add small const */
+        size = (st.st_size | 0x3ff) + 1;
+
+        total = 0;
+        buf = NULL;
+        while (1) {
+                if (to_read < size)
+                        size = to_read;
+                buf = xrealloc(buf, total + size + 1);
+                rd_size = full_read(fd, buf + total, size);
+                if ((ssize_t)rd_size < 0) { /* error */
+                        free(buf);
+                        return NULL;
+                }
+                total += rd_size;
+                if (rd_size < size) /* EOF */
+                        break;
+                to_read -= rd_size;
+                if (to_read <= 0)
+                        break;
+                /* grow by 1/8, but in [1k..64k] bounds */
+                size = ((total / 8) | 0x3ff) + 1;
+                if (size > 64*1024)
+                        size = 64*1024;
+        }
+        xrealloc(buf, total + 1);
+        buf[total] = '\0';
+
+        if (sizep)
+                *sizep = total;
+        return buf;
+}
+#endif