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authorOndrej Oprala <ooprala@redhat.com>2013-01-22 14:21:23 +0100
committerPádraig Brady <P@draigBrady.com>2013-04-14 01:00:45 +0100
commit8901e010fa24ba375d53e3e37fc7819621adcf19 (patch)
tree1f20f49bb0c455525b042e838462d4396c97a314 /src
parent4114c93af398d7aecb5eb253f90d9b4cc0785643 (diff)
downloadcoreutils-8901e010fa24ba375d53e3e37fc7819621adcf19.tar.xz
dd: avoid buffer allocations unless needed
* src/dd.c: Add new static global variable ibuf. (alloc_ibuf, alloc_obuf): New functions factored from dd_copy(). (dd_copy): Call the new functions to allocate memory for ibuf and obuf when necessary. (skip): Likewise. * tests/dd/no-allocate.sh: New test. * tests/local.mk: Reference the test.
Diffstat (limited to 'src')
-rw-r--r--src/dd.c135
1 files changed, 82 insertions, 53 deletions
diff --git a/src/dd.c b/src/dd.c
index c98e578fe..f727a5ef9 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -236,6 +236,9 @@ static uintmax_t r_truncate = 0;
static char newline_character = '\n';
static char space_character = ' ';
+/* Input buffer. */
+static char *ibuf;
+
/* Output buffer. */
static char *obuf;
@@ -646,6 +649,65 @@ Options are:\n\
exit (status);
}
+static char *
+human_size (size_t n)
+{
+ static char hbuf[LONGEST_HUMAN_READABLE + 1];
+ int human_opts =
+ (human_autoscale | human_round_to_nearest | human_base_1024
+ | human_space_before_unit | human_SI | human_B);
+ return human_readable (n, hbuf, human_opts, 1, 1);
+}
+
+/* Ensure input buffer IBUF is allocated. */
+
+static void
+alloc_ibuf (void)
+{
+ if (ibuf)
+ return;
+
+ char *real_buf = malloc (input_blocksize + INPUT_BLOCK_SLOP);
+ if (!real_buf)
+ error (EXIT_FAILURE, 0,
+ _("memory exhausted by input buffer of size %zu bytes (%s)"),
+ input_blocksize, human_size (input_blocksize));
+
+ real_buf += SWAB_ALIGN_OFFSET; /* allow space for swab */
+
+ ibuf = ptr_align (real_buf, page_size);
+}
+
+/* Ensure output buffer OBUF is allocated/initialized. */
+
+static void
+alloc_obuf (void)
+{
+ if (obuf)
+ return;
+
+ if (conversions_mask & C_TWOBUFS)
+ {
+ /* Page-align the output buffer, too. */
+ char *real_obuf = malloc (output_blocksize + OUTPUT_BLOCK_SLOP);
+ if (!real_obuf)
+ error (EXIT_FAILURE, 0,
+ _("memory exhausted by output buffer of size %zu bytes (%s)"),
+ output_blocksize, human_size (output_blocksize));
+ obuf = ptr_align (real_obuf, page_size);
+ }
+ else
+ {
+ alloc_ibuf ();
+ obuf = ibuf;
+ }
+
+ /* Write a sentinel to the slop after the buffer,
+ to allow efficient checking for NUL blocks. */
+ assert (sizeof (uintptr_t) <= OUTPUT_BLOCK_SLOP);
+ memset (obuf + output_blocksize, 1, sizeof (uintptr_t));
+}
+
static void
translate_charset (char const *new_trans)
{
@@ -1526,7 +1588,7 @@ skip_via_lseek (char const *filename, int fdesc, off_t offset, int whence)
/* Throw away RECORDS blocks of BLOCKSIZE bytes plus BYTES bytes on
file descriptor FDESC, which is open with read permission for FILE.
- Store up to BLOCKSIZE bytes of the data at a time in BUF, if
+ Store up to BLOCKSIZE bytes of the data at a time in IBUF or OBUF, if
necessary. RECORDS or BYTES must be nonzero. If FDESC is
STDIN_FILENO, advance the input offset. Return the number of
records remaining, i.e., that were not skipped because EOF was
@@ -1535,7 +1597,7 @@ skip_via_lseek (char const *filename, int fdesc, off_t offset, int whence)
static uintmax_t
skip (int fdesc, char const *file, uintmax_t records, size_t blocksize,
- size_t *bytes, char *buf)
+ size_t *bytes)
{
uintmax_t offset = records * blocksize + *bytes;
@@ -1607,6 +1669,18 @@ skip (int fdesc, char const *file, uintmax_t records, size_t blocksize,
}
/* else file_size && offset > OFF_T_MAX or file ! seekable */
+ char *buf;
+ if (fdesc == STDIN_FILENO)
+ {
+ alloc_ibuf ();
+ buf = ibuf;
+ }
+ else
+ {
+ alloc_obuf ();
+ buf = obuf;
+ }
+
do
{
ssize_t nread = iread_fnc (fdesc, buf, records ? blocksize : *bytes);
@@ -1823,26 +1897,12 @@ set_fd_flags (int fd, int add_flags, char const *name)
}
}
-static char *
-human_size (size_t n)
-{
- static char hbuf[LONGEST_HUMAN_READABLE + 1];
- int human_opts =
- (human_autoscale | human_round_to_nearest | human_base_1024
- | human_space_before_unit | human_SI | human_B);
- return human_readable (n, hbuf, human_opts, 1, 1);
-}
-
/* The main loop. */
static int
dd_copy (void)
{
- char *ibuf, *bufstart; /* Input buffer. */
- /* These are declared static so that even though we don't free the
- buffers, valgrind will recognize that there is no "real" leak. */
- static char *real_buf; /* real buffer address before alignment */
- static char *real_obuf;
+ char *bufstart; /* Input buffer. */
ssize_t nread; /* Bytes read in the current block. */
/* If nonzero, then the previously read block was partial and
@@ -1869,45 +1929,12 @@ dd_copy (void)
It is necessary when accessing raw (i.e. character special) disk
devices on Unixware or other SVR4-derived system. */
- real_buf = malloc (input_blocksize + INPUT_BLOCK_SLOP);
- if (!real_buf)
- error (EXIT_FAILURE, 0,
- _("memory exhausted by input buffer of size %zu bytes (%s)"),
- input_blocksize, human_size (input_blocksize));
-
- ibuf = real_buf;
- ibuf += SWAB_ALIGN_OFFSET; /* allow space for swab */
-
- ibuf = ptr_align (ibuf, page_size);
-
- if (conversions_mask & C_TWOBUFS)
- {
- /* Page-align the output buffer, too. */
- real_obuf = malloc (output_blocksize + OUTPUT_BLOCK_SLOP);
- if (!real_obuf)
- error (EXIT_FAILURE, 0,
- _("memory exhausted by output buffer of size %zu bytes (%s)"),
- output_blocksize, human_size (output_blocksize));
- obuf = ptr_align (real_obuf, page_size);
- }
- else
- {
- real_obuf = NULL;
- obuf = ibuf;
- }
-
- /* Write a sentinel to the slop after the buffer,
- to allow efficient checking for NUL blocks. */
- assert (sizeof (uintptr_t) <= OUTPUT_BLOCK_SLOP);
- memset (obuf + output_blocksize, 1, sizeof (uintptr_t));
-
if (skip_records != 0 || skip_bytes != 0)
{
uintmax_t us_bytes = input_offset + (skip_records * input_blocksize)
+ skip_bytes;
uintmax_t us_blocks = skip (STDIN_FILENO, input_file,
- skip_records, input_blocksize, &skip_bytes,
- ibuf);
+ skip_records, input_blocksize, &skip_bytes);
us_bytes -= input_offset;
/* POSIX doesn't say what to do when dd detects it has been
@@ -1927,8 +1954,7 @@ dd_copy (void)
{
size_t bytes = seek_bytes;
uintmax_t write_records = skip (STDOUT_FILENO, output_file,
- seek_records, output_blocksize, &bytes,
- obuf);
+ seek_records, output_blocksize, &bytes);
if (write_records != 0 || bytes != 0)
{
@@ -1955,6 +1981,9 @@ dd_copy (void)
if (max_records == 0 && max_bytes == 0)
return exit_status;
+ alloc_ibuf ();
+ alloc_obuf ();
+
while (1)
{
if (r_partial + r_full >= max_records + !!max_bytes)